Chesapeake Bay Basin

Toxics Loading and Release Inventory

May 1999

Chesapeake Bay Program

410 Severn Avenue, Suite 109

Annapolis, Maryland 21403

1-800 YOUR BAY

Printed by the U.S. Environmental Protection Agency for the Chesapeake Bay Program

http://www.chesapeakebay.net
i-1

I. WHAT IS THE PURPOSE OF THIS

INVENTORY?

This Toxics Loading and Release Inventory

is one of many tools the Chesapeake Bay

Program is using to set more targeted

source reduction and pollution prevention

goals to reduce and eliminate toxic impacts

in the Bay. The overall goal of the 1994

Chesapeake Bay Basinwide Toxics

Reduction and Prevention Strategy is “a

Chesapeake Bay free of toxics by reducing

or eliminating the input of chemical

contaminants from all controllable sources

to levels that result in no toxic or

bioaccumulative impact on the living

resources that inhabit the Bay or on human

health.”

To address that goal, the Bay Program has

been following these steps (Figure 1):

1. Identifying areas of the Bay impacted

by toxics.

2. Determining chemicals causing the

toxic impacts.

3. Determining the origin of those

chemicals.

4. Implementing management actions to

reduce inputs of those chemicals to

levels that will result in no toxic or

bioaccumulative impacts on the Bay’s

living resources or on human health,

based on available data and current

state of science.

Figure 1. Chesapeake Bay Program process for managing chemical contaminant-related problems in the Bay

and its rivers. This figure illustrates that the loading data reported in this inventory are only one piece of the

overall toxics management picture. The inventory must be used in conjunction with data on toxics impacts

and impairing chemicals in order to identify sources to control.

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Since the signing of the 1994 strategy, the

Bay Program has made significant progress

in identifying toxic impacts in the Bay and

chemicals causing the impacts. In early

1999, the Bay Program completed its

characterization of toxic impacts in all tidal

rivers of the Bay. This toxics

characterization will supplement existing

characterizations carried out by Bay

Program partners and will provide a

scientifically-based description of the

distribution and extent of chemical

contaminant impacts in the Bay. This

characterization and other state efforts have

identified chemicals which cause problems

in localized areas of the Bay’s rivers. In

addition, the Bay Program has developed a

Chesapeake Bay Toxics of Concern List of

chemicals which cause, or have the potential

to cause, adverse impacts on the Bay system. 

The information on impacts and

chemicals causing impacts, coupled with

this updated 1999 Chesapeake Bay

Basinwide Toxics Loading and Release

Inventory, will enable managers,

scientists, and stakeholders to target their

toxics reduction and prevention activities

toward specific sources and chemicals in

impacted areas of the Bay. 

This inventory can be used by managers,

scientists, and the public in the following

ways:

< Scientists, managers, and stakeholders

can use this inventory, coupled with the

toxics characterization, to set reduction

targets for sources of chemicals causing

toxic impacts in the Bay’s tidal rivers.

< Managers can use the assessment of the

relative importance of point and

nonpoint sources of chemical

contaminants to better target their

management programs to the most

important sources.

< Scientists can use this inventory to

identify the greatest data needs to

improve future loads estimates.

< The public can use this inventory to

learn about their waterbodies of interest

– the types of chemicals entering these

waters, the magnitude of the loads, and

chemical sources. This information,

coupled with the toxics characterization

of these waters, will help the public

identify how and when to act to reduce

chemical loads to these waters.

This inventory reports chemical contaminant

loads to the Bay and its rivers but does not

report what the loads mean to the Bay’s

living resources or which specific sources

and chemicals are causing impacts. A big

load of a chemical contaminant does not

necessarily mean a big impact, nor does a

small load always indicate a small impact. 

A big load of chemical contaminants from a

particular source also does not mean that the

source is uncontrolled. For example, point

source dischargers may be in compliance

with their permits, but may still produce a

substantial load to the Bay and tidal rivers. 

This is often the case with large flow

facilities (i.e., wastewater treatment plants)

that emit a very low concentration of a

chemical into the Bay and tidal rivers, but

their flow is so large that it results in a large

load. As stated previously, this inventory can

be used in conjunction with the toxics

characterization to help managers target

management actions toward specific

geographic areas, chemicals, and sources. 

Toxicity of a chemical depends on many factors

such as the concentration, chemical/physical

form, and persistence of the chemical; the

chemical/physical properties of the waterbody

it is entering (i.e., pH, sediment type, etc.); and

the type and life stage of the living resources

exposed to the chemical.
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II. WHAT IS THE FOCUS FOR THIS

INVENTORY?

Loads and Releases

This inventory reports both loadings and

releases to the Bay watershed. Loadings are

estimates of the quantity of chemical

contaminants that reach the Bay and tidal

rivers, from sources such as point sources

discharging into the Bay or its rivers, urban

runoff, atmospheric deposition on the Bay or

its rivers, shipping and boating, and acid

mine drainage. Releases are the estimates of

the quantity of chemical contaminants

emitted to the Bay’s watershed that have the

potential to reach the Bay. The only release

information in this inventory is for pesticide

usage.

Loads to Tidal Rivers and Bay

The Chesapeake Bay has a direct connection

with the Atlantic Ocean. Because of the

ocean tides, saltwater from the Atlantic is

mixed in the Bay with freshwater derived

from land runoff. The part of the Bay and

its rivers that is influenced by the tide is

referred to as the “tidal Bay” and “tidal

rivers.” Moving upstream, there comes a

point at which the rivers are no longer

influenced by the ocean tide. The portions

of the rivers that are not under the influence

of the tide is referred to as “non-tidal.” The

boundary between the non-tidal and tidal

portions of a river is called the “fall line.” 

The fall line is the physiographic boundary

representing the natural geographic break

between the non-tidal and tidal regions of

the Bay watershed. For example, in the

Potomac River, the fall line is at Great Falls. 

The tidal portions of rivers appear to be

efficient traps for chemical contaminants,

which may be a reason why only low levels

of chemical contaminants are detected in the

Bay. This inventory mainly reports chemical

contaminant loads to the Bay and its tidal

rivers, as opposed to non-tidal waters,

because tidal waters are the focus of the Bay

Program’s toxics efforts. The sites of many

of the known toxics problems are in tidal

waters and most of the urban areas and

toxics-related land use activities are adjacent

to tidal waters. However, it is important to

note that non-tidal waters -- above the fall

line -- are also sources of chemical

contamination. Chemical contaminant loads

can enter the Bay and its rivers above the fall

line (non-tidal waters) or below the fall line

(tidal waters). Measurements taken at the fall

line are used to represent the fraction of

upstream loads (whether from point or

nonpoint sources) that make it to the tidal

waters. Upstream sources can originate from

point sources such as industries, federal

facilities (e.g., military bases), and

wastewater treatment plants or nonpoint

sources such as agricultural or urban runoff. 

In this inventory, chemical contaminant loads

entering the rivers above the fall line are

reported for point sources, urban runoff, and

acid mine drainage only. Loads to the tidal

rivers, below the fall line, are reported for

point sources, urban runoff, atmospheric

deposition, and shipping and boating spills.

(Figure 2)
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Fall line loads

Point Source Loads

Urban Stormwater Runoff Loads

Atmospheric Deposition

Loads

Shipping and Boating

Loads

Point Source Loads

Urban Stormwater Runoff Loads

Acid Mine Drainage Loads

Above Fall Line

NON-TIDAL

Below Fall Line

TIDAL

Fall line

Watershed (land)

River

River

Figure 2. The sources of chemical contaminant loads to the Bay, above the fall line and below the fall line,

reported in this inventory.

Chemicals Reported

Loadings are reported for chemicals on the

Chesapeake Bay Toxics of Concern List

(TOC) and the Chemicals of Potential

Concern List. These chemicals cause or

have the potential to cause adverse effects on

the Bay’s living resources. Other chemicals

that are not on these lists, but having very

high loads, are also reported. The TOC list

represents inorganic contaminants such as

metals (copper, lead, mercury) and organic

contaminants such as polynuclear aromatic

hydrocarbons (PAHs) and polychlorinated

biphenyls (PCBs). Metals come from both

point and nonpoint sources from a variety of

activities. PAHs come from the combustion

of fossil fuels and from oil and grease used

in cars. PCBs were used as fire retardants

and can be found in older electric

transformers and other machinery. Although

PCBs are banned, they are still found in the

environment and we still report them where

found.
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Controlling Toxic Inputs: Concentrations

Versus Cumulative Loads

Historically, the regulatory focus for

controlling toxic inputs to waterbodies has

been on controlling concentrations at the end

of a pipe, or point sources, with very little

focus on nonpoint sources. Discharges of

chemicals to the Bay and its rivers are

allowed if they fall below the levels thought

to cause impacts on the Bay’s living

resources. Managing concentrations of

contaminants in this way may be appropriate

for those chemicals that do not linger in the

water or sediment, either because they break

down or they are in well-flushed systems. In

this case, living resources may not be

exposed to these chemicals for a sufficient

amount of time to cause an impact. 

However, for persistent chemicals in poorlyflushed systems (i.e., harbors), managing the

cumulative load of those chemicals may be

more appropriate. In this case, persistent

chemicals may accumulate in the water or

sediment in a poorly-flushed system and

result in ambient concentrations that pose a

greater threat to the living resources exposed

to them.

Nationally, we are starting to see a shift from

managing end-of-pipe concentrations to

controlling cumulative loads from both point

and nonpoint sources through state

implementation of the Clean Water Act’s

Total Maximum Daily Loads program. This

approach complements and enhances

traditional approaches of controlling

chemical concentrations exiting pipes by

addressing the ambient concentration of

contaminants (resulting from all sources) to

which living resources may be exposed. 

From the perspective of the Bay’s living

resources, what matters is the concentration

of a chemical to which they are exposed,

what form it is in, and how long it persists. 

Some of these chemicals persist and

accumulate in the environment, while some

degrade or are flushed out of the Bay and

tidal rivers. Some may interact with each

other to become more or less toxic. The

physical and chemical properties of the

living resource’s habitat may impact the

toxicity of the chemicals as well. By

managing the loads, we can take into account

impacts that may result from cumulative

loads coming from many different sources,

synergistic effects of multiple contaminants

and other factors that may affect toxicity. 

This approach recognizes that all sources

(not just the largest sources) may play a part

in causing an impact and, therefore, may play

a part in reducing or eliminating the impact. 

As the Bay Program and states evolve toward

a more loads-based system for toxics

management, inventories such as this one

will become more important in helping

managers to target their source reduction

efforts in impacted areas. Data collection

efforts will need to evolve to reflect this

evolution by improving measurements that

allow for easier and more certain loads

estimates.
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III. WHAT IMPROVEMENTS HAVE

BEEN MADE SINCE THE 1994

INVENTORY?

Point Source Loads in this inventory are

reported for industries, federal facilities, and

municipalities discharging a flow of 0.5

million gallons per day or larger into the Bay

and are based on measured data from sources

such as the Permit Compliance System. In

the 1994 inventory, point source loads relied

more heavily on the national Toxics Release

Inventory (TRI). The TRI database is of

limited value in estimating point source

loads (or releases) to the surface waters of

the Bay and tidal rivers because data are

based on estimates rather than measured

values; the database represents only a small

fraction (approximately 5%) of all point

sources; and releases to surface waters

appear to be overestimated. Estimates of

point source loads have been improved by

including nearly twice as many facilities as

the 1994 inventory. Estimates for facilities

above and below the fall line are based on

more monitored data sources collected over a

consistent period of time for more chemicals. 

Urban Runoff Loads are from chemical

contaminants on urban land (both impervious

and pervious surfaces) that are transported to

the Bay and its rivers by stormwater runoff. 

These estimates are much improved because

they are based on recent stormwater

monitoring data collected by each

jurisdiction in the watershed in support of the

National Pollutant Discharge and

Elimination System stormwater permitting

program. Previous estimates were based on

nationwide data, mostly from the early

1980s. Estimates are reported from above

the fall line and below the fall line. 

Atmospheric Deposition Loads are loads

from chemical contaminants in the air that

are deposited onto the Bay and its tidal

rivers. These estimates are updated and

expanded using recent field measurements

and improved theoretical understanding of

deposition processes. Volatilization of

organic contaminants from the surface waters

to the air is considered for the first time in

calculating a “net” atmospheric loading to

the Bay and tidal rivers. Initial estimates of

the contribution of urban areas to

atmospheric deposition loads to the Bay and

tidal rivers also are reported. Only loads

below the fall line are reported. The TRI

database for industrial air releases was not

included in this inventory, as it was in 1994,

since the improved and expanded

atmospheric loadings data (below the fall

line) are based on measured data and are a

much better representation of loads than the

TRI data estimates of releases.

Shipping and Boating Loads are chemical

contaminants entering the Bay and tidal

rivers from boating-related spills. These

estimates are improved because they are

based on additional data sources; recovery

data were used to calculate net spill

quantities; and spills were more accurately

located based on better geographic data. 

Only loads to the Bay and tidal rivers, below

the fall line, are reported.

Acid Mine Drainage Loads are chemical

contaminants, typically metals, from active

and abandoned coal mines. These loads are

reported for the first time, based on a

comprehensive literature synthesis of

contaminant levels found in acid mine

drainage entering streams in the upper

portion of the watershed. These loads are

above the fall line, where the mines are

located.

Fall Line Loads represent the aggregate of

point and nonpoint sources above the fall

line that make it to the tidal waters. These

loads are much improved due to upgrades in
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analytical methods and load estimation

techniques. Loads from the Susquehanna

and James rivers are updated and new loads

are reported for the Potomac, Patuxent,

Choptank, Nanticoke, Pamunkey, Mattaponi,

and Rappahannock rivers. 

Pesticide Releases to the watershed were

based on much improved pesticide usage

data from a variety of national databases and

data from state surveys and pesticide experts

collected over a consistent period of time. 

However, pesticide usage was not translated

into loads.

Relative Importance of Sources to the Bay

and its tidal rivers is reported in this

inventory for the first time to provide

managers, scientists, and the public with

information on the most important sources of

estimated chemical contaminant loads. 

Loadings from sources with the most

widespread and available data were reported

from point sources, urban runoff, and

atmospheric deposition. Shoreline erosion

loads of several metals were estimated for

this “relative importance of sources” chapter,

but were not included as a separate chapter

because data are so sparse. Upstream

contaminant loads to the tidal waters from all

sources are represented by the fall line

loadings data. 

Mass Balance of Chemical Contaminants is

a new section of the inventory which

provides (1) a gross check and balance on

whether or not loadings estimates are

consistent and realistic, (2) an idea of the fate

of contaminants in the Bay and its tributaries,

(3) a management tool for predicting results

from load reductions, and (4) a consistent

way to identify key data gaps and

uncertainties that need to be addressed for

management/scientific purposes.

IV. WHAT ARE THE LIMITATIONS

OF THE 1999 INVENTORY?

These loading and release data represent the

best data available to date. However, there

are still many uncertainties and limitations of

the data which are highlighted at the end of

each chapter. Where feasible, confidence

levels in the data have been quantified. It is

important to note that most of the data that

were used to calculate loads were not

collected with that purpose in mind. Many

problems are inherent in these types of

calculations including a general lack of

quality data, incomparability of chemical

measurements and forms from each source

category, and incomplete reporting of the

various sources as discussed in the individual

loading chapters. Although this inventory is

much improved over the 1994 inventory, it is

still a work in progress with some limitations

listed below.

The inventory is not comprehensive: 

This updated inventory, although more

complete than the 1994 inventory, is not a

comprehensive accounting of all loads of all

chemical contaminants to the Bay and its

tidal rivers. Loads are reported for only a

subset of all chemicals released in the

watershed. Additionally, some sources of

chemical contaminant loads are not

quantified or completely accounted for as

described below.

< Point source loads are only estimated

for major facilities (facilities with a flow

of 0.5 million gallons per day or greater)

and have not been estimated for the

approximately 3,700 minor facilities in

the watershed because data from the

Permit Compliance System are often

incomplete for these smaller facilities.
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< Atmospheric deposition loads are only

those deposited directly to the water. 

The loads that are carried off the

watershed (i.e., the land) into the Bay

and tidal rivers by stormwater runoff are

not accounted for in the atmospheric

deposition loads category. However,

these loads from the upper portion of the

watershed, above the fall line, are

partially accounted for in the fall line

loads estimates for those chemicals that

were measured at the fall line. Loads

from the lower part of the watershed are

partially accounted for by the below fall

line urban runoff estimates.

< Agricultural loads (i.e., pesticides from

cropfields, metals from poultry

production), as in the 1994 inventory,

are not reported as a separate source

category in this inventory because very

little data on pesticide loads are

available and it is difficult to translate

pesticide usage data into loads. 

However, loads from agricultural lands

upstream are accounted for in the fall

line loadings estimates for those

chemicals that were measured at the fall

line. Below the fall line, loadings for

select pesticides are accounted for in the

atmospheric deposition loadings data. 

< Groundwater loads are not reported as a

separate source category and are only

accounted for in the fall line loadings

data for those chemicals measured at the

fall line. There are no available data to

estimate groundwater loads below the

fall line.

< Natural background loads have not

been quantified as a separate source

category because data were not available

to determine the portion of loads

originating from natural processes such

as mechanical or chemical weathering of

rock, which results in metal loads. The

shoreline erosion loads estimates for

select metals in the “relative importance

of sources” chapter provides a partial

accounting of natural background loads.

Point source loads estimates are uncertain:

Point source loads are important, but

uncertainty in loading estimates is large in

some cases. Loads may not have been

adjusted to account for pollutants that are

present in a facility’s intake water. 

Additionally, reporting programs in which

data were collected were not set up with the

objective of calculating loads, but rather for

determining compliance with regulated

parameters in discharge permits. For certain

organic contaminants -- all PCBs, pesticides,

and most PAHs -- values were reported as

below the detection limits. With the data

available for these organic contaminants, the

load may be as low as zero or as high as the

detection limit multiplied by the flow. Using

zero for organic contaminants could grossly

underestimate the load, but using the high

value for organic contaminants could grossly

overestimate the load. This uncertainty is

not the case for the metals data, since most

metals are above the detection limit.

To get an idea of the magnitude of loads of

organic contaminants from point sources in

the Potomac river watershed, PCB

concentrations in wastewater treatment plant

effluent in the New York/New Jersey Harbor

estuary were used to estimate loads. These

PCB concentrations were measured at much

lower detection limits than used in this

inventory. Based on this analysis, if lower

detection limits were used to measure endof-pipe concentrations of organic

contaminants, the estimated point source

loads may be substantial (up to 60% of the

total PCB load entering the tidal Potomac

river) but still less than the high load in the
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range described above.

The contribution of specific upstream

sources to tidal loads are unknown:

More information is needed regarding the

fate, transport, and attenuation processes of

chemical contaminants above the fall line, in

order to determine the important contributors

of upstream sources of chemical

contaminants to the Bay and its tidal rivers.

Updated loadings cannot be compared to the

1994 inventory to assess trends:

The 1999 inventory is an important step

forward in the Bay Program’s efforts to

compile a comprehensive, high quality

inventory of point and nonpoint source loads

to the Bay. The Bay Program has made

significant improvements to the previous

1994 inventory by increasing the sources

quantified and improving analytical and

loadings estimate techniques. Since the

loadings estimates in this inventory include

many more sources and new and improved

analytical and loadings estimation

techniques, they cannot be compared to those

from the 1994 inventory to assess trends. 

Also annual fluctuations in meteorology

affect our ability to compare fall line

loadings and nonpoint source loads from

year to year. Therefore, this inventory does

not report on loadings trends since the 1994

inventory.
Executive Summary

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Sources

AD FL UR SE PS Other

Mercury (lb/yr X 1000)

0

2

4

6

8

Mercury

Total Input: 9,500 lb/yr

?

AD FL UR SE PS Other

Arsenic (lb/yr X 1000)

0

10

20

80

120

160

?

Arsenic

Sources

Total Input: 140,000 lb/yr

V. MAJOR FINDINGS

Sources of contaminants to the Bay and its tidal rivers vary by chemical and by land use and

activities on the watershed. Through analysis of loadings data estimated using data collected

between 1990 and 1997, some clear patterns are observed:

< Upstream sources, from either point or nonpoint sources to non-tidal waters above the

fall line, provide substantial loads of metals to the Bay and tidal rivers. Fall line loads

account for between 60% for mercury to 87% for arsenic of total loads to the Bay and its tidal

rivers.

< Point sources below the fall line account for a substantial load of metals, such as copper

and mercury, to the entire Bay and its tidal rivers. Point source loads of copper and

mercury account for 11% and 28% of total loads respectively.

Total loads of mercury and arsenic to the tidal waters of the Bay from atmospheric deposition (AD); fall line

(FL); urban runoff (UR); shoreline erosion (SE); and point sources (PS). Examples of “Other Sources” not

fully quantified may include loads from smaller point sources, agricultural runoff, atmospheric deposition,

groundwater, and natural sources.
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Sources

AD FL UR SE PS Other

Copper (lb/yr X 1000)

0

50

100

300

400

500

600

?

Copper

Total Input: 710,000 lb/yr

Sources

AD FL UR SE PS Other

Cadmium (lb/yr X 1000)

0

10

20

50

75

100

?

Cadmium

Total Input: 94,000 lb/yr

Total loads of copper and cadmium to the tidal waters of the Bay from atmospheric deposition (AD); fall line

(FL); urban runoff (UR); shoreline erosion (SE); and point sources (PS). Examples of “Other Sources” not

fully quantified may include loads from smaller point sources, agricultural runoff, atmospheric deposition,

groundwater, and natural sources. For copper, the variability in the shoreline erosion estimate is smaller than

the symbol representing the average.
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AD FL UR SE PS Other

Lead (lb/yr X 1000)

0

100

200

300

400

500

?

Lead

Sources

Total Input: 560,000 lb/yr

Sources

AD FL UR SE PS Other

Zinc (lb/yr X 1000)

0

500

1000

1500

2000

2500

3000

Zinc

Total Input: 3,300,000 lb/yr

?

Total loads of lead and zinc to the tidal waters of the Bay from atmospheric deposition (AD); fall line

(FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples of “Other Sources”

not fully quantified may include loads from smaller point sources, agricultural runoff, atmospheric

deposition, groundwater, and natural sources. For lead, the variability in the shoreline erosion estimate

is smaller than the symbol representing the average, and for zinc, the variability in the point source

estimate is smaller than the symbol representing the average.
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Sources

AD FL UR SE PS Other

Benzo[a]pyrene (lb/yr X 1000)

0

5

10

15

20

50

100

150

Benzo[a]pyrene

Total Input: 64,000 lb/yr

?

< Point sources below the fall line are important loads to the different tidal rivers and can

account for up to approximately 10% of the total quantified load for some metals. Organic

contaminant loads are very uncertain at this time, but data suggest that point source loads of

PCBs can be substantial and should be the target of additional monitoring and analysis.

< Urban runoff below the fall line is a substantial source of select organic contaminants

(PAHs) to the Bay and tidal rivers. Given that point source loads estimates are highly

uncertain (as indicated by the large uncertainty bar in the figures), urban stormwater runoff is

the most substantial known source of PAH loads to the Bay and tidal rivers. Urban runoff

loads of PAHs to individual rivers are also substantial as illustrated in the Patuxent River

figure. 

 

Total loads of the PAH benzo[a]pyrene to the tidal waters of the Bay from atmospheric deposition (AD); fall

line (FL); urban runoff (UR); shoreline erosion (SE); and point sources (PS). Examples of “Other Sources”

not fully quantified may include loads from smaller point sources, agricultural runoff, atmospheric deposition,

groundwater, and natural sources. The variability in the atmospheric deposition and fall line estimates is

smaller than the symbol representing the average.
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Sources

AD FL UR SE PS Other

Chrysene (lb/yr X 1000)

0

10

20

50

100

150

Chrysene

Total Input: 64,000 lb/yr

?

Sources

AD FL UR SE PS Other

Phenanthrene (lb/yr X 1000)

0

25

100

200

300

Phenanthrene

Total Input: 130,000 lb/yr

?

Total loads of the PAHs chrysene and phenanthrene to the tidal waters of the Bay from atmospheric deposition

(AD); fall line (FL); urban runoff (UR); shoreline erosion (SE); and point sources (PS). Examples of “Other

Sources” not fully quantified may include loads from smaller point sources, agricultural runoff, atmospheric

deposition, groundwater, and natural sources. For chrysene, the variability in the atmospheric deposition and

fall line estimates is smaller than the symbol representing the average.
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Sources

AD FL UR SE PS Other

Pyrene (lb/yr X 1000)

0

10

20

80

120

160

200

Pyrene

Total Input: 88,000 lb/yr

?

Sources

AD FL UR SE PS Other

Benzo[a]pyrene (lb/yr X 1000)

0.0

0.1

0.2

0.3

0.4

0.5

Benzo[a]pyrene

Total Input: 320 lb/yr

?

Total loads of pyrene to the tidal waters of the Bay from atmospheric deposition (AD); fall line (FL); urban

runoff (UR); shoreline erosion (SE); and point sources (PS). Examples of “Other Sources” not fully quantified

may include loads from smaller point sources, agricultural runoff, atmospheric deposition, groundwater, and

natural sources.

Total loads of benzo[a]pyrene to the tidal Patuxent River from atmospheric deposition (AD); fall line (FL);

urban runoff (UR); shoreline erosion (SE); and point sources (PS). Examples of “Other Sources” not fully

quantified may include loads from smaller point sources, agricultural runoff, atmospheric deposition,

groundwater, and natural sources. The variability in the atmospheric deposition and fall line estimates is

smaller than the symbol representing the average.
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Sources

AD FL UR SE PS Other

Cadmium (lb/yr X 1000)

0.0

0.1

0.2

0.3

0.4

?

Cadmium

Total Input: 390 lb/yr

Sources

AD FL UR CSO PS Other

Cadmium (lb/yr X 1000)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

?

Cadmium

Total Input: 340 lb/yr

< Urban runoff below the fall line is a substantial source of metals to the Patuxent and

Anacostia Rivers as illustrated in the figures summarizing cadmium loads. Ranges were not

calculated for the Anacostia River loads due to a lack of data (and lack of uncertainty

reporting) from the different data sources. 

Total loads of cadmium to the tidal Patuxent River from atmospheric deposition (AD); fall line (FL); urban

runoff (UR); shoreline erosion (SE); and point sources (PS). Examples of “Other Sources” not fully quantified

may include loads from smaller point sources, agricultural runoff, atmospheric deposition, groundwater, and

natural sources.

Total loads of cadmium to the tidal Anacostia River from atmospheric deposition (AD); fall line (FL); urban

runoff (UR); combined sewer overflow (CSO); and point sources (PS). Point source loadings were not

reported. Examples of “Other Sources” not fully quantified may include loads from smaller point sources,

agricultural runoff, atmospheric deposition, groundwater, and natural sources. Uncertainties were not

calculated due to a lack of data and reported ranges.
Executive Summary

i-17

< Point sources of organic contaminants (PAHs and PCBs) are highly uncertain because

of measurement methods currently used for permit compliance monitoring; therefore, loads

are largely unknown. 

< Loadings are dependent on land use characteristics on the watershed and not the size of

the watershed. For example, the Anacostia River watershed, a relatively small urban

watershed, produces 12 times the loads of the metal, lead, than any of the other major river

watersheds.

Trace metal total watershed yields for selected tributaries of the Bay.

Susquehanna Potomac James Patuxent Anacostia

Copper 4.05 3.90 3.95 1.75 13.1 

Cadmium 0.61 0.61 0.35 0.16 0.46 

Lead 2.44 4.17 3.15 1.54 42.9 

Mercury 0.052 0.084 0.055 0.018 0.026 

Units: lb/km2-yr.

< Below the fall line, atmospheric deposition loads increase in areas of the Bay and tidal

rivers adjacent to urban areas.

< Shipping and boating-related spills from 1990 - 1996 resulted in 154 substances such as

jet fuel, gasoline, diesel oil, asphalt, and PCBs being loaded into Bay and tidal rivers in

4,736 recorded incidents. Most of the materials were spilled in the mainstem Bay or in

areas such as the West Chesapeake Basin and the tidal James River where large port,

industrial, or military installations are located.

< Acid mine drainage has impacted 1100 miles in 158 streams in the Chesapeake

watershed according to the 1996 state 303(d) reports. The causes cited for water quality

degradation from acid mine drainage are related to low pH and/or metals contamination (iron,

manganese, and aluminum). 

< Pesticide loads to the Bay and tidal rivers are largely unknown. 7,749,000 pounds of

pesticide active ingredient were applied to the four major crops in the watershed in

1996: corn, soybeans, small grains, and alfalfa. Some of these pesticides have been detected

in surface and groundwater. Studies are needed to quantify the fraction of pesticides that end

up in the Bay and its tidal rivers.
Executive Summary

i-18

VI. WHAT ACTIONS CAN BE TAKEN TO IMPROVE THE INVENTORY?

This inventory represents the most comprehensive loadings analysis for chemical contaminants

compiled to date for the Bay and tidal rivers. This inventory can serve as a useful planning tool

for directing future management and monitoring activities in the watershed. Specific

recommendations for improving loads estimates for each source are detailed in the individual

chapters of this inventory. Some overall recommendations for improving the inventory are:

< Continue to increase the number of accountable sources and improve analytical and loads

estimation techniques. 

< Improve the point source loadings estimates, particularly for the organic contaminants, by

obtaining more information on wastewater characteristics and by considering better methods

for detecting organic contaminants. 

< Determine the important upstream sources of chemical contaminants to the Bay and tidal

rivers by increasing our understanding of contaminant transport and attenuation processes. 

< Quantify other potentially significant sources of loads from agricultural lands and

groundwater. Specific studies to quantify the fraction of pesticides used that are loaded into

the Bay and its tidal rivers would be particularly useful.
ii-1

Acknowledgments

Special recognition goes to the Toxics Subcommittee’s Directed Toxics Assessment Workgroup

and the Toxics Subcommittee Fellows for their input into the development and review of this

report. This inventory can be found on the Chesapeake Bay Program web page at

http://www.chesapeakebay.net or contact the Bay Program Office at 1-800 YOUR BAY.

Directed Toxics Assessment Workgroup Members

Kelly Eisenman, Toxics Coordinator

USEPA Chesapeake Bay Program 

Heather Daniel, Toxics Fellow

Chesapeake Research Consortium

Carrie McDaniel, Toxics Fellow

Chesapeake Research Consortium

Joel Baker

University of Maryland

Alan Messing

Old Dominion University

Mike Unger

VA Institute of Marine Sciences

David Burdige

Old Dominion University

Cherie Miller 

U.S. Geological Survey

Nathalie Valette-Silver

NOAA

Jeffrey Cornwell

University of Maryland

Percy Pacheco

NOAA

David Velinsky

Academy of Natural Sciences

Anita Key

DC Department of Health

Mark Richards

VA Dept. of Environmental Quality

Allison Wiedeman

USEPA Chesapeake Bay Program 

Joe Macknis

USEPA Chesapeake Bay Program 

Joseph Scudlark

University of Delaware
iii-1

Table of Contents

I. Executive Summary.........................................................................................................i-1

II. Acknowledgments...........................................................................................................ii-1

III. Table of Contents................................................................................................................iii-1

List of Tables/Figures ...........................................................................................................iii-4

IV. Description of Inventory Chapters....................................................................................iv-1

V. Loadings

Chapter 1

Point Source Loadings .....................................................................................................................1-1

Introduction ............................................................................................................................1-1

Temporal and Spatial Coverage .............................................................................................1-1

Chemicals Reported ...............................................................................................................1-5

Mapping of Point Source Facilities .......................................................................................1-5

Methodology .........................................................................................................................1-6

Uncertainty and Data Handling .............................................................................................1-8

Discussion ............................................................................................................................1-11

Correlation with 1994 TLRI ................................................................................................1-17

Recommendations ................................................................................................................1-17

Chapter 2

Urban Stormwater Loadings.............................................................................................................2-1

Introduction ............................................................................................................................2-1

Temporal and Spatial Coverage .............................................................................................2-1

Methodology ..........................................................................................................................2-4

Uncertainty ............................................................................................................................2-6

Discussion and Comparison with 1994 Toxics Loading and Release Inventory...................2-8

Recommendations ................................................................................................................2-19

Chapter 3

Atmospheric Deposition Loadings....................................................................................................3-1

Introduction ............................................................................................................................3-1

Temporal and Spatial Coverage ............................................................................................3-2

Methodology .........................................................................................................................3-3

Uncertainty ............................................................................................................................3-6

Loading Estimates .................................................................................................................3-8
Table of Contents

iii-2

Comparison with 1994 Toxics Loading and Release Inventory.............................................3-8

Recommendations ..................................................................................................................3-9

Chapter 4

Shipping and Boating Loadings.......................................................................................................4-1

Introduction ............................................................................................................................4-1

Temporal and Spatial Coverage .............................................................................................4-1

Methodology ..........................................................................................................................4-1

Uncertainty ............................................................................................................................4-3

Discussion ..............................................................................................................................4-4

Correlation with 1994 Toxics Loading and Release Inventory .............................................4-5

Recommendations ..................................................................................................................4-5

Chapter 5

Acid Mine Drainage Loadings .........................................................................................................5-1

Introduction ............................................................................................................................5-1

Temporal and Spatial Coverage .............................................................................................5-2

Methodology ..........................................................................................................................5-2

Uncertainty ...........................................................................................................................5-3

Discussion ..............................................................................................................................5-3

Recommendations ..................................................................................................................5-9

VI. The Fall Line

Chapter 6

Fall Line Loadings...........................................................................................................................6-1

Introduction ............................................................................................................................6-1

Temporal and Spatial Coverage ........................................................................................... 6-1

Methodology ..........................................................................................................................6-6

Uncertainty ............................................................................................................................6-7

Discussion ..............................................................................................................................6-8

Correlation with 1994 Toxics Loading and Release Inventory............................................6-10

Recommendations ................................................................................................................6-10

VII. Releases

Chapter 7

Pesticide Use .....................................................................................................................................7-1

Introduction ............................................................................................................................7-1

Pesticide Usage Analysis .......................................................................................................7-1

Discussion of Data Gathering Techniques and Limitations ..................................................7-4

Pesticides in Surface and Ground Water ...............................................................................7-5
Table of Contents

iii-3

Recommendations ..................................................................................................................7-6

VIII. Relative Importance of Point and Non-point Sources to the Bay....................................8-1

Chapter 8

Introduction ...........................................................................................................................8-1

Methodology ..........................................................................................................................8-1

Inputs to the Tidal Chesapeake Bay ......................................................................................8-8

Inputs to the Tributaries of Chesapeake Bay........................................................................8-10

Discussion and Recommendations ......................................................................................8-14

IX. Mass Balance of Chemical Contaminants within Chesapeake Bay.................................9-1

Chapter 9

Introduction.............................................................................................................................9-1

Model Framework .................................................................................................................9-2

Results and Discussion ..........................................................................................................9-4

Summary and Conclusions ..................................................................................................9-14

X. References.............................................................................................................................r-1

XI. Appendices...........................................................................................................................A-1
Table of Contents

iii-4

LIST OF TABLES/FIGURES

Chapter 1 - Point Source Loadings

Table 1.1. Toxic point source data sources.....................................................................................1-3

Table 1.2. Total Chesapeake Bay watershed load estimates by chemical.....................................1-20

Table 1.3. Point source load estimates and percentage by major basin.........................................1-22

Table 1.4. Point source load estimates by state.............................................................................1-70

Figure 1.1. Chesapeake Bay basin major point source discharges...................................................1-4

Figure 1.2. Relative low Chesapeake Bay basin point source loads by chemical category............1-13

Figure 1.3. Relative high Chesapeake Bay basin point source loads by chemical category..........1-14

Figure 1.4. Loading estimates of metals by major basin................................................................1-15

Figure 1.5. Loading estimates of PCB’s by major basin................................................................1-15

Figure 1.6. Loading estimates of pesticides by major basin...........................................................1-15

Figure 1.7. Loading estimates of PAH’s by major basin................................................................1-15

Figure 1.8. Loading estimates of inorganics by major basin..........................................................1-16

Figure 1.9. Loading estimates of organics by major basin.............................................................1-16

Chapter 2 - Urban Stormwater Loadings

Table 2.1. Potential Sources for Common Pollutants in Urban Stormwater ..................................2-3

Table 2.2. Average Annual Precipitation Runoff from All Urban Lands in the Chesapeake Bay

Basin, 1984-1991 .........................................................................................................2-10

Table 2.3. Jurisdictions in the Chesapeake Bay Basin with available NPDES stormwater data and

land uses sampled ........................................................................................................2-11

Table 2.4. Chemicals Above Detection Level (ADL) in Chesapeake Bay Basin NPDES Stormwater

Sampling Data .........................................................................................2-12

Table 2.5. Descriptive Statistics and EMCs for selected chemicals detected in Chesapeake Bay

Basin NPDES Stormwater Sampling Data (μg/L).......................................................2-13

Table 2.6. Comparison of EMC values with those from a previous estimate contaminant loads in

the Chesapeake Bay Basin (μg/L)................................................................................2-15

Table 2.7a. Average annual chemical contaminant loads in stormwater runoff.............................2-16

Table 2.7b. Average annual chemical contaminant loads in stormwater runoff.............................2-17

Table 2.8. Comparison of Baywide loads with those from a previous estimate of contaminant loads

in the Chesapeake Bay Basin ......................................................................................2-18

Figure 2.1. Chesapeake Bay Watershed Model segments ...............................................................2-5

Chapter 3 - Atmospheric Deposition Loadings

Table 3.1. Data sources for 1998 atmospheric deposition estimates.............................................3-11

Table 3.2. Surface water segments below the fall lines used to calculate atmospheric deposition

loads .............................................................................................................................3-12

Table 3.3. Average annual atmospheric deposition fluxes to the Chesapeake Bay......................3-13

Table 3.4a. Wet deposition loads to the Chesapeake Bay below the fall lines...............................3-15

Table 3.4b. Dry aerosol deposition loads to the Chesapeake Bay below the fall lines...................3-16
Table of Contents

iii-5

Table 3.4c. Net gas exchange deposition loads to the Chesapeake Bay below the fall lines..........3-17

Table 3.4d. Total atmospheric deposition loads to the Chesapeake Bay below the fall lines.........3-18

Table 3.5. Influence of urban areas on atmospheric deposition loadings to the Bay....................3-19

Table 3.6. Comparison of 1994 and 1998 TLRI atmospheric deposition loadings.......................3-20

Chapter 4 - Shipping and Boating Loadings

Table 4.1. Chemicals selected for the 1996 Chesapeake Bay Toxics of Concern List, the Chemicals

of Potential Concern List, and Delisted Chemicals........................................................4-7

Table 4.2a. Spills of toxic materials containing chemicals on the Chesapeake Bay Toxics of

Concern and Chemicals of Potential Concern Lists [Ranked alphabetically]................4-8

Table 4.2b. Spills of toxic materials containing chemicals on the Chesapeake Bay Toxics of

Concern and Chemicals of Potential Concern Lists [Ranked by total loading].............4-9

Table 4.2c. Spills of toxic materials containing chemicals on the Chesapeake Bay Toxics of

Concern and Chemicals of Potential Concern Lists [Ranked alphabetically]..............4-10

Table 4.2d. Spills of toxic materials containing chemicals on the Chesapeake Bay Toxics of

Concern and Chemicals of Potential Concern Lists [Ranked by total loading]...........4-11

Table 4.3a. Spills of toxic materials from ships and land facilities to the Chesapeake Bay and its

tidal tributaries [Ranked by total loading]....................................................................4-12

Table 4.3b. Spills of toxic materials from ships and land facilities to the Chesapeake Bay and its

tidal tributaries [Ranked alphabetically]......................................................................4-18

Chapter 5 - Acid Mine Drainage Loadings

Table 5.1. Streams in the Chesapeake drainage affected by acid mine drainage and miles

impacted.........................................................................................................................5-4

Table 5.2. Summary of cumulative acid mine drainage chemical constituent loads in the

Susquehanna River tributaries draining the anthracite coal fields in Pennsylvania.....5-10

Table 5.3. Summary of cumulative acid mine drainage chemical constituent loads in the West

Branch Susquehanna River tributaries draining the bituminous coal fields in

Pennsylvania ................................................................................................................5-12

Table 5.4. Summary of cumulative acid mine drainage chemical constituent loads in the North

Branch Potomac River tributaries draining the bituminous coal fields in Maryland and

West Virginia ..............................................................................................................5-14

Chapter 6 - Fall Line Loadings

Table 6.1. Summary of Chesapeake Bay Fall Line Toxics Monitoring Program sampling between

1992 and 1997 ...............................................................................................................6-2

Table 6.2. List of organonitrogen and organophosphorus pesticides monitored at the fall line by

year ................................................................................................................................6-3

Table 6.3. List of polycyclic aromatic hydrocarbons monitored at the fall line by year.................6-3

Table 6.4. List of organochlorine contaminants monitored at the fall line by year.........................6-4

Table 6.5. List of trace metals monitored at the fall line by year....................................................6-5

Table 6.6. Annual loads of organonitrogen and organophosphorus pesticides above the fall line of
Table of Contents

iii-6

the Susquehanna River.................................................................................................6-12

Table 6.7. Annual loads of organonitrogen and organophosphorus pesticides above the fall line of

the Potomac River .......................................................................................................6-12

Table 6.8. Annual loads of organonitrogen and organophosphorus pesticides above the fall line of

the James River ...........................................................................................................6-13

Table 6.9. Annual loads of polycyclic aromatic hydrocarbons above the fall line of the

Susquehanna River ......................................................................................................6-13

Table 6.10. Annual loads of polycyclic aromatic hydrocarbons above the fall line of the Potomac

River ............................................................................................................................6-14

Table 6.11. Annual loads of polycyclic aromatic hydrocarbons above the fall line of the James

River.............................................................................................................................6-14

Table 6.12 Annual loads of organochlorines above the fall line of the Susquehanna River..........6-15

Table 6.13. Annual loads of organochlorines above the fall line of the Potomac River..................6-16

Table 6.14. Annual loads of organochlorines above the fall line of the James River.....................6-17

Table 6.15. Annual loads of trace metals above the fall line of the Susquehanna River................6-18

Table 6.16. Annual loads of trace metals above the fall line of the Potomac River........................6-18

Table 6.17. Annual loads of trace metals above the fall line of the James River............................6-19

Table 6.18. Instantaneous loads of organonitrogen and organophosphorus pesticides above the fall

lines or head of tide of the nine major tributaries of Chesapeake Bay from March 26

through May 5, 1994 ...................................................................................................6-19

Table 6.19. Instantaneous loads of organonitrogen and organophosphorus pesticides above the fall

lines or head of tide of the nine major tributaries of Chesapeake Bay from November

8 through November 18, 1994 .....................................................................................6-20

Table 6.20. Instantaneous loads of polycyclic aromatic hydrocarbons above the fall lines or head of

tide of the nine major tributaries of Chesapeake Bay from March 26 through May 5,

1994 .............................................................................................................................6-20

Table 6.21. Instantaneous loads of polycyclic aromatic hydrocarbons above the fall lines or head of

tide of the nine major tributaries of Chesapeake Bay from November 8 through

November 18, 1994 .....................................................................................................6-21

Table 6.22. Instantaneous loads of organochlorines above the fall lines or head of tide of the nine

major tributaries of Chesapeake Bay from March 26 through May 5, 1994................6-21

Table 6.23. Instantaneous loads of organochlorines above the fall lines or head of tide of the nine

major tributaries of Chesapeake Bay from November 8 through November 18,

1994..............................................................................................................................6-22

Table 6.24. Instantaneous loads of total trace metals above the fall lines or head of tide of the nine

major tributaries of Chesapeake Bay from March 26 through May 5, 1994................6-22

Table 6.25. Instantaneous loads of total trace metals above the fall lines or head of tide of the nine

major tributaries of Chesapeake Bay from November 8 through November 18,

1994..............................................................................................................................6-23

Figure 6.1. Map of Chesapeake Bay region showing nine watersheds monitored in 1994 synoptic

study...............................................................................................................................6-7
Table of Contents

iii-7

Chapter 7 - Pesticide Use

Table 7.1. Pesticide usage on the four major crops grown within the Chesapeake Bay Watershed

by chemical name, 1996.................................................................................................7-7

Table 7.2. Pesticide usage on corn in the Chesapeake Bay Watershed by chemical name, 1996...7-8

Table 7.3. Pesticide usage on alfalfa in the Chesapeake Bay Watershed by chemical name,

1996................................................................................................................................7-9

Table 7.4. Pesticide usage on soybeans in the Chesapeake Bay Watershed by chemical name,

1996..............................................................................................................................7-10

Table 7.5. Pesticide usage on small grains in the Chesapeake Bay Watershed by chemical name,

1996..............................................................................................................................7-11

Table 7.6. High use pesticides in surface water sampled in the Chesapeake Bay Watershed (1993-

1996).............................................................................................................................7-12

Table 7.7. High use pesticides in ground water sampled in the Chesapeake Bay Watershed (1993-

1996).............................................................................................................................7-13

Figure 7.1. Surface water pesticide detection sites ........................................................................7-14

Figure 7.2. Ground water pesticide detection sites ........................................................................7-15

Figure 7.3. Multiple acres treated with pesticides within the watershed........................................7-16

Figure 7.4. Pounds of pesticide Active Ingredients applied to agricultural lands within the

watershed......................................................................................................................7-16

Chapter 8 - Relative Importance of Point and Non-point Sources to the Bay

Table 8.1. Trace metal total watershed yields for selected tributaries of the Bay.........................8-13

Figure 8.1. Conceptual framework used in developing contaminant budgets for the tidal Chesapeake

Bay................................................................................................................................8-17

Figure 8.2. Total loads o f PCBs to the tidal Potomac River..........................................................8-18

Figure 8.3. Total estimated loads o f PCBs to the tidal Potomac River based on TPC..................8-18

Figure 8.4. Total loads of cadmium to the tidal water of Chesapeake Bay....................................8-19

Figure 8.5. Total loads of copper to the tidal water of Chesapeake Bay........................................8-19

Figure 8.6. Total loads of lead to the tidal water of Chesapeake Bay............................................8-20

Figure 8.7. Total loads of mercury to the tidal water of Chesapeake Bay.....................................8-20

Figure 8.8. Total loads of zinc to the tidal water of Chesapeake Bay............................................8-21

Figure 8.9. Total loads of arsenic to the tidal water of Chesapeake Bay........................................8-21

Figure 8.10.Total loads of benzo[a]pyrene to the tidal water of Chesapeake Bay..........................8-22

Figure 8.11.Total loads of chrysene to the tidal water of Chesapeake Bay....................................8-22

Figure 8.12.Total loads of phenanthrene to the tidal water of Chesapeake Bay..............................8-23

Figure 8.13.Total loads of pyrene to the tidal water of Chesapeake Bay.........................................8-23

Figure 8.14.Total loads of cadmium to the tidal James River.........................................................8-24

Figure 8.15.Total loads of copper to the tidal James River..............................................................8-24

Figure 8.16.Total loads of lead to the tidal James River..................................................................8-25

Figure 8.17.Total loads of benzo[a]pyrene to the tidal James River................................................8-25

Figure 8.18.Total loads of phenanthrene to the tidal James River...................................................8-26

Figure 8.19.Total loads of cadmium to the tidal Potomac River......................................................8-26
Table of Contents

iii-8

Figure 8.20.Total loads of copper to the tidal Potomac River..........................................................8-27

Figure 8.21.Total loads of lead to the tidal Potomac River..............................................................8-27

Figure 8.22.Total loads of benzo[a]pyrene to the tidal Potomac River............................................8-28

Figure 8.23.Total loads of phenanthrene to the tidal Potomac River...............................................8-28

Figure 8.24.Total loads of cadmium to the tidal Patuxent River......................................................8-29

Figure 8.25.Total loads of copper to the tidal Patuxent River..........................................................8-29

Figure 8.26.Total loads of lead to the tidal Patuxent River..............................................................8-30

Figure 8.27.Total loads of benzo[a]pyrene to the tidal Patuxent River............................................8-30

Figure 8.28.Total loads of phenanthrene to the tidal Patuxent River...............................................8-31

Figure 8.29.Total loads of cadmium to the tidal Anacostia River....................................................8-31

Figure 8.30.Total loads of copper to the tidal Anacostia River....................................................8-32

Figure 8.31.Total loads of lead to the tidal Anacostia River............................................................8-32

Figure 8.32.Total loads of zinc to the tidal Anacostia River....................................................8-33

Chapter 9 - Mass Balance of Chemical Contaminants within Chesapeake Bay

Table 9.1. Loadings of total copper to Chesapeake Bay...............................................................9-10

Table 9.2. Losses of total copper from the mainstem Chesapeake Bay........................................9-10

Table 9.3. Loadings of mercury to Chesapeake Bay.....................................................................9-11

Table 9.4. Losses of mercury from the mainstem Chesapeake Bay..............................................9-11

Table 9.5. Loadings of total PCBs to Chesapeake Bay.................................................................9-12

Table 9.6. Losses of total PCBs from the mainstem Chesapeake Bay..........................................9-12

Table 9.7. Loadings of phenanthrene to Chesapeake Bay.............................................................9-13

Table 9.8. Losses of phenanthrene from the mainstem Chesapeake Bay......................................9-13

Figure 9.1. Schematic of Chesapeake Bay Chemical Contaminant Mass Balance Model...............9-2

Figure 9.2. Flows of chemical contaminants into and from model cells..........................................9-3
iv-1

The inventory is divided into the following six sections:

< Executive Summary summarizes the purpose of this inventory, improvements since the

1994 inventory, limitations of loading and release estimates, and major findings, with an

emphasis on comparing the relative contributions of point and nonpoint sources of metals

and organic contaminants entering the Bay and its major tidal tributaries.

< Loadings are estimates of the quantity of chemical contaminants that reach the Bay

waters. These loadings can enter the Bay above the fall line or below the fall line. The

fall line is the physiographic boundary between the Piedmont and the Atlantic Coastal

Plain provinces, representing the natural geographic break between the tidal and non-tidal

regions of the Bay watershed. 

• Loads to the non-tidal portions of the Bay’s and its rivers (above the fall line) are

reported from acid mine drainage. 

• Loads to the tidal portion of the Bay and its rivers (below the fall line) are

reported from atmospheric deposition and shipping and boating. 

• Both above the fall line (non-tidal) loadings and below the fall line (tidal)

loadings are reported for point sources and urban runoff. 

< Fall Line Loadings estimates represent the aggregate of chemical contaminant loads

from upstream point and nonpoint sources that make their way to the tidal portion of the

Bay and its rivers. These estimates are based on measurements taken at the fall line.

< Releases are estimates of the quantity of chemical contaminants emitted to the Bay’s

watershed that have the potential to reach the Bay. Only pesticide usage data are

summarized in this section. While not a direct measure of loads, the pesticide usage data

can provide inference about the quantity of pesticides released onto the watershed, a

fraction of which may end up in the groundwater or surface waters of the Bay. 

< Relative Importance of Point and Non-Point Sources of Chemical Contaminants to

Chesapeake Bay and its rivers is reported in this inventory for the first time to provide

managers, scientists, and the public with information on the most important sources of

chemical contaminant loads. Loadings from sources with the most widespread and

available data were reported from point sources, urban runoff, atmospheric deposition,

and shoreline erosion (where available). Upstream contaminant loads to the tidal waters

from all sources are represented by the fall line loadings data. 

< Mass Balance of Chemical Contaminants is a new section of the inventory which

provides (1) a gross check and balance on whether or not loadings estimates are

consistent and realistic, (2) an idea of the fate of contaminants in the Bay and its

tributaries, (3) a management tool for predicting results from load reductions, and (4) a

consistent way to identify key data gaps and uncertainties that need to be addressed for

management/scientific purposes.

DESCRIPTION OF INVENTORY CHAPTERS
1-1

CHAPTER 1 - Point Source Loadings

Allison Wiedeman Cory Dippel Ning Zhou

Chesapeake Bay Program Chesapeake Bay Program Chesapeake Bay Program

Environmental Protection Agency Chesapeake Research Consortium Virginia Tech

410 Severn Avenue, Suite 109 410 Severn Avenue, Suite 109 410 Severn Avenue, Suite109 

Annapolis, MD 21403 Annapolis, MD 21403 Annapolis, MD 21403

INTRODUCTION

The purpose of this chapter is to present data on chemical contaminants discharged to

surface waters by point sources located within the Chesapeake Bay watershed. Point sources are

end-of-pipe discharges from industrial, municipal, or federal facilities. The information

presented herein is an assimilation of data obtained from EPA’s National Pollution Discharge

Elimination System (NPDES) Permit Compliance System (PCS) and other effluent reporting or

sampling programs performed by the Bay jurisdictions. Data was obtained in terms of chemical

effluent concentration and discharge flows, and analyses were performed by the Chesapeake Bay

Program Office to calculate total estimated discharged load. The loads are presented as pounds

of chemical discharged per year. Analyses were performed after consultation with the

Chesapeake Bay Program’s Toxic Subcommittee’s Directed Toxic Assessment (DTA)

Workgroup. The data sources, methodologies, and assumptions used to calculate discharged

loads as well as the total estimated loads are presented in detail in the following sections of this

chapter. 

Three appendicies accompany this chapter of the Toxics Loading and Release Inventory

document. These appendicies include Appendix A: List of chemicals and default detection

limits, Appendix B: Loads of chemical categories by Standard Industrial Classification (SIC)

codes, and Appendix C: Inventory of Point Source Loads by Facility. Appendix C is published

separately from this document and is available from the Chesapeake Bay Program Office.

TEMPORAL AND SPATIAL COVERAGE

There are approximately 4000 industrial, municipal, and federal point source dischargers

within the Chesapeake Bay watershed. Of these, 316 are classified as currently operating

“major” dischargers in the PCS database, discharging greater than 0.5 million gallons per day

(MGD). This inventory includes 276 of these major point sources discharging to the Chesapeake

Bay watershed for which data was available to evaluate loadings. Figure 1.1 shows the location

of all 316 major point source dischargers in the Chesapeake Bay basin. However, only 228

facilities had data for the specified list of chemicals analyzed in this inventory (see “Chemicals

Reported” section).

The loadings in this section include data from Pennsylvania, Maryland, Virginia, and the
Point Source Loadings

1-2

D.C. Blue Plains waste water treatment plant collected between 1992 - 1996. This range was

chosen because it spans 5 years, the same as the (NPDES) monitoring program permit cycle.

Every facility will have had their permit reissued at some point during this time frame.

The data sources for each state are summarized in Table 1.1. The complete inventory of

point source loadings by facility, including all chemicals for which loads were calculated can be

found in Appendix C.

Data from the Toxic Release Inventory (TRI) database are not included in this chapter. 

The data summarized in this report are estimated using actual measured concentrations, flows,

and loadings whereas TRI data are estimated releases. Combining these very different data

sources would introduce a large margin of error.
Point Source Loadings

1-3

Table 1.1. Toxic Point Source data sources.

DATA 

CATEGORY

DATA

SOURCES

VIRGINIA MARYLAND DISTRICT OF

COLUMBIA

(BLUE PLAINS)

PENNSYLVANIA

1.

NPDES

FORM 2C

& FORM A

Hard copy*

NPDES

Application

forms (2c &

A) 1

Collected when

available and

within the time

frame (1992-

1996)

Collected for 63 facilities

which had a current

(1992-1996) application

form in their file. 

NONE COLLECTED,

Monthly operating reports

collected instead

NONE

COLLECTED,

data is entered

into PCS

2.

NPDES

DMR

A.

NPDES

DMR Reports

from PCS 2

COLLECTED COLLECTED COLLECTED COLLECTED

B.

NPDES

DMR Reports

in hard copy 

Monthly operating reports

for Blue Plains WWTP were

collected from the District of

Columbia Dept. of Health.

3.

VA TMP

TMP (Toxics

Management

Program) 3

Data from 5

regions were

collected. 

NOT APPLICABLE NOT APPLICABLE NOT

APPLICABLE

* Where data is listed as a hardcopy source, the CBPO loaded the data into an electronic database.

1

 Application form descriptions

Form 2c is required for any facility which discharges to waters of the U.S. This form includes information such as outfall descriptions, flows,

latitude/longitude, and sources of pollutants within the facility. In addition, the form contains a list of 165 pollutants (the 126 priority pollutants

as designated by US EPA, and standard water chemistry parameters). Which of those chemicals facilities are required to report is dependent on

the type of facility. For every pollutant the facility has reason to believe is present in their discharge in concentrations of 10 ppb or greater, they

must submit quantitative data. Form A is used for municipal WWTP. This form contains much of the same information as Form 2c with only

55 chemicals listed for which the facility may describe their wastewater.

Limitations: The main limitation of this data source is that for many parameters, only one sampling event occurred to obtain the data. Data are

not originally in electronic format.

2

 Permit Compliance System (PCS) data

Discharge Monitoring Reports (DMR’s) from the NPDES program are entered for the major dischargers and sometimes minor dischargers into

this national database. This database contains data for all the states. PCS is the principal source of toxics data which was supplemented, where

appropriate, by various data sources as described in the data source table. 

Limitations: Database is lacking consistent temporal coverage, spatial data is inconsistently present, all fields in the database are text, missing

data and errors are not uncommon, units are often not reported, or are inconsistently reported (ie., some chemicals are reported in both mg/l and

ug/l), detection limits are not always present for a non-detect chemical, and data on minor facilities (discharging less than 0.5 MGD) may be

lacking or insufficient.

3

 Virginia TMP data

The VA TMP is part of the NPDES program in Virginia. TMP data is generated from quarterly or semiannual sampling efforts depending upon

the facility. The TMP is a separate program from NPDES which monitors compliance of 405 facilities in VA with biomonitoring and chemical

analyses. The TMP monitors the same chemicals as those found on Form 2c. The TMP computerized database does not hold the chemical data

which the facilities must report on their effluent. It only holds information on facility permit compliance. The chemical data remains in hard

copy and is stored in the NPDES permit files at the regional offices in Virginia. This is the data which the CBPO has obtained for this loadings

analysis.

Limitations: For some parameters only one sampling event occurred to obtain the data. Data are not originally in electronic format.
Point Source Loadings

1-4

Figure 1.1. Chesapeake Bay Basin major point source dischargers.
Point Source Loadings

1-5

CHEMICALS REPORTED

Between all the above data sources, there are over 800 chemicals reported, the majority of

which are reported through the VA TMP. To calculate loadings for 800 chemicals would have

been too immense of an undertaking in the time allowed for this report. Therefore, it was

decided to include only a subset of these chemicals in this report. The 231 chemicals chosen

include all of the potentially toxic chemical parameters in PCS, the priority pollutants, the Toxics

of Concern list chemicals, and the Chemicals of Potential Concern. Appendix C includes a

complete list of loadings for all facilities and all 231 chemicals. Appendix A lists the 231

parameters for which data were available to calculate loadings. Due to the large amount of data,

Tables 1.2 - 1.4 provide a summary for only a subset of the 231 parameters. This chemical

subset of 79 parameters includes the 1990 list of Toxics of Concern (as well as the draft revised

1996 list of the Toxics of Concern), the 1990 list of Chemicals of Potential Concern, and

individual PCB’s and PAH’s. Because some facilities did not report any of the chemical subset,

only 228 facilities were used for the loading analysis. 

This report also summarizes data in terms of the chemical categories of metals, PCBs,

pesticides, PAHs, organics, and inorganics. Metals are substances or mixtures such as lead,

copper, or mercury. PCBs (Polychlorinated biphenyls), although banned, are used as fire

retardants and can be found in electric transformers and other machinery. Pesticides are

compounds, either organic or inorganic which are used to control the growth of plants

(herbicides), insects (insecticides), or fungus (fungicides). PAHs (Polycyclic Aromatic

Hydrocarbons) are compounds such as naphthalene, or phenanthrene, which come from the

combustion of fossil fuels and from oil and grease. Organic chemicals include compounds

containing hydrocarbons and their derivatives (hydrocarbon combined with other elements,

principally nitrogen and oxygen). Organics discussed in this report include all organic chemicals

except PCBs, PAHs and pesticides. Inorganic chemicals include compounds other than organic

chemicals and metals.

MAPPING OF POINT SOURCE FACILITIES

In coordination with the calculation of loads for facilities, an effort was made to

accurately map all of the major point sources. Location information (latitude/longitude, address,

county, zip codes) from PCS was compiled for all major facilities. The information was used to

map each facility in ArcView in the following ways: If a facility had an accurate

latitude/longitude it was used first. If a correct lat/long was unattainable, the facility was mapped

using address matching. If neither an accurate lat/long or address was available, the facility was

mapped using zip code centroid matching. Figure 1.1 shows the accurate location of all major

point source dischargers in the Chesapeake Bay watershed. 
Point Source Loadings

1-6

METHODOLOGY

There are over 4000 point source dischargers in the Chesapeake Bay Watershed. The

majority of these facilities are minor facilities, and depending upon the state, data for them are

generally not reported in PCS unless they are minors deemed “significant”. Calculating loads for

all the watershed facilities was too large of an undertaking for this report. In order to maintain

consistency between all the jurisdictions, only major facilities are included in the loadings

analysis.

Monthly flows were matched with monthly concentration values and the load calculated

according to the formula below. Monthly loads for each individual year were averaged to obtain

an annual load. 

The following formula was used to estimate the annual average load of chemical

contaminants for all states:

Annual Load (lbs/yr) = Concentration x Flow x 8.344 x # of days in the year for which data was

available

where:

Load = pounds /year (lbs/yr)

Concentration = milligrams/liter (mg/L)

Flow = million gallons/day (MGD)

8.344 = a factor for converting MGD and mg/L into lbs/day

Outfalls within each facility were identified, when possible, as effluent, influent, internal,

etc. All outfalls identified as effluent were summed, by year, to obtain an annual load for the

facility. The annual loads for each year for each facility were averaged to obtain the load

estimates as reported in this chapter.

In cases where a concentration was present but the corresponding flow was not and vise

versa, a zero was assumed and put in place of the missing value. Due to this method, some of the

loading estimates may be recorded as a zero. A zero may also indicate the chemical was nondetect, or that the concentration value was not recorded in the PCS database. 

For each year at any given facility, the average concentration for any given chemical was

used in the loads calculation regardless of how many data points were present for each year. If

there were no data points for a given year, the average did not include that year. For example, if

a copper load was only obtainable for a given facility for the years of 1992, 1994, 1995, and

1996, the average would be the sum of the loads for those years, divided by the four years for

which there was data available. 
Point Source Loadings

1-7

District of Columbia

Blue Plains WWTP was the only facility in DC for which data was obtainable. There are

3 additional active major facilities in D.C. for which data was unavailable in PCS.

Data collected from PCS was supplemented by data from Monthly Operation Reports

where there were missing parameters or monthly values from PCS. Using monthly average

concentration and flow values, annual average concentrations and flows were calculated. For

some pollutants only a single data value was available to estimate the average concentration.

Maryland

Data collected from PCS was supplemented by data from permit applications where there

were missing parameters or monthly values from PCS. If DMR (PCS) data existed for a

particular chemical, these data alone were used to calculate loads. If only permit application data

existed for a particular chemical, these data along with PCS flows were used to calculate loads. 

For some pollutants at some facilities, however, only a single data value was available to

estimate the average concentration. Using monthly average concentration and monthly average

flow values, annual average concentrations and flows were calculated.

Virginia

Data collected from PCS was supplemented by data from permit applications and data

from the VA TMP program where there were missing parameters or monthly values from PCS. 

If DMR (PCS) data existed for a particular chemical, these data alone were used to calculate

loads. If only TMP data exist for a particular chemical, these data along with PCS flows were

used to calculate loads. If only permit application data exist for a particular chemical, these data

along with PCS flows were used to calculate loads. For some pollutants at some facilities,

however, only a single data value was available to estimate the average concentration. Using

monthly average concentration and monthly average flow values, annual average concentrations

and flows were calculated.

Pennsylvania

Data collected from PCS was the only data source used in the calculation of annual loads. 

Annual loads were calculated using monthly average concentration and monthly average flow

data from the PCS database. For some pollutants at some facilities, however, only a single data

value was available to estimate the average concentration. 
Point Source Loadings

1-8

UNCERTAINTY AND DATA HANDLING

Coverage

The non-electronic data for this chapter was collected over a period of 14 months

beginning in July of 1996 through September of 1997. Data collected in the beginning may not

have the same temporal coverage as the data collected towards the end of the data collection

process. For instance, data collected in July of 1996 will not have a complete year of data for

1996. PCS data was retrieved from 1992 through September of 1996.

The point source loading estimates to the Chesapeake Bay are underestimated due to the

inclusion of only major dischargers within the signatory states/Districts (Maryland, Virginia,

Pennsylvania, and the District of Columbia). The loadings of minor dischargers collectively may

be significant. It was decided to maintain consistency between all states in choosing only major

dischargers, and as time allows in future efforts, to assimilate data for minor facilities as well. 

Non-detects of various chemicals

The definition of the Detection Limit (DL) is the lowest value to which a compound can

be reliably measured as being present. A Quantitation Limit (QL) is the level at which the

quantity or concentration of a pollutant can be reliably determined. Detection Limits and

Quantitation Limits for any given chemical vary depending upon the analytical method and/or the

laboratory conducting the analysis. It is often uncertain as to whether a detection limit, or a

quantitation limit was reported. Approximately 80% of the data collected for this chapter was

non-detect. The method in which non-detect (ND) concentrations are treated can result in very

different loading estimates. Non-detect concentrations can be set equal to zero, to the detection

limit, or some value in between (such as half the detection limit), with each option resulting in a

different loading estimate.

For these loading estimates, the loadings are presented in a range, setting all ND to both

zero and the DL. In cases where a chemical was reported as ND, but was missing a DL, a default

detection limit value was used. Default values were obtained from EPA’s Environmental

Monitoring Methods Index (EMMI). The EMMI database contains an inventory of information

on environmentally significant analyses monitored by the US EPA and methods for their

analyses. The detection limit with the most appropriate method was chosen for each chemical

missing a detection limit. The list of EMMI default detection limits can be found in Appendix B,

along with the complete chemical list.

All tables in this chapter present the loading estimates by a range. The low estimate of

loadings represents the average of both non-detects (set to zero) and detected values. The high

estimate of loadings represents the average of non-detects (set to the detection limit) and detected

values. It is important to note that for certain chemicals (all PCB’s, pesticides, and most PAH’s),
Point Source Loadings

1-9

virtually all values were non-detect, therefore, the detection limits are driving the high range of

the loads.

The estimated load may vary significantly depending upon whether the non-detects used

to calculate the loadings are set to zero or the detection limit. As an example, Figure 1.2

represents the relative loadings of point source chemical categories with the non-detects of point

sources set equal to zero. With this treatment of the non-detects, metals are the predominant

chemical load with PCBs, PAHs and pesticides virtually zero. Figure 1.3 represents the relative

loadings of all chemical categories with the non-detects set equal to the detection limit. Using

this treatment of non-detects, the relative loads of PCBs and pesticides dominate all other

chemical categories.

The chapter entitled “Relative Importance of Point and Non-Point Sources of Chemical

Contaminants to the Chesapeake Bay” uses the average of the low and high loading estimates for

point sources. This chapter further discusses the uncertainty in dealing with data containing

many non-detects.

PCS Reporting

Data in PCS is entered into the database in many different ways. There are many fields

for which chemical and flow data can be entered: average load, maximum load, concentration

minimum, concentration average, and concentration maximum. Concentration average was the

preferred value, however, in cases where this was missing, concentration maximum or minimum

was assumed to represent the average. Records for which concentration maximum or minimum

were used were documented in the comments field in the database. In cases where average load

or maximum load existed, and a concentration value was lacking, the flow and the load were

used to back calculate to the concentration. The back calculated concentrations were then used

in the loading calculations as were all other concentrations. Records for which a back calculated

concentration was generated were documented in the comments field in the database.

Data was also inconsistently reported between each jurisdiction. Each state has different

methods and requisites of entering data into PCS. These differences proved challenging when

the data for all states was compiled into a database. Consistency between all states had to be

restored before the data could be used to produce loadings.

Metals Reporting in a Variety of Forms

Several metals were reported in a variety of forms (such as copper appearing as total

copper, dissolved copper and total recoverable copper). For presentation and summary purposes,

wherever multiple forms of a particular chemical were reported, they were consolidated into one

parameter to produce Table 1.2. A hierarchy was implemented when consolidating such

chemical parameter which was to use the highest value whenever more than one form per facility
Point Source Loadings

1-10

was reported.

Nitrogen Reporting

A similar situation exists regarding reporting of nitrogen and nitrogen species as for

metals discussed above. Nitrogen and nitrogen species are reported in various ways in the point

source database including ammonia plus unionized ammonia, ammonia nitrogen, nitrate

nitrogen, nitrate dissolved nitrogen, and nitrite plus nitrate. The inventory has combined these

data where appropriate in an effort to determine one representative load of a certain species. For

example, ammonia plus unionized ammonia and nitrogen ammonia total are combined to present

one load for ammonia nitrogen. In cases where a facility supplied data for both parameters, the

highest value only was used. Nitrogen nitrate dissolved and nitrogen nitrate total are combined

into nitrate nitrogen. Nitrite plus nitrate is listed as nitrite and nitrate nitrogen.

Outfalls

Outfalls are often not identified clearly in PCS. It was difficult to distinguish effluent,

influent, stormwater, and internal outfalls within the PCS database. Best efforts were made to

verify effluent outfalls with each state before including them in the loadings calculations,

however, some outfalls may have been double counted or missed.

Influent concentrations/Cooling water discharges

Influent concentration values are often present for larger facilities such as power plants,

which use stream water for cooling purposes. Due to the complexity of the data, influent data

were not used unless specifically available to calculate the “net effluent” chemical

concentrations. Loads for those facilities may be overestimated due to the fact that influent

loadings were not taken into account.

Stormwater Outfalls

There are many facilities which have stormwater related outfalls. The discharge of these

outfalls is dependent upon rainfall, hence they do not discharge 365 days/year. Every attempt

was made to accurately identify and discount these outfalls, however, some may have missed. In

these cases, the loadings may be overestimated. 

Unit inconsistencies

Units are not consistently reported in PCS. In addition, units for any given parameter

may be inconsistently and inaccurately reported in the PCS database. For instance, flow values

may have been reported in MGD, gallons per day, or thousand gallons per day, depending upon

the facility, outfall, and/or who entered the data into PCS. It was often difficult to ascertain the
Point Source Loadings

1-11

correct units in questionable cases. Questionable flows and concentrations were sent to each

state and the District of Columbia for review and correction.

Data Review

The Chesapeake Bay Program requested review of data for 25 facilities where questions

arose in the database. Responses from 22 facilities were received which allowed corrections to

be made in the inventory regarding flow quantities, unit errors or typos, and concentrations.

Off-Line Facilities

Some facilities in the inventory stopped discharging during the years of 1992-1996. Only

the years of actual discharge were used for load calculations for facilities which ceased

discharging during the period of data collection.

DISCUSSION

Table 1.2 presents the total Chesapeake Bay basin point source load estimates for a subset

of the 79 chemical parameters analyzed for the purposes of this chapter. Note that only 51

chemicals are included in Table 1.2. This is because, as explained earlier in this report, where

related chemicals were reported in a variety of parameters, they were consolidated to one

parameter for summary purposes in Table 1.2. 

The top 18 chemicals with the highest loads are presented below in descending order. 

These are the chemicals whose low load estimates are greater than 1000 lbs/yr.
Point Source Loadings

1-12

Top 18 Chemicals with the highest loads

CHEMICAL Loads* (lbs/year)

AMMONIA NITROGEN 212,027,519.36

NITRATE NITROGEN 17,150,864.30

NITRITE + NITRATE NITROGEN 5,706,187.43

IRON 1,932,958.60

ALUMINUM 662,631.32

ZINC 563,786.40

MANGANESE 531,045.18

PETROLEUM HYDROCARBONS 367,803.65

COPPER 114,224.75

NICKEL 42,435.87

CHROMIUM 20,972.61

LEAD 19,221.61

CADMIUM 9,997.50

NAPHTHALENE 8,543.91

ARSENIC 3,165.52

CHLORPYRIFOS 2,878.05

MERCURY 1,390.99

2,4-DINITROPHENOL 1,254.00

This list includes chemicals with low load estimates higher than 1000 lbs/year.

* Based on low estimates. 

Tables 1.3a-p present the point source load estimates and percent total by major basin. 

Tables 1.3 and 1.4 include all 79 chemical parameters in their unconsolidated forms. 

Table 1.4 presents point source load estimates by individual states. Note that for the 80

facilities in Pennsylvania, data are unavailable for many parameters. This is due to the sources of

data (see Table 1.1), which for Pennsylvania, is much less voluminous than for the other

jurisdictions. Thus, it’s not necessarily true that loads are less in Pennsylvania, but that less data

is available. 

Appendix B presents the loadings for chemical categories by industry type or standard

industrial code (SIC code) for 227 out the 228 facilities for which loads were calculated for the

79 chemical parameters subset. There is one facility for which the SIC code was unavailable.

Out of the 227 facilities, the majority (134) are classified as sewerage, and 20 provide electrical

services. The chemical categories summarized in Appendix B are Inorganics, Metals, Organics,

PAHs, PCBs, and Pesticides. Based on the low load estimates, the loads of pesticides are only

coming from sewerage. PCBs were only recorded for a General Medical/Surgical Hospital
Point Source Loadings

1-13

RELATIVE LOW LOADS BY CHEMICAL CATEGORIES

METALS

91%

PCBs

0%

PESTICIDES

0%

PAHs

0%

ORGANICS

9%

facility. The highest loads of PAHs are from sewerage, plastic materials/synthesized resins, and

paper mills. The highest loads of organics are from electrical services, sewerage, and

ammunition. Industrial classes of sewerage, inorganic pigments, and medical chemicals

represent the highest loads of metals, and classes of nitrogen fertilizers, sewerage and paper mills

represent the highest loads of inorganics. Based on the high load estimates, the highest loads of

pesticides, PCBs, PAHs, and organics are coming from electrical services, plastic materials, and

synthesized resins. The highest loads of metals are coming from the same industrial class for

metals' low load estimates, which are sewerage, inorganic pigments, and medical chemicals. 

The same situation applied to inorganics, its high load and low load estimates have the same

source for highest loading, which are nitrogen fertilizers, sewerage and paper mills.

Figures 1.2 and 1.3 show the relative total low and high Chesapeake Bay Basin point

source loads by chemical category. Note that the inorganic category is not included in these

figures. This is because approximately 98% of the point source load is from inorganics,

primarily nitrogen compounds. And as mentioned previously the amount of pesticides and

organics are driven by their detection limits, as seen in Figure 1.3 as compared to Figure 1.2.

Figure 1.2. Relative Low Chesapeake Bay Basin point source loads by chemical category.
Point Source Loadings

1-14

RELATIVE HIGH LOADS BY CHEMICAL CATEGORIES

METALS

13% ORGANICS

12%

PESTICIDES

31%

PCBs

37%

PAHs

7%

Figure 1.3. Relative High Chesapeake Bay Basin point source loads by chemical category. 

Figures 1.4 - 1.9 show the low and high loading estimates of each individual chemical

category by the major basins (Note that Figure 1.8, loading estimates for Inorganics, is primarily

driven by the nitrogen compounds). Data from Table 1.2, using consolidated methods and

nitrogen species parameters, were used to produce these graphs. Graphs not showing a low

estimate indicate that the majority of the values were non-detect. As shown in Figures 1.5 - 1.7,

the high loadings for PCB’s, pesticides, and PAH’s are driven primarily by the detection limit. 

The low estimates for these chemical categories are mostly zero, indicating that nearly all the

concentrations were non-detect. Graphs which show a large low estimate and a small high

estimate indicate that most of the concentrations were detected. The highest loadings of metals

are in the Potomac, and are due primarily to iron, aluminum, manganese, zinc, and copper. 

Highest loadings of Inorganics are in the James which is primarily due to nitrogen species.
1-15

METALS

0

200,000

400,000

600,000

800,000

1 , 000,000

1 , 200,000

1 , 400,000

1 , 600,000

1 , 800,000

ES J M PT PX RA SU W C YK

MAJOR BASIN

LOADING ESTIMATE 

(lbs/year)

high estimate

low estimate

PCB'S

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

8,000,000

ES J M P T PX R A SU WC YK

MAJOR BASIN

LOADING ESTIMATE 

(lbs/year)

high estimate

low estimate

PAH'S

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

ES J M P T PX R A SU WC YK

MAJOR BASIN

LOADING ESTIMATE 

(lbs/year)

high estimate

low estimate

PESTICIDES

0

1 , 000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

ES JM P T P X R A SU WC YK

MAJOR BASIN

LOADING ESTIMATE 

(lbs/year)

high estimate

low estimate

Figure 1.4. Loading estimates of metals by major basin. Figure 1.5. Loading estimates of PCB's by major basin.

Figure 1.6. Loading estimates of pesticides by major basin. Figure 1.7. Loading estimates of PAH's by major basin.
1-16

INORGANICS

0

20,000,000

40,000,000

60,000,000

80,000,000

100,000,000

120,000,000

140,000,000

160,000,000

180,000,000

200,000,000

ES J M P T P X R A SU WC YK

MAJOR BASIN

LOADING ESTIMATE (lbs/year)

high estimate

low estimate

ORGANICS

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1,600,000

ES J M P T P X R A SU WC YK

MAJOR BASIN

LOADING ESTIMATE (lbs/year)

high estimate

low estimate

Figure 1.8. Loading estimates of inorganics by major basin. Figure 1.9. Loading estimates of organics by major basin.

ES = Eastern Shore

JM = James

PT = Potomac

PX = Patuxent

RA = Rappahannock

SU = Susquehanna

WC = West Chesapeake

YK = York
Point Source Loadings

1-17

CORRELATION WITH 1994 TOXICS LOADING AND RELEASE INVENTORY

The results in this chapter cannot be directly compared to the results in the Point Source

chapter of the 1994 TLRI. The time period of data collected for the last report varied depending

upon state. Facilities included in the 1994 TLRI comprised about one third of the majors.

Additionally, the sources of data are more comprehensive in this analysis than in the previous

TLRI. For these reasons, the loadings in this new chapter may appear greater when compared to

the last report. 

This version of the Point Source chapter of the TLRI provides more comprehensive and

up-to-date loading estimates when compared to the 1994 report. This inventory includes nearly

twice as many facilities, additional and different data sources collected over a consistent time

period, and reports loadings on more chemicals. Careful consideration needs to be taken with

regards to the limitations, assumptions, and caveats of the data presented in this chapter when

comparing any of the results from this inventory with the results of the 1994 inventory. 

RECOMMENDATIONS

< Further efforts should be made to include additional D.C. facilities, especially majors. 

Insufficient data exists for the 3 remaining D.C. majors: Washington Aquaduct-Delecarlia

Plant, Pepco-Potomac Electric Company, and Potomac Electric Power Company.

< EPA’s PCS system should be improved and be made useful for the purpose of calculating

loadings for point source dischargers.

< Special training and discussion seminars should be held for all personnel from the Bay

jurisdictions who are responsible for PCS entry. A standard approach for entering data

should be firmly established.

< Incorporate a new application requirement that a pre-existing facility must report average

annual loadings for all pollutants identified in their application and also for those listed

on their previous permit. This submission should be maintained in an appropriate

database.

< Incorporate a standard permit requirement that facilities submit an annual summary of

total loads during that year using a combination of actual DMR data and estimates based

on their previous permit application data. Maintain these annual loadings in an

appropriate database.

< The following inaccuracies and inconsistencies within PCS need to be amended:

C Units for all parameters need to be consistently and accurately reported in the PCS

database.

C Duplicate parameter codes in PCS need to be eliminated. The use of CAS
Point Source Loadings

1-18

numbers as a unique chemical identifier should be implemented. 

C Records of missing data without an explanation code should either be filled in

with data, or explained with a code in the database.

C Data for metals should be properly recorded as total, total recoverable, or

dissolved in PCS.

C Numeric data should be stored in fields with numeric formatting. Any qualifying

text should be placed in a separate field from numeric data.

< A consistent criteria for including priority minor dischargers in future inventory updates

should be developed.

< States should clearly identify outfalls for facilities with intake pipes, and/or non-contact

cooling water from the same water body. The net effluent load should be determined

using the influent loads.

< To better estimate the loads of chemicals with non-detects, such as PCB’s, further

anaylses must be conducted to assess typical pollutant concentrations in point source

discharges. The recent published report entitled the “Study of the Loading of PCB’s from

Tributaries and Point Sources Discharging to the Tidal Delaware River,” put out by the

Delaware River Basin Commission, contains data that may provide better estimates of

PCB loads for those facilities with non-detects.

< The mapping effort verified the location of all major dischargers in the Chesapeake Bay

watershed. This list of facilities, along with any related location information should be

updated in the PCS database. 

< Involve dischargers in the review of the data for future loading inventories.

< A discharger outreach program should be established focusing on new uses of DMR data

as well as education on completing DMR’s properly. In addition, the importance of

correct flow values and units should be emphasized.

< A zero present in the loading estimates can have several meanings. It may indicate the

chemical was non-detect, or that flow was reported as zero for a given record, or that the

concentration was reported as zero for a given record, or that the concentration was not

recorded in the PCS database. A procedure for distinguishing between each of the above

cases should be established for future inventory and database updates.

< Any point source data not reported in PCS should be submitted to the Chesapeake Bay

Program in accordance to the data submittal requirements of the Information

Management System.

< Data for point sources within the Chesapeake Bay Watershed in non-signatory states
Point Source Loadings

1-19

(West Virginia, Delaware, and New York) should be included in future inventory

updates.

< Additional analyses of intake cooling waters should be performed to determine net

discharge loads where not done previously.

< Loads for the approximate 3700 minors should be investigated.

< Indirect discharges to the POTW’s should be investigated.

< Consider including other chemicals than the list of 79 that were included in this chapter’s

analysis.
Point Source Loadings

1-20

Table 1.2. Total Chesapeake Bay Watershed Load Estimates by Chemical.

TOTAL CHESAPEAKE BAY WATERSHED

LOAD ESTIMATE (lbs/year)

CHEMICAL LOW HIGH

2,4,6-TRICHLOROPHENOL 231.87 200,451.21

2,4-DICHLOROPHENOL 32.24 223,189.26

2,4-DIMETHYLPHENOL 221.71 209,598.20

2,4-DINITROPHENOL 1,254.00 2,375,251.21

2-METHYL-4-CHLOROPHENOL 0.00 316,221.58

2-METHYLNAPTHTHALENE 0.00 928.84

ACENAPHTHENE 1.92 74,103.75

ALDRIN 540.41 92,405.67

ALUMINUM 662,631.32 672,864.16

AMMONIA NITROGEN 212,027,519.36 212,115,969.45

ARSENIC 3,165.52 12,061.04

BENZO[A]ANTHRACENE 54.92 626,162.00

BENZO[A]PYRENE 54.73 115,160.68

BENZO[GHI]PERYLENE 3.84 167,453.58

CADMIUM 9,997.50 14,220.73

CHLORDANE 0.00 392,854.86

CHLORPYRIFOS 2,878.05 3,024.96

CHROMIUM 20,972.61 126,599.92

CHRYSENE 185.62 115,212.50

COPPER 114,224.75 122,642.80

DIBENZO(A,H)ANTHRACENE 3.84 121,761.66

DIELDRIN 0.10 178,967.89

DIOXIN 0.07 4,203.26

ENDOSULFAN - ALPHA 0.00 2,274,682.66

ENDOSULFAN - BETA 0.00 2,803,653.33

ENDRIN ALDEHYDE 0.00 2,410,241.49

FLUORANTHENE 55.88 103,693.64

FLUORENE 42.86 103,566.19

INDENO(1,2,3-CD)PYRENE 3.84 165,240.85

IRON 1,932,958.60 1,933,405.83

LEAD 19,221.61 61,741.28

MANGANESE 531,045.18 532,168.84

MERCURY 1,390.99 7,103.98

NAPHTHALENE 8,543.91 170,764.04

NICKEL 42,435.87 77,609.57

NITRATE NITROGEN 17,150,864.30 17,168,223.99

NITRITE + NITRATE NITROGEN 5,706,187.43 5,718,090.97

PCB 1221 0.00 1,173,074.17

PCB 1232 0.00 1,904,299.62

PCB 1242 0.00 1,904,268.49

PCB 1254 0.00 1,393,319.56

PCB-1016 0.00 1,904,225.58

PCB-1248 0.00 1,904,030.00
Point Source Loadings

1-21

CHEMICAL LOW HIGH

PCB-1260 0.15 1,904,119.68

PENTACHLOROBIPHENYL 0.00 97.73

PETROLEUM HYDROCARBONS 367,803.65 395,822.06

PHENANTHRENE 76.94 216,302.01

POLYCHLORINATED BIPHENYLS (PCBS) 0.00 15,481.95

PYRENE 84.51 162,085.78

TOXAPHENE 0.00 2,008,422.57

ZINC 563,786.40 568,580.05
Table 1.3a. Estern Shore Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 10

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL

2,4-DICHLOROPHENOL

2,4-DIMETHYLPHENOL

2,4-DINITROPHENOL

2-METHYL-4-CHLOROPHENOL

2-METHYLNAPTHTHALENE

ACENAPHTHENE

ALDRIN

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA 56,562.75 0.79 56,562.75

ARSENIC, DISSOLVED

ARSENIC, TOTAL

ARSENIC, TOTAL RECOVERABLE

BENZO[A]ANTHRACENE

BENZO[A]PYRENE

BENZO[GHI]PERYLENE

CADMIUM, DISSOLVED

CADMIUM, TOTAL

CADMIUM, TOTAL RECOVERABLE

CHLORDANE

CHLORPYRIFOS

CHROMIUM, DISSOLVED

CHROMIUM, HEXAVALENT

CHROMIUM, HEXAVALENT DISSOLVED

CHROMIUM, HEXAVALENT TOTAL 

CHROMIUM, TOTAL

CHROMIUM, TOTAL RECOVERABLE

CHROMIUM, TRIVALENT

(No AFL for Eastern Shore) EASTERN SHORE BFL

10

 1-22 
Table 1.3a. Estern Shore Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 10

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

(No AFL for Eastern Shore) EASTERN SHORE BFL

10

CHRYSENE

COPPER, DISSOLVED

COPPER, TOTAL 328.05 0.35 328.05

COPPER, TOTAL RECOVERABLE

DIBENZO(A,H)ANTHRACENE

DIELDRIN

DIOXIN

ENDOSULFAN - ALPHA

ENDOSULFAN - BETA

ENDRIN ALDEHYDE

FLUORANTHENE

FLUORENE

INDENO(1,2,3-CD)PYRENE

IRON, DISSOLVED

IRON, TOTAL

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED

LEAD, TOTAL

LEAD, TOTAL RECOVERABLE

MANGANESE, DISSOLVED

MANGANESE, TOTAL

MERCURY, DISSOLVED

MERCURY, TOTAL

MERCURY, TOTAL RECOVERABLE

NAPHTHALENE

NICKEL, DISSOLVED

NICKEL, TOTAL 1.52 4.67E-03 1.52

NICKEL, TOTAL RECOVERABLE

NITRITE PLUS NITRATE 259,201.34 4.54 259,201.34

NITROGEN, AMMONIA TOTAL 1,545,791.42 0.74 1,545,791.42

NITROGEN, NITRATE DISSOLVED

 1-23 
Table 1.3a. Estern Shore Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 10

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

(No AFL for Eastern Shore) EASTERN SHORE BFL

10

NITROGEN, NITRATE TOTAL 45,420.71 0.27 45,420.71

PCB 1221

PCB 1232

PCB 1242

PCB 1254

PCB-1016

PCB-1248

PCB-1260

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS 1,301.59 0.35 1,301.59

PHENANTHRENE

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE

TOXAPHENE

ZINC, DISSOLVED

ZINC, TOTAL 24.13 4.81E-03 24.13

ZINC, TOTAL RECOVERABLE

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.

 1-24 
Table 1.3b. James River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 35

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 226.39 97.64 0.00 0.00 226.39

2,4-DICHLOROPHENOL 30.05 93.20 0.00 0.00 30.05

2,4-DIMETHYLPHENOL 210.96 95.15 0.00 0.00 210.96

2,4-DINITROPHENOL 0.00 0.00 1,245.77 99.34 1,245.77

2-METHYL-4-CHLOROPHENOL 0.00 0.00 0.00 0.00 0.00

2-METHYLNAPTHTHALENE 0.00 0.00 0.00

ACENAPHTHENE 0.00 0.00 0.00 0.00 0.00

ALDRIN 0.00 0.00 0.00 0.00 0.00

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL 95,551.75 16.42 95,551.75

ALUMINUM, TOTAL RECOVERABLE 1,242.59 1.79 1,242.59

AMMONIA+UNIONIZED AMMONIA 0.00 0.00 3,321,361.22 46.32 3,321,361.22

ARSENIC, DISSOLVED 0.00 0.00 0.00 0.00 0.00

ARSENIC, TOTAL 491.19 17.31 0.00 0.00 491.19

ARSENIC, TOTAL RECOVERABLE 0.00 0.00 59.91 18.25 59.91

BENZO[A]ANTHRACENE 0.00 0.00 52.73 96.01 52.73

BENZO[A]PYRENE 0.00 0.00 44.43 81.17 44.43

BENZO[GHI]PERYLENE 0.00 0.00 0.00 0.00 0.00

CADMIUM, DISSOLVED 21.74 2.11 672.29 65.25 694.03

CADMIUM, TOTAL 125.20 1.60 602.46 7.70 727.67

CADMIUM, TOTAL RECOVERABLE 19.54 1.27 1,460.87 95.01 1,480.42

CHLORDANE 0.00 0.00 0.00 0.00 0.00

CHLORPYRIFOS 0.00 0.00 0.00

CHROMIUM, DISSOLVED 464.30 21.25 370.89 16.98 835.19

CHROMIUM, HEXAVALENT 42.10 6.12 208.95 30.36 251.05

CHROMIUM, HEXAVALENT DISSOLVED 929.31 71.56 280.36 21.59 1,209.67

CHROMIUM, HEXAVALENT TOTAL 12.83 100.00 0.00 0.00 12.83

CHROMIUM, TOTAL 732.58 4.40 2,762.79 16.59 3,495.37

CHROMIUM, TOTAL RECOVERABLE 929.75 55.98 261.68 15.75 1,191.43

CHROMIUM, TRIVALENT

CHRYSENE 0.00 0.00 42.90 23.11 42.90

COPPER, DISSOLVED 3,435.67 63.27 1,550.29 28.55 4,985.96

COPPER, TOTAL 851.76 0.92 11,201.74 12.06 12,053.50

COPPER, TOTAL RECOVERABLE 1,481.07 7.29 7,628.09 37.55 9,109.15

DIBENZO(A,H)ANTHRACENE 0.00 0.00 0.00 0.00 0.00

DIELDRIN 0.00 0.00 0.00 0.00 0.00

DIOXIN 0.00 0.00 0.00 0.00 0.00

JAMES RIVER AFL JAMES RIVER BFL

16 19

 1-25
Table 1.3b. James River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 35

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

JAMES RIVER AFL JAMES RIVER BFL

16 19

ENDOSULFAN - ALPHA 0.00 0.00 0.00 0.00 0.00

ENDOSULFAN - BETA 0.00 0.00 0.00 0.00 0.00

ENDRIN ALDEHYDE 0.00 0.00 0.00 0.00 0.00

FLUORANTHENE 12.18 21.80 41.78 74.77 53.96

FLUORENE 0.00 0.00 40.66 94.88 40.66

INDENO(1,2,3-CD)PYRENE 0.00 0.00 0.00 0.00 0.00

IRON, DISSOLVED

IRON, TOTAL 47,521.92 2.46 329.03 0.02 47,850.94

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED 557.63 52.25 221.30 20.74 778.93

LEAD, TOTAL 757.40 4.69 4,487.67 27.79 5,245.07

LEAD, TOTAL RECOVERABLE 282.31 9.89 1,873.42 65.61 2,155.73

MANGANESE, DISSOLVED

MANGANESE, TOTAL 41,440.93 8.94 236,573.89 51.03 278,014.82

MERCURY, DISSOLVED 451.63 93.48 10.58 2.19 462.21

MERCURY, TOTAL 8.98 1.31 24.40 3.57 33.39

MERCURY, TOTAL RECOVERABLE 4.68 1.99 221.84 94.56 226.51

NAPHTHALENE 0.00 0.00 39.55 0.46 39.55

NICKEL, DISSOLVED 1,127.28 9.29 6,580.59 54.24 7,707.87

NICKEL, TOTAL 5,582.46 17.12 6,218.59 19.08 11,801.04

NICKEL, TOTAL RECOVERABLE 482.61 20.92 613.80 26.61 1,096.40

NITRITE PLUS NITRATE 100,926.75 1.77 58,006.91 1.02 158,933.66

NITROGEN, AMMONIA TOTAL 30,636,158.06 14.61 163,398,337.46 77.92 194,034,495.51

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL 191,905.02 1.13 959,786.65 5.65 1,151,691.67

PCB 1221 0.00 0.00 0.00 0.00 0.00

PCB 1232 0.00 0.00 0.00 0.00 0.00

PCB 1242 0.00 0.00 0.00 0.00 0.00

PCB 1254 0.00 0.00 0.00 0.00 0.00

PCB-1016 0.00 0.00 0.00 0.00 0.00

PCB-1248 0.00 0.00 0.00 0.00 0.00

PCB-1260 0.00 0.00 0.00 0.00 0.00

PENTACHLOROBIPHENYL 0.00 0.00 0.00

PETROLEUM HYDROCARBONS 0.00 0.00 0.00

PHENANTHRENE 21.32 27.71 53.70 69.80 75.02

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 0.00 0.00 33.18 39.26 33.18

TOXAPHENE 0.00 0.00 0.00 0.00 0.00

 1-26
Table 1.3b. James River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 35

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

JAMES RIVER AFL JAMES RIVER BFL

16 19

ZINC, DISSOLVED 12,739.65 23.98 18,759.44 35.30 31,499.09

ZINC, TOTAL 9,530.44 1.90 39,231.44 7.82 48,761.88

ZINC, TOTAL RECOVERABLE 8,925.40 16.21 28,217.30 51.24 37,142.70

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.

 1-27
Table 1.3c. Potomac River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 55

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 0.00 0.00 0.00 0.00 0.00

2,4-DICHLOROPHENOL 0.00 0.00 0.00 0.00 0.00

2,4-DIMETHYLPHENOL 0.00 0.00 9.11 4.11 9.11

2,4-DINITROPHENOL 0.00 0.00 0.00 0.00 0.00

2-METHYL-4-CHLOROPHENOL 0.00 0.00 0.00 0.00 0.00

2-METHYLNAPTHTHALENE 0.00 0.00 0.00

ACENAPHTHENE 0.00 0.00 0.00 0.00 0.00

ALDRIN 0.00 0.00 0.00 0.00 0.00

ALUMINUM, ACID SOLUABLE 29,252.37 36.31 51,316.16 63.69 80,568.53

ALUMINUM, DISSOLVED 11,018.40 100.00 11,018.40

ALUMINUM, TOTAL 267,910.11 46.03 33,571.64 5.77 301,481.75

ALUMINUM, TOTAL RECOVERABLE 2,643.55 3.80 65,671.11 94.41 68,314.65

AMMONIA+UNIONIZED AMMONIA 160,110.69 2.23 967,043.68 13.49 1,127,154.38

ARSENIC, DISSOLVED 0.00 0.00 0.00 0.00 0.00

ARSENIC, TOTAL 1,842.08 64.91 2.58 0.09 1,844.67

ARSENIC, TOTAL RECOVERABLE 32.62 9.94 173.67 52.91 206.29

BENZO[A]ANTHRACENE 0.00 0.00 0.00 0.00 0.00

BENZO[A]PYRENE 0.10 0.19 0.00 0.00 0.10

BENZO[GHI]PERYLENE 0.00 0.00 0.00 0.00 0.00

CADMIUM, DISSOLVED 24.83 2.41 307.68 29.86 332.51

CADMIUM, TOTAL 14.66 0.19 250.15 3.20 264.81

CADMIUM, TOTAL RECOVERABLE 50.53 3.29 6.12 0.40 56.65

CHLORDANE 0.00 0.00 0.00 0.00 0.00

CHLORPYRIFOS 0.00 0.00 2,878.05 100.00 2,878.05

CHROMIUM, DISSOLVED 984.62 45.07 0.00 0.00 984.62

CHROMIUM, HEXAVALENT 200.15 29.08 67.66 9.83 267.82

CHROMIUM, HEXAVALENT DISSOLVED 53.47 4.12 0.00 0.00 53.47

CHROMIUM, HEXAVALENT TOTAL 0.00 0.00 0.00 0.00 0.00

CHROMIUM, TOTAL 923.26 5.54 16.62 0.10 939.88

CHROMIUM, TOTAL RECOVERABLE 358.11 21.56 64.29 3.87 422.41

CHROMIUM, TRIVALENT 0.01 100.00 0.01

CHRYSENE 0.00 0.00 0.00 0.00 0.00

COPPER, DISSOLVED 4.55 0.08 419.28 7.72 423.83

COPPER, TOTAL 8,892.93 9.58 16,317.65 17.58 25,210.58

COPPER, TOTAL RECOVERABLE 1,674.04 8.24 4,791.34 23.58 6,465.38

DIBENZO(A,H)ANTHRACENE 0.00 0.00 0.00 0.00 0.00

DIELDRIN 0.00 0.00 0.10 100.00 0.10

DIOXIN 0.07 100.00 0.00 0.00 0.07

POTOMAC RIVER AFL POTOMAC RIVER BFL

41 14

 1-28
Table 1.3c. Potomac River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 55

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

POTOMAC RIVER AFL POTOMAC RIVER BFL

41 14

ENDOSULFAN - ALPHA 0.00 0.00 0.00 0.00 0.00

ENDOSULFAN - BETA 0.00 0.00 0.00 0.00 0.00

ENDRIN ALDEHYDE 0.00 0.00 0.00 0.00 0.00

FLUORANTHENE 0.00 0.00 0.00 0.00 0.00

FLUORENE 0.00 0.00 0.00 0.00 0.00

INDENO(1,2,3-CD)PYRENE 0.00 0.00 0.00 0.00 0.00

IRON, DISSOLVED 1.06 0.01 2,096.41 10.72 2,097.47

IRON, TOTAL 352,893.66 18.26 566,402.01 29.30 919,295.67

IRON, TOTAL RECOVERABLE 6.44 100.00 6.44

LEAD, DISSOLVED 123.11 11.54 8.36 0.78 131.47

LEAD, TOTAL 233.24 1.44 3,287.47 20.35 3,520.72

LEAD, TOTAL RECOVERABLE 172.35 6.04 525.51 18.40 697.87

MANGANESE, DISSOLVED 2,335.20 2.18 104,680.80 97.82 107,016.01

MANGANESE, TOTAL 17,966.37 3.88 84,564.07 18.24 102,530.44

MERCURY, DISSOLVED 11.12 2.30 4.03 0.83 15.15

MERCURY, TOTAL 112.78 16.50 81.51 11.92 194.29

MERCURY, TOTAL RECOVERABLE 8.09 3.45 0.00 0.00 8.09

NAPHTHALENE 1.02 0.01 8,407.45 98.40 8,408.47

NICKEL, DISSOLVED 306.60 2.53 3,923.69 32.34 4,230.30

NICKEL, TOTAL 561.92 1.72 831.19 2.55 1,393.11

NICKEL, TOTAL RECOVERABLE 592.45 25.68 578.50 25.08 1,170.95

NITRITE PLUS NITRATE 1,929,118.39 33.81 1,186,612.78 20.80 3,115,731.17

NITROGEN, AMMONIA TOTAL 823,116.22 0.39 5,358,260.03 2.56 6,181,376.25

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL 563,077.21 3.31 12,988,363.83 76.44 13,551,441.04

PCB 1221 0.00 0.00 0.00 0.00 0.00

PCB 1232 0.00 0.00 0.00 0.00 0.00

PCB 1242 0.00 0.00 0.00 0.00 0.00

PCB 1254 0.00 0.00 0.00 0.00 0.00

PCB-1016 0.00 0.00 0.00 0.00 0.00

PCB-1248 0.00 0.00 0.00 0.00 0.00

PCB-1260 0.15 100.00 0.00 0.00 0.15

PENTACHLOROBIPHENYL 0.00 0.00 0.00 0.00 0.00

PETROLEUM HYDROCARBONS 6,593.79 1.79 42,749.06 11.62 49,342.84

PHENANTHRENE 0.00 0.00 0.00 0.00 0.00

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 0.00 0.00 0.00 0.00 0.00

TOXAPHENE 0.00 0.00 0.00 0.00 0.00

 1-29
Table 1.3c. Potomac River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 55

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

POTOMAC RIVER AFL POTOMAC RIVER BFL

41 14

ZINC, DISSOLVED 0.88 0.00 14,814.64 27.88 14,815.52

ZINC, TOTAL 10,962.59 2.19 66,629.49 13.29 77,592.08

ZINC, TOTAL RECOVERABLE 4,155.60 7.55 1,685.55 3.06 5,841.16

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.

 1-30
Table 1.3d. Patuxent River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 0.00 0.00 0.00

2,4-DICHLOROPHENOL 0.00 0.00 0.00

2,4-DIMETHYLPHENOL 0.00 0.00 0.00

2,4-DINITROPHENOL 0.00 0.00 0.00

2-METHYL-4-CHLOROPHENOL

2-METHYLNAPTHTHALENE

ACENAPHTHENE 0.00 0.00 0.00

ALDRIN 540.41 100.00 540.41

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL 0.00 0.00 0.00

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA 72,948.78 1.02 72,948.78

ARSENIC, DISSOLVED

ARSENIC, TOTAL 0.00 0.00 0.00

ARSENIC, TOTAL RECOVERABLE

BENZO[A]ANTHRACENE 0.00 0.00 0.00

BENZO[A]PYRENE 0.00 0.00 0.00

BENZO[GHI]PERYLENE 0.00 0.00 0.00

CADMIUM, DISSOLVED

CADMIUM, TOTAL 7.69 0.10 7.69

CADMIUM, TOTAL RECOVERABLE

CHLORDANE

CHLORPYRIFOS

CHROMIUM, DISSOLVED

CHROMIUM, HEXAVALENT

CHROMIUM, HEXAVALENT DISSOLVED

CHROMIUM, HEXAVALENT TOTAL 

CHROMIUM, TOTAL 14.97 0.09 14.97

CHROMIUM, TOTAL RECOVERABLE

CHROMIUM, TRIVALENT

CHRYSENE 0.00 0.00 0.00

COPPER, DISSOLVED

COPPER, TOTAL 325.76 0.35 325.76

COPPER, TOTAL RECOVERABLE

DIBENZO(A,H)ANTHRACENE 0.00 0.00 0.00

DIELDRIN

DIOXIN

(No AFL for Patuxent River) PATUXENT RIVER BFL

8

 1-31
Table 1.3d. Patuxent River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

(No AFL for Patuxent River) PATUXENT RIVER BFL

8

ENDOSULFAN - ALPHA

ENDOSULFAN - BETA

ENDRIN ALDEHYDE

FLUORANTHENE 0.00 0.00 0.00

FLUORENE 0.00 0.00 0.00

INDENO(1,2,3-CD)PYRENE 0.00 0.00 0.00

IRON, DISSOLVED

IRON, TOTAL

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED

LEAD, TOTAL 44.46 0.28 44.46

LEAD, TOTAL RECOVERABLE 1.91 0.07 1.91

MANGANESE, DISSOLVED

MANGANESE, TOTAL

MERCURY, DISSOLVED

MERCURY, TOTAL 0.00 0.00 0.00

MERCURY, TOTAL RECOVERABLE

NAPHTHALENE 0.00 0.00 0.00

NICKEL, DISSOLVED

NICKEL, TOTAL 138.34 0.42 138.34

NICKEL, TOTAL RECOVERABLE 36.50 1.58 36.50

NITRITE PLUS NITRATE 384,135.62 6.73 384,135.62

NITROGEN, AMMONIA TOTAL 79,271.49 0.04 79,271.49

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL 407,443.24 2.40 407,443.24

PCB 1221

PCB 1232

PCB 1242

PCB 1254

PCB-1016

PCB-1248

PCB-1260

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS 91.17 0.02 91.17

PHENANTHRENE 0.00 0.00 0.00

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 0.00 0.00 0.00

TOXAPHENE

 1-32
Table 1.3d. Patuxent River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

(No AFL for Patuxent River) PATUXENT RIVER BFL

8

ZINC, DISSOLVED

ZINC, TOTAL 930.83 0.19 930.83

ZINC, TOTAL RECOVERABLE

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.

 1-33
Table 1.3e. Rappahannock River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 0 0 0.00 0.00 0.00

2,4-DICHLOROPHENOL 0 0 0.00 0.00 0.00

2,4-DIMETHYLPHENOL 0 0 0.00 0.00 0.00

2,4-DINITROPHENOL 0 0 0.00 0.00 0.00

2-METHYL-4-CHLOROPHENOL 0 0 0.00 0.00 0.00

2-METHYLNAPTHTHALENE

ACENAPHTHENE 0 0 0.00 0.00 0.00

ALDRIN 0 0 0.00 0.00 0.00

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA

ARSENIC, DISSOLVED 23.56 100.00 23.56

ARSENIC, TOTAL 0.79 0.03 0.79

ARSENIC, TOTAL RECOVERABLE 30.15 9.19 1.48 0.45 31.64

BENZO[A]ANTHRACENE 0 0 0.00 0.00 0.00

BENZO[A]PYRENE 0 0 0.00 0.00 0.00

BENZO[GHI]PERYLENE 0 0 0.00 0.00 0.00

CADMIUM, DISSOLVED 0 0 3.79 0.37 3.79

CADMIUM, TOTAL 0.01 1.44E-04 0.01

CADMIUM, TOTAL RECOVERABLE 0.53 0.03 0.53

CHLORDANE 0.00 0.00 0.00 0.00 0.00

CHLORPYRIFOS 0.00 0.00 0.00

CHROMIUM, DISSOLVED 37.93 1.74 37.93

CHROMIUM, HEXAVALENT 0.00 0.00 55.28 8.03 55.28

CHROMIUM, HEXAVALENT DISSOLVED 35.42 2.73 35.42

CHROMIUM, HEXAVALENT TOTAL 

CHROMIUM, TOTAL 1.76 0.01 23.48 0.14 25.23

CHROMIUM, TOTAL RECOVERABLE 47.14 2.84 47.14

CHROMIUM, TRIVALENT

CHRYSENE 0.00 0.00 140.80 75.85 140.80

COPPER, DISSOLVED 20.33 0.37 20.33

COPPER, TOTAL 2.13 0.00 2.13

COPPER, TOTAL RECOVERABLE 104.37 0.51 301.24 1.48 405.61

DIBENZO(A,H)ANTHRACENE 0 0 0.00 0.00 0.00

DIELDRIN 0 0 0.00 0.00 0.00

DIOXIN 0 0 0.00

RAPPAHANNOCK AFL RAPPAHANNOCK BFL

5 3

 1-34
Table 1.3e. Rappahannock River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

RAPPAHANNOCK AFL RAPPAHANNOCK BFL

5 3

ENDOSULFAN - ALPHA 0 0 0.00 0.00 0.00

ENDOSULFAN - BETA 0 0 0.00 0.00 0.00

ENDRIN ALDEHYDE 0 0 0.00 0.00 0.00

FLUORANTHENE 0 0 0.00 0.00 0.00

FLUORENE 0 0 0.00 0.00 0.00

INDENO(1,2,3-CD)PYRENE 0 0 0.00 0.00 0.00

IRON, DISSOLVED

IRON, TOTAL 203.44 0.01 203.44

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED 2.28 0.21 33.30 3.12 35.58

LEAD, TOTAL 0 0 0.00

LEAD, TOTAL RECOVERABLE 0 0 0.00

MANGANESE, DISSOLVED

MANGANESE, TOTAL

MERCURY, DISSOLVED 0 0 2.75 0.57 2.75

MERCURY, TOTAL 0 0 0.00

MERCURY, TOTAL RECOVERABLE 0 0 0.00

NAPHTHALENE 0 0 0.00 0.00 0.00

NICKEL, DISSOLVED 9.59 0.08 123.07 1.01 132.66

NICKEL, TOTAL 0.68 0.00 0.68

NICKEL, TOTAL RECOVERABLE 2.92 0.13 2.92

NITRITE PLUS NITRATE

NITROGEN, AMMONIA TOTAL 2,867.79 1.37E-03 69,642.74 0.03 72,510.53

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL

PCB 1221 0 0 0.00 0.00 0.00

PCB 1232 0 0 0.00 0.00 0.00

PCB 1242 0 0 0.00 0.00 0.00

PCB 1254 0 0 0.00 0.00 0.00

PCB-1016 0 0 0.00 0.00 0.00

PCB-1248 0 0 0.00 0.00 0.00

PCB-1260 0 0 0.00 0.00 0.00

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS

PHENANTHRENE 0 0 0.00 0.00 0.00

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 0 0 48.26 57.10 48.26

TOXAPHENE 0 0 0.00 0.00 0.00

 1-35
Table 1.3e. Rappahannock River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

RAPPAHANNOCK AFL RAPPAHANNOCK BFL

5 3

ZINC, DISSOLVED 0 0 0.00

ZINC, TOTAL 175.62 0.04 2,809.07 0.56 2,984.69

ZINC, TOTAL RECOVERABLE 336.42 0.61 336.42

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.

 1-36
Table 1.3f. Susquehanna River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 75

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 0 0 0.00

2,4-DICHLOROPHENOL 0 0 0.00

2,4-DIMETHYLPHENOL

2,4-DINITROPHENOL 0 0 0.00

2-METHYL-4-CHLOROPHENOL

2-METHYLNAPTHTHALENE

ACENAPHTHENE

ALDRIN

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL 100,179.21 17.21 100,179.21

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA 1,571.51 0.02 1,571.51

ARSENIC, DISSOLVED

ARSENIC, TOTAL 353.85 12.47 353.85

ARSENIC, TOTAL RECOVERABLE

BENZO[A]ANTHRACENE

BENZO[A]PYRENE

BENZO[GHI]PERYLENE

CADMIUM, DISSOLVED

CADMIUM, TOTAL 6,749.88 86.26 6,749.88

CADMIUM, TOTAL RECOVERABLE

CHLORDANE

CHLORPYRIFOS

CHROMIUM, DISSOLVED

CHROMIUM, HEXAVALENT 78.29 11.37 78.29

CHROMIUM, HEXAVALENT DISSOLVED

CHROMIUM, HEXAVALENT TOTAL 

CHROMIUM, TOTAL 518.61 3.11 518.61

CHROMIUM, TOTAL RECOVERABLE

CHROMIUM, TRIVALENT

CHRYSENE

COPPER, DISSOLVED

COPPER, TOTAL 7,882.89 8.49 7,882.89

COPPER, TOTAL RECOVERABLE

DIBENZO(A,H)ANTHRACENE

DIELDRIN

DIOXIN

SUSQUEHANNA, AFL SUSQUEHANNA, BFL

74 1

 1-37
Table 1.3f. Susquehanna River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 75

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

SUSQUEHANNA, AFL SUSQUEHANNA, BFL

74 1

ENDOSULFAN - ALPHA

ENDOSULFAN - BETA

ENDRIN ALDEHYDE

FLUORANTHENE

FLUORENE

INDENO(1,2,3-CD)PYRENE

IRON, DISSOLVED 6,162.06 31.52 6,162.06

IRON, TOTAL 112,798.79 5.84 112,798.79

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED

LEAD, TOTAL 4,028.38 24.94 4,028.38

LEAD, TOTAL RECOVERABLE

MANGANESE, DISSOLVED

MANGANESE, TOTAL 11,296.97 2.44 11,296.97

MERCURY, DISSOLVED

MERCURY, TOTAL 4.62 0.68 4.62

MERCURY, TOTAL RECOVERABLE

NAPHTHALENE

NICKEL, DISSOLVED

NICKEL, TOTAL 3,518.07 10.79 3,518.07

NICKEL, TOTAL RECOVERABLE

NITRITE PLUS NITRATE 8,661.66 0.15 8,661.66

NITROGEN, AMMONIA TOTAL 2,589,657.53 1.23 2,073.14 0.00 2,591,730.68

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL

PCB 1221

PCB 1232

PCB 1242

PCB 1254

PCB-1016

PCB-1248 0.00 0.00 0.00

PCB-1260

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS

PHENANTHRENE

POLYCHLORINATED BIPHENYLS (PCBS) 0.00 0.00 0.00

PYRENE 0.06 0.07 0.06

TOXAPHENE

 1-38
Table 1.3f. Susquehanna River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 75

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

SUSQUEHANNA, AFL SUSQUEHANNA, BFL

74 1

ZINC, DISSOLVED

ZINC, TOTAL 358,509.13 71.50 38.17 0.01 358,547.30

ZINC, TOTAL RECOVERABLE

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.

 1-39
Table 1.3g. West Chesapeake Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 33

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 5.48 2.36 5.48

2,4-DICHLOROPHENOL 2.19 6.80 2.19

2,4-DIMETHYLPHENOL 1.64 0.74 1.64

2,4-DINITROPHENOL 8.22 0.66 8.22

2-METHYL-4-CHLOROPHENOL

2-METHYLNAPTHTHALENE

ACENAPHTHENE 1.92 100.00 1.92

ALDRIN 0.00 0.00 0.00

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL 72,488.35 12.45 12,354.62 2.12 84,842.97

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA 3,954.81 0.06 2,499,363.73 34.86 2,503,318.54

ARSENIC, DISSOLVED

ARSENIC, TOTAL 147.59 5.20 147.59

ARSENIC, TOTAL RECOVERABLE

BENZO[A]ANTHRACENE 2.19 3.99 2.19

BENZO[A]PYRENE 10.20 18.64 10.20

BENZO[GHI]PERYLENE 3.84 100.00 3.84

CADMIUM, DISSOLVED

CADMIUM, TOTAL 75.40 0.96 75.40

CADMIUM, TOTAL RECOVERABLE

CHLORDANE 0.00 0.00 0.00

CHLORPYRIFOS

CHROMIUM, DISSOLVED 256.65 11.75 256.65

CHROMIUM, HEXAVALENT 35.91 5.22 35.91

CHROMIUM, HEXAVALENT DISSOLVED 0.00 0.00 0.00

CHROMIUM, HEXAVALENT TOTAL 

CHROMIUM, TOTAL 11,309.40 67.92 11,309.40

CHROMIUM, TOTAL RECOVERABLE

CHROMIUM, TRIVALENT

CHRYSENE 1.92 1.03 1.92

COPPER, DISSOLVED

COPPER, TOTAL 1,162.86 1.25 45,879.90 49.42 47,042.75

COPPER, TOTAL RECOVERABLE

DIBENZO(A,H)ANTHRACENE 3.84 100.00 3.84

DIELDRIN 0.00 0.00 0.00

DIOXIN 0.00 0.00 0.00

WEST CHESAPEAKE BASIN, AFL WEST CHESAPEAKE BASIN, BFL

6 27

 1-40
Table 1.3g. West Chesapeake Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 33

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

WEST CHESAPEAKE BASIN, AFL WEST CHESAPEAKE BASIN, BFL

6 27

ENDOSULFAN - ALPHA

ENDOSULFAN - BETA

ENDRIN ALDEHYDE 0.00 0.00 0.00

FLUORANTHENE 1.92 3.43 1.92

FLUORENE 2.19 5.12 2.19

INDENO(1,2,3-CD)PYRENE 3.84 100.00 3.84

IRON, DISSOLVED 11,291.29 57.75 11,291.29

IRON, TOTAL 852,803.30 44.12 852,803.30

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED 121.27 11.36 121.27

LEAD, TOTAL 3,312.50 20.51 3,312.50

LEAD, TOTAL RECOVERABLE

MANGANESE, DISSOLVED

MANGANESE, TOTAL 71,753.28 15.48 71,753.28

MERCURY, DISSOLVED

MERCURY, TOTAL 10.91 1.60 440.43 64.42 451.35

MERCURY, TOTAL RECOVERABLE

NAPHTHALENE 95.89 1.12 95.89

NICKEL, DISSOLVED

NICKEL, TOTAL 15,747.82 48.31 15,747.82

NICKEL, TOTAL RECOVERABLE 0.00

NITRITE PLUS NITRATE 420,535.36 7.37 1,025,930.14 17.98 1,446,465.50

NITROGEN, AMMONIA TOTAL 682,494.60 0.33 3,315,468.87 1.58 3,997,963.47

NITROGEN, NITRATE DISSOLVED 204,161.00 100.00 204,161.00

NITROGEN, NITRATE TOTAL 1,513,471.15 8.91 1,513,471.15

PCB 1221

PCB 1232 0.00 0.00 0.00

PCB 1242 0.00 0.00 0.00

PCB 1254 0.00 0.00 0.00

PCB-1016 0.00 0.00 0.00

PCB-1248 0.00 0.00 0.00

PCB-1260 0.00 0.00 0.00

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS 312,287.04 84.91 4,781.00 1.30 317,068.04

PHENANTHRENE 1.92 2.49 1.92

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 3.02 3.57 3.02

TOXAPHENE 0.00 0.00 0.00

 1-41
Table 1.3g. West Chesapeake Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 33

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

WEST CHESAPEAKE BASIN, AFL WEST CHESAPEAKE BASIN, BFL

6 27

ZINC, DISSOLVED 5,407.98 10.18 5,407.98

ZINC, TOTAL 8,254.97 1.65 8,254.97

ZINC, TOTAL RECOVERABLE 10,755.53 19.53 10,755.53

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.

 1-42
Table 1.3h. York River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 4

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 0 0 0.00 0.00 0.00

2,4-DICHLOROPHENOL 0 0 0.00 0.00 0.00

2,4-DIMETHYLPHENOL 0 0 0.00 0.00 0.00

2,4-DINITROPHENOL 0 0 0.00 0.00 0.00

2-METHYL-4-CHLOROPHENOL 0 0 0.00 0.00 0.00

2-METHYLNAPTHTHALENE

ACENAPHTHENE 0 0 0.00 0.00 0.00

ALDRIN 0 0 0.00 0.00 0.00

ALUMINUM, ACID SOLUABLE 0 0 0.00

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL 0 0 0.00

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA 0 0 87,093.40 1.21 87,093.40

ARSENIC, DISSOLVED 0.00 0.00 0.00

ARSENIC, TOTAL 0 0 0.00

ARSENIC, TOTAL RECOVERABLE 0 0 30.39 9.26 30.39

BENZO[A]ANTHRACENE 0 0 0.00 0.00 0.00

BENZO[A]PYRENE 0 0 0.00 0.00 0.00

BENZO[GHI]PERYLENE 0 0 0.00 0.00 0.00

CADMIUM, DISSOLVED 0 0 0.00 0.00 0.00

CADMIUM, TOTAL 0 0 0.00

CADMIUM, TOTAL RECOVERABLE 0.00 0.00 0.00

CHLORDANE 0 0 0.00 0.00 0.00

CHLORPYRIFOS

CHROMIUM, DISSOLVED 70.09 3.21 70.09

CHROMIUM, HEXAVALENT 0.00 0.00 0.00

CHROMIUM, HEXAVALENT DISSOLVED 0.00 0.00 0.00

CHROMIUM, HEXAVALENT TOTAL 0.00 0.00 0.00

CHROMIUM, TOTAL 0 0 348.07 2.09 348.07

CHROMIUM, TOTAL RECOVERABLE 0.00 0.00 0.00

CHROMIUM, TRIVALENT

CHRYSENE 0 0 0.00 0.00 0.00

COPPER, DISSOLVED 0.00 0.00 0.00

COPPER, TOTAL 0 0 0.00

COPPER, TOTAL RECOVERABLE 0 0 4,336.07 21.34 4,336.07

DIBENZO(A,H)ANTHRACENE 0 0 0.00 0.00 0.00

DIELDRIN 0 0 0.00 0.00 0.00

DIOXIN 0.00 0.00 0.00

YORK RIVER, AFL YORK RIVER, BFL

1 3

 1-43
Table 1.3h. York River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 4

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

YORK RIVER, AFL YORK RIVER, BFL

1 3

ENDOSULFAN - ALPHA 0 0 0.00 0.00 0.00

ENDOSULFAN - BETA 0 0 0.00 0.00 0.00

ENDRIN ALDEHYDE 0 0 0.00 0.00 0.00

FLUORANTHENE 0 0 0.00 0.00 0.00

FLUORENE 0 0 0.00 0.00 0.00

INDENO(1,2,3-CD)PYRENE 0 0 0.00 0.00 0.00

IRON, DISSOLVED

IRON, TOTAL 0 0 0.00

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED 0 0 0.00 0.00 0.00

LEAD, TOTAL 0 0 0.00

LEAD, TOTAL RECOVERABLE 0.00 0.00 0.00

MANGANESE, DISSOLVED

MANGANESE, TOTAL 0 0 0.00

MERCURY, DISSOLVED 0 0 3.04 0.63 3.04

MERCURY, TOTAL 0 0 0.00

MERCURY, TOTAL RECOVERABLE 0.00 0.00 0.00

NAPHTHALENE 0 0 0.00 0.00 0.00

NICKEL, DISSOLVED 0 0 60.78 0.50 60.78

NICKEL, TOTAL 0 0 0.00

NICKEL, TOTAL RECOVERABLE 0.00 0.00 0.00

NITRITE PLUS NITRATE 1.28 2.24E-05 333,057.20 5.84 333,058.48

NITROGEN, AMMONIA TOTAL 712.98 3.40E-04 1,201,235.86 0.57 1,201,948.85

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL 321,776.82 1.89 321,776.82

PCB 1221 0 0 0.00 0.00 0.00

PCB 1232 0 0 0.00 0.00 0.00

PCB 1242 0 0 0.00 0.00 0.00

PCB 1254 0 0 0.00 0.00 0.00

PCB-1016 0 0 0.00 0.00 0.00

PCB-1248 0 0 0.00 0.00 0.00

PCB-1260 0 0 0.00 0.00 0.00

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS 0.00 0.00 0.00

PHENANTHRENE 0 0 0.00 0.00 0.00

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 0 0 0.00 0.00 0.00

TOXAPHENE 0 0 0.00 0.00 0.00

 1-44
Table 1.3h. York River Basin low load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 4

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

YORK RIVER, AFL YORK RIVER, BFL

1 3

ZINC, DISSOLVED 1,413.38 2.66 1,413.38

ZINC, TOTAL 0 0 4,286.07 0.85 4,286.07

ZINC, TOTAL RECOVERABLE 992.85 1.80 992.85

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.

 1-45
 1-46

Table 1.3i. Estern Shore Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 10

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL

2,4-DICHLOROPHENOL

2,4-DIMETHYLPHENOL

2,4-DINITROPHENOL

2-METHYL-4-CHLOROPHENOL

2-METHYLNAPTHTHALENE

ACENAPHTHENE

ALDRIN

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA 56,562.75 0.78 56,562.75

ARSENIC, DISSOLVED

ARSENIC, TOTAL

ARSENIC, TOTAL RECOVERABLE

BENZO[A]ANTHRACENE

BENZO[A]PYRENE

BENZO[GHI]PERYLENE

CADMIUM, DISSOLVED

CADMIUM, TOTAL

CADMIUM, TOTAL RECOVERABLE

CHLORDANE

CHLORPYRIFOS

CHROMIUM, DISSOLVED

CHROMIUM, HEXAVALENT

CHROMIUM, HEXAVALENT DISSOLVED

CHROMIUM, HEXAVALENT TOTAL 

CHROMIUM, TOTAL

CHROMIUM, TOTAL RECOVERABLE

CHROMIUM, TRIVALENT

CHRYSENE

COPPER, DISSOLVED

COPPER, TOTAL 328.05 0.32 328.05

COPPER, TOTAL RECOVERABLE

DIBENZO(A,H)ANTHRACENE

DIELDRIN

DIOXIN

(No AFL for Eastern Shore) EASTERN SHORE BFL

10
 1-47

Table 1.3i. Estern Shore Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 10

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

(No AFL for Eastern Shore) EASTERN SHORE BFL

10

ENDOSULFAN - ALPHA

ENDOSULFAN - BETA

ENDRIN ALDEHYDE

FLUORANTHENE

FLUORENE

INDENO(1,2,3-CD)PYRENE

IRON, DISSOLVED

IRON, TOTAL

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED

LEAD, TOTAL

LEAD, TOTAL RECOVERABLE

MANGANESE, DISSOLVED

MANGANESE, TOTAL

MERCURY, DISSOLVED

MERCURY, TOTAL

MERCURY, TOTAL RECOVERABLE

NAPHTHALENE

NICKEL, DISSOLVED

NICKEL, TOTAL 1.52 0.00 1.52

NICKEL, TOTAL RECOVERABLE

NITRITE PLUS NITRATE 259,201.34 4.53 259,201.34

NITROGEN, AMMONIA TOTAL 1,546,483.57 0.74 1,546,483.57

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL 45,420.71 0.27 45,420.71

PCB 1221

PCB 1232

PCB 1242

PCB 1254

PCB-1016

PCB-1248

PCB-1260

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS 1,301.59 0.33 1,301.59

PHENANTHRENE

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE

TOXAPHENE
 1-48

Table 1.3i. Estern Shore Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 10

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

(No AFL for Eastern Shore) EASTERN SHORE BFL

10

ZINC, DISSOLVED

ZINC, TOTAL 24.13 0.00 24.13

ZINC, TOTAL RECOVERABLE

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.
 1-49

Table 1.3j. James River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 35

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 5,459.82 2.72 61,140.14 30.50 66,599.96

2,4-DICHLOROPHENOL 9,675.91 4.34 122,549.04 54.91 132,224.95

2,4-DIMETHYLPHENOL 9,216.09 4.40 115,293.49 55.01 124,509.58

2,4-DINITROPHENOL 73,020.89 3.07 907,946.98 38.23 980,967.88

2-METHYL-4-CHLOROPHENOL 13,088.35 4.14 158,166.32 50.02 171,254.67

2-METHYLNAPTHTHALENE 889.65 95.78 889.65

ACENAPHTHENE 5,728.69 7.73 15,088.37 20.36 20,817.06

ALDRIN 3,271.05 3.54 56,410.33 61.05 59,681.39

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL 102,891.54 17.38 102,891.54

ALUMINUM, TOTAL RECOVERABLE 1,242.59 1.79 1,242.59

AMMONIA+UNIONIZED AMMONIA 0.00 0.00 3,322,800.08 45.70 3,322,800.08

ARSENIC, DISSOLVED 112.82 6.89 1,064.32 64.96 1,177.15

ARSENIC, TOTAL 737.97 8.97 1,363.25 16.57 2,101.22

ARSENIC, TOTAL RECOVERABLE 300.55 7.11 1,972.77 46.66 2,273.32

BENZO[A]ANTHRACENE 26,346.53 4.21 348,078.47 55.59 374,425.00

BENZO[A]PYRENE 5,115.24 4.44 56,944.81 49.45 62,060.05

BENZO[GHI]PERYLENE 7,592.71 4.53 90,864.90 54.26 98,457.61

CADMIUM, DISSOLVED 116.16 5.87 953.02 48.13 1,069.19

CADMIUM, TOTAL 174.21 1.50 747.29 6.44 921.50

CADMIUM, TOTAL RECOVERABLE 31.30 1.66 1,708.66 90.65 1,739.96

CHLORDANE 23,796.36 6.06 225,378.53 57.37 249,174.90

CHLORPYRIFOS 61.02 2.02 61.02

CHROMIUM, DISSOLVED 493.41 8.49 370.89 6.38 864.31

CHROMIUM, HEXAVALENT 881.95 1.20 3,878.99 5.30 4,760.94

CHROMIUM, HEXAVALENT DISSOLVED 2,149.40 9.24 7,280.26 31.29 9,429.66

CHROMIUM, HEXAVALENT TOTAL 57.98 49.61 0.00 0.00 57.98

CHROMIUM, TOTAL 6,694.35 6.68 4,459.44 4.45 11,153.79

CHROMIUM, TOTAL RECOVERABLE 969.91 23.67 2,183.62 53.30 3,153.53

CHROMIUM, TRIVALENT

CHRYSENE 5,513.19 4.79 56,306.50 48.87 61,819.69

COPPER, DISSOLVED 3,458.02 56.96 1,779.90 29.32 5,237.92

COPPER, TOTAL 4,800.78 4.73 11,316.55 11.15 16,117.33

COPPER, TOTAL RECOVERABLE 1,851.94 7.85 7,993.29 33.89 9,845.23

DIBENZO(A,H)ANTHRACENE 5,592.45 4.59 56,027.28 46.01 61,619.72

DIELDRIN 7,068.18 3.95 108,306.97 60.52 115,375.16

DIOXIN 296.72 7.06 2,214.47 52.68 2,511.19

JAMES RIVER AFL JAMES RIVER BFL

16 19
 1-50

Table 1.3j. James River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 35

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

JAMES RIVER AFL JAMES RIVER BFL

16 19

ENDOSULFAN - ALPHA 94,018.16 4.13 1,298,633.38 57.09 1,392,651.54

ENDOSULFAN - BETA 122,266.96 4.36 1,685,083.13 60.10 1,807,350.10

ENDRIN ALDEHYDE 99,022.49 4.11 1,376,986.55 57.13 1,476,009.04

FLUORANTHENE 4,526.13 4.36 50,102.79 48.32 54,628.92

FLUORENE 4,514.67 4.36 50,053.80 48.33 54,568.47

INDENO(1,2,3-CD)PYRENE 6,985.61 4.23 80,968.15 49.00 87,953.77

IRON, DISSOLVED

IRON, TOTAL 47,521.92 2.46 329.03 0.02 47,850.94

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED 745.27 10.58 4,108.75 58.31 4,854.02

LEAD, TOTAL 20,431.72 38.09 4,686.95 8.74 25,118.67

LEAD, TOTAL RECOVERABLE 337.30 7.50 2,877.18 63.94 3,214.47

MANGANESE, DISSOLVED

MANGANESE, TOTAL 42,564.59 9.16 236,573.89 50.91 279,138.48

MERCURY, DISSOLVED 477.52 64.54 176.88 23.91 654.40

MERCURY, TOTAL 40.32 0.71 226.33 4.01 266.65

MERCURY, TOTAL RECOVERABLE 14.39 1.51 912.47 95.57 926.85

NAPHTHALENE 6,936.67 4.06 83,218.79 48.73 90,155.45

NICKEL, DISSOLVED 1,516.39 8.43 7,212.42 40.10 8,728.81

NICKEL, TOTAL 9,848.20 15.53 7,743.61 12.21 17,591.82

NICKEL, TOTAL RECOVERABLE 918.25 14.58 3,252.93 51.65 4,171.18

NITRITE PLUS NITRATE 105,464.63 1.84 58,006.91 1.01 163,471.55

NITROGEN, AMMONIA TOTAL 30,638,002.63 14.61 163,398,337.46 77.91 194,036,340.09

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL 209,264.71 1.23 959,786.65 5.64 1,169,051.36

PCB 1221 50,848.68 4.33 692,621.32 59.04 743,469.99

PCB 1232 81,203.67 4.26 1,107,722.39 58.17 1,188,926.06

PCB 1242 81,203.67 4.26 1,107,690.87 58.17 1,188,894.54

PCB 1254 59,955.18 4.30 817,885.91 58.70 877,841.09

PCB-1016 80,931.45 4.25 1,107,816.92 58.18 1,188,748.37

PCB-1248 80,913.31 4.25 1,107,731.84 58.18 1,188,645.15

PCB-1260 80,913.31 4.25 1,107,731.84 58.18 1,188,645.15

PENTACHLOROBIPHENYL 6.88 7.04 6.88

PETROLEUM HYDROCARBONS 0.00 0.00 0.00

PHENANTHRENE 9,412.59 4.35 118,735.44 54.89 128,148.04

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 6,996.62 4.32 83,262.89 51.37 90,259.51

TOXAPHENE 79,140.87 3.94 1,212,742.17 60.38 1,291,883.04
 1-51

Table 1.3j. James River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 35

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

JAMES RIVER AFL JAMES RIVER BFL

16 19

ZINC, DISSOLVED 12,740.95 23.86 18,759.44 35.13 31,500.39

ZINC, TOTAL 9,621.94 1.90 39,235.10 7.76 48,857.04

ZINC, TOTAL RECOVERABLE 8,925.40 15.88 28,335.26 50.41 37,260.66

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.
 1-52

Table 1.3k. Potomac River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 55

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 2,024.80 1.01 12,830.38 6.40 14,855.18

2,4-DICHLOROPHENOL 1,799.24 0.81 25,268.25 11.32 27,067.49

2,4-DIMETHYLPHENOL 1,797.77 0.86 23,560.03 11.24 25,357.81

2,4-DINITROPHENOL 7,655.64 0.32 187,374.07 7.89 195,029.71

2-METHYL-4-CHLOROPHENOL 1,975.48 0.62 33,095.12 10.47 35,070.60

2-METHYLNAPTHTHALENE 39.20 4.22 39.20

ACENAPHTHENE 1,767.38 2.39 14,044.29 18.95 15,811.67

ALDRIN 413.91 0.45 8,407.49 9.10 8,821.40

ALUMINUM, ACID SOLUABLE 29,252.37 36.31 51,316.16 63.69 80,568.53

ALUMINUM, DISSOLVED 11,213.68 100.00 11,213.68

ALUMINUM, TOTAL 268,226.98 45.30 35,378.26 5.98 303,605.24

ALUMINUM, TOTAL RECOVERABLE 2,643.55 3.80 65,671.11 94.41 68,314.65

AMMONIA+UNIONIZED AMMONIA 187,954.69 2.58 967,043.68 13.30 1,154,998.37

ARSENIC, DISSOLVED 15.17 0.93 139.76 8.53 154.93

ARSENIC, TOTAL 2,004.29 24.36 107.59 1.31 2,111.88

ARSENIC, TOTAL RECOVERABLE 848.74 20.07 883.82 20.90 1,732.57

BENZO[A]ANTHRACENE 1,866.10 0.30 72,565.75 11.59 74,431.85

BENZO[A]PYRENE 1,605.40 1.39 12,007.03 10.43 13,612.43

BENZO[GHI]PERYLENE 1,972.67 1.18 18,508.59 11.05 20,481.26

CADMIUM, DISSOLVED 112.53 5.68 686.47 34.67 799.00

CADMIUM, TOTAL 149.27 1.29 837.09 7.21 986.36

CADMIUM, TOTAL RECOVERABLE 94.07 4.99 41.11 2.18 135.18

CHLORDANE 606.31 0.15 42,844.04 10.91 43,450.36

CHLORPYRIFOS 84.06 2.78 2,878.05 95.14 2,962.11

CHROMIUM, DISSOLVED 1,188.61 20.45 279.52 4.81 1,468.13

CHROMIUM, HEXAVALENT 1,137.85 1.55 228.82 0.31 1,366.66

CHROMIUM, HEXAVALENT DISSOLVED 492.11 2.12 13.86 0.06 505.96

CHROMIUM, HEXAVALENT TOTAL 58.89 50.39 0.00 0.00 58.89

CHROMIUM, TOTAL 2,617.82 2.61 3,417.25 3.41 6,035.07

CHROMIUM, TOTAL RECOVERABLE 829.66 20.25 66.48 1.62 896.14

CHROMIUM, TRIVALENT 31.68 100.00 31.68

CHRYSENE 1,772.23 1.54 12,007.03 10.42 13,779.26

COPPER, DISSOLVED 19.71 0.32 419.28 6.91 438.99

COPPER, TOTAL 9,446.50 9.31 17,069.04 16.82 26,515.54

COPPER, TOTAL RECOVERABLE 2,082.82 8.83 6,313.21 26.77 8,396.03

DIBENZO(A,H)ANTHRACENE 1,959.91 1.61 11,711.53 9.62 13,671.45

DIELDRIN 373.97 0.21 19,147.66 10.70 19,521.64

DIOXIN 197.20 4.69 456.44 10.86 653.64

POTOMAC RIVER AFL POTOMAC RIVER BFL

41 14
 1-53

Table 1.3k. Potomac River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 55

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

POTOMAC RIVER AFL POTOMAC RIVER BFL

41 14

ENDOSULFAN - ALPHA 362.29 0.02 264,015.07 11.61 264,377.36

ENDOSULFAN - BETA 364.39 0.01 191,936.98 6.85 192,301.36

ENDRIN ALDEHYDE 497.96 0.02 282,966.16 11.74 283,464.12

FLUORANTHENE 1,810.90 1.75 10,657.90 10.28 12,468.80

FLUORENE 1,786.69 1.73 10,621.02 10.26 12,407.71

INDENO(1,2,3-CD)PYRENE 1,927.89 1.17 16,795.06 10.16 18,722.96

IRON, DISSOLVED 1.09 0.01 2,096.41 10.37 2,097.50

IRON, TOTAL 352,893.66 18.25 566,507.88 29.30 919,401.54

IRON, TOTAL RECOVERABLE 6.44 100.00 6.44

LEAD, DISSOLVED 209.91 2.98 1,058.13 15.02 1,268.05

LEAD, TOTAL 1,406.74 2.62 4,444.31 8.29 5,851.04

LEAD, TOTAL RECOVERABLE 561.15 12.47 669.91 14.89 1,231.05

MANGANESE, DISSOLVED 2,335.20 2.18 104,680.80 97.82 107,016.01

MANGANESE, TOTAL 17,966.37 3.87 84,564.07 18.20 102,530.44

MERCURY, DISSOLVED 18.75 2.53 49.99 6.76 68.74

MERCURY, TOTAL 135.20 2.39 2,823.87 49.97 2,959.07

MERCURY, TOTAL RECOVERABLE 25.09 2.63 0.92 0.10 26.01

NAPHTHALENE 1,732.42 1.01 25,539.01 14.96 27,271.43

NICKEL, DISSOLVED 763.98 4.25 6,903.32 38.38 7,667.30

NICKEL, TOTAL 1,218.05 1.92 1,475.67 2.33 2,693.72

NICKEL, TOTAL RECOVERABLE 1,039.30 16.50 578.50 9.18 1,617.79

NITRITE PLUS NITRATE 1,929,118.39 33.74 1,186,612.78 20.75 3,115,731.17

NITROGEN, AMMONIA TOTAL 828,185.88 0.39 5,358,970.00 2.56 6,187,155.88

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL 563,077.21 3.31 12,988,363.83 76.36 13,551,441.04

PCB 1221 429.87 0.04 128,523.48 10.96 128,953.35

PCB 1232 444.00 0.02 214,105.16 11.24 214,549.17

PCB 1242 444.39 0.02 214,105.16 11.24 214,549.55

PCB 1254 494.44 0.04 154,197.99 11.07 154,692.43

PCB-1016 431.51 0.02 214,223.36 11.25 214,654.88

PCB-1248 447.78 0.02 214,116.98 11.25 214,564.76

PCB-1260 500.25 0.03 214,116.98 11.24 214,617.24

PENTACHLOROBIPHENYL 22.28 22.80 68.57 70.16 90.85

PETROLEUM HYDROCARBONS 6,621.81 1.67 70,682.00 17.86 77,303.82

PHENANTHRENE 1,813.39 0.84 24,744.35 11.44 26,557.74

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 1,870.22 1.15 17,467.55 10.78 19,337.78

TOXAPHENE 828.80 0.04 214,378.71 10.67 215,207.50
 1-54

Table 1.3k. Potomac River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 55

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

POTOMAC RIVER AFL POTOMAC RIVER BFL

41 14

ZINC, DISSOLVED 84.19 0.16 14,814.64 27.74 14,898.83

ZINC, TOTAL 11,821.56 2.34 66,653.96 13.18 78,475.52

ZINC, TOTAL RECOVERABLE 4,670.71 8.31 1,685.55 3.00 6,356.26

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.
 1-55

Table 1.3l. Patuxent River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 50.10 0.02 50.10

2,4-DICHLOROPHENOL 50.10 0.02 50.10

2,4-DIMETHYLPHENOL 50.10 0.02 50.10

2,4-DINITROPHENOL 250.50 0.01 250.50

2-METHYL-4-CHLOROPHENOL

2-METHYLNAPTHTHALENE

ACENAPHTHENE 50.10 0.07 50.10

ALDRIN 4,801.14 5.20 4,801.14

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL 337.20 0.06 337.20

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA 72,948.78 1.00 72,948.78

ARSENIC, DISSOLVED

ARSENIC, TOTAL 16.86 0.20 16.86

ARSENIC, TOTAL RECOVERABLE

BENZO[A]ANTHRACENE 50.10 0.01 50.10

BENZO[A]PYRENE 50.10 0.04 50.10

BENZO[GHI]PERYLENE 50.10 0.03 50.10

CADMIUM, DISSOLVED

CADMIUM, TOTAL 82.64 0.71 82.64

CADMIUM, TOTAL RECOVERABLE

CHLORDANE

CHLORPYRIFOS

CHROMIUM, DISSOLVED

CHROMIUM, HEXAVALENT

CHROMIUM, HEXAVALENT DISSOLVED

CHROMIUM, HEXAVALENT TOTAL 

CHROMIUM, TOTAL 119.64 0.12 119.64

CHROMIUM, TOTAL RECOVERABLE

CHROMIUM, TRIVALENT

CHRYSENE 50.10 0.04 50.10

COPPER, DISSOLVED

COPPER, TOTAL 384.54 0.38 384.54

COPPER, TOTAL RECOVERABLE

DIBENZO(A,H)ANTHRACENE 50.10 0.04 50.10

DIELDRIN

DIOXIN

(No AFL for Patuxent River) PATUXENT RIVER BFL

8
 1-56

Table 1.3l. Patuxent River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

(No AFL for Patuxent River) PATUXENT RIVER BFL

8

ENDOSULFAN - ALPHA

ENDOSULFAN - BETA

ENDRIN ALDEHYDE

FLUORANTHENE 50.10 0.05 50.10

FLUORENE 50.10 0.05 50.10

INDENO(1,2,3-CD)PYRENE 50.10 0.03 50.10

IRON, DISSOLVED

IRON, TOTAL

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED

LEAD, TOTAL 312.53 0.58 312.53

LEAD, TOTAL RECOVERABLE 8.40 0.19 8.40

MANGANESE, DISSOLVED

MANGANESE, TOTAL

MERCURY, DISSOLVED

MERCURY, TOTAL 3.37 0.06 3.37

MERCURY, TOTAL RECOVERABLE

NAPHTHALENE 50.10 0.03 50.10

NICKEL, DISSOLVED

NICKEL, TOTAL 155.20 0.24 155.20

NICKEL, TOTAL RECOVERABLE 141.56 2.25 141.56

NITRITE PLUS NITRATE 388,004.62 6.79 388,004.62

NITROGEN, AMMONIA TOTAL 81,023.57 0.04 81,023.57

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL 407,443.24 2.40 407,443.24

PCB 1221

PCB 1232

PCB 1242

PCB 1254

PCB-1016

PCB-1248

PCB-1260

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS 148.61 0.04 148.61

PHENANTHRENE 50.10 0.02 50.10

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 50.10 0.03 50.10

TOXAPHENE
 1-57

Table 1.3l. Patuxent River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

(No AFL for Patuxent River) PATUXENT RIVER BFL

8

ZINC, DISSOLVED

ZINC, TOTAL 1,021.35 0.20 1,021.35

ZINC, TOTAL RECOVERABLE

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.
 1-58

Table 1.3m. Rappahannock River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 55.85 2.79E-02 143.56 0.07 199.41

2,4-DICHLOROPHENOL 16.98 7.61E-03 145.33 0.07 162.31

2,4-DIMETHYLPHENOL 16.98 8.10E-03 145.33 0.07 162.31

2,4-DINITROPHENOL 213.87 9.00E-03 1,078.57 0.05 1,292.44

2-METHYL-4-CHLOROPHENOL 15.03 4.75E-03 166.56 0.05 181.59

2-METHYLNAPTHTHALENE

ACENAPHTHENE 12.97 1.75E-02 131.17 0.18 144.13

ALDRIN 5.04 5.45E-03 4.94 5.35E-03 9.98

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA

ARSENIC, DISSOLVED 23.56 1.44 23.56

ARSENIC, TOTAL 0.79 0.01 0.79

ARSENIC, TOTAL RECOVERABLE 91.84 2.17 100.14 2.37 191.99

BENZO[A]ANTHRACENE 68.62 0.01 235.64 0.04 304.26

BENZO[A]PYRENE 55.35 0.05 132.80 0.12 188.15

BENZO[GHI]PERYLENE 23.99 0.01 170.12 0.10 194.11

CADMIUM, DISSOLVED 16.21 0.82 7.83 0.40 24.04

CADMIUM, TOTAL 0.01 0.00 0.01

CADMIUM, TOTAL RECOVERABLE 9.65 0.51 9.65

CHLORDANE 4.82 1.23E-03 67.23 0.02 72.05

CHLORPYRIFOS 1.83 0.06 1.83

CHROMIUM, DISSOLVED 37.93 0.65 37.93

CHROMIUM, HEXAVALENT 71.49 0.10 167.18 0.23 238.67

CHROMIUM, HEXAVALENT DISSOLVED 127.83 0.55 127.83

CHROMIUM, HEXAVALENT TOTAL 

CHROMIUM, TOTAL 13.32 1.33E-02 106.96 0.11 120.28

CHROMIUM, TOTAL RECOVERABLE 47.14 1.15 47.14

CHROMIUM, TRIVALENT

CHRYSENE 55.35 0.05 269.79 0.23 325.14

COPPER, DISSOLVED 111.60 1.84 111.60

COPPER, TOTAL 2.13 2.10E-03 2.13

COPPER, TOTAL RECOVERABLE 150.01 0.64 301.24 1.28 451.25

DIBENZO(A,H)ANTHRACENE 100.99 0.08 141.79 0.12 242.78

DIELDRIN 6.77 3.78E-03 4.94 0.00 11.72

DIOXIN 0.02 4.34E-04 0.02

RAPPAHANNOCK AFL RAPPAHANNOCK BFL

5 3
 1-59

Table 1.3m. Rappahannock River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

RAPPAHANNOCK AFL RAPPAHANNOCK BFL

5 3

ENDOSULFAN - ALPHA 0.96 4.24E-05 4.94 2.17E-04 5.91

ENDOSULFAN - BETA 0.96 3.44E-05 6.72 2.40E-04 7.69

ENDRIN ALDEHYDE 0.05 2.14E-06 11.17 4.63E-04 11.22

FLUORANTHENE 54.60 0.05 136.48 0.13 191.07

FLUORENE 53.85 0.05 131.17 0.13 185.01

INDENO(1,2,3-CD)PYRENE 103.99 0.06 163.04 0.10 267.03

IRON, DISSOLVED

IRON, TOTAL 508.61 0.03 508.61

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED 26.57 0.3770291 61.54 0.87 88.11

LEAD, TOTAL 0.11 2.10E-04 0.11

LEAD, TOTAL RECOVERABLE 46.22 1.027132104 46.22

MANGANESE, DISSOLVED

MANGANESE, TOTAL

MERCURY, DISSOLVED 1.46 1.98E-01 6.56 0.89 8.02

MERCURY, TOTAL 0.02 3.99E-04 0.02

MERCURY, TOTAL RECOVERABLE 1.94 0.20 1.94

NAPHTHALENE 53.09 0.03 125.85 0.07 178.95

NICKEL, DISSOLVED 192.14 1.07 206.29 1.15 398.43

NICKEL, TOTAL 0.68 1.07E-03 0.68

NICKEL, TOTAL RECOVERABLE 368.03 5.84 368.03

NITRITE PLUS NITRATE

NITROGEN, AMMONIA TOTAL 4,027.99 1.92E-03 69,642.74 0.03 73,670.73

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL

PCB 1221 80.35 6.85E-03 201.69 0.02 282.03

PCB 1232 9.73 5.11E-04 201.69 0.01 211.42

PCB 1242 9.73 5.11E-04 201.69 0.01 211.42

PCB 1254 95.35 6.84E-03 201.69 0.01 297.03

PCB-1016 7.67 4.03E-04 201.69 0.01 209.36

PCB-1248 5.42 2.85E-04 201.69 0.01 207.11

PCB-1260 5.42 2.85E-04 201.69 0.01 207.11

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS

PHENANTHRENE 30.50 0.01 205.94 0.10 236.44

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 53.85 0.03 166.62 0.10 220.47

TOXAPHENE 45.69 0.00 446.71 0.02 492.40
 1-60

Table 1.3m. Rappahannock River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 8

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

RAPPAHANNOCK AFL RAPPAHANNOCK BFL

5 3

ZINC, DISSOLVED 182.55 0.34 182.55

ZINC, TOTAL 213.13 0.04 2,809.07 0.56 3,022.21

ZINC, TOTAL RECOVERABLE 336.42 0.60 336.42

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.
 1-61

Table 1.3n. Susquehanna River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 75

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 77447.19 38.64 77,447.19

2,4-DICHLOROPHENOL 160.86 0.07 160.86

2,4-DIMETHYLPHENOL

2,4-DINITROPHENOL 739990.84 31.15 739,990.84

2-METHYL-4-CHLOROPHENOL

2-METHYLNAPTHTHALENE

ACENAPHTHENE

ALDRIN

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL 100410.98 16.96 100,410.98

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA 1,571.51 0.02 1,571.51

ARSENIC, DISSOLVED

ARSENIC, TOTAL 353.97 4.30 353.97

ARSENIC, TOTAL RECOVERABLE

BENZO[A]ANTHRACENE

BENZO[A]PYRENE

BENZO[GHI]PERYLENE

CADMIUM, DISSOLVED

CADMIUM, TOTAL 7029.60 60.57 7,029.60

CADMIUM, TOTAL RECOVERABLE

CHLORDANE

CHLORPYRIFOS

CHROMIUM, DISSOLVED

CHROMIUM, HEXAVALENT 66214.27 90.44 66,214.27

CHROMIUM, HEXAVALENT DISSOLVED

CHROMIUM, HEXAVALENT TOTAL 

CHROMIUM, TOTAL 66941.32 66.76 66,941.32

CHROMIUM, TOTAL RECOVERABLE

CHROMIUM, TRIVALENT

CHRYSENE

COPPER, DISSOLVED

COPPER, TOTAL 8781.64 8.65 8,781.64

COPPER, TOTAL RECOVERABLE

DIBENZO(A,H)ANTHRACENE

DIELDRIN

DIOXIN

SUSQUEHANNA, AFL SUSQUEHANNA, BFL

74 1
 1-62

Table 1.3n. Susquehanna River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 75

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

SUSQUEHANNA, AFL SUSQUEHANNA, BFL

74 1

ENDOSULFAN - ALPHA

ENDOSULFAN - BETA

ENDRIN ALDEHYDE

FLUORANTHENE

FLUORENE

INDENO(1,2,3-CD)PYRENE

IRON, DISSOLVED 6162.06 30.49 6,162.06

IRON, TOTAL 112818.61 5.84 112,818.61

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED

LEAD, TOTAL 5286.23 9.86 5,286.23

LEAD, TOTAL RECOVERABLE

MANGANESE, DISSOLVED

MANGANESE, TOTAL 11296.97 2.43 11,296.97

MERCURY, DISSOLVED

MERCURY, TOTAL 1596.96 28.26 1,596.96

MERCURY, TOTAL RECOVERABLE

NAPHTHALENE

NICKEL, DISSOLVED

NICKEL, TOTAL 13705.14 21.61 13,705.14

NICKEL, TOTAL RECOVERABLE

NITRITE PLUS NITRATE 8,661.66 0.15 8,661.66

NITROGEN, AMMONIA TOTAL 2590676.24 1.24 2,129.18 1.02E-03 2,592,805.42

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL

PCB 1221

PCB 1232

PCB 1242

PCB 1254

PCB-1016

PCB-1248 0.00 0.00 0.00

PCB-1260

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS

PHENANTHRENE

POLYCHLORINATED BIPHENYLS (PCBS) 15481.95 100.00 15,481.95

PYRENE 28.64 0.02 28.64

TOXAPHENE
 1-63

Table 1.3n. Susquehanna River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 75

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

SUSQUEHANNA, AFL SUSQUEHANNA, BFL

74 1

ZINC, DISSOLVED

ZINC, TOTAL 358591.98 70.89 38.48 0.01 358,630.45

ZINC, TOTAL RECOVERABLE

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.
 1-64

Table 1.3o. West Chesapeake Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 33

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 7,152.06 3.57 7,152.06

2,4-DICHLOROPHENOL 7,176.18 3.22 7,176.18

2,4-DIMETHYLPHENOL 7,175.63 3.42 7,175.63

2,4-DINITROPHENOL 35,821.74 1.51 35,821.74

2-METHYL-4-CHLOROPHENOL

2-METHYLNAPTHTHALENE

ACENAPHTHENE 6,963.33 9.40 6,963.33

ALDRIN 2.67 0.00 2.67

ALUMINUM, ACID SOLUABLE

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL 72,488.35 12.24 12,359.90 2.09 84,848.26

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA 3,954.81 0.05 2,571,539.80 35.36 2,575,494.61

ARSENIC, DISSOLVED

ARSENIC, TOTAL 3,643.86 44.28 3,643.86

ARSENIC, TOTAL RECOVERABLE

BENZO[A]ANTHRACENE 6,965.76 1.11 6,965.76

BENZO[A]PYRENE 6,975.20 6.06 6,975.20

BENZO[GHI]PERYLENE 7,005.25 4.18 7,005.25

CADMIUM, DISSOLVED

CADMIUM, TOTAL 2,584.95 22.27 2,584.95

CADMIUM, TOTAL RECOVERABLE

CHLORDANE 26.68 0.01 26.68

CHLORPYRIFOS

CHROMIUM, DISSOLVED 3,297.89 56.73 3,297.89

CHROMIUM, HEXAVALENT 76.07 0.10 76.07

CHROMIUM, HEXAVALENT DISSOLVED 12,334.52 53.02 12,334.52

CHROMIUM, HEXAVALENT TOTAL 

CHROMIUM, TOTAL 15,560.80 15.52 15,560.80

CHROMIUM, TOTAL RECOVERABLE

CHROMIUM, TRIVALENT

CHRYSENE 6,963.55 6.04 6,963.55

COPPER, DISSOLVED

COPPER, TOTAL 1,162.86 1.15 48,176.44 47.48 49,339.30

COPPER, TOTAL RECOVERABLE

DIBENZO(A,H)ANTHRACENE 7,004.67 5.75 7,004.67

DIELDRIN 3.92 0.00 3.92

DIOXIN 0.00 0.00 0.00

WEST CHESAPEAKE BASIN, AFL WEST CHESAPEAKE BASIN, BFL

6 27
 1-65

Table 1.3o. West Chesapeake Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 33

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

WEST CHESAPEAKE BASIN, AFL WEST CHESAPEAKE BASIN, BFL

6 27

ENDOSULFAN - ALPHA

ENDOSULFAN - BETA

ENDRIN ALDEHYDE 3.92 0.00 3.92

FLUORANTHENE 7,148.31 6.89 7,148.31

FLUORENE 7,148.47 6.90 7,148.47

INDENO(1,2,3-CD)PYRENE 7,189.97 4.35 7,189.97

IRON, DISSOLVED 11,949.75 59.13 11,949.75

IRON, TOTAL 852,819.69 44.11 852,819.69

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED 573.27 8.14 573.27

LEAD, TOTAL 17,068.54 31.82 17,068.54

LEAD, TOTAL RECOVERABLE

MANGANESE, DISSOLVED

MANGANESE, TOTAL 71,753.28 15.44 71,753.28

MERCURY, DISSOLVED

MERCURY, TOTAL 25.01 0.44 799.69 14.15 824.70

MERCURY, TOTAL RECOVERABLE

NAPHTHALENE 7,883.26 4.62 7,883.26

NICKEL, DISSOLVED

NICKEL, TOTAL 29,269.32 46.15 29,269.32

NICKEL, TOTAL RECOVERABLE 0.00

NITRITE PLUS NITRATE 423,996.66 7.42 1,025,965.49 17.94 1,449,962.15

NITROGEN, AMMONIA TOTAL 683,015.17 0.33 3,326,156.42 1.59 4,009,171.59

NITROGEN, NITRATE DISSOLVED 204,161.00 100.00 204,161.00

NITROGEN, NITRATE TOTAL 1,513,471.15 8.90 1,513,471.15

PCB 1221

PCB 1232 13.91 0.00 13.91

PCB 1242 13.91 0.00 13.91

PCB 1254 26.39 0.00 26.39

PCB-1016 13.91 0.00 13.91

PCB-1248 13.91 0.00 13.91

PCB-1260 26.39 0.00 26.39

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS 312,287.04 78.90 4,781.00 1.21 317,068.04

PHENANTHRENE 6,964.61 3.22 6,964.61

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 6,964.43 4.30 6,964.43

TOXAPHENE 166.90 0.01 166.90
 1-66

Table 1.3o. West Chesapeake Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 33

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

WEST CHESAPEAKE BASIN, AFL WEST CHESAPEAKE BASIN, BFL

6 27

ZINC, DISSOLVED 5,407.98 10.13 5,407.98

ZINC, TOTAL 11,539.91 2.28 11,539.91

ZINC, TOTAL RECOVERABLE 11,268.86 20.05 11,268.86

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.
 1-67

Table 1.3p. York River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 4

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

2,4,6-TRICHLOROPHENOL 0 0 34,147.32 17.04 34,147.32

2,4-DICHLOROPHENOL 0 0 56,347.38 25.25 56,347.38

2,4-DIMETHYLPHENOL 0 0 52,342.78 24.97 52,342.78

2,4-DINITROPHENOL 0 0 421,898.10 17.76 421,898.10

2-METHYL-4-CHLOROPHENOL 0 0 109,714.72 34.70 109,714.72

2-METHYLNAPTHTHALENE

ACENAPHTHENE 0 0 30,317.45 40.91 30,317.45

ALDRIN 0 0 19,089.08 20.66 19,089.08

ALUMINUM, ACID SOLUABLE 0 0 0.00

ALUMINUM, DISSOLVED

ALUMINUM, TOTAL 0 0 0.00

ALUMINUM, TOTAL RECOVERABLE

AMMONIA+UNIONIZED AMMONIA 0 0 87,093.40 1.20 87,093.40

ARSENIC, DISSOLVED 282.91 17.27 282.91

ARSENIC, TOTAL 0 0 0.00

ARSENIC, TOTAL RECOVERABLE 0 0 30.39 0.72 30.39

BENZO[A]ANTHRACENE 0 0 169,985.03 27.15 169,985.03

BENZO[A]PYRENE 0 0 32,274.75 28.03 32,274.75

BENZO[GHI]PERYLENE 0 0 41,265.25 24.64 41,265.25

CADMIUM, DISSOLVED 0 0 87.80 4.43 87.80

CADMIUM, TOTAL 0 0 0.00

CADMIUM, TOTAL RECOVERABLE 0.00 0.00 0.00

CHLORDANE 0 0 100,130.87 25.49 100,130.87

CHLORPYRIFOS

CHROMIUM, DISSOLVED 145.42 2.50 145.42

CHROMIUM, HEXAVALENT 557.34 0.76 557.34

CHROMIUM, HEXAVALENT DISSOLVED 867.14 3.73 867.14

CHROMIUM, HEXAVALENT TOTAL 0.00 0.00 0.00

CHROMIUM, TOTAL 0 0 348.07 0.35 348.07

CHROMIUM, TOTAL RECOVERABLE 0.00 0.00 0.00

CHROMIUM, TRIVALENT

CHRYSENE 0 0 32,274.75 28.01 32,274.75

COPPER, DISSOLVED 282.91 4.66 282.91

COPPER, TOTAL 0 0 0.00

COPPER, TOTAL RECOVERABLE 0 0 4,893.41 20.75 4,893.41

DIBENZO(A,H)ANTHRACENE 0 0 39,172.94 32.17 39,172.94

DIELDRIN 0 0 44,055.47 24.62 44,055.47

DIOXIN 1,038.41 24.70 1,038.41

YORK RIVER, AFL YORK RIVER, BFL

1 3
 1-68

Table 1.3p. York River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 4

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

YORK RIVER, AFL YORK RIVER, BFL

1 3

ENDOSULFAN - ALPHA 0 0 617,647.86 27.15 617,647.86

ENDOSULFAN - BETA 0 0 803,994.18 28.68 803,994.18

ENDRIN ALDEHYDE 0 0 650,753.19 27.00 650,753.19

FLUORANTHENE 0 0 29,206.43 28.17 29,206.43

FLUORENE 0 0 29,206.43 28.20 29,206.43

INDENO(1,2,3-CD)PYRENE 0 0 51,057.03 30.90 51,057.03

IRON, DISSOLVED

IRON, TOTAL 0 0 0.00

IRON, TOTAL RECOVERABLE

LEAD, DISSOLVED 0 0 263.41 3.74 263.41

LEAD, TOTAL 0 0 0.00

LEAD, TOTAL RECOVERABLE 0.00 0.00 0.00

MANGANESE, DISSOLVED

MANGANESE, TOTAL 0 0 0.00

MERCURY, DISSOLVED 0 0 8.70 1.18 8.70

MERCURY, TOTAL 0 0 0.00

MERCURY, TOTAL RECOVERABLE 0.00 0.00 0.00

NAPHTHALENE 0 0 45,224.85 26.48 45,224.85

NICKEL, DISSOLVED 0 0 1,192.41 6.63 1,192.41

NICKEL, TOTAL 0 0 0.00

NICKEL, TOTAL RECOVERABLE 0.00 0.00 0.00

NITRITE PLUS NITRATE 1.28 2.23E-05 333,057.20 5.82 333,058.48

NITROGEN, AMMONIA TOTAL 1,019.97 4.86E-04 1,201,235.86 0.57 1,202,255.84

NITROGEN, NITRATE DISSOLVED

NITROGEN, NITRATE TOTAL 321,776.82 1.89 321,776.82

PCB 1221 0 0 300,368.79 25.61 300,368.79

PCB 1232 0 0 500,599.07 26.29 500,599.07

PCB 1242 0 0 500,599.07 26.29 500,599.07

PCB 1254 0 0 360,462.62 25.87 360,462.62

PCB-1016 0 0 500,599.07 26.29 500,599.07

PCB-1248 0 0 500,599.07 26.29 500,599.07

PCB-1260 0 0 500,623.79 26.29 500,623.79

PENTACHLOROBIPHENYL

PETROLEUM HYDROCARBONS 0.00 0.00 0.00

PHENANTHRENE 0 0 54,345.08 25.12 54,345.08

POLYCHLORINATED BIPHENYLS (PCBS)

PYRENE 0 0 45,224.85 27.90 45,224.85

TOXAPHENE 0 0 500,672.73 24.93 500,672.73
 1-69

Table 1.3p. York River Basin high load estimates and percentage of total Chesapeake Bay Watershed load estimates

# of facilities in estimate 4

CHEMICAL SUBSTANCE

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

BASIN LOAD 

(lbs/year)

% OF TOTAL 

CHESAPEAKE 

BAY WATERSHED 

LOAD

TOTAL AFL+BFL 

BASIN LOAD 

(lbs/year)

YORK RIVER, AFL YORK RIVER, BFL

1 3

ZINC, DISSOLVED 1,413.38 2.65 1,413.38

ZINC, TOTAL 0 0 4,286.07 0.85 4,286.07

ZINC, TOTAL RECOVERABLE 992.85 1.77 992.85

Note: Empty spaces mean no data available for facilities in a given basin. Zeros present in the loading estimates can have several meanings. A zero 

may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.
 1-70

LOW HIGH LOW HIGH LOW HIGH LOW HIGH

2,4,6-TRICHLOROPHENOL 5.48 7,246.98 226.39 115,757.05 0.00 77,447.19

2,4-DICHLOROPHENOL 2.19 7,271.10 30.05 215,757.30 0.00 160.86

2,4-DIMETHYLPHENOL 1.64 7,270.55 220.06 202,327.65

2,4-DINITROPHENOL 8.22 36,398.36 1,245.77 1,598,862.00 0.00 739,990.84

CHLOROPHENOL 0.00 316,221.58

2-METHYLNAPTHTHALENE 0.00 928.84

ACENAPHTHENE 1.92 7,054.47 0.00 67,049.28

ALDRIN 540.41 4,813.28 0.00 87,592.39

SOLUABLE 29,252.37 29,252.37 51,316.16 51,316.16

ALUMINUM, DISSOLVED 11,018.40 11,213.68

ALUMINUM, TOTAL 172,672.04 173,331.41 309,204.42 318,350.84 100,179.21 100,410.98

ALUMINUM, TOTAL 

RECOVERABLE 2,643.55 2,643.55 66,913.70 66,913.70

AMMONIA+UNIONIZED 

AMMONIA 2,794,446.98 2,866,691.54 4,375,563.59 4,404,777.95

ARSENIC, DISSOLVED 23.56 1,638.54

ARSENIC, TOTAL 147.59 3,664.80 2,336.64 4,209.81 353.85 353.97

ARSENIC, TOTAL 

RECOVERABLE 0.00 18.88 328.23 4,209.37

BENZO[A]ANTHRACENE 2.19 7,084.83 52.73 619,077.17

BENZO[A]PYRENE 10.30 7,088.26 44.43 108,072.42

BENZO[GHI]PERYLENE 3.84 7,144.56 0.00 160,309.02

CADMIUM, DISSOLVED 1,030.33 1,980.03

CADMIUM, TOTAL 243.14 243.14 83.26 2,734.28 746.82 1,595.48 6,752.23 7,032.16

CADMIUM, TOTAL 

RECOVERABLE 3.78 3.78 1,533.81 1,881.02

CHLORDANE 0.00 140.76 0.00 392,714.09

CHLORPYRIFOS 2,878.05 3,024.96

CHROMIUM, DISSOLVED 256.65 3,486.72 1,927.83 2,326.97

CHROMIUM, HEXAVALENT 0.00 0.00 51.43 162.75 558.15 6,834.83 78.77 66,216.38

CHROMIUM, HEXAVALENT 

DISSOLVED 0.00 12,334.52 1,298.56 10,930.58

CHROMIUM, HEXAVALENT 

TOTAL RECOVERABLE 12.83 116.87

CHROMIUM, TOTAL 12,223.69 16,586.19 3,905.44 16,743.54 522.40 66,949.24

CHROMIUM, TOTAL 

RECOVERABLE 188.82 188.82 1,472.15 3,907.98

CHROMIUM, TRIVALENT 0.01 31.68

CHRYSENE 1.92 7,057.53 183.70 108,154.97

COPPER, DISSOLVED 5,430.12 6,071.43

COPPER, TOTAL 12,434.57 12,434.57 52,021.64 55,220.04 13,026.26 17,549.63 15,363.19 16,264.29

PA

AVERAGE LOAD ESTIMATES (LBS/YEAR)

Table 1.4. Point Source Load estimates by state.

Chemical Substance

DC MD VA
 1-71

LOW HIGH LOW HIGH LOW HIGH LOW HIGH

PA

AVERAGE LOAD ESTIMATES (LBS/YEAR)

Chemical Substance

DC MD VA

COPPER, TOTAL 

RECOVERABLE 496.87 496.87 19,819.35 23,089.05

E 3.84 7,136.40 0.00 114,625.25

DIELDRIN 0.00 9.61 0.10 178,958.29

DIOXIN 0.07 0.07 0.00 4,203.20

ENDOSULFAN - ALPHA 0.00 0.03 0.00 2,274,682.63

ENDOSULFAN - BETA 0.00 0.03 0.00 2,803,653.30

ENDRIN ALDEHYDE 0.00 117.47 0.00 2,410,124.01

FLUORANTHENE 1.92 7,240.86 53.96 96,452.77

FLUORENE 2.19 7,239.61 40.66 96,326.08 0.00 0.50

INDENO(1,2,3-CD)PYRENE 3.84 7,308.51 0.00 157,932.34

IRON, DISSOLVED 11,291.29 11,949.75 2,097.47 2,097.50 6,162.06 6,162.06

IRON, TOTAL 284,687.16 284,687.16 1,044,428.50 1,044,445.11 491,037.70 491,448.50 112,798.79 112,818.61

RECOVERABLE 6.44 6.44

LEAD, DISSOLVED 121.27 573.27 945.98 6,473.58

LEAD, TOTAL 3,283.47 3,283.47 3,358.48 17,546.72 5,309.11 27,346.92 4,200.06 5,460.01

RECOVERABLE 83.65 234.53 2,771.85 4,265.61

MANGANESE, DISSOLVED 107,016.01 107,016.01

MANGANESE, TOTAL 77,605.50 77,605.50 374,693.04 375,816.70 11,296.97 11,296.97

MERCURY, DISSOLVED 483.16 739.85

MERCURY, TOTAL 0.16 1,971.01 474.76 857.25 204.10 1,225.57 4.62 1,596.96

MERCURY, TOTAL 

RECOVERABLE 0.00 3.78 234.61 951.03

NAPHTHALENE 95.89 7,972.97 8,448.01 162,790.86 0.01 0.21

NICKEL, DISSOLVED 12,131.60 17,986.95

NICKEL, TOTAL 17,003.17 30,697.18 12,075.28 19,009.53 3,522.14 13,710.69

NICKEL, TOTAL 

RECOVERABLE 206.79 311.85 2,099.98 5,986.71

NITRITE PLUS NITRATE 5,194,752.43 5,202,118.08 511,435.00 515,972.88

TOTAL 1,035,121.97 1,035,428.64 6,422,003.84 6,439,557.08 199,603,134.87 199,606,446.63 2,644,827.52 2,647,474.35

NITROGEN, NITRATE 

DISSOLVED 204,161.00 204,161.00

TOTAL 11,501,718.58 11,501,718.58 2,419,834.20 2,419,834.20 3,069,691.83 3,087,051.52

PCB 1221 0.00 1,173,074.17

PCB 1232 0.00 18.43 0.00 1,904,281.19

PCB 1242 0.00 20.31 0.00 1,904,248.17

PCB 1254 0.00 38.47 0.00 1,393,281.10

PCB-1016 0.00 20.31 0.00 1,904,205.27

PCB-1248 0.00 22.20 0.00 1,904,007.79 0.00 0.00

PCB-1260 0.00 44.13 0.15 1,904,075.55

PENTACHLOROBIPHENYL 0.00 97.73
 1-72

LOW HIGH LOW HIGH LOW HIGH LOW HIGH

PA

AVERAGE LOAD ESTIMATES (LBS/YEAR)

Chemical Substance

DC MD VA

PETROLEUM 

HYDROCARBONS 341,418.95 366,211.50 26,384.70 29,610.57

PHENANTHRENE 1.92 7,072.32 75.02 209,228.27 0.00 1.43

POLYCHLORINATED 

BIPHENYLS (PCBS) 0.00 15,481.95

PYRENE 3.02 7,055.56 81.44 155,001.57 0.06 28.64

TOXAPHENE 0.00 366.25 0.00 2,008,056.32

ZINC, DISSOLVED 5,407.98 5,407.98 47,727.99 47,995.16

ZINC, TOTAL 53,190.28 53,190.28 13,414.51 16,791.52 75,170.22 76,184.84 359,606.95 359,690.04

RECOVERABLE 11,699.65 12,212.98 43,369.01 44,002.07

# of facilities in load 

estimate

Note: In the loading estimates, Empty spaces represent NOT APPLICABLE, and Zeros can have several meanings. A zero may indicate the chemical 

was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a given record, or that the 

concentration value was not recorded in the PCS database.

1 78 69 80
2-1

CHAPTER 2 - Urban Stormwater Runoff Loadings from

the Chesapeake Bay Basin

Barry Gruessner Russ Mandel

Lake Champlain Basin Program ICPRB

P.O. Box 204 6110 Executive Boulevard, Suite 300

Grand Isle, VT 05458 Rockville, MD 20852-3903

INTRODUCTION

Over the past 25 years, chemical contaminant loads to the Chesapeake Bay and its

tributaries have been reduced by placing limits on releases from industrial discharges and other

point sources. As a result, stormwater runoff is now thought to be the most significant source of

chemical contaminants to many waterbodies in the Chesapeake Bay basin, particularly in urban

areas. Precipitation in urban areas falls through polluted air and washes over roads, buildings,

parking areas and other features of the urban landscape. When runoff forms, it can transport a

variety of chemical contaminants to sewers and streams and potentially to the Chesapeake Bay. 

The contaminants commonly include metals and organic chemicals used in everything from

automobile brake pad linings to pesticides (Table 2.1). Once in the Bay waters, these

contaminants may impact the living resources in the Chesapeake Bay basin.

A number of techniques have been developed to estimate annual pollutant loads from

urban runoff (Horner et al., 1994). A hydrologic model is typically used to estimate the average

annual runoff volume from the urban area, and stormwater monitoring data is used to develop a

series of “event mean concentrations” (EMCs) for each chemical whose load is being

determined. If one assumes that the EMCs reflect the average concentrations of the chemicals in

all runoff produced by an urban area, the estimated average annual chemical contaminant loads

can be calculated by multiplying the runoff volume and the EMC concentration.

This chapter summarizes a larger report that presents estimates of annual chemical

contaminant loads in stormwater from urban lands in the Chesapeake Bay basin (Gruessner et al.,

1998). Combined with the load estimates from other sources in the watershed presented in this

report, these stormwater loads will lead to increased understanding of chemical contaminant

sources, transport, and fate in the Chesapeake Bay basin (Velinsky, 1996) and will help focus

management efforts that seek to protect the health of the basin’s ecosystem, including it’s human

population.

TEMPORAL AND SPATIAL COVERAGE

Annual runoff volumes for urban land in the Chesapeake Bay basin were estimated using

Chesapeake Bay Program’s Watershed Model, based on rainfall data for the years 1984-1991. 
Urban Stormwater Runoff Loadings

2-2

EMC values for selected contaminants were calculated based on available data collected by 20

urban jurisdictions in the Chesapeake Bay basin in support of stormwater discharge permitting

under the National Pollution Discharge Elimination System (NPDES). Data were collected

between 1992 and 1995 and analyzed together.
Urban Stormwater Runoff Loadings

2-3

Table 2.1. Potential Sources for Common Pollutants in Urban Stormwater

Chemical Some Potential Urban Sources

Aluminum natural sources, coal combustion

Antimony gasoline, paints, plastics

Arsenic fossil fuel combustion, smelting, pesticides

Berylium fossil fuel combustion

Cadmium automobile tires and brakes, sludge and other fertilizers, pesticides

Chromium metal corrosion, engine part wear, dyes, paints, fertilizers, pesticides

Copper automobile tires and brakes, building material corrosion, engine part wear, pesticides

Iron natural sources, automobile corrosion, coke and coal combustion, landfill leachate

Lead some gasolines, automobile tires, paints

Manganese automobile tires and brakes, paints, dyes, fertilizers

Mercury coal combustion, paints, dental wastes

Nickel metal corrosion, engine part wear

Selenium coal combustion

Silver pesticides, dental and medical wastes, coal combustion

Thallium dyes, pigments

Zinc automobile tires and brakes, metal corrosion

Polychlorinated Biphenyls electrical transformers, landfills, lubricants, hydraulic fluids

Polycyclic Aromatic Hydrocarbons

(e.g., naphthalene, benzo(a)pyrene)

organic material combustion, automobile seepage, creosote-treated wood

Halogenated Aliphatics

(e.g., chlorinated methanes, ethanes,

ethylenes, propanes and propenes)

industrial solvents, aerosols

Benzenes, chlorinated benzenes,

and toluenes

fuel spills and combustion, pesticides, solvents, asphalt

Phenols resins, dyes, preservatives, pesticides

Phthalate Esthers plastics, landfills, incinerators

Pesticides

(e.g., chlordane, DDTs, acrolein)

land and water application, organic combustion

Adapted from Makepeace, et al., 1995.
Urban Stormwater Runoff Loadings

2-4

METHODOLOGY

Calculating Average Annual Runoff Estimates

The Chesapeake Bay Watershed Model was selected as the source for average annual

runoff estimates after a review of several runoff calculation methods (Mandel et al., 1997). The

model improves upon the method used in the previous estimate of urban stormwater loads (CBP,

1994a; Olsenholler, 1991) because it uses a well-accepted, supported and calibrated modeling

framework to simulate conditions in the entire Chesapeake Bay basin. The same runoff estimates

are used by the Chesapeake Bay Program to calculate nutrient loads in the basin.

The Chesapeake Bay Watershed Model estimates runoff for 87 discrete modeling

segments in the Bay basin (Figure 2.1), based on land use classifications developed from US

EPA’s 1990 Environmental Monitoring and Assessment (EMAP) and USGS’s Geographic

Information Retrieval and Analysis System (GIRAS) land use data (Gutierrez-Magness et al.,

1997). Annual runoff values for urban land in each segment were provided by the Chesapeake

Bay Program. 

Calculating EMC Values

An event mean concentration (EMC) is the flow-weighted average concentration of a

chemical in stormwater runoff over the course of a typical rain event. In general, developing

EMC values is problematic since suitable rain events are difficult to predict and monitor. At

minimum, the rain events must be of sufficient size to produce runoff. To allow for contaminant

build-up on the land in the monitored basin, it is also better to sample rain events that follow

several days of dry weather. Lastly, to adequately sample fast-moving stormwater in urban areas,

sampling must commence soon after the rainfall begins, requiring rapid mobilization of

monitoring personnel and equipment.

The previous urban stormwater load estimates were based primarily on limited

concentration data from the Priority Pollutant Monitoring Project of the US EPA-led Nationwide

Urban Runoff Program or NURP (Athayde et al., 1983; Cole et al., 1983), conducted in the early

1980s. EMC values from NURP were also supplemented with additional values from several

other studies (Olsenholler, 1991). The EMC values used in the current study, however, were

calculated from monitoring data collected by jurisdictions within the Chesapeake Bay basin in

support of NPDES stormwater permitting. Jurisdictions with municipal separate storm sewer

systems that serve (or are expected to serve soon) more than 100,000 people were required to

monitor stormwater discharges from 5-10 representative land uses during three representative

storms each (US EPA, 1993). No other sources of EMC values were used to supplement those

derived from the NPDES stormwater data.
Urban Stormwater Runoff Loadings

2-5

Figure 2.1. Chesapeake Bay Watershed Model segments. 

Source: Chesapeake Bay Program Office.
Urban Stormwater Runoff Loadings

2-6

The NPDES stormwater monitoring data were examined to investigate potential

differences between contaminant concentrations in runoff from different general land uses. The

results of this analysis are presented in detail in the full report (Gruessner et al., 1998). 

Few significant differences or consistent trends in detected chemical concentrations were

observed by this analysis. Due to the lack of definitive differences between land uses, data from

all land uses were combined to calculate basinwide EMC values.

Basinwide EMC values were calculated from the geometric means of the available

concentration data from all of the monitored sites for all chemicals detected in at least three

samples. Exceptions were those chemicals that were detected in only one jurisdiction, and those

that were suspected to be laboratory contaminants based on quality control data. The geometric

mean was chosen over the arithmetic mean because the data approximate a log-normal

distribution, similar to the findings in other studies (Horner et al., 1994; Athayde et al., 1983).

Because the analysis results were often below the detection limit for a given chemical, the

exact EMCs could not be calculated directly from the data. For below detection limit results, the

actual concentration of a given chemical could be anything from zero to the detection limit value. 

Adapting the method used by Olsenholler (1991) and Cole et al. (1983), lower and upper

geometric means were calculated by substituting one-tenth the average available detection limit

or the average available detection limit, respectively, for below detection limit results. The

average detection limit was used instead of the actual detection limit values because these were

not available for all of the individual analyses. One-tenth the average detection limit was

selected instead of zero for the lower geometric mean because geometric means cannot be

calculated from datasets with zero values. Finally, the EMC value used to calculate the load

estimates was defined as the midpoint between the lower and upper geometric means.

Calculating Chemical Contaminant Load Estimates

Chemical contaminant load estimates were calculated by multiplying the average annual

runoff volume from urban land for each model segment of the Chesapeake Bay Model by the

basinwide EMC concentrations developed from the NPDES stormwater monitoring database. 

Although not all contaminants were detected at all sites, it was assumed that the EMC values

developed from the basinwide data represent the typical occurrence and concentrations of

stormwater contaminants throughout the Chesapeake Bay basin.

UNCERTAINTY

The uncertainty in the load estimates cannot be rigorously determined, but a global, order

of magnitude estimate of the quantifiable uncertainty is presented below. Other, unquantifiable

sources of error are also discussed.
Urban Stormwater Runoff Loadings

2-7

Three main sources of quantifiable error have been identified: modeling error in the

average annual runoff estimates, interannual variability in the those estimates, and variability in

the measured chemical contaminant concentrations. A comparison of the basinwide urban land

use data that is used in the Chesapeake Bay Watershed Model with more detailed county-level

land use data suggested an order of magnitude estimate of about 10% error in the amount of

urban land and the percentage of impervious surface within those urban areas (Mandel et al.,

1997), both of which affect the average annual runoff estimates. There is some additional

uncertainty associated with the average annual runoff estimates due to interannual variability in

rainfall amounts. To develop an order of magnitude estimate of this uncertainty, 95% confidence

intervals were calculated around the mean annual runoff estimates for each segment for each year

from 1986-1993. The magnitudes of the confidence intervals in either direction, expressed as the

percent of the mean, ranged from 9 to 26% and the average was 16%. Combining the ±10%

estimate of modeling error due to land use with the ±16% error from the interannual runoff

variability, the uncertainty in the calculated runoff values is likely to be about ±25%.

A similar approach was taken to determine order of magnitude estimates in the

uncertainty of the EMC values. To assess the variability in the measured concentrations, 95%

confidence intervals were determined around the geometric means of the above detection limit

concentrations for each chemical. The magnitude of the confidence intervals in either direction,

expressed as the percent of the mean, ranged from 10 to 3365%, and the average was about

354%. Several chemicals had very large confidence intervals due to high variability and low

number of values. If the five chemicals from Table 2.4 above that were detected in fewer than

five samples (acrolein, ethylbenzene, acenaphthene, di-n-octyl phthalate, indeno(1,2,-cd)pyrene)

are removed from the preceding analysis, the average confidence interval drops to 54% of the

mean. Note that if the complete dataset that was used to calculate the EMCs (i.e., with one-tenth

the average detection level or the average detection level substituted for the “below detection

level” results), the average size of the confidence interval drops to about 6% of the geometric

mean. To be conservative, ±54% was selected as an order of magnitude estimate of the

uncertainty in the EMC values.

Since the load estimates are calculated from the product of the runoff and EMC values,

the combined quantifiable uncertainties suggest that the average annual loads presented here are

between one-third and twice the true loads. This is not a true confidence interval around the load

estimates, but merely an attempt to quantify some of the uncertainty.

In addition, there are several sources of uncertainty that cannot be quantified. To avoid

misapplying data that are not characteristic to this region, EMCs and contaminant loads were not

calculated for any chemicals that were not detected at sites within the basin. Several factors may

have reduced the number of chemicals that were commonly detected by the NPDES stormwater

monitoring, thereby also reducing the number of EMC values and loads that were calculated. 

The detection limits achieved by most of the laboratories are generally high for measuring

ambient concentrations in stormwater. Also, as in all stormwater monitoring, it is difficult to
Urban Stormwater Runoff Loadings

2-8

capture the “first flush”portion of a storm, which may have more chemicals at higher

concentrations. Conversely, applying EMC values developed from basinwide data to all urban

land in the basin may have artificially created loads for contaminants in some areas where they

are not actually present. Lastly, the loads may have been overestimated because the calculations

did not account for attenuation of contaminant concentrations during transport from waters that

receive runoff to the main tributaries or the Bay.

In summary, the loads presented here are general, Baywide estimates of loads to the Bay’s

hydrologic system. Although they are based on the best data available, it is possible that a

smaller or larger number of chemicals may be entering receiving waters in runoff, especially

from some localized areas. Determining the ultimate fate of these contaminants and their

potential effects on living resources will require more complex modeling.

DISCUSSION AND COMPARISON WITH 1994 TOXICS LOADING AND RELEASE

INVENTORY

Average Annual Runoff Estimates

Table 2.2 presents the average annual runoff estimates from urban lands for each

Chesapeake Bay Program Watershed model segment. The complete runoff data for pervious and

impervious urban lands in each segment during each year modeled is presented in the full report

(Gruessner et al., 1998).

Event Mean Concentrations (EMC)

Data for 20 of the 23 jurisdictions (counties or cities) in the Chesapeake Bay basin that

were required to collect stormwater monitoring data were assembled into a single database. 

Nearly all of the 115 watersheds monitored in these jurisdictions were sampled on three

occasions (others were sampled from one to six times) for a total of 374 samples. Table 2.3 lists

the jurisdictions and the predominant land uses in the monitored watersheds. Watersheds

draining predominately commercial land uses were most common, followed by those with

predominantly medium and low density residential land uses.

Table 2.4 lists the 39 chemicals that were found above method detection limits in at least

one sample, the percent of samples above detection limits, and the number of jurisdictions and

watersheds where they were detected. Eighteen of these 39 chemicals have been identified as

being of some level of concern across the basin by the Chesapeake Bay Program’s Toxics

Subcommittee (CBP, 1998), yet only twelve of the 39 were detected in greater than 10% of the

samples. The chemicals detected most frequently were zinc, copper, lead and other metals,

similar to what was found in the NURP study (Athayde et al., 1983). Other than oil and grease,

the organic compounds were infrequently detected. Quality control data for methylene chloride

and bis (2-ethylhexyl) phthalate, common laboratory contaminants, indicate that their source is
Urban Stormwater Runoff Loadings

2-9

likely to have been sample contamination.

Table 2.5 lists a series of descriptive statistics for the 29 chemicals that were detected in

more than three samples and in more than one jurisdiction (excluding suspected laboratory

contaminants). Lower and upper geometric means, calculated by substituting one-tenth the

average detection limit or the full average detection limit for below detection limit results,

respectively, are presented, as are the EMC values (the midpoints between the lower and upper

geometric means). The geometric means for above the detection limit values only (all below

detection limit results excluded) are also presented for comparison. The EMC values were 

lower than the geometric means for the subset of above detection limit data in all but four cases

where the chemicals had high average detection limits.
Urban Stormwater Runoff Loadings

2-10

Table 2.2. Average Annual Precipitation Runoff from all Urban Land in the Chesapeake Bay Basin, 1984-1991.

Modeling Urban Land Annual Modeling Urban Land Annual

Segment (acres) Average Segment (acres) Average

Runoff Runoff

(inches) (inches)

10 91238 13.6 470 40965 12.7

20 144710 17.7 480 56152 15.1

30 124801 16.3 490 59752 14.6

40 69450 18.9 500 75666 8.7

50 24246 19.9 510 13581 11.9

60 49185 15.7 540 79372 14.5

70 27785 16.1 550 103022 11.5

80 66499 16.3 560 36136 12.2

90 11182 13.4 580 2234 8.1

100 46912 13.0 590 33906 13.1

110 121532 15.8 600 187311 15.2

120 6039 16.0 610 51224 14.1

140 2423 17.6 620 26324 15.1

160 34196 19.6 630 11817 16.5

170 14921 15.4 700 4968 14.1

175 10617 15.7 710 13423 15.8

180 27996 14.9 720 51168 18.0

190 95703 12.1 730 19326 17.0

200 60177 8.9 740 42220 14.4

210 32413 13.8 750 6571 15.4

220 119735 13.6 760 7559 14.1

230 51509 14.9 770 1915 6.2

235 4054 11.7 780 2003 8.6

240 6314 12.6 800 4513 12.5

250 6441 17.1 810 2735 13.6

260 16297 16.9 820 6543 15.3

265 2582 12.7 830 12606 14.3

270 65583 14.1 840 5878 12.8

280 127491 15.5 850 16159 10.4

290 27756 14.3 860 50002 17.7

300 24182 11.0 870 14251 12.0

310 1809 12.4 880 32489 11.9

330 6384 11.1 890 42565 17.1

340 51995 14.0 900 115723 13.7

370 530 11.4 910 68150 11.5

380 6465 10.1 920 53981 8.6

390 3139 11.5 930 1575 8.6

400 12400 11.7 940 11004 13.6

410 19980 12.5 950 33362 19.1

420 18081 12.2 960 110296 18.4

430 14202 9.2 970 6983 12.6

440 11784 10.9 980 37146 10.7

450 38671 12.0 990 5478 10.4

Source: Chesapeake Bay Program Modeling Subcommittee
Urban Stormwater Runoff Loadings

2-11

Table 2.3. Jurisdictions in the Chesapeake Bay Basin With Available NPDES Stormwater Data and

Land Uses Sampled

Number of Stations Sampled

By Predominant Land Use in Watershed1

Jurisdiction Industrial2 Commercial High Density Medium Density Low Density Other3

 Residential Residential Residential

Anne Arundel County 1 2 2 

Baltimore City 1 1 1 

Baltimore County 1 2 1 1 

Carroll County 2 1 1 1 

Charles County 1 1 1 1 

Chesapeake, VA 1 2 1 3 

Chesterfield County 1 2 1 1 

District of Columbia 1 1 3 1 

Fairfax County 1 2 3 3 

Hampton, VA 3 2 2 

Harford County 1 2 2 

Henrico County 2 2 2 

Howard County 2 1 1 1 

Montgomery County 1 2 1 1 

Newport News, VA 1 3 1 1 4 

Norfolk, VA 5 1 3 

Portsmouth,VA 2 1 2 

Prince Georges

County

1 2 2 

Virginia Beach, VA 2 1 2 3 1 

Total 18 35 7 25 22 8

 1 General predominant land use category, as reported by the jurisdictions.

 2 This category includes watersheds with predominantly industrial or light industrial/commercial land use.

 

3 This category includes watersheds with some urban but predominantly agricultural or park land uses.
Urban Stormwater Runoff Loadings

2-12

Table 2.4. Chemicals Above Detection Level (ADL) in Chesapeake Bay Basin NPDES Stormwater Sampling Data

Chemical Total

Samples

Total

Samples ADL

Percent

ADL

Jurisdictions

ADL

Watersheds

ADL

Oil and Grease 350 150 42.9% 18 83

Cyanide 339 24 7.1% 8 17

Total Phenols 337 82 24.3% 12 44

Acrolein 341 1 0.3% 1 1

Chloroform 358 8 2.2% 3 6

Ethylbenzene 358 1 0.3% 1 1

Methylene Chloride1357 96 26.9% 11 46

Toluene 358 4 1.1% 1 4

Phenol 356 3 0.8% 2 3

Acenaphthene2357 1 0.3% 1 1

Anthracene 358 2 0.6% 1 2

Benzo(a)anthracene2,3 358 4 1.1% 3 4

Benzo(a)pyrene2,3 358 3 0.8% 2 3

3,4-benzofluoranthene 345 6 1.7% 4 5

Benzo(ghi)perylene2358 2 0.6% 1 2

Benzo(k)fluroanthene 358 3 0.8% 2 3

Bis(2-chloroethoxy)methane 358 3 0.8% 2 3

Bis(2-ethylhexyl)phthalate1358 54 15.1% 11 36

Chrysene2,3 358 3 0.8% 2 2

1,4-dichlorobenzene 362 21 5.8% 2 14

Di-n-octyl phthalate 358 1 0.3% 1 1

Fluoranthene3,4 357 16 4.5% 12 8

Fluorene2358 3 0.8% 3 3

Indeno(1,2,-cd)pyrene2358 1 0.3% 1 1

Phenanthrene4353 11 3.1% 6 9

Pyrene2358 16 4.5% 6 12

Antimony 337 22 6.5% 7 15

Arsenic2,5 357 119 33.3% 15 62

Berylium 337 36 10.7% 9 27

Cadmium2,3 361 124 34.3% 15 64

Chromium2,3 341 184 54.0% 17 87

Copper3,4 361 318 88.1% 19 112

Lead3,4 361 241 66.8% 17 97

Mercury2,3 338 18 5.3% 9 16

Nickel2356 142 39.9% 15 60

Selenium 353 25 7.1% 7 17

Silver 337 18 5.3% 9 16

Thallium 337 5 1.5% 4 5

Zinc2,5 361 5650 97.2% 20 119

1

 Common laboratory contaminant, suspect data.

2

 Draft Revised Chemicals of Potential Concern List 

3

 1990 Toxics of Concern List

4

 Draft Revised Toxics of Concern List

5

 1990 Chemicals of Potential Concern List
Urban Stormwater Runoff Loadings

2-13

Table 2.5. Descriptive Statistics and EMCs for Selected Chemicals Detected in Chesapeake Bay Basin

NPDES Stormwater Sampling Data (μg/L).

Chemical Min. Max. Geometric Average Lower Upper EMC

Detected Detected Mean of Available Geometric Geometric (Middle 

Value Value Detected Detection Mean Mean Geometric 

Values Limit Mean)

Oil and Grease 200.00 570000.00 5650.00 4510.00 1330.00 4970.00 3149.00 

Cyanide 5.00 60.0 13.56 12.75 1.51 12.80 7.16 

Total Phenols 0.13 381.0 15.08 36.10 5.11 29.19 17.15 

Chloroform 1.21 6.8 3.33 2.15 0.23 2.17 1.20 

Phenol 2.00 9.2 5.53 3.38 0.35 3.39 1.87 

Benzo(a)anthracene 2.60 760.0 21.52 3.67 0.38 3.74 2.06 

Benzo(a)pyrene 2.60 510.0 27.09 3.22 0.33 3.27 1.80 

3,4-benzofluoranthene 1.50 31.6 5.47 3.75 0.39 3.78 2.09 

Benzo(k)fluroanthene 1.20 720.0 22.96 3.37 0.35 3.42 1.89 

Bis(2-chloroethoxy)methane 3.70 32.3 15.69 3.89 0.40 3.94 2.17 

Chrysene 1.60 820.0 28.15 3.21 0.33 3.27 1.80 

1,4-dichlorobenzene 2.00 9.2 3.08 4.80 0.53 4.68 2.61 

Fluoranthene 2.40 2290.0 12.30 4.13 0.48 4.34 2.41 

Fluorene 1.00 1700.0 43.22 3.11 0.32 3.18 1.75 

Phenanthrene 2.00 3840.0 11.05 5.87 0.64 5.98 3.31 

Pyrene 2.00 1970.0 6.92 2.97 0.34 3.09 1.72 

Antimony 1.00 69.0 7.46 33.44 3.52 30.32 16.92 

Arsenic 1.00 310.0 3.38 3.03 0.68 3.14 1.91 

Berylium 0.30 56.0 1.38 1.07 0.14 1.10 0.62 

Cadmium 0.10 21.0 0.98 2.76 0.43 1.94 1.18 

Chromium 1.00 140.0 5.53 7.63 2.22 6.41 4.32 

Copper 2.00 396.0 13.25 10.95 9.85 12.96 11.40 

Lead 1.00 368.0 17.92 27.15 9.57 20.58 15.07 

Mercury 0.12 1.3 0.23 0.32 0.04 0.31 0.17 

Nickel 2.00 110.0 9.46 16.27 3.28 13.10 8.19 

Selenium 1.00 9.0 2.29 24.73 2.46 20.89 11.68 

Silver 0.20 290.0 2.62 4.31 0.47 4.20 2.34 

Thallium 1.00 51.0 7.66 48.28 4.86 46.97 25.92 

Zinc 3.00 1078.0 96.17 41.34 88.14 93.95 91.04 

See text for description of how geometric means were calculated.
Urban Stormwater Runoff Loadings

2-14

Table 2.6 lists the EMC values from Table 2.1 alongside those used in a previous

estimate of chemical contaminant loads in stormwater to the Chesapeake Bay (Olsenholler,

1991). In general, the EMCs calculated for this report tended to be higher for organic

compounds and slightly lower for metals. One notably large difference is in the EMC values for

lead, where the newly calculated EMC value is more than four times larger than the one used

previously. The previous study reduced the EMC value for lead developed from the NURP

study, assuming that lead from gasoline sources has been reduced dramatically since the early

1980s when the NURP data were collected (Cole et al., 1983). The more recent data indicate that

this assumption may not have been warranted. In general, the new EMC values should better

reflect recent conditions within the Chesapeake Bay basin.

Chemical Contaminant Load Estimates

Tables 2.7a and 2.7b present the average annual load estimates for chemical contaminants

in stormwater runoff. These estimates represent loads in stormwater runoff reaching any

receiving waters and have not been adjusted to reflect attenuation during transport to the

mainstem Bay. The total loads are presented first, followed by loads for each major sub-basin. 

The loads are also further divided into above or below the “fall line” loads. The fall line marks

the boundary of two physiographic provinces (roughly following the western edges of Richmond,

VA, Washington, DC and Baltimore, MD), and generally indicates the upstream extent of tidal

action in the Bay’s tributaries.

Table 2.8 summarizes the current total load estimates for the entire Bay basin and, for

selected chemicals, compares them to those from the previous estimate (CBP, 1994a;

Olsenholler, 1991). Because the models used in these studies tend to predict similar runoff

volumes (Mandel et al., 1997), the two sets of load estimates compare as would be expected from

the patterns in the EMC values discussed above. Namely, the loads for organic compounds

presented here are generally higher than those from the previous study and the loads for metals

are generally lower.

The load estimate for “oil and grease” is particularly high. “Oil and grease” is a

collective term used for a group of related petroleum hydrocarbons that are measured together. It

includes several parameters whose loads were also calculated individually (e.g., PAHs such as

fluorene and benzo(a)pyrene). The sources of these hydrocarbons include direct seepage from

engines, other automobile-related activities, and general fossil fuel combustion (Shepp, 1996;

Makepeace et al., 1995). Also notable is the high estimated load for lead. The previous estimate

of urban stormwater loads assumed that lead in stormwater would be reduced greatly from the

early 1980s when the NURP data was collected, yet this does not appear to be the case.
Urban Stormwater Runoff Loadings

2-15

Table 2.6. Comparison of EMC Values With Those From a Previous Estimate Contaminant Loads in the

Chesapeake Bay Basin (μg/L).

Chemical Current Study Previous Load

EMC Estimate

EMC1

Oil and Grease 3149.04 

Cyanide 7.16 9.9 

Total Phenols 17.15 

Chloroform 1.20 

Phenol 1.87 

Benzo(a)anthracene 2.06 0.087 

Benzo(a)pyrene 1.80 0.098 

3,4-benzofluoranthene 2.09 

Benzo(k)fluroanthene 1.89 

Bis(2-chloroethoxy)methane 2.17 

Chrysene 1.80 0.25 

1,4-dichlorobenzene 2.61 

Fluoranthene 2.41 0.36 

Fluorene 1.75 0.08 

Phenanthrene 3.31 0.32 

Pyrene 1.72 0.28 

Antimony 16.92 2.5 

Arsenic 1.91 4.4 

Berylium 0.62 14.6 

Cadmium 1.18 1.1 

Chromium 4.32 6.3 

Copper 11.40 17.6 

Lead 15.07 3.8 

Mercury 0.17 0.2 

Nickel 8.19 12.5 

Selenium 11.68 22.1 

Silver 2.34 

Thallium 25.92 2.7 

Zinc 91.04 96.8 

1

 Values from CBP, 1994; Olsenholler, 1991
2-16

Table 2.7a. Average Annual Chemical Contaminant Loads in Stormwater Runoff

AFL=Above Fall Line, BFL=Below Fall Line

All values in Kilograms

Chesapeake Bay Western Shore Eastern Shore

Chemical Total Susquehanna MD MD Patuxent Potomac

AFL BFL Total Total AFL BFL Total Total AFL BFL Total AFL BFL Total

(All AFL) (All AFL)

Oil and Grease 8,437 6,772 1.52 x 1074,519 34 1,297 1,332 581 259 232 491 2,039 2,065 4,104 

Cyanide 3,209 2,576 5,785 1,719 13 493 507 221 99 88 187 776 785 1,561 

Total Phenols 19,172 15,389 34,561 10,268 78 2,948 3,026 1,320 589 527 1,115 4,634 4,692 9,326 

Chloroform 45,952 36,885 82,836 24,610 187 7,066 7,253 3,164 1,411 1,262 2,673 11,106 11,245 22,351 

Phenol 5,009 4,021 9,030 2,683 20 770 791 345 154 138 291 1,211 1,226 2,437 

Benzo(a)anthracene 5,522 4,432 9,954 2,957 23 849 872 380 170 152 321 1,335 1,351 2,686 

Benzo(a)pyrene 4,833 3,879 8,713 2,588 20 743 763 333 148 133 281 1,168 1,183 2,351 

3,4-benzofluoranthene 5,590 4,487 10,077 2,994 23 860 882 385 172 154 325 1,351 1,368 2,719 

Benzo(k)fluroanthene 5,051 4,054 9,105 2,705 21 777 797 348 155 139 294 1,221 1,236 2,457 

Bis(2-chloroethoxy)methane 5,815 4,667 10,482 3,114 24 894 918 400 179 160 338 1,405 1,423 2,828 

Chrysene 4,824 3,872 8,696 2,583 20 742 761 332 148 133 281 1,166 1,180 2,346 

1,4-dichlorobenzene 6,985 5,606 12,591 3,741 28 1,074 1,102 481 214 192 406 1,688 1,709 3,397 

Fluoranthene 6,453 5,180 11,634 3,456 26 992 1,019 444 198 177 375 1,560 1,579 3,139 

Fluorene 4,687 3,762 8,450 2,510 19 721 740 323 144 129 273 1,133 1,147 2,280 

Phenanthrene 8,879 7,127 16,006 4,755 36 1,365 1,401 611 273 244 516 2,146 2,173 4,319 

Pyrene 4,597 3,690 8,287 2,462 19 707 726 317 141 126 267 1,111 1,125 2,236 

Antimony 45,336 36,390 81,726 24,280 185 6,971 7,156 3,122 1,392 1,245 2,637 10,957 11,095 22,052 

Arsenic 5,120 4,109 9,229 2,742 21 787 808 353 157 141 298 1,237 1,253 2,490 

Berylium 1,662 1,334 2,996 890 7 256 262 114 51 46 97 402 407 808 

Cadmium 3,165 2,541 5,706 1,695 13 487 500 218 97 87 184 765 775 1,540 

Chromium 11,563 9,282 20,845 6,193 47 1,778 1,825 796 355 318 673 2,795 2,830 5,624 

Copper 30,549 24,521 55,069 16,361 125 4,697 4,822 2,104 938 839 1,777 7,383 7,476 14,859 

Lead 40,386 32,417 72,803 21,630 165 6,210 6,375 2,781 1,240 1,109 2,349 9,761 9,883 19,644 

Mercury 464 372 837 249 2 71 73 32 14 13 27 112 114 226 

Nickel 21,953 17,621 39,574 11,757 90 3,376 3,465 1,512 674 603 1,277 5,306 5,372 10,678 

Selenium 31,282 25,109 56,391 16,754 128 4,810 4,938 2,154 960 859 1,820 7,561 7,655 15,216 

Silver 6,259 5,024 11,284 3,352 26 962 988 431 192 172 364 1,513 1,532 3,045 

Thallium 69,442 55,739 125,181 37,191 283 10,678 10,961 4,782 2,132 1,908 4,039 16,784 16,994 33,777 

Zinc 243,935 195,801 439,736 130,644 995 37,508 38,503 16,798 7,488 6,701 14,190 58,957 59,695 118,652 
2-17

Table 2.7b. Average Annual Chemical Contaminant Loads in Stormwater Runoff

AFL=Above Fall Line, BFL=Below Fall Line

All values in Kilograms, except Oil and Grease in 10002 of Kg.

Western Shore Eastern Shore

VA VA Rappahannock York James

Chemical Total Total AFL BFL Total AFL BFL Total AFL BFL Total

(All BFL) (All BFL)

Oil and Grease 922 42 249 143 392 166 144 310 1,171 1,348 2,518

Cyanide 351 16 95 54 149 63 55 118 445 513 958

Total Phenols 2,095 94 566 325 891 377 326 704 2,661 3,062 5,723

Chloroform 5,021 226 1,356 778 2,134 904 782 1,686 6,377 7,339 13,716

Phenol 547 25 148 85 233 99 85 184 695 800 1,495

Benzo(a)anthracene 603 27 163 94 256 109 94 203 766 882 1,648

Benzo(a)pyrene 528 24 143 82 224 95 82 177 671 772 1,443

3,4-benzofluoranthene 611 28 165 95 260 110 95 205 776 893 1,668

Benzo(k)fluroanthene 552 25 149 86 235 99 86 185 701 807 1,508

Bis(2-chloroethoxy)methane 635 29 172 99 270 114 99 213 807 929 1,736

Chrysene 527 24 142 82 224 95 82 177 669 770 1,440

1,4-dichlorobenzene 763 34 206 118 324 137 119 256 969 1,116 2,085

Fluoranthene 705 32 190 109 300 127 110 237 896 1,031 1,926

Fluorene 512 23 138 79 218 92 80 172 650 749 1,399

Phenanthrene 970 44 262 150 412 175 151 326 1,232 1,418 2,650

Pyrene 502 23 136 78 214 90 78 169 638 734 1,372

Antimony 4,954 223 1,338 768 2,106 892 771 1,664 6,291 7,241 13,532

Arsenic 559 25 151 87 238 101 87 188 710 818 1,528

Berylium 182 8 49 28 77 33 28 61 231 265 496

Cadmium 346 16 93 54 147 62 54 116 439 506 945

Chromium 1,264 57 341 196 537 228 197 424 1,605 1,847 3,451

Copper 3,338 150 901 518 1,419 601 520 1,121 4,239 4,879 9,118

Lead 4,413 199 1,192 684 1,876 795 687 1,482 5,605 6,450 12,055

Mercury 51 2 14 8 22 9 8 17 64 74 139

Nickel 2,399 108 648 372 1,020 432 373 806 3,046 3,506 6,553

Selenium 3,418 154 923 530 1,453 616 532 1,148 4,341 4,996 9,337

Silver 684 31 185 106 291 123 106 230 869 1,000 1,868

Thallium 7,588 342 2,049 1,176 3,225 1,367 1,181 2,548 9,637 11,091 20,727

Zinc 26,656 1,201 7,198 4,132 11,330 4,801 4,150 8,951 33,852 38,959 72,811
Urban Stormwater Runoff Loadings

2-18

Table 2.8. Comparison of Baywide Loads With Those From a Previous Estimate of Contaminant Loads

in the Chesapeake Bay Basin. 

Chemical Current Study Previous Study

Total Load Total Load1

(Kg/yr) (Kg/yr)

Oil and Grease 15,209,876

Cyanide 34,561 58,968

Total Phenols 82,836

Chloroform 5,785

Phenol 9,030

Benzo(a)anthracene 9,954 168

Benzo(a)pyrene 8,713 181

3,4-benzofluoranthene 10,077

Benzo(k)fluroanthene 9,105

Bis(2-chloroethoxy)methane 10,482

Chrysene 8,696 454

1,4-dichlorobenzene 12,591

Fluoranthene 11,633 680

Fluorene 8,450

Phenanthrene 16,006

Pyrene 8,287

Antimony 81,726 14,515

Arsenic 9,229 25,855

Berylium 2,996 86,184

Cadmium 5,706 6,350

Chromium 20,845 37,195

Copper 55,069 104,328

Lead 72,803 22,226

Mercury 837 1,179

Nickel 39,574 72,576

Selenium 56,391 131,544

Silver 11,284

Thallium 125,181 15,876

Zinc 439,736 589,680

1

 Values from CBP, 1994; Olsenholler, 1991 converted from pounds.
Urban Stormwater Runoff Loadings

2-19

RECOMMENDATIONS

The load estimates for chemical contaminants in stormwater runoff from urban lands in

the Chesapeake Bay watershed presented here reflect runoff estimates that are consistent with

those used for other Bay Program efforts and stormwater monitoring data collected from urban

areas within the basin. As such, they improve upon a previous load estimate that used other

runoff values and contaminant concentrations that were measured at sites across the country.

It is important to remember that, since the same EMC values were applied to all urban

land uses throughout the Chesapeake Bay basin, the differences in estimated loads from one part

of the basin to another are due only to differences in the amount of urban land and the degree of

imperviousness within it. The loads do not indicate which urban areas are likely to be

contributing chemical contaminants out of proportion to their size. Also, users of this report may

want to exercise caution when applying EMC values and load estimates for those chemicals that

were detected in only a few samples.

The load estimates show that certain metals (arsenic, cadmium, copper, lead, nickel, and

zinc) are commonly detected in urban stormwater in the Chesapeake Bay basin, confirming what

was predicted from the local and national stormwater data (Olsenholler, 1991) and from what is

known about the typical sources of metals in urban areas (Table 2.1; Makepeace et al., 1995). 

The general class of hydrocarbons measured as “oil and grease” was also commonly detected and

may be of Baywide concern as well.

Other metals and a number of organic compounds were detected less often and in fewer

areas. These chemicals may be more localized problems or they may have not been effectively

captured by the limited sampling in each watershed, given the high variability in rainfall amounts

and antecedent conditions. Polycyclic Aromatic Hydrocarbons or PAHs (a subset of “oil and

grease”), including 3,4-benzofluoranthene, fluoranthene, phenanthrene, and pyrene, were the

most commonly detected organic compounds. Their sources are primarily seepage from

automobiles and organic matter combustion (Shepp, 1996; Schueler, 1994). It is interesting to

note that no pesticides or PCBs were found in Chesapeake Bay basin stormwater, even though

these chemicals have been observed in other studies (Makepeace et al., 1995).

Further improvements to urban stormwater load estimates will require both better runoff

volume estimates and more accurate EMC values that are specific to a particular geographic

region, or even to each land use within that region. Runoff estimates could be improved

somewhat by developing better urban land use data for the watershed model. Improved EMC

values may be developed by expanding and further analyzing the combined dataset assembled for

this study as additional NPDES stormwater monitoring data from urban areas is collected. The

NPDES stormwater monitoring data will provide a more accurate picture of contaminants in

stormwater if detection limits can be lowered by using refined sampling and analytical

techniques.
Urban Stormwater Runoff Loadings

2-20

It is difficult to predict how the contaminants entering the Bay and its tributaries in urban

stormwater will ultimately affect the Bay’s living resources. Further study of the specific sources

of the chemicals commonly detected in NPDES stormwater monitoring, along with their

transport and fate, may be warranted in certain urban areas. These estimates of contaminant

loads in urban stormwater, when combined with similar estimates of loads from other sources,

can be used to assess the relative importance of various sources of contaminants to the Bay

system and focus management efforts appropriately.

If, as suspected, urban stormwater is found to be a significant contributor of chemical

contaminants relative to other sources, these load estimates provide a starting point for

determining which chemicals should be targeted for general source reduction activities such as

pollution prevention or best management practices. The analysis of the NPDES stormwater data

presented here, along with other information, may also help determine which areas of the basin

are in need of further study. Intensive monitoring and modeling in a particular subwatershed may

then provide enough information about chemical loads, transport, and fate to allow reduction

targets to be set for that subwatershed.
3-1

CHAPTER 3 - Atmospheric Deposition Loadings

Joel Baker

Chesapeake Biological Laboratory

University System of Maryland 

P.O. Box 38 

Solomons, MD 20688

The objective of this chapter is to describe atmospheric deposition processes and to

synthesize currently available information to estimate atmospheric deposition loadings of

chemical contaminants to the Chesapeake Bay surface waters below the fall-lines. This chapter

updates and expands the 1994 Chesapeake Bay Basin Toxics Loading and Release Inventory

(CBP, 1994a) using recent field measurements and improved theoretical understanding of

deposition processes.

INTRODUCTION

Defining Atmospheric Deposition Processes

Wet Deposition 

Wet deposition includes all processes that transport atmospheric chemicals to the Earth’s

surface during precipitation events. While precipitation events include rain, snow, sleet, fog

impaction, and perhaps dew formation, rainfall contributes the vast majority of wet deposition to

the Chesapeake Bay region and is assumed in this chapter to be the sole wet deposition form to

the Chesapeake Bay. Transport of chemicals by precipitation depends both upon the

concentration of chemical in the raindrops and upon the precipitation amount. Chemicals may be

incorporated into cloud droplets and into falling drops below the clouds (see review by Poster

and Baker, 1997). Gaseous contaminants adsorb to solid aerosol particles and dissolve into

liquid droplets. Mass transfer rates of gases into hydrometers are rapid relative to droplet

transport times, allowing gas scavenging to be modeled as an equilibrium process. Aerosol

particles are incorporated into droplets during initial formation (i.e., they act as condensation

nuclei) or are scavenged into existing droplets within or below clouds. The efficiency with

which particles and their associated contaminants are incorporated into raindrops depends upon

the size distribution and hygroscopicity of the particle population, the droplet size spectra, and

the amount of atmospheric turbulence during the precipitation event.

Dry Aerosol Deposition 

Dry aerosol deposition results from the transport of aerosol particles to the Earth’s

surface. Several mechanisms deposit particles to terrestrial and aquatic surfaces, ranging from

eddy diffusion of small (<0.1 μm diameter) particles to gravitational settling of large (>10 μm)
Atmospheric Deposition Loadings

3-2

particles. These deposition processes strongly depend upon the size distribution of the ambient

aerosol particles and upon the extent of turbulence near the deposition surface (see Zufall and

Davidson, 1997 and Ondov et al., 1997 for reviews of dry aerosol deposition processes). Dry

aerosol deposition rates to water surfaces are generally lower than those to adjacent terrestrial

surfaces due to enhanced turbulent transfer over the rougher vegetation and soils. Similarly, dry

aerosol deposition fluxes are larger under the unstable meteorological conditions that exist when

cooler air moves over warm water. Changes in particle size distribution, which may significantly

alter dry aerosol deposition fluxes, result from growth of hygroscopic particles under high

humidity (Ondov et al., 1997), particle coagulation, or changes in emission size distributions.

Gas Exchange 

Volatile chemicals exchange across the air-water interface by passive diffusion (see

Eisenreich et al., 1997 and Bidleman and M Connell, 1995 for recent reviews of gas exchange). c

Exchange of simple gases such as oxygen and carbon dioxide across the air-water interface are

well studied, and form the conceptual basis for exchange of volatile chemical contaminants. 

Overall net gas exchange fluxes are calculated as the product of a diffusional gradient and a mass

transfer coefficient. The diffusion gradient is the difference between the measured dissolved

chemical concentration in the surface water and that dissolved concentration that is in

equilibrium with the measured gas phase concentration in the overlying air mass. For

semivolatile contaminants, Henry’s Law describes the equilibrium condition. Chemical

compound-specific Henry’s Law equilibrium constants are quite sensitive to temperature

(Bamford et al., 1999a), resulting in a temperature-dependent diffusional gradient. The

diffusional mass transfer coefficient depends upon the molecular diffusivity of the compound in

water and air and upon the extent of turbulence at the air-water interface (as commonly

parameterized by correlations with wind speed; Nelson et al., 1998).

The process of gas exchange actively transports volatile chemicals concurrently in both

directions across the air-water interface. In this chapter, net gas exchange fluxes, equal to the

difference between the gross absorptive and volatilization fluxes, are presented. To more

accurately demonstrate the coupling between the atmosphere and surface waters, gross absorptive

fluxes are included in the discussion of relative loadings and mass balances in Chapter 8.

TEMPORAL AND SPATIAL COVERAGE

In this report, we consider the CBADS sampling sites to represent the regional

background deposition signal weakly or unaffected by localized urban influences. Ambient

concentrations and deposition fluxes at these sites are similar to those reported at remote sites in

the Great Lakes (Baker et al., 1997; Hoff et al., 1996), supporting this designation as regional

background sites. Recently, the influence of elevated contaminant levels in urban atmospheres

on enhanced deposition to adjacent coastal waters has been demonstrated (Offenberg and Baker,

1997; Gustafson and Dickhut, 1997). To quantify this enrichment in the Chesapeake Bay urban
Atmospheric Deposition Loadings

3-3

areas, the Atmospheric Exchange Over Lakes and Seas (AEOLOS) program conducted a series

of intensive sampling campaigns in and downwind of the Baltimore metropolitan area. While

much of the AEOLOS data are not yet final, initial results confirm enhanced deposition in the

urban area (Offenberg and Baker, 1999; Bamford et al., 1999b). For this effort, we have

estimated that 10% of the Bay’s surface waters below the fall lines are influenced by urban

deposition. As seen in Table 3.5, the overall Bay-wide atmospheric deposition loadings are quite

sensitive to the fraction of the Bay that falls under the urban influence. Further meteorological

analysis of mesoscale wind patterns are needed to refine the extent of the urban influence.

METHODOLOGY

Wet Deposition 

In this report, the wet deposition fluxes of compound I (Fi,wet, μg/m -year) at a site are 2

calculated as the product of volume-weighted mean chemical contaminant concentrations

measured in precipitation (C , μg/m ) and the corresponding precipitation amount (P, m/year): i,ppt

3

Fi,wet = Ci,ppt x P

In the available studies, weekly- or semi-weekly-integrated precipitation samples were analyzed. 

Annual wet deposition fluxes were calculated for each parameter at each site.

The 1994 TLRI used wet deposition data from the three rural Chesapeake Bay

Atmospheric Deposition Study (CBADS) sites collected from June/July 1990 through the end of

1991 (Table 3.1). Measured parameters included elements (aluminum, iron, manganese, copper,

chromium, lead, zinc, arsenic, and cadmium), polycyclic aromatic hydrocarbons, and

polychlorinated biphenyl congeners. Annual wet deposition fluxes to the three CBADs sites

were similar for most parameters and an areally-integrated annual load (g/year) was calculated by

multiplying the three site-specific fluxes by their representative water surface area below the falllines (CBP, 1994a). At the time of the 1994 TLRI, no consistent measurements of mercury or

current-use agrichemicals in precipitation had been made, and no wet deposition loading

estimates were made for these chemicals. Also, no information about wet deposition in

Chesapeake Bay’s urban areas was available for any chemical species. Therefore, the 1994 TLRI

wet deposition load estimates represented regional background loadings.

The 1998 TLRI wet deposition loadings were calculated using exactly the same method

used in the 1994 TLRI but with additional data (Table 3.1). An additional 21 months of CBADS

wet deposition (bringing the total study period to June/July 1990 - September 1993) are

incorporated into the refined wet deposition loadings. Mercury wet deposition loadings are now

estimated using the studies of Mason et al. (1997a; 1997b). Wet deposition of agrichemicals is

estimated from the work of Harman in the Patuxent River basin (Harman, 1996; Harman-Fetcho

et al., 1998). While studies of wet deposition to urban areas are underway, only initial data are
Atmospheric Deposition Loadings

3-4

currently available to estimate the urban influence (Offenberg and Baker, 1999). Until other data

are finalized, here we assume from the initial data that wet deposition fluxes of metals, PAHs,

and PCBs are enriched two-, four, and ten-fold over regional background, respectively

(Offenberg and Baker, 1999). Mason et al. (1997a) report that urban wet deposition of mercury

is nearly twice the regional background.

Dry Aerosol Deposition 

There is no uniformly accepted method to directly measure dry aerosol deposition fluxes

to water surfaces. Numerous investigators have employed surrogate surfaces (e.g., Holsen et al.,

1997 and references therein) and semi-empirical models (Zufall and Davidson, 1997 and

references therein; Wu et al., 1992; Wu et al., 1994) to estimate dry aerosol deposition fluxes. In

the Chesapeake Bay region, surrogate surface have not been routinely used to estimate fluxes,

and the CBADS program estimated dry aerosol fluxes (F , μg/m -year) as the product of dry

2

measured ambient aerosol-associated contaminant concentrations (C , μg/m ) and a chemical- aero

3

specific and meteorological-averaged dry deposition velocity (V , m/year): d

Fdry = Caero x Vd

In the 1994 TLRI, measured aerosol-associated chemical contaminant concentrations

were measured at regular intervals (weekly for elements and semi-weekly for PAHs and PCBs)

from June/July 1990 until December 1991. Measured concentrations of elements were

apportioned into ‘crustal’ and ‘non-crustal’ fractions using aluminum as the crustal tracer and

typical crustal elemental abundances. The crustal and non-crustal fraction dry deposition

velocities were estimated to be 0.26 and 1.4 cm/sec, respectively (Wu et al., 1992) and were

assumed invariant among the three CBADS sites. Aerosol-bound organic contaminants were

deposited with a velocity of 0.49 cm/sec (Leister and Baker, 1994). Since aerosol-bound

polychlorinated biphenyls were not routinely detected in the CBADS samples, we used the

Junge-Pankow model to estimate the sorbed PCB concentrations from the corresponding gas

phase levels (Leister and Baker, 1994). Site-specific annual dry aerosol deposition fluxes were

multiplied by the respective surface area of the Bay below the fall-lines to estimate Bay-wide

loadings.

The 1998 TLRI dry aerosol deposition loadings were calculated in a similar manner as

used in 1994. As with wet deposition, the longer CBADS data record was available for these

revised calculations. Element deposition was calculated using the same dry deposition velocities

as were used in 1994. However, further investigation of the size distributions of organic

chemicals on ambient aerosols (Poster et al., 1995) has led us to reduce the organic contaminant

deposition from 0.49 to 0.2 cm/sec. This lower value is likely more representative with the sootlike particles that transport most organic contaminants, and is consistent with the value used in

the Great Lakes Integrated Atmospheric Deposition Network (IADN; Hoff et al., 1996).
lnHT

'lnH298%26.39&

7868

T

Atmospheric Deposition Loadings

3-5

Gas Exchange 

The application of two film transport models to calculate fluxes of semivolatile organic

contaminants has recently been reviewed (Bidleman and M Connell, 1995; Eisenreich et al., c

1997). Instantaneous gas exchange rates across the air-water interface are modeled using the

paired dissolved and gas phase measurements, temperature-corrected Henry’s Law constants

(Tateya et al., 1988; Bamford et al., 1999a), and estimates of mass transfer coefficients (K s) OL

based on correlations with wind speed. To be consistent with previously reported PCB gas

exchange rates in Green Bay (Achman et al., 1993) and Lake Michigan (Hornbuckle et al., 1995),

we adopted the approach of those studies to estimate mass transfer coefficients and temperaturecorrected Henry’s Law constants (see Nelson et al., 1998 and references therein for details). 

Henry’s Law constants of semivolatile organic contaminants are very sensitive to temperature,

with H increasing approximately ten-fold with a 25 C increase in temperature (Tataya et al., o

1988; Bamford et al., 1999a). We used the equation proposed by Tataya et al. (1988) to estimate

temperature-corrected H values for PCBs:

where H and H are the Henry’s Law constants at temperature T and 298 K, respectively. T 298

Temperature-corrected PAH H values were calculated using the compound-specific enthalpies

and entropies of phase change measured by Bamford et al. (1999a). The gas exchange mass

transfer coefficient was estimated from correlations with wind speed (as a surrogate measure of

surface turbulence) and molecular diffusivity in air and water, as described in Hornbuckle et al.

(1995) and detailed in Nelson et al. (1998).

No gas exchange fluxes were included in the 1994 TLRI. Data from several recent

publications were used to estimate gas exchange fluxes in the 1998 TLRI. Nelson et al. (1998)

and M Connell et al. (1997) measured gas exchange fluxes of organic contaminants and c

pesticides, respectively, during four Bay-wide cruises in 1993. Gustafson and Dickhut (1997)

measured PAH gas exchange rates in the southern Chesapeake Bay. Harman (1996) estimated

gas exchange rates of current-use agrichemicals in the Patuxent River in 1995. More recently,

Bamford et al. (1999b) estimated exchange fluxes of PAHs across the air-water interface of the

urban Patapsco River during three intensive studies in June 1996 and February and July 1997. 

Here we rely primarily on the Nelson et al. (1998) and Harman (1996) studies to estimate

regional background gas exchange rates of PCBs, PAHs, and agrichemicals, and the work of

Bamford et al. (1999b) for urban-enhanced gas exchange rates. As seen in Table 3.3, gas

exchange rates of PAHs in the urban Patapsco River system are much different than those in the

open Bay. Many PAHs, including fluorene, anthracene, fluoranthene, and pyrene volatilize from
Atmospheric Deposition Loadings

3-6

surface waters in the urban area, as elevated dissolved concentrations drive the diffusional

gradient. In contrast, the net flux of phenanthrene is into the urban surface water (Bamford et al.,

1999b) at rates similar to those observed in the mainstem Chesapeake (Nelson et al., 1998). 

Comparable phenanthrene exchange rates in the urban and regional waters do not imply similar

concentration of this PAH. Rather, both the urban atmosphere and surface water are enriched in

phenanthrene, resulting in a comparable gradient as seen in the mainstem Bay waters.

UNCERTAINTY

Error Analysis in Wet Deposition Calculations 

Sources of random error in wet deposition loading estimates include the measurement

errors association with quantifying chemical concentration in precipitation and the rainfall

amount. Here we adopt the error analysis of the CBADS program, and assign propagated

uncertainties to the wet metals and organics fluxes of ±10% and ±20%, respectively. Another

potentially larger but unquantified source of uncertainty in wet deposition loadings results from

the spatial interpolation among the few regional and single urban deposition sites. This is

especially problematic when applying the ‘urban influence’ to a specific area. However, any

spatial variation in the regional background appears to be relatively small on an annual basis,

perhaps a factor of two. Recently, wet deposition of metals has been measured to the Bear

Branch watershed in Thurmont, Maryland (Church et al., 1998). The Bear Branch metals annual

wet deposition fluxes are equal to or slightly greater than those used in this study (Bear Branch

receives higher annual average precipitation than the Bay-wide average). The similarities

between the wet deposition fluxes estimated here and the independently determined fluxes at

Bear Branch suggest that the uncertainties of extrapolation of the regional background wet

deposition fluxes are not large.

Error Analysis in Dry Aerosol Deposition Calculations

The largest uncertainty in the dry aerosol deposition estimates results from our poor

understanding of the chemical-specific dry deposition velocities. Dry deposition strongly

depends upon the over-water wind speed and the size distribution of the aerosol particles. Both

are known to vary greatly spatially and temporally. However, integrating dry deposition fluxes

over time to estimate annual loadings tends to dampen out this variability. Nonetheless, the

estimated dry aerosol deposition loadings here are likely accurate to within a factor of 2-3.

Error Analysis in Gas Exchange Calculations 

Uncertainty in calculated instantaneous gas exchange fluxes result from systematic and

random measurement errors, systematic errors in the values of H values, and uncertainties due to

the mass transfer coefficient calculations. To assess the relative magnitude of random errors in

the instantaneous gas exchange flux calculations, propagation of error analysis was performed:
F

2

(F)'(

*F

*KOL

)

2

(FKOL)

2%(

*F

*Cd

)

2

(FCd)

2%(

*F

*Ca

)

2

(FCa)

2%(

*F

*H

)

2

(FH)

2

Atmospheric Deposition Loadings

3-7

where F is the instantaneous gas exchange flux resulting from the difference in dissolved (C )d

and gas phase (Ca) concentrations, accounting for H. Total propagated variance [F (F)] is the 2

linear combination of the weighted contribution of the variances (F ) of the mass transfer 2

coefficient, H, and measured concentrations. The FH term is assumed equal to zero because H is

a constant and under any singular condition there is no random error (deviations in estimated H

values from their true values are systematic, not random errors). To estimate the overall random

error in the flux calculation, measurement precision was estimated to be 10%, based upon

repeated sample injections. While the total analytical uncertainly is likely greater than 10%, the

overall propagated error in the flux is relatively insensitive to the error in the concentration term

(see below). Uncertainty in KOL was determined by propagating random errors in the air- and

water-side transfer velocities, which here we assume to be 40% based on inspection of k versus w

wind speed plots in Wanninkhof et al. (1990). Using these estimated errors, we calculate the

overall random error of a typical instantaneous gas exchange flux as ca. 40%, with a majority of

the uncertainty arising from KOL. As a specific example, the flux of fluorene into Site 1 on 8

March 1993 is 413 ± 139 ng/m -day (Nelson et al., 1998), with 88% of the random error due to 2

uncertainty in KOL, and 11% and <1% of the error due to uncertainty in the measured gas phase

and dissolved concentrations, respectively. Propagation of error demonstrates that the significant

improvements in estimating gas exchange fluxes will require better understanding of the mass

transfer process itself rather than improved characterization of the concentration gradients.

Significant sources of possible systematic errors include improper quantification of the

concentration gradient due to including colloidally bound contaminants in the ‘dissolved’ phase

measurement, underestimations of the wind effects on K , and using inaccurate values of H. OL

Henry’s Law constants of organic compounds increase with salinity due to an increase in the

aqueous activity coefficient. Based on their review of studies that compared H values measured

in freshwater and seawater, Staudinger and Roberts (1996) concluded that these constants

increase at most six-fold but more commonly two- to four-fold in seawater, with the effect of

salinity more pronounced for larger molecules. The salinity of the Chesapeake Bay surface

waters ranged from 0‰ in the north to 27‰ in the south during this study, suggesting that H

values may have increased 2-3 fold from north to south. Due to the lack of compound-specific

H-salinity relationships, we could not make this correction in our calculations.

LOADING ESTIMATES

Bay-wide atmospheric deposition loading estimates are summarized in Table 3.4. Here
Atmospheric Deposition Loadings

3-8

we divide the Bay’s surface waters below the fall-lines into sub-regions to be consistent with the

1994 TLRI. Bay-wide regional background fluxes were calculated by linear averaging all

available data from non-urban sites. Urban fluxes were estimated as multiples of the regional

background fluxes as described above and detailed in Table 3.3. Bay-wide loads equal the

average annual fluxes multiplied by the surface area of each sub-region, with the total below fallline area equal to 1.15 x 10 m .

10 2

CORRELATION WITH 1994 TOXICS LOADING AND RELEASE INVENTORY

Estimates of total annual, Bay-wide atmospheric deposition loads of metals are very

similar between the 1994 and 1998 TLRIs, with arsenic, cadmium, chromium, copper, lead and

zinc all within ±20% (Table 3.6). These differences are well within the uncertainty of the

loadings estimates. The agreement between the two reports reflects a common source of the wet

deposition data (CBADS) and a consistent modeling of the dry aerosol deposition flux. Note that

we have assumed a conservative two-fold enhanced metals deposition in urban areas. If studies

currently underway document a larger enrichment, the metals loadings will increase from the

1998 TLRI values.

Estimates of organic contaminant deposition loadings are dramatically different between

the 1994 and 1998 TLRIs (Table 3.6), reflecting the large number of recent studies. The two

main differences between the two reports is the inclusion of gas exchange fluxes in 1998 and the

reduction of the dry aerosol deposition velocity from 0.49 to 0.2 cm/sec. The estimated

fluoranthene loading was similar between the two reports (635 and 595 kg/year), as including net

gas exchange was offset by lower aerosol deposition estimates. Net gas exchange flux represents

90% of the total fluoranthene load from the atmosphere. In contrast, loadings estimates of

benz[a]anthracene, chrysene, and benzo[a]pyrene all decrease by 70-80% between the two

inventories. These decreases result from the reduction in dry aerosol deposition attributed to the

lower deposition velocity and from the volatilization of these PAHs from surface waters adjacent

to urban areas. The somewhat paradoxical result of lower atmospheric loading estimates when

urban influences are considered is explained by the increased contaminant inventory in the water

column (resulting in enhanced volatilization).

The largest difference between the 1994 and 1998 estimates is for total polychlorinated

biphenyls (t-PCBs). The 1994 estimate only considered wet and dry aerosol deposition, both

advective processes resulting in net deposition. The 1998 estimate not only updates these

estimates, but now considers the role of gas exchange. As shown by Nelson et al. (1998), the

Chesapeake Bay surface waters are supersaturated with dissolved PCBs relative to the overlying

atmosphere, resulting in large volatilization fluxes. Our best estimates are that the Chesapeake

Bay is currently out-gassing 400 kg PCB/year, which is more than an order of magnitude more

than the wet and dry aerosol deposition combined. In fact, volatilization appears to be the

dominant loss process for PCBs from the estuary, and may control the overall removal of PCBs

(and perhaps other organochlorines) from this system.
3-9

RECOMMENDATIONS

In order to further improve upon these estimates of atmospheric deposition loadings, the

following information is required:

< Improved Estimates of Atmospheric Deposition to Water Surfaces

C Measure meteorological and chemical parameters at an array of stationary sites

located in the mainstem of the Chesapeake Bay in order to get true over-water

measurements.

C Establish and maintain atmospheric deposition monitoring sites along gradients

within the major urban areas of the Bay (Baltimore, Washington, Norfolk).

C Conduct intensive sampling campaigns in urban and agricultural areas during

contrasting wet and dry periods.

C Continue to monitor atmospheric deposition at one or more of the regional CBADS

sites to document longer term trends.

C Characterize the spatial and temporal distribution of atmospheric stability and airwater interface turbulence for improved gas exchange and dry aerosol deposition

estimates.

C Measure chemical-specific aerosol size distributions in urban and rural atmospheres

adjacent to the Bay to better character dry aerosol deposition. This might be done in

collaboration with USEPA’s PM monitoring programs. 2.5

C Refine regional scale atmospheric transport models for use as ‘interpolators’ of

measured deposition fluxes.

< Improved estimates of atmospheric deposition to the watershed. Neither the 1994 or

1998 TLRIs attempted to estimate atmospheric deposition loadings to the watershed of

the Bay. Determining the atmospheric component of the ‘fall-line loads’ of contaminants

remains an important unresolved question, and data should be obtained so that the next

TLRI can include initial estimates.

C Establish and maintain at least one monitoring station in each representative

watershed (agricultural, forested, urban) to measure the deposition of specific

chemical contaminants.

C Conduct intensive studies at the watershed scale to determine retention of deposited

atmospheric chemicals by watersheds of differing land uses (similar to the Bear

Branch study; Church et al., 1998).

C Conduct atmospheric deposition studies in concert with ‘fall-lines’ monitoring studies

in order to estimate the atmospheric component of the fall-line chemical contaminant

loads.

C Investigate contaminant inventories in the soils and vegetation of the Bay’s watershed

in order to estimate the ‘storage’ of atmospherically-derived chemicals.

C Develop watershed-scale models of atmospheric transport, deposition, and retention,

perhaps building on the CBPO nutrient watershed model.
3-10

Table 3.1. Data Sources for 1998 Atmospheric Deposition Estimates.

Chemical Dates Location Wet Aerosol Exchange Reference

Dry Gas

PAHs July 1990 - Sept. 1993 Wye, Elms, Haven Beach X X Baker et al., 1997

PCBs July 1990 - Sept. 1993 Wye, Elms, Haven Beach X X Baker et al., 1997

Metals July 1990 - Sept. 1993 Wye, Elms, Haven Beach X X Baker et al., 1997

PAHs March, April, June, and Mainstem Chesapeake X Nelson et al., 1998

September 1993

PAHs August 1995, June 1996; Patapsco River and northern X Bamford et al., 1999b

February and July 1997 Chesapeake Bay

PCBs March, April, June, and Mainstem Chesapeake X Nelson et al., 1998

September 1993

Chloropyrifos March, April, June, and Mainstem Chesapeake X X X McConnell et al., 1997

September 1993

PAHs Jan. 1994 - June 1995 Southern - Western Shore X Gustafson and Dickhut,

1997

Mercury Sept. 1995 - Sept. 1996 Hart-Miller Island, X Mason et al., 1997

Stillpond, Kent County MD

Mercury May 1995 - Present Chesapeake Biological X

Laboratory, Solomons

Agrochemicals April - June 1995 Patuxent River X X Harman, 1996
Atmospheric Deposition Loadings

3-11

Table 3.2. Surface Water Segments Below the Fall Lines Used to Calculate Atmospheric Deposition

Loads (From 1994 Chesapeake Bay Basin Toxics Loading and Release Inventory).

Basin Area (10 m ) Urban

Surface Water Percent

6 2

Mainstem Bay 7466 10%

Susquehanna 14 10%

West Chesapeake 435 10%

Patuxent 278 10%

Potomac 1216 10%

Rappahannock 452 10%

York 262 10%

James 681 10%

Eastern Shore 694 10%

TOTAL 11498
3-12

Table 3.3. Average Annual Atmospheric Deposition Fluxes (Fg/m2-year) to the Chesapeake Bay.

Wet Deposition Dry Aerosol Deposition Gas Exchange Total Deposition (1) (2) (3)

Regional Urban Regional Urban Regional Urban Regional Urban

Aluminum 11,500 23,000 107,000 214,000 none none 118,500 237,000

Arsenic 54 108 100 200 none none 154 308

Cadmium 62 124 26 52 none none 88 176

Chromium 100 200 200 400 none none 300 600

Copper 370 740 340 680 none none 710 1,420

Iron 10,500 21,000 58,500 117,000 none none 69,000 138,000

Manganese 1,050 2,100 1,200 2,400 none none 2,250 4,500

Nickel 330 660 570 1,140 none none 900 1,800

Lead 450 900 710 1,420 none none 1,160 2,320

Selenium 110 220 260 520 none none 370 740

Zinc 1,500 3,000 2,100 4,200 none none 3,600 7,200

Fluorene 1.2 4.8 0.3 1.4 33 -200 35 -194

Phenanthrene 4.8 19.2 2.7 10.8 250 220 258 250

Anthracene 0.5 2.1 0.2 0.8 11 -36 12 -33

Fluoranthene 5.1 20.4 3.1 12.4 59 -120 67 -87

Pyrene 5.0 20.0 2.9 11.6 31 -130 39 -98

Benz[a]anthracene 0.9 3.6 1.0 3.8 -0 ca.0 1 7

Chrysene 2.2 8.8 2.4 9.6 3 -2 7 16

Benzo[b]fluoranthane 2.6 10.4 2.7 10.8 ca.0 ca.0 5 21

Benzo[k]fluoranthene 1.6 6.4 1.8 7.2 ca.0 ca.0 3 14

Benzo[e]pryene 2.0 8.0 1.9 7.6 ca.0 ca.0 4 19

Benzo[a]pyrene 1.3 5.2 1.0 4.0 ca.0 ca.0 2 9

Indeno[123cd]perylene 1.5 6.0 2.0 8.0 ca.0 ca.0 4 14

Dibenz[a,h]anthracene 0.5 2.1 0.4 1.7 ca.0 ca.0 1 4

Benzo[ghi]perylene 1.4 5.6 1.5 6.0 ca.0 ca.0 3 12

Total PCBs 0.8 8.3 0.8 8.0 -35 -35 -33 16

Mercury 13 24 3 5 -10 -10 6 29 (4)

Chlorpyrifos 2.80 2.80 0.13 0.13 -0.48 -0.48 2.5 2.5

Metolachlor 40.3 40.3 1.90 1.90 0.27 0.27 42.5 4215
3-13

Footnote

a) No urban metal deposition data are currently available; assume urban =2x regional as conservative estimate.

b) Dry aerosol deposition fluxes calculated from measured ambient aerosol concentrations, using 0.2 cm/sec deposition velocity for organics, 0.26 cm/sec for non-crustal metals, and 1.4 cm/sec for

crustal metals).

c) PCB dry aerosol deposition flux calculated from the measured gaseous PCB concentrations and the Junge-Pankow sorption model (see Baker et al., 1997).

d) Urban wet and dry aerosol deposition of organics based on Offenberg and Baker, 1999; assuming 4x and 10x increase in PAH and PCB wet deposition, respectively, and 4x and 10x increase in PCB

and PAH concentrations in the urban atmosphere, respectively.

References

(1) Metals in wet and dry aerosol deposition: Baker et al., 1997 (average of data from 3 CBADS sites June 1990 - September 1993).

(2) Organics in wet and dry aerosol deposition: Baker et al., 1997 (average of data from 3 CBADS sites June 1990 - September 1993. NB: organics deposition velocity changed from 0.49 to 0.2 cm/sec

to reflect refined estimates (see Wu et al., 1992).

(3) Organics gas exchange : Nelson et al., 1998, average of 7 mainstem sites during 4 cruises in 1993; Bamford et al., 1999; average of several consecutive daily transects in the Patapsco River system

during June 1996, and February and July 1997.

(4) Mercury: Mason et al., 1997, urban data from Hart-Miller Island; regional from CBL).
3-14

Table 3.4a. Wet Deposition Loads (kg/year) to the Chesapeake Bay Below the Fall-Lines.

Mainstem Susquehanna Chesapeake Patuxent Potomac Rappahannock York James Shore Total

West Eastern

Surface Area (m^2) 7.5E+09 1.4E+07 4.4E+08 2.8E+08 1.2E+09 4.5E+08 6.8E+08 6.8E+08 6.9E+08 1.1E+010

Percent Urban 10% 10% 10% 10% 10% 10% 10% 10% 10%

Aluminum 94,400 180 5,500 3,500 15,400 5,700 3,300 8,600 8,800 145,400

Arsenic 400 1 26 17 72 27 16 40 41 700

Cadmium 500 1 30 19 83 31 18 46 47 800

Chromium 800 2 48 31 130 50 29 75 76 1,300

Copper 3,000 6 180 100 500 180 100 300 300 4,700

Iron 86,200 160 5,000 3,200 14,000 5,200 3,000 7,900 8,000 132,800

Manganese 8,600 16 500 300 1,400 520 300 800 800 13,000

Nickel 2,710 5 160 100 440 160 95 250 250 4,200

Lead 3,700 7 200 140 600 200 130 300 3300 5,700

Selenium 900 2 53 34 150 55 32 82 84 1,4000

Zinc 12,300 23 700 460 2,000 700 430 1,100 1,100 19,000

Fluorene 11.6 0.02 0.7 0.4 1.9 0.7 0.4 1.1 1.1 17.9

Phenanthrene 46.6 0.09 2.7 1.7 7.6 2.8 1.6 4.2 4.3 71.7

Anthracene 5.1 0.01 0.3 0.2 0.8 0.3 0.2 0.5 0.5 7.9

Fluoranthene 49.5 0.09 2.9 1.8 8.1 3.0 1.7 4.5 4.6 76.2

Pyrene 48.5 0.09 2.8 1.8 7.9 2.9 1.7 4.4 4.5 74.7

Benz[a]anthracene 8.7 0.02 0.5 0.3 1.4 0.5 0.3 0.8 0.8 13.5

Chrysene 21.4 0.04 1.2 0.8 3.5 1.3 0.7 1.9 2.0 32.9

Benzo[b]fluoranthane 25.2 0.05 1.5 0.9 4.1 1.5 0.9 2.3 2.3 38.9

Benzo[k]fluoranthene 15.5 0.03 0.9 0.6 2.5 0.9 0.5 1.4 1.4 23.9

Benzo[e]pryene 19.4 0.04 1.1 0.7 3.2 1.2 0.7 1.8 1.8 29.9

Benzo[a]pyrene 12.6 0.02 0.7 0.5 2.1 0.8 0.4 1.2 1.2 19.4

Indeno[123cd]perylene 14.6 0.03 0.8 0.5 2.4 0.9 0.5 1.3 1.4 22.4

Dibenz[a,h]anthracene 5.1 0.01 0.3 0.2 0.8 0.3 0.2 0.5 0.5 7.9

Benzo[ghi]perylene 13.6 0.03 0.8 0.5 2.2 0.8 0.5 1.2 1.3 20.9

Total PCBs 11.8 0.02 0.7 0.4 1.9 0.7 0.4 1.1 1.1. 18.1

Mercury 105.3 0.20 6.1 3.9 17.1 6.4 3.7 9.6 9.8 162.1

Chloropyrifos 20.9 0.04 1.2 0.8 3.4 1.3 0.7 1.9 1.9 32.2

Metolachlor 300.9 0.56 17.5 11.2 49.0 18.2 10.6 27.4 28.0 463.4
3-15

Table 3.4b. Dry Aerosol Deposition Loads (kg/year) to the Chesapeake Bay Below the Fall-Lines.

Mainstem Susquehanna Patuxent Potomac Rappahannock Total

West Eastern

Chesapeake York James Shore

Surface Area (m^2) 7.5E+09 1.4E+07 4.4EE+08 2.8E+08 1.2E+09 4.5E+08 6.8E+08 6.8E+08 6.9E+08 1.1E+010

Percent Urban 10% 10% 10% 10% 10% 10% 10% 10% 10%

Aluminum 878,700 1,600 51,200 32,700 143,100 53,200 30,800 80,200 81,700 1,350,000

Arsenic 800 2 48 31 130 50 29 75 76 1,300

Cadmium 200 0 12 8 35 13 7 19 20 330

Chromium 1,600 3 96 61 270 99 58 150 150 2,500

Copper 2,800 5 160 100 460 170 98 260 260 4,300

Iron 480,400 900 28,000 17,900 78,300 29,100 16,860 43,800 44,700 740,000

Manganese 9,900 18 600 370 1,600 600 350 900 900 15,200

Nickel 4,700 9 300 170 770 280 160 420 430 7,200

Lead 5,800 11 300 200 950 350 200 530 540 8,900

Selenium 2,100 4 100 80 350 130 75 200 200 3,300

Zinc 17,200 32 1,000 640 2,800 1,000 600 1,600 1,600 26,600

Fluorene 3.3 0.01 0.2 0.1 0.5 0.2 0.1 0.3 0.3 5.1

Phenanthrene 26.2 0.05 1.5 1.0 4.3 1.6 0.9 2.4 2.4 40.4

Anthracene 1.9 0.00 0.1 0.1 0.3 0.1 0.1 0.2 0.2 3.0

Fluoranthene 30.1 0.06 1.8 1.1 4.9 1.8 1.1 2.7 2.8 46.3

Pyrene 28.1 0.05 1.6 1.0 4.6 1.7 1.0 2.6 2./6 43.3

Benz[a]anthracene 9.2 0.02 0.5 0.3 1.5 0.6 0.3 0.8 0.9 14.2

Chrysene 23.3 0.04 1.4 0.9 3.8 1.4 0.8 2.1 2.2 35.9

Benzo[b]fluoranthane 26.2 0.05 1.5 1.0 4.3 1.6 0.9 2.4 2.4 40.4

Benzo[k]fluoranthene 17.5 0.03 1.0 0.7 2.8 1.1 0.6 1.6 1.6 26.9

Benzo[e]pryene 18.4 0.03 1.1 0.7 3.0 1.1 0.6 1.7 1.7 28.4

Benzo[a]pyrene 9.7 0.02 0.6 0.4 1.6 0.6 0.3 0.9 0.9 14.9

Indeno[123cd]perylene 19.4 0.04 1.1 0.7 3.2 1.2 0.7 1.8 1.8 29.9

Dibenz[a,h]anthracene 4.1 0.01 0.2 0.2 0.7 0.2 0.1 0.4 0.4 6.3

Benzo[ghi]perylene 14.6 0.03 0.8 0.5 2.4 0.9 0.5 1.3 1.4 22.4

Total PCBs 11.3 0.02 0.7 0.4 1.8 0.7 0.4 1.0 1.1 17.5

Mercury 21.1 0.04 1.2 0.8 3.4 1.3 0.7 1.9 2.0 32.4

Chloropyrifos 1.0 0.002 0.06 0.04 0.16 0.06 0.03 0.09 0.09 1.5

Metolachlor 14.2 0.027 0.83 0.53 2.31 0.86 0.50 1.29 1.32 21.8

]
3-16

Table 3.4c. Net Gas Exchange Deposition Loads (kg/year) to the Chesapeake Bay Below the Fall-Lines (negative=atmosphere is net sink).

Mainstem Susquehanna Chesapeake Patuxent Potomac Rappahannock York James Shore Total

West Eastern

Surface Area (m^2) 7.5E+009 1.4E+007 4.4EE+008 2.8E+008 1.2E+009 4.5E+008 6.8E+008 6.8E+008 6.9E+008 1.1E+010

Percent Urban 10% 10% 10% 10% 10% 10% 10% 10% 10%

Aluminum 0 0 0 0 0 0 0 0 0 0

Arsenic 0 0 0 0 0 0 0 0 0 0

Cadmium 0 0 0 0 0 0 0 0 0 0

Chromium 0 0 0 0 0 0 0 0 0 0

Copper 0 0 0 0 0 0 0 0 0 0

Iron 0 0 0 0 0 0 0 0 0 0

Manganese 0 0 0 0 0 0 0 0 0 0

Nickel 0 0 0 0 0 0 0 0 0 0

Lead 0 0 0 0 0 0 0 0 0 0

Selenium 0 0 0 0 0 0 0 0 0 0

Zinc 0 0 0 0 0 0 0 0 0 0

Fluorene 72 0.1 4 3 12 4 3 7 7 100

Phenanthrene 1,800 3.5 110 69 300 100 65 170 180 2,800

Anthracene 47 0.1 3 2 8 3 2 4 4 72

Fluoranthene 307 0.6 18 11 50 19 11 28 29 500

Pyrene 100 0.2 6 4 18 7 4 10 10 180

Benz[a]anthracene -3 -0.0 -0 -1 -0 09 -0 -0 -0 -4

Chrysene 15 0.0 1 1 2 1 1 1 1 24

Benzo[b]fluoranthane 0 0.0 0 0 0 0 0 0 0 0

Benzo[k]fluoranthene 0 0.0 0 0 0 0 0 0 0 0

Benzo[e]pryene 0 0.0 0 0 0 0 0 0 0 0

Benzo[a]pyrene 0 0.0 0 0 0 0 0 0 0 0

Indeno[123cd]perylene 0 0.0 0 0 0 0 0 0 0 0

Dibenz[a,h]anthracene 0 0.0 0 0 0 0 0 0 0 0

Benzo[ghi]perylene 0 0.0 0 0 0 0 0 0 0 0

Total PCBs -261 -0.5 -15 -10 -43 -16 -9 -24 -24 -402

Mercury -75 -0.1 -4 -3 -12 -5 -3 -7 -7 -115

Chloropyrifos -3.6 -0.01 -0.21 -0.13 -0.58 -0.22 -0.13 -0.33 -0.33 -5.5

Metolachlor 2.0 0.00 0.12 0.08 0.33 0.12 0.07 0.18 0.19 3.1
3-17

Table 3.4d. Total Atmospheric Deposition Loads (kg/year) to the Chesapeake Bay Below the Fall-Lines.

Mainstem Susquehanna Chesapeake Patuxent Potomac Rappahannock York James Shore Total

West Eastern

Surface Area (m^2) 7.5E+09 1.4E+07 4.4EE+08 2.8E+08 1.2E+09 4.5E+08 6.8E+08 6.8E+08 6.9E+08 1.1E+010

Percent Urban 10% 10% 10% 10% 10% 10% 10% 10% 10%

Aluminum 973,200 1,800 56,700 36,200 158,500 58,900 34,200 88,800 90,500 1,499,000

Arsenic 1,300 2 74 47 200 77 44 110 100 2,000

Cadmium 700 1 42 27 100 44 25 66 67 1,100

Chromium 2,500 5 140 92 400 150 86 200 200 4,800

Copper 5,900 11 340 200 950 350 200 500 500 9,000

Iron 566,700 1,100 33,000 21,100 92,300 34,300 19,900 51,700 52,700 873,000

Manganese 18,500 35 1,080 700 3,010 1,100 650 1,700 1,800 28,500

Nickel 7,400 14 430 300 1,200 450 300 700 700 11,400

Lead 9,500 18 600 400 1,600 600 300 900 900 14,700

Selenium 3,000 6 200 110 500 200 100 3000 300 4,700

Zinc 29,600 55 1,800 1,100 4,800 1,800 1,000 2,700 2,700 45,500

Fluorene 87.4 0.16 5.1 3.3 14.2 5.3 3.1 8.0 8.1 135

Phenanthrene 1,916.9 3.59 111.7 71.4 312.2 116.1 67.3 174.8 178.2 2950

Anthracene 54.1 0.10 3.2 2.0 8.8 3.3 1.9 4.9 5.0 83

Fluoranthene 386.4 0.72 22.5 14.4 62.9 23.4 13.6 35.2 35.9 595

Pyrene 187.9 0.35 10.9 7.0 30.6 11.4 6.6 17.1 17.5 289

Benz[a]anthracene 15.3 0.03 0.9 0.6 2.5 0.9 0.5 1.4 1.4 24

Chrysene 60.0 0.11 3.5 2.2 9.8 3.6 2.1 5.5 5.6 92

Benzo[b]fluoranthane 51.4 0.10 3.0 1.9 8.4 3.1 1.8 4.7 4.8 79

Benzo[k]fluoranthene 33.0 0.06 1.9 1.2 5.4 2.0 1.2 3.0 3.1 51

Benzo[e]pryene 37.9 0.07 2.2 1.4 6.2 2.3 1.3 3.5 3.5 58

Benzo[a]pyrene 22.3 0.04 1.3 0.8 3.6 1.4 0.8 2.0 2.1 34

Indeno[123cd]perylene 34.0 0.06 2.0 1.3 5.5 2.1 1.2 3.1 3.2 52

Dibenz[a,h]anthracene 9.2 0.02 0.5 0.3 1.5 0.6 0.3 0.8 0.9 14

Benzo[ghi]perylene 28.1 0.05 1.6 1.0 4.6 1.7 1.0 2.6 2.6 43

Total PCBs -238.2 -0.45 -13.9 -8.9 -38.8 -14.4 -8.4 -21.7 -22.1 -367

Mercury 51.7 0.10 3.0 1.9 8.4 3.1 1.8 4.7 4.8 80

Chloropyrifos 18 0.0 1.1 0.7 3.0 1.1 0.6 1.7 1.7 28

Metolachlor 317 0.6 18.5 11.8 51.6 19.2 11.1 28.9 29.5 490
Atmospheric Deposition Loadings

3-18

Table 3.5. Influence of Urban Areas on Atmospheric Deposition Loadings (kg/y) to the Chesapeake Bay.

Percent Urban

0% 5% 10% 20% 30%

Aluminum 1,363,000 1,430,000 1,499,000 1,635,000 1,770,000

Arsenic 1,800 1,900 2,000 2,100 2,300

Cadmium 1,000 1,100 1,100 1,200 1,300

Chromium 3,400 3,600 3,800 4,100 4,500

Copper 8,200 8,600 9,000 9,800 10,600

Iron 793,000 833,000 873,000 952,000 1,030,000

Manganese 25,900 27,200 28,500 31,000 33,700

Nickel 10,300 10,900 11,400 12,400 13,400

Lead 13,300 14,000 14,700 16,000 17,300

Selenium 4,300 4,500 4,700 5,100 5,500

Zinc 41,400 43,500 45,500 49,700 53,800

Fluorene 400 300 100 -128 -391

Phenanthrene 3000 3000 3000 3000 3000

Anthracene 100 100 83 32 -20

Fluoranthene 800 700 600 400 240

Pyrene 400 400 300 100 -26

Benz[a]anthracene 17 20 24 30 37

Chrysene 82 87 92 100 114

Benzo[b]fluoranthane 61 70 79 98 116

Benzo[k]fluoranthene 39 45 51 63 74

Benzo[e]pryene 45 52 58 72 85

Benzo[a]pyrene 26 30 34 42 50

Indeno[123cd]perylene 40 46 52 64 76

Dibenz[a,h]anthracene 11 13 14 17 21

Benzo[ghi]perylene 33 38 43 53 63

Total PCBs -384 -375 -367 -350 -333

Mercury 64 72 80 95 110

Chloropyrifos 28 28 28 28 28

Metolachlor 488 488 488 488 488
3-19

Table 3.6. Comparison of 1994 and 1998 TLRI Atmospheric Deposition Loadings.

1994 1998 Difference Main Cause of Difference

%

Arsenic 1,800 2,000 13% Difference less than uncertainty in loading estimate

Cadmium 1,200 1,100 -9% Difference less than uncertainty in loading estimate

Chromium 3,400 3,800 12% Difference less than uncertainty in loading estimate

Copper 10,900 9,000 -18% Difference less than uncertainty in loading estimate

Lead 14,500 14,700 1% Difference less than uncertainty in loading estimate

Zinc 41,300 45,500 10% Difference less than uncertainty in loading estimate

Fluoranthene 600 600 -6% Difference less than uncertainty in loading estimate

Benz[a]anthracene 100 24 -83% Decreased deposition velocity; Including gas exchange

Chrysene 300 92 -71% Decreased deposition velocity; Including gas exchange

Benzo[a]pyrene 100 34 -73% Decreased deposition velocity; Including gas exchange

Total PCBs 59 -367 -722% Including gas exchange
4-1

CHAPTER 4 - Shipping and Boating Loadings

Roland Steiner

Interstate Commission on the Potomac River Basin

6110 Executive Boulevard, Suite 300

Rockville, MD 20852-3903

INTRODUCTION

The tidal waters of the Bay and its tributaries support a wide variety of commercial,

recreational and military activities. Toxic substances are associated with these activities as

cargo; consumable products such as fuel, lubricants, paints, antifreeze; and by-products such as

contaminated bilge water, sewage, and dredge spoil. These materials can reach the tidal waters

by accidental and/or intentional discharges from water craft, land based facilities adjacent to the

water, and aircraft accidents. This section provides analyses and summary of the reported spills

of this nature. 

The intention of this analysis is to update the material for the 1980 to 1989 period

presented in the Shipping and Boating Loadings chapter of the 1994 edition of the Chesapeake

Bay Basinwide Toxics Loading and Release Inventory (1994 TLRI). This work provides spill

loadings below the fall line in order to supplement the toxics loading information developed

from the fall line monitoring program. Upstream spills may be accounted for in monitoring at

the fall line. The greatest quantities of materials spilled during the 1990 to 1996 period were of

petroleum based products: fuels, lubricants, and asphalt. These products are on and near the Bay

in large quantities as cargo and as consumables. Information with respect to materials and

quantities spilled is collected and maintained by several agencies, notably the US Coast Guard

and the US Environmental Protection Agency.

TEMPORAL AND SPATIAL COVERAGE

Spill data for calendar years 1990 through 1996 were obtained from several information

management agencies. This period extends the 1980 to 1989 period covered in the 1994 edition

of the TLRI for shipping and boating loadings. The data were initially screened for location to

include the tidal waters of the Bay and adjacent land by state, county, and city. The data for the

land based spills were further refined to include only those which were from stationary facilities

or mobile sources to tidal waters (below the fall line).

METHODOLOGY

The loads of toxic materials included in this section of the inventory were derived from

data provided by the Emergency Response Notification System (ERNS) which is managed by the

US EPA, and the US Coast Guard Marine Safety Information System (MSIS). The ERNS
Shipping and Boating Loadings

4-2

maintains a computer database containing information on release notifications of oil and

hazardous substances that have occurred throughout the United States and have been reported to

the National Response Center, the ten US EPA Regions, or the US Coast Guard. Some data on

file with the US Coast Guard appeared not to be included in the ERNS database; therefore,

similar information requests were made to both organizations for completeness. These data

include spills associated with cargo and by-products from commercial, recreational and military

activities.

Data were also requested and received from the relevant regional offices of the Virginia

Department of Environmental Quality, Virginia Department of Emergency Services, and

Maryland Department of the Environment. The data from these agencies were examined and

found to lack key information for this analysis, or were not compatible with each other or the

ERNS or MSIS data; therefore, they are not included in the inventory. However, there is likely

considerable overlap between the incidents contained in the state agency databases and those in

the ERNS and MSIS due to common reporting requirements.

The data requests to the data management agencies sought information concerning:

material spilled, quantity of spill, quantity recovered, units of measurement, restricted location to

tidal counties and independent cities around the Chesapeake Bay, whether to water or not,

address of spill, whether from a water vessel or land based facility or aircraft accident, date

restricted to 1990 through 1996, time of day, and notes or comments. A list of Chesapeake Bay

tidal counties and independent cities was provided as part of the data request. The raw data

which were received consisted of 5,647 records from ENRS and 4,109 records from MSIS

containing various information parameters for each spill incident. The major analytical tasks

included developing specific and consistent location, material, and quantity information.

Locational analysis was by far the most difficult task. The objective was to provide

information on only those spills which were directly to tidal waters (or indirectly by runoff from

adjacent land based facilities). No parameters existed in the data sets which would allow such

sorting entirely by computer methods. The location information available from the data

management agencies included: state, and/or county, and/or city, and/or street address, and/or

receiving water body. The data were sorted successively by each of the stated classes of location

information, and those records that were not potentially in the tidal Chesapeake region were

discarded. The information provided for some spills was insufficient to determine if the spill

directly reached tidal waters, and those record were discarded. The last locational task was to

assign a Chesapeake Bay basin watershed designation individually to each record; however, this

task was performed only after all other data sorting and reduction tasks were completed.

The ERNS and MSIS data sets differed from each other in the number and order of 

parameters recorded. Within and between the data sets there were inconsistencies in the way

substances were reported, e.g. fuel-diesel, oil-diesel, fuel oil-diesel, diesel oil, and diesel fuel. In

computer based sorting, different names for the same materials all appeared as different
Shipping and Boating Loadings

4-3

substances, and were combined manually. Nevertheless, some potentially similar materials are

listed in the inventory as separate substances, e.g. Oil with PCBs 5ppm, and Polychlorinated

Biphenyls.

The presentation of quantities of materials spilled and their units of measurement was

another challenge for consistency. Spills recorded in tons, pounds, barrels, gallons, liters, quarts,

pints, and cups were converted to pounds and gallons. 

After discarding duplicate, irrelevant, and incomplete records, 4,736 remained to be

assigned to one of the nine major drainage basins in the Chesapeake Bay region. When this task

was complete, the quantities of each of the resulting 154 substances were summed and divided

by seven to convert to annual loads for each of the major drainage basins.

UNCERTAINTY

The origination of the information accessed for this inventory and the analyses conducted

to present it in its current form involved uncertainty at multiple steps. There were opportunities

for both systematic and random errors to enter the process. The major attributes of concern

where uncertainty in the recorded data may arise involve location of spill, identification of

substance, and estimation of quantity spilled. There is also almost total uncertainty associated

with sources of toxics to the Bay which are not part of the recorded information analyzed for this

inventory, but which represent toxics released as a result of normal activities such as fuel

combustion by-products and leached wood preservatives and anitfoulant paints.

During the analyses of data for this inventory, the data were discarded if the location

information associated with a spill record was insufficient to allow the assignment of a Bay

region major drainage basin. It was clear from the raw data that there was a large number of

compound and duplicate entries. The compound entries, which included multiple substances

spilled in a single incident, were disaggregated such that each substance constituted a separate

record. Duplicate entries originated from the combining of data from two sources and from

multiple entries in the same data bases. Obvious duplicates were eliminated by examination after

sorting the records by date, time of day, location, substance, and quantity information.

Illegal discharges are likely to be reported only if they are observed by another party. 

Those that are recorded in the ERNS and MSIS data bases often have only the sketchiest of

information with respect to substance identification and quantity spilled. Another systematic

source of uncertainty arises from the purpose for which the data bases are created and

maintained, as distinguished from this inventory. Both the ERNS and MSIS exist to assist

agencies to respond to environmental emergencies and account for their activities; whereas, this

inventory is created to identify the most accurate information on toxics loadings to identify and

reduce their impacts on the living resources in the Bay. The recorded quantities of materials

spilled were likely based on estimates in most cases, especially where no source could be
Shipping and Boating Loadings

4-4

identified. Some records included an estimate of the quantity of spilled material which was

subsequently recovered. The records of quantity recovered refer to substance spilled, and do not

include associated water which may also have been picked up in the recovery process. Where

this information was given, the data were adjusted to present the net spill for this inventory. 

There is uncertainty with regard to this issue, because most records are based on initial

notification of a spill in order to fulfill the requirements of the responding organization and are

not necessarily up-dated with information concerning recovery operations conducted after spill

information was first recorded. 

DISCUSSION

In total, many thousands of pounds of pollutants were spilled or discharged to the tidal

waters of the Chesapeake Bay and its tributaries during the period 1990 through 1996. In

particular, 154 substances were reported spilled in 4,736 recorded incidents.

A number of the recorded discharges contained chemicals on the Chesapeake Bay Toxics

of Concern and Chemicals of Potential Concern lists. Those materials and recorded average

annual amounts discharged to each major Chesapeake Bay drainage basins are presented in Table

4.2.

The analysis of all the data show that many substances were spilled in relatively small

amounts. However, a significant number were spilled in relatively large amounts (see Table 4.3). 

Those with average annual spills in excess of 1,000 pounds or 1,000 gallons include: ammonium

sulfate, asphalt, corrosive water, cyclohexanone, jet fuel, gasoline, diesel oil, other heavier fuel

and lubricating oils, unknown and waste oily substances, polychlorinated biphenyls, sulfuric acid,

and industrial waste water.

With regard to geographical distribution, a significant amount of spilled materials were

discharged to the mainstem of the Bay. However, several of the tidal tributaries received the

bulk of the spills. In particular, the tidal James River (including its tidal tributaries in the vicinity

of Hampton Roads) received the largest quantities in many categories of substances. These

appeared to be mainly associated with the large naval and air force installations in the region. 

The West Chesapeake Basin which includes the port and industrial areas in the Baltimore region

also received a large number of spills of many substances. The least amounts of materials were

spilled in the tidal areas of the Rappahannock River and Susquehanna River.

Although even small spills of toxic and hazardous substances are required by law to be

reported to emergency management agencies, it is a fair assumption that an unknown--and

potentially large--number of such spills never do get reported. Other systematic unrecorded

sources of toxics loadings to the Bay involve the leaching of preservatives and antifoulants. 

Creosote and/or arsenic compounds are present in most wood products which are used for

exposed applications in or near tidal waters. Some of these preservative materials eventually
Shipping and Boating Loadings

4-5

leach into the Bay. There are also large numbers of commercial and recreational water craft on

the Bay and its tidal tributaries; and it can be assumed that most of these vessels use antifoulant

hull paints containing tin or copper which leach over time into the Bay. In addition, water craft

fuel combustion by-products and expended lubricants are delivered directly to tidal waters

through exhaust ports and propeller shaft bearings in the course of normal boating and shipping

activities. And, in spite of pump-out facilities and regulations to the contrary, it must be assumed

that some sewage generated on-board with associated deodorizers and treatment chemicals gets

discharged to tidal waters from commercial and recreational water craft.

CORRELATION WITH 1994 TOXICS LOADING AND RELEASE INVENTORY

Both the present work and the Shipping and Boating Loadings section of the 1994 TLRI

estimated spill loadings to Chesapeake Bay and its tidal tributaries by accessing the US Coast

Guard MSIS data base. However, there are significant differences in methodology between this

analysis and those of the 1994 TLRI. 

In this analysis, data from the MSIS were supplemented by data from the US EPA ERNS

data base. Also in this work, where information existed with regard to recovery of spilled

material, that information was used to develop net spilled quantities. Net spilled quantities were

not calculated and reported in the 1994 TLRI. Where spill location information was missing,

vague, or clearly indicated a spill inland or one to the Atlantic side of the Delmarva Peninsula,

the records were discarded in this work. Location screening for the 1994 TLRI was on a coarser

scale, resulting in some reported spills likely not entering the Bay’s tidal waters.

With regard to substances spilled and their distribution among the major drainage basins

of the Bay, the results of the present work show strong similarities to the 1994 TLRI.

RECOMMENDATIONS

With regard to federal, state, and regional data bases, it is understandable that there is

some desire for development, use, and maintenance at each level of government. However, all

information should periodically be consolidated in one national data base for wider coverage on a

consistent basis. For ease of future analysis, there should be an effort to harmonize reported

information and its quality.

In so far as possible, spill attributes and their values or identifiers should be selected from

predetermined lists in order to avoid problems of inconsistency such as multiple names for the

same substance being entered in different records and the occurrence of spelling errors in the data

bases.

In order to develop a more complete mass balance of toxic pollutants delivered directly to

the tidal waters of the Bay and its tributaries, estimates of systematic pollution from the “normal”
Shipping and Boating Loadings

4-6

use of products, as distinct from spills, should be conducted. Such products and usages include

wood preservatives, antifoulant coatings, marine fuel combustion by-products, etc.

Toxic materials are incorporated in compounds and products with uncertain and

unreported concentrations; therefore, it is hard to combine information on spills with the results

of monitoring programs which identify specific elements and compounds in measured

concentrations. Some work to establish concentrations of toxic elements and compounds of

concern in commonly spilled substances would assist in the combining of spill data with

monitoring results.

A specific universal system (e.g., latitude/longitude) of spill location should be

incorporated into recorder information for ease of analysis and graphical representation.
Shipping and Boating Loadings

4-7

Table 4.1. Chemicals Selected for the 1996 Chesapeake Bay Toxics of Concern List, the Chemicals of

Potential Concern List, and Delisted Chemicals.

Toxics of Concern List Chemicals of Potential

Concern

Chemicals Removed

Current

List (1990)

Proposed

Revised List

Current

List (1990)

Proposed

Revised List

From Toxics

of Concern

List

From Chemicals

of Potential

Concern List

Alachlor Alachlor

Aldrin Aldrin

Arsenic Arsenic

Atrazine Atrazine

Benz[a]anthracene Other PAHs1

Benzo[a]pyrene 1

Cadmium Cadmium

Chlordane Chlordane

Chromium Chromium

Chrysene Chrysene

Copper Copper

Dieldrin Dieldrin

Diflubenzuron3

Fenvalerate Fenvalerate

Fluoranthene Fluoranthene

Lead Lead

Mercury Mercury

Metolachlor Metolachlor

Naphthalene Naphthalene

Nickel

Permethrin Permethrin

Phenanthrene

PCBs Arochlor 1260 Other PCBs2

Pyrene

Tributyltin (TBT) Tributyltin (TBT)

Toxaphene Toxaphene

Zinc Zinc

Bold indicates new additions to the Toxics of Concern and Chemicals of Potential Concern Lists.

1 Other PAHs include: benzo[b]fluoranthene, benz[a]anthracene, benzo[a]pyrene, benzo[e]pyrene, acenaphthene, dibenzo[a,h]anthracene,

fluorene, 2-methyl naphthalene, pyrene, benzo[g,h,i]perylene, ideno[1,2,3,cd]pyrene. Note that benzo[a]pyrene and benz[a]anthracene

were previously listed as Toxics of Concern.

2 Other PCBs include: PCB cogeners 126 and 169, PCB Arochlors 1016, 1232, 1242, 1248, pentachlorobiphenyls, tetrachlorobiphenyls,

and polychlorinated biphenyl.

3 Diflubenzuron was removed from the Chemicals of Potential Concern List in 1992 with the approval of the Toxics Subcommittee.
4-8

Table 4.2a. Spills of Toxic Materials Containing Chemicals on the Chesapeake Bay Toxics of Concern and Chemicals

of Potential Concern Lists. 

From Ships and Land Facilities to the Chesapeake Bay and Its Tidal Tributaries

(Average annual spill loadings: 1990-1996) Ranked alphabetically by substance

ToC/CoPC* Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

ARSENIC TRIOXIDE 2 GAL 10.0 0.0 10.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

CADMIUM SULFATE 2 LBS 0.3 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0

CHROMIC ANHYDRIDE 2 GAL 185.7 0.0 185.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0

CHROMIC ANHYDRIDE 2 LBS 1.1 0.0 1.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0

COPPER, SOFT 1 GAL 0.7 0.0 0.0 0.0 0.0 0.0 0.7 0.0 0.0 0.0

LEAD NITRATE 1 LBS 5.6 0.0 0.0 0.0 5.6 0.0 0.0 0.0 0.0 0.0

LEAD SULFATE 1 LBS 8.0 0.0 0.0 0.0 0.0 0.0 0.0 5.9 0.0 2.1

NAPTHALENE (MOLTEN) 1 GAL 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1

OIL WITH PCB'S 5PPM 2 GAL 0.3 0.0 0.0 0.0 0.3 0.0 0.0 0.0 0.0 0.0

POLYCHLORINATED

BIPHENYLS

2 GAL 1245.9 0.0 4.3 0.0 1235.9 0.0 0.0 5.7 0.0 0.0

ZINC ORTHOPHOSPHATE 2 GAL 114.3 0.0 0.0 0.0 0.0 0.0 0.0 114.3 0.0 0.0

*1 Material Containing Chemical on the Chesapeake Bay Toxics of Concern List (Rev. March 6, 1997)

 2 Material Containing Chemical on the Chesapeake Bay Chemicals of Potential Concern List (Rev. March 6, 1997)
4-9

Table 4.2b. Spills of Toxic Materials Containing Chemicals on the Chesapeake Bay Toxics of Concern and Chemicals

of Potential Concern Lists. 

From Ships and Land Facilities to the Chesapeake Bay and Its Tidal Tributaries

(Average annual spill loadings: 1990-1996) Ranked by Annual Total Loading

ToC/CoPC* Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

POLYCHLORINATED

BIPHENYLS

2 GAL 1245.9 0.0 4.3 0.0 1235.9 0.0 0.0 5.7 0.0 0.0

CHROMIC ANHYDRIDE 2 GAL 185.7 0.0 185.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0

ZINC ORTHOPHOSPHATE 2 GAL 114.3 0.0 0.0 0.0 0.0 0.0 0.0 114.3 0.0 0.0

ARSENIC TRIOXIDE 2 GAL 10.0 0.0 10.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

LEAD SULFATE 1 LBS 8.0 0.0 0.0 0.0 0.0 0.0 0.0 5.9 0.0 2.1

LEAD NITRATE 1 LBS 5.6 0.0 0.0 0.0 5.6 0.0 0.0 0.0 0.0 0.0

CHROMIC ANHYDRIDE 2 LBS 1.1 0.0 1.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0

COPPER, SOFT 1 GAL 0.7 0.0 0.0 0.0 0.0 0.0 0.7 0.0 0.0 0.0

OIL WITH PCB'S 5PPM 2 GAL 0.3 0.0 0.0 0.0 0.3 0.0 0.0 0.0 0.0 0.0

CADMIUM SULFATE 2 LBS 0.3 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0

NAPTHALENE (MOLTEN) 1 GAL 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1

*1 Material Containing Chemical on the Chesapeake Bay Toxics of Concern List (Rev. March 6, 1997)

 2 Material Containing Chemical on the Chesapeake Bay Chemicals of Potential Concern List (Rev. March 6, 1997)
4-10

Table 4.2c. Spills of Toxic Materials Containing Chemicals on the Chesapeake Bay Toxics of Concern and Chemicals

of Potential Concern Lists. 

From Ships and Land Facilities to the Chesapeake Bay and Its Tidal Tributaries

(Average annual spill loadings: 1990-1996) Ranked alphabetically by substance

ToC/CoPC* Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

ARSENIC TRIOXIDE 2 GAL 10.0 0.0 10.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

CADMIUM SULFATE 1 LBS 0.3 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0

CHROMIC ANHYDRIDE 1 GAL 185.7 0.0 185.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0

CHROMIC ANHYDRIDE 1 LBS 1.1 0.0 1.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0

COPPER, SOFT 1 GAL 0.7 0.0 0.0 0.0 0.0 0.0 0.7 0.0 0.0 0.0

LEAD NITRATE 1 LBS 5.6 0.0 0.0 0.0 5.6 0.0 0.0 0.0 0.0 0.0

LEAD SULFATE 1 LBS 8.0 0.0 0.0 0.0 0.0 0.0 0.0 5.9 0.0 2.1

NAPTHALENE (MOLTEN) 1 GAL 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1

OIL WITH PCB'S 5PPM 1 GAL 0.3 0.0 0.0 0.0 0.3 0.0 0.0 0.0 0.0 0.0

POLYCHLORINATED

BIPHENYLS

1 GAL 1245.9 0.0 4.3 0.0 1235.9 0.0 0.0 5.7 0.0 0.0

ZINC ORTHOPHOSPHATE 2 GAL 114.3 0.0 0.0 0.0 0.0 0.0 0.0 114.3 0.0 0.0

*1 Material Containing Chemical on the Chesapeake Bay Toxics of Concern List (1990)

 2 Material Containing Chemical on the Chesapeake Bay Chemicals of Potential Concern List (1990)
4-11

Table 4.2d. Spills of Toxic Materials Containing Chemicals on the Chesapeake Bay Toxics of Concern and Chemicals

of Potential Concern Lists. 

From Ships and Land Facilities to the Chesapeake Bay and Its Tidal Tributaries

(Average annual spill loadings: 1990-1996) Ranked by Annual Total Loading

ToC/CoPC* Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

POLYCHLORINATED

BIPHENYLS

1 GAL 1245.9 0.0 4.3 0.0 1235.9 0.0 0.0 5.7 0.0 0.0

CHROMIC ANHYDRIDE 1 GAL 185.7 0.0 185.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0

ZINC ORTHOPHOSPHATE 2 GAL 114.3 0.0 0.0 0.0 0.0 0.0 0.0 114.3 0.0 0.0

ARSENIC TRIOXIDE 2 GAL 10.0 0.0 10.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

LEAD SULFATE 1 LBS 8.0 0.0 0.0 0.0 0.0 0.0 0.0 5.9 0.0 2.1

LEAD NITRATE 1 LBS 5.6 0.0 0.0 0.0 5.6 0.0 0.0 0.0 0.0 0.0

CHROMIC ANHYDRIDE 1 LBS 1.1 0.0 1.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0

COPPER, SOFT 1 GAL 0.7 0.0 0.0 0.0 0.0 0.0 0.7 0.0 0.0 0.0

CADMIUM SULFATE 1 LBS 0.3 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0

OIL WITH PCB'S 5PPM 1 GAL 0.3 0.0 0.0 0.0 0.3 0.0 0.0 0.0 0.0 0.0

NAPTHALENE (MOLTEN) 1 GAL 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1

*1 Material Containing Chemical on the Chesapeake Bay Toxics of Concern List (1990)

 2 Material Containing Chemical on the Chesapeake Bay Chemicals of Potential Concern List (1990)
4-12

Table 4.3a. Spills of Toxic Materials from Ships and Land Facilities to the Chesapeake Bay and Its Tidal Tributaries.

(Average annual spill loadings: 1990-1996)

 Ranked by Annual Total Loading

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

AMMONIUM SULFATE LBS 467714.3 467714.3

OIL, MISC: LUBRICATING GAL 23362.6 2.9 256.1 0.4 4.6 19.4 23063.1 4.7 11.3

OIL, DIESEL GAL 10792.4 8.9 924.0 25.1 142.1 107.1 90.4 7778.7 156.0 1560.0

CORROSIVE WATER PH LEVEL 11.5 GAL 10000.0 10000.0

FUEL, JET: JP-5 GAL 7030.1 69.0 94.3 4.1 6559.3 303.4

OIL, FUEL: NO. 2-D GAL 6642.7 489.9 2.6 183.4 4.3 1860.1 4038.6 45.9 18.0

ASPHALT GAL 4705.7 4705.7

OIL, FUEL: NO. 4 GAL 4593.7 496.3 58.9 4038.6

WASTE WATER, INDUSTRIAL GAL 4591.0 176.0 4415.0

OIL, UNKNOWN GAL 3374.4 697.9 0.3 113.6 4.7 22.9 2452.0 35.7 47.4

OIL, WASTE GAL 3339.0 1557.0 0.6 3.0 12.4 1610.3 82.3 73.4

CYCLOHEXANONE LBS 3244.3 3244.3

OIL, FUEL: NO. 2 GAL 3003.0 41.4 623.3 15.4 679.7 0.7 108.1 1310.1 68.0 156.1

SULFURIC ACID GAL 2525.1 71.4 10.7 28.6 1271.4 1143.0

OIL, FUEL: NO. 6 GAL 1673.7 426.3 39.4 7.1 0.1 440.4 702.4 57.9

POLYCHLORINATED BIPHENYLS GAL 1245.9 4.3 1235.9 5.7

UNKNOWN GAL 1037.1 48.4 1.1 3.3 975.6 6.6 2.1

CORROSION INHIBITOR/MICR IN

WATER

 GAL 900.0 900.0

GASOLINE, AUTOMOTIVE

(UNLEADED)

 GAL 744.6 21.4 40.3 0.1 32.4 0.9 49.3 15.0 585.1

GASOLINE, AUTOMOTIVE (4.23G

PB/G

 GAL 627.6 3.3 186.3 1.1 60.6 2.9 31.3 202.7 26.4 113.0

FERRIC ACID GAL 571.4 571.4

CAPROLACTAM SOLUTION LBS 479.0 479.0

AMMONIA, ANHYDROUS LBS 478.6 428.6 50.0

OIL, FUEL GAL 467.6 2.1 28.6 436.9

SEWAGE GAL 461.7 172.9 271.3 10.4 7.1

CHLORINE SOLUTION GAL 457.1 457.1
4-13

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

OIL, CRUDE GAL 436.4 130.1 0.3 300.3 5.7

SULFURIC ACID LBS 389.3 389.3

OIL, WASH GAL 378.9 350.3 28.6

CORROSION INHIBITOR LBS 358.4 358.4

CAPROLACTAM SOLUTION GAL 357.1 357.1

CYCLOHEXANONE GAL 357.1 357.1

OIL, FUEL: NO. 5 GAL 353.1 353.1

COAL DUST LBS 318.6 12.3 304.9 1.4

PHOSPHATE, ORGANIC GAL 271.4 271.4

AQUEOUS FIRE FIGHTING FOAM GAL 262.1 247.9 14.3

OIL, HYDRAULIC GAL 257.7 0.7 2.7 8.7 2.7 216.6 16.7 9.6

SODIUM HYDROXIDE LBS 242.9 242.9

CHROMIC ANHYDRIDE GAL 185.7 185.7

SODIUM HYDROXIDE GAL 179.3 12.9 166.4

FERRIC CHLORIDE GAL 151.4 7.9 143.6

ETHYLENE GLYCOL GAL 132.9 45.0 57.1 0.1 8.1 22.4

FUEL, JET: JP-4 GAL 128.7 107.9 20.9

RESIN, AMBERLITE IR-122 GAL 128.6 128.6

TCLP ASH OR KO44 WASTE LBS 120.0 120.0

ZINC ORTHOPHOSPHATE GAL 114.3 114.3

KEROSENE GAL 109.7 43.4 2.3 9.7 54.3

OIL, MISC: MOTOR GAL 101.7 24.9 0.4 2.9 0.3 70.0 1.9 1.4

PESTICIDE GAL 71.4 71.4

DISTILLATES: FLASHED FEED

STOCKS

 GAL 71.4 71.4

ALKYLATE GAL 71.4 71.4

FLY ASH LBS 71.4 71.4

DYE GAL 64.3 0.7 60.0 3.6

OIL, MISC: TRANSFORMER GAL 57.9 2.1 15.1 32.9 2.9 3.1 1.7

OIL, MISC: BUNKER C GAL 51.0 51.0

ETHYLENE GLYCOL LBS 50.4 50.4
4-14

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

FUEL, ROCKET LBS 49.7 49.7

COSTIC SODA SOLUTION GAL 43.0 42.9 0.1

NITROGEN, LIQUEFIED GAL 42.9 42.9

BILGE WATER WITH RESIDUAL OIL GAL 38.6 7.7 0.4 30.4

OIL, FUEL: F-76 GAL 35.9 35.9

BATTERY, ATON LBS 32.1 2.1 30.0

PAINT, OIL BASED GAL 28.9 2.1 2.4 7.1 16.6 0.6

OIL, MISC: PETROLEUM DISTILLATE GAL 28.6 28.6

GASOLINE GAL 24.6 20.0 3.6 .0.7 0.3

OIL, FUEL: INTERMEDIATE (IFO 180) GAL 22.6 9.7 12.9

ASPHALT BLENDING STOCKS:

ROOFERS FLUX

 GAL 21.4 21.4

FUEL, JET: JP-8 GAL 20.1 0.1 15.0 5.0

OIL, FUEL: NO. 1-D GAL 19.1 0.4 6.1 1.4 11.1

PARRAFIN/OLEFIN WAX/ NONREGULATED/NON-HAZARD GAL 19.0 4.3 0.3 13.4 1.0

HYDROCHLORIC ACID GAL 16.1 14.3 1.9

FUEL, MARINE DIESEL GAL 16.0 1.4 14.6

OIL, FUEL: NO. 1 GAL 15.9 12.9 0.1 2.9

POLLEN LBS 15.7 15.7

2-2 BUTOXY ETHOXI LBS 15.0 15.0

POTASSIUM HYDROXIDE GAL 14.3 14.3

LATEX, LIQUID NATURAL GAL 12.9 11.4 1.4

DETERGENT/DEGREASER GAL 12.1 0.3 6.7 2.9 2.3

TAR BALLS GAL 10.6 0.1 5.1 5.3

HYDROGEN PEROXIDE GAL 10.0 10.0

ARSENIC TRIOXIDE GAL 10.0 10.0

OIL, HOME HEATING GAL 10.0 5.7 4.3

OIL, MISC: MINERAL GAL 8.6 5.0 3.6

PRESERVATIVE GAL 8.1 8.1

LEAD SULFATE LBS 8.0 5.9 2.1
4-15

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

COSMOLINE GAL 7.9 0.1 7.7

ALUMINUM CHLORIDE LIQUOR LBS 7.4 7.4

GASOLINE, AVIATION (4.86 G

PB/GAL)

 GAL 7.3 7.1 0.1

OIL, DECANTED GAL 7.3 0.1 7.1

OIL, COAL TAR GAL 7.1 7.1

OIL, MISC: TURBINE GAL 6.0 0.3 5.7

PAINT, MISC. GAL 5.9 2.9 1.4 1.6

LEAD NITRATE LBS 5.6 5.6

OIL, LIGHT GAL 5.4 0.1 0.3 5.0

DICHLOROMONOFLUOROMETHANE GAL 5.3 4.6 0.7

PAINT THINNER GAL 5.1 5.1

OIL, TRANSMISSION GAL 5.1 0.6 4.6

OIL, COOKING GAL 5.0 0.7 4.3

ETHO CHLORO HYDRINE GAL 4.6 4.6

OIL, HEAT TRANSFER -MOBIL

THERM 60

 GAL 4.3 4.3

OIL, FUEL: IF 30 GRADE SHIP GAL 4.3 4.3

ASPHALT BLENDING STOCKS:

STRAIGHT RUN RESIDUE

 GAL 4.1 3.6 0.6

OIL, MISC: ROAD GAL 3.7 3.7

PAINT CHIPS GAL 3.6 3.6

POLYVINYL ACETATE EMULSION GAL 3.6 3.6

OIL, FUEL: NAVY STANDARD GAL 3.6 3.6

GASOLINE, AROMATIC GAL 3.6 3.6

PAINT, EPOXY GAL 3.1 2.7 0.4

OIL, THERMAL GAL 2.9 2.9

PETROLATUM GAL 2.3 0.1 2.1

CARBARYL SOLUTION

(INSECTICIDE)

 GAL 2.1 2.1

FERTILIZER GAL 2.1 2.1
4-16

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

CHLORINE SOLUTION LBS 1.7 1.7

PAINT, LATEX GAL 1.6 1.6

OIL, EMULSIFIED GAL 1.4 1.4

SOAP GAL 1.4 1.4

G BASE GAL 1.4 1.4

DFM GAL 1.4 1.4

OIL, BLACK GAL 1.4 1.4

OIL, GAS: DESULFURIZED GAL 1.4 1.4

CHROMIC ANHYDRIDE LBS 1.1 1.1

OIL, EDIBLE: FISH GAL 1.0 1.0

FLOCOAT GAL 0.9 0.9

OIL, EDIBLE: SOYA BEAN GAL 0.9 0.9

OIL, EDIBLE: VEGETABLE GAL 0.9 0.3 0.6

GASOLINE BLENDING STOCKS:

ALKYLATES

 GAL 0.7 0.7

OIL, FUEL: NAVY SPECIAL GAL 0.7 0.7

OIL, FUEL: INTERMEDIATE 380

INNERMIX

 GAL 0.7 0.7

RC250 GAL 0.7 0.7

COPPER, SOFT GAL 0.7 0.7

TURPENTINE GAL 0.7 0.7

CREOSOTE (COAL TAR) GAL 0.7 0.7

OIL, TERRESTIC GAL 0.6 0.6

PHENOL LBS 0.6 0.6

BUTYL CARBITOL LBS 0.6 0.6

HYDRAZINE GAL 0.4 0.4

OIL, MISC: SPRAY GAL 0.3 0.1 0.1

ANTI-FREEZE GAL 0.3 0.3

DREDGE SPOILS GAL 0.3 0.3

GREASE, MISC. GAL 0.3 0.3

OIL, MISC: RESIN GAL 0.3 0.1 0.1
4-17

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

CADMIUM SULFATE LBS 0.3 0.3

OIL WITH PCB'S 5PPM GAL 0.3 0.3

OIL, GAS: CRACKED GAL 0.3 0.3

PETROLEUM PRODUCT GAL 0.3 0.3

METRO SPERSE #269 GAL 0.1 0.1

MTBE, GAS ADDITIVE GAL 0.1 0.1

NAPTHALENE (MOLTEN) GAL 0.1 0.1

LATEX, SYNTHETIC LBS 0.1 0.1

OIL, EDIBLE: WALNUT GAL 0.1 0.1

CARBON LBS 0.1 0.1

HYDROFLUORIC ACID GAL 0.1 0.1

OIL, GAS GAL 0.1 0.1

OIL, MISC: SPINDLE GAL 0.1 0.1

SOOT GAL 0.1 0.1

ALUMINUM SULFATE GAL 0.1 0.1

METHYL CHLORIDE GAL 0.1 0.1

PHOSPHORIC SOLUTION < RQ GAL 0.1 0.1

OIL, MISC: RANGE GAL 0.1 0.1
4-18

Table 4.3b. Spills of Toxic Materials from Ships and Land Facilities to the Chesapeake Bay and Its Tidal Tributaries.

(Average annual spill loadings: 1990-1996)

 Ranked alphabetically by substance

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

2-2 BUTOXY ETHOXI LBS 15.0 15.0

ALKYLATE GAL 71.4 71.4

ALUMINUM CHLORIDE LIQUOR LBS 7.4 7.4

ALUMINUM SULFATE GAL 0.1 0.1

AMMONIA, ANHYDROUS LBS 478.6 428.6 50.0

AMMONIUM SULFATE LBS 467714.3 467714.3

ANTI-FREEZE GAL 0.3 0.3

AQUEOUS FIRE FIGHTING FOAM GAL 262.1 247.9 14.3

ARSENIC TRIOXIDE GAL 10.0 10.0

ASPHALT GAL 4705.7 4705.7

ASPHALT BLENDING STOCKS:

ROOFERS FLUX

 GAL 21.4 21.4

ASPHALT BLENDING STOCKS:

STRAIGHT RUN RESIDUE

 GAL 4.1 3.6 0.6

BATTERY, ATON LBS 32.1 2.1 30.0

BILGE WATER WITH RESIDUAL OIL GAL 38.6 7.7 0.4 30.4

BUTYL CARBITOL LBS 0.6 0.6

CADMIUM SULFATE LBS 0.3 0.3

CAPROLACTAM SOLUTION GAL 357.1 357.1

CAPROLACTAM SOLUTION LBS 479.0 479.0

CARBARYL SOLUTION

(INSECTICIDE)

 GAL 2.1 2.1

CARBON LBS 0.1 0.1

CHLORINE SOLUTION GAL 457.1 457.1

CHLORINE SOLUTION LBS 1.7 1.7

CHROMIC ANHYDRIDE GAL 185.7 185.7

CHROMIC ANHYDRIDE LBS 1.1 1.1

COAL DUST LBS 318.6 12.3 304.9 1.4
4-19

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

COPPER, SOFT GAL 0.7 0.7

CORROSION INHIBITOR LBS 358.4 358.4

CORROSION INHIBITOR/MICR IN

WATER

 GAL 900.0 900.0

CORROSIVE WATER PH LEVEL 11.5 GAL 10000.0 10000.0

COSMOLINE GAL 7.9 0.1 7.7

COSTIC SODA SOLUTION GAL 43.0 42.9 0.1

CREOSOTE (COAL TAR) GAL 0.7 0.7

CYCLOHEXANONE GAL 357.1 357.1

CYCLOHEXANONE LBS 3244.3 3244.3

DETERGENT/DEGREASER GAL 12.1 0.3 6.7 2.9 2.3

DFM GAL 1.4 1.4

DICHLOROMONOFLUOROMETHANE GAL 5.3 4.6 0.7

DISTILLATES: FLASHED FEED

STOCKS

 GAL 71.4 71.4

DREDGE SPOILS GAL 0.3 0.3

DYE GAL 64.3 0.7 60.0 3.6

ETHO CHLORO HYDRINE GAL 4.6 4.6

ETHYLENE GLYCOL GAL 132.9 45.0 57.1 0.1 8.1 22.4

ETHYLENE GLYCOL LBS 50.4 50.4

FERRIC ACID GAL 571.4 571.4

FERRIC CHLORIDE GAL 151.4 7.9 143.6

FERTILIZER GAL 2.1 2.1

FLOCOAT GAL 0.9 0.9

FLY ASH LBS 71.4 71.4

FUEL, JET: JP-4 GAL 128.7 107.9 20.9

FUEL, JET: JP-5 GAL 7030.1 69.0 94.3 4.1 6559.3 303.4

FUEL, JET: JP-8 GAL 20.1 0.1 15.0 5.0

FUEL, MARINE DIESEL GAL 16.0 1.4 14.6

FUEL, ROCKET LBS 49.7 49.7

G BASE GAL 1.4 1.4
4-20

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

GASOLINE GAL 24.6 20.0 3.6 0.7 0.3

GASOLINE BLENDING STOCKS:

ALKYLATES

 GAL 0.7 0.7

GASOLINE, AROMATIC GAL 3.6 3.6

GASOLINE, AVIATION (4.86 G

PB/GAL)

 GAL 7.3 7.1 0.1

GASOLINE, AUTOMOTIVE (4.23G

PB/G

 GAL 627.6 3.3 186.3 1.1 60.6 2.9 31.3 202.7 26.4 113.0

GASOLINE, AUTOMOTIVE

(UNLEADED)

 GAL 744.6 21.4 40.3 0.1 32.4 0.9 49.3 15.0 585.1

GREASE, MISC. GAL 0.3 0.3

HYDRAZINE GAL 0.4 0.4

HYDROCHLORIC ACID GAL 16.1 14.3 1.9

HYDROFLUORIC ACID GAL 0.1 0.1

HYDROGEN PEROXIDE GAL 10.0 10.0

KEROSENE GAL 109.7 43.4 2.3 9.7 54.3

LATEX, LIQUID NATURAL GAL 12.9 11.4 1.4

LATEX, SYNTHETIC LBS 0.1 0.1

LEAD NITRATE LBS 5.6 5.6

LEAD SULFATE LBS 8.0 5.9 2.1

METHYL CHLORIDE GAL 0.1 0.1

METRO SPERSE #269 GAL 0.1 0.1

MTBE, GAS ADDITIVE GAL 0.1 0.1

NAPTHALENE (MOLTEN) GAL 0.1 0.1

NITROGEN, LIQUEFIED GAL 42.9 42.9

OIL WITH PCB'S 5PPM GAL 0.3 0.3

OIL, BLACK GAL 1.4 1.4

OIL, COAL TAR GAL 7.1 7.1

OIL, COOKING GAL 5.0 0.7 4.3

OIL, CRUDE GAL 436.4 130.1 0.3 300.3 5.7

OIL, DECANTED GAL 7.3 0.1 7.1

OIL, DIESEL GAL 10792.4 8.9 924.0 25.1 142.1 107.1 90.4 7778.7 156.0 1560.0
4-21

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

OIL, EDIBLE: FISH GAL 1.0 1.0

OIL, EDIBLE: SOYA BEAN GAL 0.9 0.9

OIL, EDIBLE: VEGETABLE GAL 0.9 0.3 0.6

OIL, EDIBLE: WALNUT GAL 0.1 0.1

OIL, EMULSIFIED GAL 1.4 1.4

OIL, FUEL GAL 467.6 2.1 28.6 436.9

OIL, FUEL: F-76 GAL 35.9 35.9

OIL, FUEL: IF 30 GRADE SHIP GAL 4.3 4.3

OIL, FUEL: INTERMEDIATE (IFO 180) GAL 22.6 9.7 12.9

OIL, FUEL: INTERMEDIATE 380

INNERMIX

 GAL 0.7 0.7

OIL, FUEL: NAVY SPECIAL GAL 0.7 0.7

OIL, FUEL: NAVY STANDARD GAL 3.6 3.6

OIL, FUEL: NO. 1 GAL 15.9 12.9 0.1 2.9

OIL, FUEL: NO. 1-D GAL 19.1 0.4 6.1 1.4 11.1

OIL, FUEL: NO. 2 GAL 3003.0 41.4 623.3 15.4 679.7 0.7 108.1 1310.1 68.0 156.1

OIL, FUEL: NO. 2-D GAL 6642.7 489.9 2.6 183.4 4.3 1860.1 4038.6 45.9 18.0

OIL, FUEL: NO. 4 GAL 4593.7 496.3 58.9 4038.6

OIL, FUEL: NO. 5 GAL 353.1 353.1

OIL, FUEL: NO. 6 GAL 1673.7 426.3 39.4 7.1 0.1 440.4 702.4 57.9

OIL, GAS GAL 0.1 0.1

OIL, GAS: CRACKED GAL 0.3 0.3

OIL, GAS: DESULFURIZED GAL 1.4 1.4

OIL, HEAT TRANSFER -MOBIL

THERM 60

 GAL 4.3 4.3

OIL, HOME HEATING GAL 10.0 5.7 4.3

OIL, HYDRAULIC GAL 257.7 0.7 2.7 8.7 2.7 216.6 16.7 9.6

OIL, LIGHT GAL 5.4 0.1 0.3 5.0

OIL, MISC: BUNKER C GAL 51.0 51.0

OIL, MISC: LUBRICATING GAL 23362.6 2.9 256.1 0.4 4.6 19.4 23063.1 4.7 11.3

OIL, MISC: MINERAL GAL 8.6 5.0 3.6
4-22

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

OIL, MISC: MOTOR GAL 101.7 24.9 0.4 2.9 0.3 70.0 1.9 1.4

OIL, MISC: PETROLEUM DISTILLATE GAL 28.6 28.6

OIL, MISC: RANGE GAL 0.1 0.1

OIL, MISC: RESIN GAL 0.3 0.1 0.1

OIL, MISC: ROAD GAL 3.7 3.7

OIL, MISC: SPINDLE GAL 0.1 0.1

OIL, MISC: SPRAY GAL 0.3 0.1 0.1

OIL, MISC: TRANSFORMER GAL 57.9 2.1 15.1 32.9 2.9 3.1 1.7

OIL, MISC: TURBINE GAL 6.0 0.3 5.7

OIL, TERRESTIC GAL 0.6 0.6

OIL, THERMAL GAL 2.9 2.9

OIL, TRANSMISSION GAL 5.1 0.6 4.6

OIL, UNKNOWN GAL 3374.4 697.9 0.3 113.6 4.7 22.9 2452.0 35.7 47.4

OIL, WASH GAL 378.9 350.3 28.6

OIL, WASTE GAL 3339.0 1557.0 0.6 3.0 12.4 1610.3 82.3 73.4

PAINT CHIPS GAL 3.6 3.6

PAINT THINNER GAL 5.1 5.1

PAINT, EPOXY GAL 3.1 2.7 0.4

PAINT, LATEX GAL 1.6 1.6

PAINT, MISC. GAL 5.9 2.9 1.4 1.6

PAINT, OIL BASED GAL 28.9 2.1 2.4 7.1 16.6 0.6

PARRAFIN/OLEFIN WAX/ NONREGULATED/NON-HAZARD GAL 19.0 4.3 0.3 13.4 1.0

PESTICIDE GAL 71.4 71.4

PETROLATUM GAL 2.3 0.1 2.1

PETROLEUM PRODUCT GAL 0.3 0.3

PHENOL LBS 0.6 0.6

PHOSPHATE, ORGANIC GAL 271.4 271.4

PHOSPHORIC SOLUTION < RQ GAL 0.1 0.1

POLLEN LBS 15.7 15.7

POLYCHLORINATED BIPHENYLS GAL 1245.9 4.3 1235.9 5.7
4-23

Units An. Total Susqueh. W. Ches. Patuxent Potomac Rappah. York James E. Shore Mainstem

POLYVINYL ACETATE EMULSION GAL 3.6 3.6

POTASSIUM HYDROXIDE GAL 14.3 14.3

PRESERVATIVE GAL 8.1 8.1

RC250 GAL 0.7 0.7

RESIN, AMBERLITE IR-122 GAL 128.6 128.6

SEWAGE GAL 461.7 172.9 271.3 10.4 7.1

SOAP GAL 1.4 1.4

SODIUM HYDROXIDE GAL 179.3 12.9 166.4

SODIUM HYDROXIDE LBS 242.9 242.9

SOOT GAL 0.1 0.1

SULFURIC ACID GAL 2525.1 71.4 10.7 28.6 1271.4 1143.0

SULFURIC ACID LBS 389.3 389.3

TAR BALLS GAL 10.6 0.1 5.1 5.3

TCLP ASH OR KO44 WASTE LBS 120.0 120.0

TURPENTINE GAL 0.7 0.7

UNKNOWN GAL 1037.1 48.4 1.1 3.3 975.6 6.6 2.1

WASTE WATER, INDUSTRIAL GAL 4591.0 176.0 4415.0

ZINC ORTHOPHOSPHATE GAL 114.3 114.3
5-1

CHAPTER 5 - Acid Mine Drainage Loadings

Michael Ziegenfuss

Patrick Center for Environmental Research

The Academy of Natural Sciences of Philadelphia

1900 Benjamin Franklin Parkway

Philadelphia, PA 19103-1195

INTRODUCTION

Land use activities in the Chesapeake Bay watershed are diverse and contribute significantly

to water quality. Because of the long history of coal mining in the upper reaches of the Chesapeake

Bay watershed, much concern has been generated regarding the impact of acid drainage from

abandoned coal mines. It is believed that active mines are not a significant source of contaminants

to the Bay since they are permitted, controlled, and treatment programs are in place. The U.S.

Environmental Protection Agency has singled out acid drainage from abandoned coal mines as the

number one water quality problem in Appalachia. The 1994 Chesapeake Bay Basinwide Toxics

Reduction and Prevention Strategy calls for establishing more complete baseline loadings and source

identification for acid mine drainage and setting reduction targets to be achieved over the next

decade. The Toxics Subcommittee funded a literature synthesis to provide initial loadings estimate

for acid mine drainage and methodologies for remediation. The key loadings information from this

literature synthesis is summarized in this chapter. This is the first time that acid mine drainage

loadings have been reported in the Toxics Loadings and Release Inventory.

Acid mine drainage from abandoned coal mines has been considered the most severe and

extensive water pollution problem in western Maryland, West Virginia, and northeast, north central

and western Pennsylvania. Within the Chesapeake Bay Basin, drainage from abandoned coal mines

poses a significant threat to water quality in the Susquehanna, West Branch Susquehanna, and

Juniata River basins in Pennsylvania, as well as the North Branch Potomac River and its tributaries

in West Virginia and Maryland. 

Acid mine drainage (AMD) is formed when mining operations expose coal and bedrock high

in pyrite (iron-disulfide) to oxygen and moisture. The drainage is characterized by low pH (less than

6.0) and high concentrations of sulfates, acidity, and metals (dissolved/particulate) such as iron,

manganese and aluminum. Other principal elements of coal mine drainage include calcium,

magnesium, sodium and potassium (Clark, 1969). Additional trace metals that have been detected

in AMD in decreasing order of abundance are strontium, zinc, nickel, cobalt, lithium, barium, boron,

copper, lead and cadmium (Wood, 1996). 

Factors that affect the concentrations of AMD chemical constituents in coal mine drainage

are mineral content of the coal, overburden (material above the coal deposits), and associated host

rock; quantity of water flowing through the mine workings; residence time of water circulation in
Acid Mine Drainage Loadings

5-2

mine workings; the availability of oxygen and dissolved oxygen in the mine water; method of mining

(e.g., deep underground or surface mining); water removal from mines through pumping; and the

exposed surface area of pyritic minerals. 

Efforts to characterize AMD discharges must consider the common variability in flow and

quality. Drainage occurs through various entryways to the mine (e.g., tunnels, shafts, slopes and

drifts). Deep mine discharges in the Anthracite Region are less numerous than in the Bituminous

Field, but contribute a much higher acid loading per discharge. Surface or strip mines in both

Anthracite and Bituminous regions also contribute to AMD. Improperly graded strip pits can trap

surface runoff and form pools containing high concentrations of dissolved salts. During periods of

heavy rainfall, the strip mine pools may overflow and discharge acidic water into nearby streams.

Water trapped in the mine pits frequently emerges as seeps downslope from the mine site causing

pollution of receiving streams. Leachate from coal refuse piles associated with abandoned mine sites

are common sources of AMD. Refuse piles usually cover large areas and provide a source of

minerals for the formation of acid drainage. 

TEMPORAL AND SPATIAL COVERAGE

Chemical contaminant loadings from acid mine drainage are summarized from the following

sources: the Susquehanna River Basin (Anthracite Coal Region), West Branch Susquehanna and

Juniata River basins (Bituminous Coal Region) in Pennsylvania, and the North Branch Potomac

River and its tributaries (Bituminous Coal Region) in West Virginia and Maryland. Much of the

available data related to mine drainage was generated during early comprehensive investigations to

identify impacted watersheds and sources of mine acid for the purpose of determining appropriate

AMD abatement measures. These investigations, for the most part, are limited to acid, iron and

sulfate loading estimates and do not contain information on additional pollutants. Consequently,

there are insufficient data on other metals directly associated with mine drainage discharges to

estimate loads from data in these reports. 

METHODOLOGY

For the most part, models used to evaluate AMD loads in surface waters have been designed

to evaluate acid loading within a watershed for purposes of designing appropriate abatement

measures to mitigate the adverse impact of acidic conditions. The extensive evaluations of AMD

impacted watersheds conducted by engineering firms in the 1970's monitored all detectable sources

of mine drainage in a watershed for chemical constituents and discharge flow data. In order to define

the extent of AMD loads, it was necessary to determine the volume and chemical quality

(concentrations) of mine drainage at discharge points within the watershed. In-stream water samples

and flow measurements were obtained in addition to mine drainage discharge data to establish stream

quality. Data used for calculating loads were generally collected at regular intervals, usually

monthly, over the course of one year to evaluate loads during low, average, and high flow conditions.
Acid Mine Drainage Loadings

5-3

UNCERTAINTY

Much of the available data related to mine drainage was generated during comprehensive

investigations conducted in the early 1970's and 1980's to identify impacted watersheds and sources

of mine acid for the purpose of determining appropriate AMD abatement measures. Although these

previous investigations thoroughly identified sources of AMD and associated loads 25-30 years ago,

there is some uncertainty as to whether the historical data are currently applicable.

Estimating AMD loads from in-stream measurements downstream from all sources leads to

uncertainties as to what is attributable to mine discharges versus other point and non-point sources

of the chemical constituents. On the other hand, estimating loads by addition of individual

discharges also has uncertainties as to what proportion of the load is ultimately delivered

downstream. Biological and chemical processes in receiving streams alter chemical concentrations

in mine drainage subsequent to discharge from the AMD source. Iron and aluminum, as well as other

trace metals in mine drainage, commonly precipitate and coat stream beds and, through oxidativereductive reactions, sorb and desorb from particles in the receiving stream. These processes alter the

delivery of mine drainage constituents downstream. Data correlating AMD loads in upper reaches

of the Chesapeake Bay watershed with loadings of contaminants entering the Bay are lacking. 

DISCUSSION

Acid mine drainage from abandoned coal mines is thought to be the single greatest source

of pollution in the Susquehanna River Basin, West Branch Susquehanna River Subbasin and North

Branch Potomac River Subbasin. Acid mine drainage has impacted 1100 mi in 158 streams in the

Chesapeake Bay drainage area, as indicated in the 1996 Pennsylvania, Maryland and West Virginia

303(d) reports (Table 5.1). The causes cited for water quality degradation from AMD are, for the

most part, related to pH and/or metals. Most of the mines that once produced coal are now

abandoned, but continue to produce and discharge acid drainage. Acid mine drainage is characterized

by low pH and elevated levels of sulfates, acidity and metals such as iron, manganese and aluminum.

Although severe stream degradation from acid occurs within subwatersheds and segments of the

Susquehanna River, West Branch Susquehanna River and North Branch Potomac River, natural

alkaline reserves are capable of neutralizing all acid downstream from the coal regions. 
Acid Mine Drainage Loadings

5-4

Table 5.1. Streams in the Chesapeake drainage affected by acid mine drainage and miles impacted. Compiled

from Pennsylvania, West Virginia and Maryland 1996 303(d) lists.

Stream Name Miles Degraded

Upper Susquehanna River Subbasin

Tioga River 3

Morris Run 1

Fall Brook 2

Long Valley Run 1.6

Upper Central Susquehanna River Subbasin

Lackawanna River 2.6

Roaring Brook 4

Aylesworth Creek 0.5

Powderly Creek 1.9

Coal Brook 1.9

Wilson Creek 0.6

Susquehanna River 20

Newport Creek 4.8

Solomon Creek 2.4

Black Creek 4.3

Little Nescopeck Creek 9.1

Catawissa Creek 27.5

Tomhickon Creek 10.6

Sugarloaf Creek 5.5

Lower Susquehanna River Subbasin

Mahanoy Creek 52.2

Zerbe Run 5.8

Crab Run 1.3

Shenandoah Creek 5

Shamokin Creek 34.7

Carbon Run 3.7

Coal Run 3

Quaker Run 1.3

Locust Creek 1.6

North Branch Shamokin Cr. 4.6

Wiconisco Creek 16.2

Rattling Creek 2.2
Acid Mine Drainage Loadings

5-5

Table 5.1 (continued). Streams in the Chesapeake drainage affected by acid mine drainage and miles impacted.

Compiled from Pennsylvania, West Virginia and Maryland 1996 303(d) lists.

Stream Name Miles Degraded

(based on length of study segment)

Lower Susquehanna River Subbasin

West Branch Rattling Cr. 5.2

Doc Smith Run 1.5

Shale Run 0.8

East Branch Rattling Cr. 3.8

Stone Cabin Run 1.8

Nine O’Clock Run 0.6

Bear Creek 4.4

Pine Creek 6

Deep Creek 4.5

Hans Yost Creek 1

Rausch Creek 1.7

West Br. Rausch Cr. 3.5

East Br. Rausch Cr. 1.9

Swatara Creek 21.3

Baird Creek 1.4

West Branch Fishing Creek 3.6

Lower Rausch Creek 6.8

Lorberry Creek 1

Stumps Run 0.4

Middle Creek 17.5

Good Spring Creek 5.8

Poplar Creek 0.9

Coal Run 1.6

Gebhard Run 1.9

Panther Creek 1.7

Upper West Branch Susquehanna River Subbasin

Sinnemahoning Creek 15.8

Bennett Branch Sinnemahoning Cr. 66.6

Dents Run 6.5

Trout Run 1

Spring Run 1.7

West Creek 12
Acid Mine Drainage Loadings

5-6

Table 5.1 (continued). Streams in the Chesapeake drainage affected by acid mine drainage and miles

impacted. Compiled from Pennsylvania, West Virginia and Maryland 1996 303(d) lists.

Stream Name Miles Degraded

(based on length of study segment)

Upper West Branch Susquehanna River Subbasin (cont’d)

Montgomery Creek 2.6

West Branch Susquehanna River 79.7

Laurel Run 1

Woods Run 3

North Branch Montgomery Cr. 0.9

Tinker Run 0.7

Hartshorn Run 1

Anderson Creek 10.3

Kratzer Run 5.1

Irvin Branch 1.5

Little Anderson Cr. 5.7

Wilson Run 1

North Camp Run 1.4

Rock Run 3

Bear Run 2.9

South Branch Bear Run 3.3

Alder Run 0.7

Sandy Creek 2.8

Big Run 1

Deer Creek 5

Surveyor Run 4

Little Surveyor Run 2

Trout Run 5

Taylor Springs Run 0.4

Pine Run 2.2

Lick Run 3.7

Fork Run 3.8

Clearfield Creek 71.9

Sanbourne Run 2.2

North Branch Upper Morgan Run 2.7

Little Muddy Run 4.5
Acid Mine Drainage Loadings

5-7

Table 5.1 (continued). Streams in the Chesapeake drainage affected by acid mine drainage and miles

impacted. Compiled from Pennsylvania, West Virginia and Maryland 1996 303(d) lists.

Stream Name Miles Degraded

(based on length of study segment)

Upper West Branch Susquehanna River Subbasin (cont’d)

Dutch Run 1.3

Brubaker Run 2

Birch Island Run 6.2

Little Birch Island Run 4.3

Amos Branch 1.6

Upper West Branch Susquehanna River Subbasin

Sterling Run 9.7

Mosquito Creek 6

Curley’s Run 1.2

Grimes Run 2

Moshannon Creek 1

Black Moshannon Creek 26.2

Cold Stream 1

Laurel Run 1

Goss Run 0.5

Central West Branch Susquehanna River Subbasin

Pine Creek 4

Otter Run 3.8

Left Fork Otter Run 1.5

Right Fork Otter Run 0.4

Babb Creek 23

Wilson Creek 2.3

West branch Susquehanna R. 50.6

Lick Run 3.7

Tangascootack Creek 8.4

Drury Run (basin) 7.3

Stony Run 1.3

Woodley Draft Run 1.7

Sandy Run 1

Kettle Run 3

Two Mile Run 1.9
Acid Mine Drainage Loadings

5-8

Table 5.1 (continued). Streams in the Chesapeake drainage affected by acid mine drainage and miles

impacted. Compiled from Pennsylvania, West Virginia and Maryland 1996 303(d) lists.

Stream Name Miles Degraded

(based on length of study segment)

Central West Branch Susquehanna River Subbasin (cont’d)

Hidden Branch Two Mile Run 2.1

Cooks Run (basin) 6.8

Crowley Hollow 3.1

Camp Run 2

Rock Run 1.2

Beech Creek (basin) 26

Middle Branch Big Run 5.5

East Branch Big Run 2.4

Logway Run 0.8

Northfork Beech Creek 5.9

Lower West Branch Susquehanna River Subbasin

Red Run 13.4

West Branch Susquehanna R. 3

Upper Juniata River Subbasin

Bear Loop Run 0.8

Beaver Dam Branch 2.3

Sugar Run 6.3

Burgoon Run 3

Kittanning Run 4.2

Glenwhite Run 3.2

Shoup Run 4.7

Miller Run 1.4

Hartman Run 0.6

Six Mile Run 3.5

Sandy Run 2.9

Longs Run 2.5

Kimber Run 2.7
Acid Mine Drainage Loadings

5-9

Table 5.1 (continued). Streams in the Chesapeake drainage affected by acid mine drainage and miles

impacted. Compiled from Pennsylvania, West Virginia and Maryland 1996 303(d) lists.

North Branch Potomac River Subbasin

Gladdens Run 11.8

Stony River 24.5

North Branch Potomac River 50

Slaughterhouse Run 2.17

Montgomery Run 2.81

Piney Swamp Run 5.51

Abram Creek 18.5

Emory Run 2.25

Glade Run 3.04

Little Creek 0.68

Deakin Run 1.15

Wills Creek NA

Georges Creek NA

Savage River NA

Tables 5.2 - 5.4 summarize the cumulative acid mine drainage chemical contaminant loads

in the tributaries of the Susquehanna River, the West Branch Susquehanna River, and the North

Branch Potomac River. 

RECOMMENDATIONS

< Current water quality and discharge flow data are needed to support or revise the estimated

loads presented. Recent mine drainage discharge data for the Anthracite Coal Fields were

limited to a single sampling sweep of large discharges. Recent data for discharges in the

West Branch Susquehanna River were not available during the preparation of this literature

synthesis; however new data are being collected by watershed groups. When they become

available, these new data will provide improved estimates of contaminant loading from coal

mine drainage. 

< Additional studies are needed to evaluate the transport of AMD chemical constituents

(metals) from the upper reaches of the watershed to the Bay.

< Data correlating AMD loads in upper reaches of the Chesapeake Bay watershed with

loadings of contaminants entering the Bay are lacking. 
5-10

Table 5.2. Summary of cumulative acid mine drainage chemical constituent loads in the Susquehanna River tributaries draining the anthracite coal

fields in Pennsylvania. Loads are estimated as pounds per day (ppd) based on chemical concentration and flow (cfs).

Tributary Date Flow Condition Sulfates Iron Manganese Aluminum

Northern Anthracite Coal Field

Lackawanna River 1971-1972 156.4 Low 73,621 1,545

1971-1972 457.5 High 1,768,601 56,983

April 1975 218 High 621,688 30,263 4,859 309

(in-stream at mouth) July 1982 75 125,578 3,569 835 158

Oct. 1991 95.7 Low 183,166 9,964 1,251

Susquehanna R discharges April 1975 35.7 High 242,439 11,521

Oct. 1991 10.9 Low 44,284 2,357

Solomon Creek (at mouth) April 1975 66 High 488,003 53,658

July 1983 37 Normal 191,851 17,732 1,549 240

Oct. 1991 25 Low 89,295

Nanticoke Creek (at mouth) April 1975 11 High 118,343 5,917

July 1982 3 16,042 717 118 33

Eastern Middle Anthracite Coal Field

Nescopeck Creek (in-stream at mouth) April 1975 89.9 High 168,924 2,412

July 1982 98 116,450 196 1,694 3,732

Oct. 1991 26.2 Low 78,636 366 1,110

Catawissa Creek (in-stream at mouth) April 1975 36.6 High 34,446 260

August 1982 66 16,042 82 246 998

October 1991 8.7 Low 11,139 59 139
5-11

Table 5.2 (continued). Summary of cumulative acid mine drainage chemical constituent loads in the Susquehanna River tributaries draining the

anthracite coal fields in Pennsylvania. Loads are estimated as pounds per day (ppd) based on chemical concentration and flow (cfs).

Tributary Date Flow Condition Sulfates Iron Manganese Aluminum

Western Middle Anthracite Coal Field

Shamokin Creek (2.7 mi. from mouth) 1969-1970 65 Year Avg. 18,100

April 1975 64.7 High 188,182 17,846

July 1985 62.4 97,740 1,011 1,180 576

Oct.-Nov. 1991 25.6 Low 54,169 4,576 589

Mahanoy Creek (at mouth) 1973-1974 311 Year Avg. 761,178 15,582

April 1975 145 High 677,617 23,093

July 1985 121.4 208,082 2,083 2,017 385

Oct.-Nov. 1991 51.4 Low 173,340 6,815 2,143

Southern Anthracite Coal Field

Swatara Creek (in-stream near Ravine) April 1975 21.3 High 19,684 656

July 1985 20.8 18,050 115 212 16

Oct. 1991 3.4 Low 2,443 98 35

Wiconisco Creek (in-stream at mouth) 1973 Year Avg. 15,250 575

April 1975 20.6 High 27,584 2,098

July 1985 33.5 11,556 73 1 6

Oct. 1991 2.7 Low 1,764 249 35

Rausch Creek 1968-1969 Year Avg. 25,850 3,050

April 1975 13 High 16,858 1,900

Oct. 1991 4 Low 7,179 582 119

Mahantango Creek (in-stream near mouth) July 1985 37.7 7,315 300 18 230
5-12

Table 5.3. Summary of cumulative acid mine drainage chemical constituent loads in the West Branch Susquehanna River tributaries draining the

bituminous coal fields in Pennsylvania. Loads are estimated as pounds per day (ppd) based on chemical concentration and flow.

Tributary Date Flow Condition Sulfates Iron Manganese Aluminum Zinc

Headwaters Area 1971 129 Year Avg. 159,447 400

Bakerton to Bower (in-stream at Bower)

Anderson Creek 1973-1974 78.4 Year Avg. 23,559 365

May 1984 247 High 76,044 1,267 1,601 1,601 107

July 1984 48 Low 22,555 75 544 467 31

Tributaries between Anderson Creek and May 1984 359 High 155,252 2,727 3,969 2,761 219

Clearfield Creek July 1984 27 Low 60,473 868 1,646 680 52

Clearfield Creek 1971 237,654 292

May 1984 1,670 High 1,262,805 39,688 15,334 20,746 992

July 1984 230 Low 33,542 1,068 4,596 2,981 186

Tributaries between Clearfield Cr. and May 1984 598 High 472,096 7,058 12,671 9,418 1,005

Moshannon Cr. July 1984 104 Low 237,810 2,009 4,551 3,290 176

Moshannon Creek 1971 240,413 52,412

May 1984 1,160 High 939,812 28,194 13,784 21,929 877

July 1984 192 Low 373,332 3,215 5,496 25,926 290

Tributaries between Moshannon Cr. and May 1984 430 High 160,113 1,396 3,064 1,973 244

Sinnemahoning Cr. July 1984 69 Low 94,003 225 1,686 643 75

Sinnemahoning Creek May 1984 3,370 High 436,851 5,825 2,730 9,109 364

July 1984 331 Low 87,602 322 483 179 36
5-13

Table 5.3 (continued). Summary of cumulative acid mine drainage chemical constituent loads in the West Branch Susquehanna River tributaries

draining the bituminous coal fields in Pennsylvania. Loads are estimated as pounds per day (ppd) based on chemical concentration and flow.

Tributary Date Flow Condition Sulfates Iron Manganese Aluminum Zinc

Cooks Run 1971 16 Year Avg. 9,936 899

May 1984 48 High 20,741 959 239 1,037 29

July 1984 36 Low 31,111 1,225 408 972 41

Kettle Creek May 1984 694 High 78,717 2,474 1,012 2,624 150

July 1984 269 Low 104,611 3,487 2,179 2,615 131

Drury Run 1971 23.4 Year Avg. 4,720 286

May 1984 34 High 18,181 40 569 422 28

July 1984 30 Low 29,167 32 972 567 36

1990 21 Year Avg. 12,543 11 331 270 15.5

Tangascootac Creek 1984 22 Year Avg. 11,012 32 262 131

Pine Creek (Contribution from Babb 1975-1976 192 Year Avg. 113,497 288

Creek)

(Contribution from Little Pine Creek) 1970-1971 Year Avg. 19,382 169

Loyalsock Creek (in-stream downstream 1975 Year Avg. 14,999 450

from all AMD sources)

Tioga River (in-stream near Tioga 1992 444 Year Avg. 92,785 547 1,224 598 101

Junction)

1994 544 Year Avg. 97,649 1,516 1,913 1,958 181
5-14

Table 5.4. Summary of cumulative acid mine drainage chemical constituent loads in the North Branch Potomac River tributaries draining the

bituminous coal fields in Maryland and West Virginia. Loads are estimated as pounds per day (ppd) based on chemical concentration and flow (cfs).

Tributary Date Flow Condition Sulfates Iron Manganese Aluminum Zinc

Georges Creek 1972-1973 95.5 Year Avg. 143,913 1,444 1,135 1,702

1990-1991 96.9 Year Avg. 161,754 1,011 847 1,065 111

Braddock Run 1972-1973 34.4 Year Avg. 54,254 650 372 112

Jennings Run 1972-1973 42.7 Year Avg. 28,137 115 46 185

North Branch upstream from Jennings 1988-1989 73.1 Low 93,352 550 678 1,370

Randolph Lake 1988-1989 974.3 High 412,115 3,472 2,474 5,226
6-1

CHAPTER 6 - Fall Line Loadings

Greg Foster Cherie Miller

George Mason University US Geological Survey

4400 University Drive 8789 Yellow Brick Road

Fairfax, VA 22030-4444 Baltimore, MD 21237

INTRODUCTION

The Chesapeake Bay Fall Line Toxics Monitoring Program (FLTMP) was established in

the spring of 1990 as a pilot study to quantify annual loadings of trace metal and organic

contaminants to the Bay from above the fall lines of the major tributaries. The fall line is the

physiographic boundary in the eastern United States between the Piedmont and Atlantic Coastal

Plain provinces, and as the natural geographic break between the tidal and non-tidal regions of

the Bay watershed, the fall line is a convenient location to measure tributary fluxes of

contaminants to the tidal Chesapeake Bay. Loadings above the river fall line represent an

integration and interaction of upstream point and nonpoint sources of contaminants. Factors such

as transport, retention, and attenuation of chemicals from upstream sources affect the loading at

the fall line.

Trace contaminants monitored by the FLTMP have included twelve individual chemicals

and polychlorinated biphenyls (PCBs) derived from the Chesapeake Bay Toxics of Concern list

in addition to other related organonitrogen and organophosphorus (organo-N/P) pesticides,

organochlorine insecticides (OCs), and polycyclic aromatic hydrocarbons (PAH). The goals of

the FLTMP since its inception have been to (a) quantify the inputs of contaminants from the

major tributaries to Chesapeake Bay, (b) assist water quality managers by determining the

concentrations of contaminants in downstream waters of the tributary basins, and (c) characterize

the hydrographic behavior of contaminants in fluvial transport at the fall lines of the major

tributaries. In addition, riverine fluxes are being used in the development of a first-order mass

balance model describing the inputs, transport, fate and cycling of contaminants within the

Chesapeake Bay (Velinsky, 1997). 

TEMPORAL AND SPATIAL COVERAGE

Results from the 1990 and 1991 FLTM have been reported previously in the 1994

Chesapeake Bay Basin Toxics Loadings and Release Inventory and will not be provided herein. 

The FLTMP has continued from 1992 through 1997, and the tributaries monitored during this

period are summarized in Table 6.1. Different tributaries have been examined in various years of

the FLTMP to provide broad spatial coverage of the Bay basin and to allow for comparisons of

loadings among the major tributary basins. Trace metal and organic contaminants analyzed

through the FLTMP are listed in Tables 6.2 - 6.5 for each year from 1992 to 1997. Monitored
Fall Line Loadings

6-2

organic compounds have included chemicals present on the Toxics of Concern List as well as

additional, structurally related contaminants. Many of the organonitrogen and organophosphorus

pesticides represent high volume agrochemicals used throughout the Chesapeake Bay basin

(Table 6.2). Monitored contaminants in the tributaries, including both inorganics and organic

contaminants, have increased through the years because of greater capabilities available through

the USGS, the University of Delaware, and the George Mason University Environmental

Chemistry Laboratory. Loadings for all monitored organic contaminants have been included in

this report.

Because trace contaminant transport is known to occur in both the dissolved and

particulate phases, loadings in many cases are provided for both phases. Knowledge of the

transport phase is relevant to understanding ultimate geochemical fate in Chesapeake Bay as well

as more accurately defining the exposure of the Bay’s living resources to contaminants. 

Table 6.1. Summary of Chesapeake Bay Fall Line Toxics Monitoring Program sampling between 1992

and 1997.

Calendar

Year 

Tributaries Monitored Sampling Frequency Constituents

1992 Susquehanna, Potomac, and James Monthly: Feb. - June

Bimonthly: July - Jan. + major storms

metals +

organics

(USGS)a

1993 Susquehanna 2-3 times daily from 3/25/93 -4/3/93

and 11 times between 4/4/93 - 5/6/93

for high flow; biweekly from June -

Dec.

metals only

(USGS)

1994 Susquehanna River

Susquehanna, Potomac, James,

Patuxent, Choptank, Nanticoke,

Pamunkey, Mattaponi, Rappahannock 

Biweekly: Feb. - July

Monthly: Aug.- Dec. + major storms

Spring and Fall synoptic

metals +

organics

metals +

organics

(USGS, UDE,

GMU)

1995 No fall line sampling - -

1996 Potomac metals only

(UDE)

1997 Chesterville Branch and Nanticoke Bimonthly + two major storms metals +

organics

(USGS, GMU)

aAgency coordinating contaminant sampling and analysis is indicated in parentheses: USGS, United States

Geological Survey; UDE, University of Delaware; and GMU, George Mason University.
Fall Line Loadings

6-3

Table 6.2. List of organonitrogen and organophosphorus pesticides monitored at the fall line by year.

Organonitrogen & Organophosphorus

Pesticides

1992 1993 1994 1995 1996

Simazine X ns X ns ns

Prometon X ns X ns ns

Atrazine X ns X ns ns

Diazinon X ns X ns ns

Alachlor X ns X ns ns

Metolachlor ns X ns ns

Malathion X ns X ns ns

Cyanazine X ns X ns ns

Hexazinone X ns X ns ns

X, constituent monitored; ns, not sampled.

Table 6.3. List of polycyclic aromatic hydrocarbons monitored at the fall line by year.

Polycyclic Aromatic Hydrocarbons 1992 1993 1994 1995 1996

Naphthalene (Nap)a X ns X ns ns

2-Methylnaphthalene (MN) ns X ns ns

2,6-Dimethylnaphthalene (DMN) ns X ns ns

Acenaphthylene (ACE) ns X ns ns

Acenaphthene (CAN) ns X ns ns

Fluorene (FLU) ns X ns ns

Phenanthrene (PHE) X ns X ns ns

Fluoranthene (FLR) X ns X ns ns

Pyrene (PYR) ns X ns ns

Benz[a]anthracene (BAA) X ns X ns ns

Chrysene (CHR) ns X ns ns

Benzo[a]pyrene (BAP) ns X ns ns

Perylene (PER) ns X ns ns

a

 PAH abbreviations; X, constituent monitored; ns, not sampled.
Fall Line Loadings

6-4

Table 6.4. List of organochlorine contaminants monitored at the fall line by year.

Organochlorines 1992 1993 1994 1995 1996

alpha-HCH ns X ns ns

beta-HCH ns X ns ns

gamma-HCH ns X ns ns

Heptachlor ns ns ns

Aldrin X ns X ns ns

Heptachlor epoxide ns ns ns

Oxychlordane X ns X ns ns

trans-Chlordane X ns X ns ns

Endosulfan I ns ns ns

cis-Chlordane X ns X ns ns

trans-Nonachlor ns X ns ns

Dieldrin X ns X ns ns

p,p'-DDE ns X ns ns

o,p'-DDD ns X ns ns

Endrin ns X ns ns

p,p'-DDD ns X ns ns

o,p'-DDD ns X ns ns

p,p'-DDT X ns X ns ns

Methoxychlor ns X ns ns

PCBs 116 CS ns 116 CS ns ns

Hexachlorobenzene ns X ns ns

cis- and trans-Permethrin X ns ns ns

X, constituent monitored; ns, not sampled; CS, PCB congeners.
Fall Line Loadings

6-5

Table 6.5. List of trace metals monitored at the fall line by year.

TRACE METALS 1992 1993 1994 1995 1996

Al (dis) X X X ns na

Al (par) X ns na

As (dis) X X X ns na

As (TR) X X ns na

Ba (TR) X ns na

Cd (dis) X X X ns na

Cd (par) X ns na

Cd (TR) X X ns na

Cr (dis) X X X ns na

Cr (par) X ns na

Cr (TR) X X ns na

Cu (dis) X X X ns na

Cu (par) X ns na

Cu (TR) X X ns na

Fe (dis) X X X ns na

Fe (par) X ns na

Fe (TR) X X ns na

Pb (dis) X X X ns na

Pb (par) X ns na

Pb (TR) X X ns na

Li (TR) X ns na

Mn (dis) X ns na

Mn (par) X ns na

Mn (TR) X ns na

Hg (dis) X X ns na

Hg (par) ns na

Hg (TR) X X ns na

Ni (dis) X X X ns na

Ni (par) X ns na

Ni (TR) X X ns na

Se (TR) X ns na

Ag (TR) X ns na

Sr (dis) X ns na

Sr (TR) X X ns na

Zn (dis) X X X ns na

Zn (par) X ns na

Zn (TR) X X ns na

X, constituent monitored; ns, not sampled; na, data not available.
Fall Line Loadings

6-6

∑ ∑ = =−

=

j

j

n

i n

ij ij

N

j 1

bf j L F c q t

∑ ∑ = =

=

nl

k 1

kl kl kl

M

l 1

sf L F q c t

METHODOLOGY

Sampling was conducted along the fall lines of the Bay's three major tributaries (Figure

6.1) using ultra-clean sampling and analysis techniques for trace metal and organic contaminants

in the river fall line samples. Thorough descriptions of sampling and analysis procedures may be

found in other reports (CBP, 1994c; Foster and Lippa, 1996; Foster et al., in press). 

Contaminant concentrations were used to estimate fall-line loadings in conjunction with

stream flow data. All contaminant loads were estimated above the fall lines. Fluvial loadings

above the fall lines were estimated for metals using a log-linear regression model (AMLE model)

described by Cohen et al. (1991) or an Interpolation-Integration (I-I) method over a twelve month

periods (Foster and Lippa, 1996). The AMLE model was preferred and used when data

requirements were met, which happened only with metals data for select years. All organic

contaminant data and some of the trace metal data were too sparse to meet the AMLE model

requirements (Cohen et al., 1991), in which case the I-I model was used. The I-I method, which

estimated baseflow (LBF) and stormflow (LSF) separately, is described by the equations below:

F = conversion factor

= mean daily discharge (m3/s) on ith day of jth period (base flow) qij

 = mean daily discharge (m3/s) on kth day of lth storm qkl

cj = concentration (dissolved + particulate) of constituent (kg/m3) in jth period

ckl = concentration (dissolved + particulate) of constituent (kg/m3) on kth day of lth storm

t

ij = hours of base flow on ith day of jth period

tkl = hours of storm flow on kth day of lth storm

nj = 0.5 number of days in jth period

nl = number of days per storm

N = number of periods 

M = number of storms

Each daily load estimated using the I-I method was considered to be derived from

baseflow, stormflow, or a combination of the two in which case daily Lbf and Lsf values were

added together as partial daily loads for the beginning and ending days of the storm event. 

Estimated daily loads were summed throughout the study period to obtain annual (i.e., 12 month)
Fall Line Loadings

6-7

loads. Data censoring was employed in the I-I method whenever a contaminant was below the

quantitation limit in the surface water samples. In these cases, separate maximum and minimum

daily loads were estimated by adjusting the sample concentrations to the detection limits

(maximum) in one scenario and to 0 (minimum) in the other. Loadings were estimated as load

intervals when the differences between maximum and minimum estimates exceeded 10%. Mean

daily stream discharges were obtained from the output of USGS gaging stations.

Figure 6.1. Map of Chesapeake Bay region showing nine watersheds monitored in 1994 synoptic study. 

(Map provided courtesy of the USGS in Baltimore, MD.)

UNCERTAINTY

Estimates of contaminant loadings above the river fall lines are extremely dependent on

river flows, which vary widely throughout the year. The FLTMP was designed to collect river

water samples during baseflow and stormflow hydrologic conditions to obtain contaminant

concentrations under wide ranges in flow. With the complexities of analyzing sub-parts-per-
Fall Line Loadings

6-8

trillion concentrations of contaminants in water, sampling was limited to 25-40 collections per

year. Therefore, the contaminant concentration data used to estimate annual loads was sparse,

especially for organic contaminants, and the spatial and temporal variability of river fall line

concentrations has not been systematically evaluated. The estimated fall line loads represent a

first-order determination of contaminant fluxes in the monitored tributaries. The most accurate

loadings exist for the Susquehanna River because the most intensive sampling effort has been

carried out for this tributary. 

Uncertainties in river fall line loading estimates have not been rigorously evaluated. The

AMLE loading estimator provides model prediction errors for each constituent and has been the

preferred method used in this study. However, the AMLE has a minimum threshold for

concentration values (~60 measured concentrations for each constituent over a two year period)

for loading estimates and has been highly dependent on the detection frequency of each

monitored contaminant. Most organic contaminants and several metals have been measured at

less frequency than the model threshold values. (The AMLE model is rarely used with organic

contaminants because the organics data is very sparse and rarely has the FLTMP monitored

organic contaminants in consecutive years, whereas metals are routinely monitored annually

providing a larger basis set for the AMLE model.) Uncertainties determined for the I-I model are

obtained through the analytical procedures. For example, for organic contaminant data the

assigned uncertainties (first evaluated in the 1994 FLTMP) from propagated errors accumulated

through the analytical method; it is assumed in this case that hydrologic uncertainties are

insignificant and remain unknown. Uncertainties are also determined through the I-I model in

the form of loading intervals. When a particular contaminant in a river fall line sample is below

the analytical detection limit, the I-I model estimates two loads. The first is determined using the

analytical detection limit of the contaminant (maximum value) and another using a concentration

of zero. When the annual loads are compiled in the I-I model, an interval may exist for the

maximum to the minimum values. Uncertainty estimates have not been standardized in the

FLTMP and remain an important variable to be addressed in future studies. 

DISCUSSION

River fall line loading estimates are a function of many hydrologic, geochemical, and

watershed variables, many of which have not been quantified or evaluated in the Chesapeake

basin. For example, the seasonal application rates of agrochemicals in the Bay’s drainage basins

have been only crudely estimated from anecdotal information and for the most part are not

known with any reasonable certainty. Fall line loadings of agrochemicals will be a function of

seasonal application rates which must be better determined in the future. The temporal

variability in river fall line contaminant concentrations at the fall line has not been well

quantified, leaving sampling variability a virtually unknown uncertainty. In addition, the impact

of large storms, annual precipitation, soil moisture, and urban influences are only understood in a

general nature because little scientific data exists which describes or models fluvial transport

dynamics. And finally, the influence of the airshed and atmospheric deposition on fall line

loadings is unknown. Therefore, the fall line loading estimates provided to date by the FLTMP

can only be viewed as preliminary, first-order flux values which provide very little in the way of
Fall Line Loadings

6-9

understanding the underlying mechanisms of transport. Other sources of information such as

land use and point source delineations also need good documentation as sources of the various

contaminants. 

Loadings above the river fall lines represent an integration and interaction of all point and

non-point source inputs upstream from the point of sampling. Major upstream contributors to the

fall line loads cannot be determined without further systematic investigation; however,

correlations have been developed between contaminants and sources. For example, the

organonitrogen and organophosphorus pesticide inputs arise primarily from agricultural (e.g.,

atrazine and metolachlor) and urban (e.g., diazinon) sources, and the PAHs are derived primarily

from urban sources where large amounts of pyrolysis by-products are formed through gas phase

combustion. PCBs and organochlorine inputs have been less well characterized and are thought

to come from contaminated industrial sites, long-term sequestration into agricultural and urban

soils, and atmospheric deposition from global transport and cycling. 

The most important variable influencing fall line loadings is river discharge because (a)

river discharge was such a large loadings driver relative to the fall line contaminant

concentrations in the loading estimation methods (given that the baseline river fall line

contaminant concentrations were generally in the low parts per billion to low parts per trillion

range), (b) and seasonal variability in river discharge in the major tributaries changed over a

greater scale than river fall line contaminant concentrations. Annual loadings for the organic

contaminants are listed in Tables 6.6 - 6.14 for the fall lines of the three major tributaries of the

Bay (Susquehanna, Potomac, and James Rivers) for the various chemical classes (organonitrogen

and organophosphorus pesticides, polycyclic aromatic hydrocarbons, and organochlorines). The

largest loadings were observed for the current use agrochemicals (e.g., atrazine, metolachlor, and

cyanazine) followed sequentially by the PAHs, PCBs, and organochlorine pesticides. The fall

line loadings estimated for the three major tributaries for most of the contaminants were

proportional to the land areas of each of the drainage basins. Thus, the Susquehanna River

fallline showed the largest loadings followed by the Potomac and James Rivers. 

Trace metal loads above the three major tributaries are listed in Tables 6.15 - 6.17. 

Aluminum had the greatest total annual load, followed by iron, then manganese. These results

reflected the crustal abundances of these metals. The lowest total load occurred for cadmium

although the loads for this element still appeared to be significantly higher than expected from

crustal abundance.

Instantaneous loads for the organic contaminants and trace metals in the nine tributary

synoptic study in 1994 are shown in Tables 6.18 - 6.25. Results of the spring tributary synoptic

study showed that for all trace metals, with the exception of iron, the largest instantaneous loads

were above the Susquehanna River fall line. However, the loads at the Potomac and James

Rivers were greater than those for all of the other seven tributaries. These loads are, in part, the

result of higher river flows measured at these three river sites than those at the other six

tributaries. Organic contaminants followed the same trend, with the largest instantaneous loads
Fall Line Loadings

6-10

occurring above the Susquehanna, Potomac, and James River fall lines. 

CORRELATION WITH 1994 TOXICS LOADING AND RELEASE INVENTORY

Organic contaminant loads reported in the 1994 TLRI included only atrazine

(Susquehanna and James Rivers), metolachlor, and alachlor (Susquehanna River only). 

Analytical detection limits were insufficient to determine accurate loads for any other organic

constituents in the 1990 and 1991 fall line toxics monitoring program. Average annual atrazine

loads above the fall line of the Susquehanna River for 1990 and 1991 were found to be 4,000 kg,

where as in 1992 and 1994, atrazine loads above the Susquehanna River fall line were estimated

to be 1,700 kg and 2,970 kg, respectively. These loading estimates are all within a factor of 3,

which is quite good considering the change in analytical methods and load estimation techniques

during 1990-1994. 

Variation in annual loads for all contaminants is most directly related to discharge above

the fall line. The average annual river discharges measured at the Susquehanna River fall line (at

Conowingo, MD) were 1,000 m3/s, 1,494 m3/s, 1,464 m3/s for 1992, 1993, and 1994,

respectively. The generally higher loadings estimated for organic and metal contaminants in

1994 in comparison to 1992, for example, can be attributed primarily to higher discharge in 1994

recorded at the Susquehanna River fall line. 

There are other factors which account for the annual variability seen in the fall line load

estimates. Changes in analytical methodology, hydrographic and sampling variability, and

changes in watershed characteristics all affect fall line loadings. None of these factors has been

previously evaluated.

RECOMMENDATIONS

Contaminant loadings above the fall lines of the major northern and western shore

tributaries have been estimated for organics and metals between 1990-1994. We now have a

picture of the magnitudes of contaminant loadings to Chesapeake Bay from the major tributaries. 

The fall line monitoring program has fulfilled the objectives of the pilot phase, which has been to

provide preliminary loading estimates for contaminants to the Bay from the rivers. Future work

should be devoted to refining the loading estimates for contaminants in the next phase of the

program: to be able to compare loadings estimated among the various sources. To accomplish

an accurate mass budget and preliminary model development for quantifying input of

contaminants to Chesapeake Bay, refined estimates of the uncertainties of loadings via the

tributaries are needed. To address this issue the following recommendations are put forward:

 

< Better define contaminant behavior above the fall lines in the watersheds. There needs to

be more mechanistic orientation of how contaminants enter and are transported in rivers.

< Include the influence of the air shed in fall line loadings. We need to better understand
Fall Line Loadings

6-11

source dynamics in the watershed. Where do the contaminants ultimately come from? 

Do they originate from contaminated soils, urban runoff, or atmospheric deposition? 

These questions need to be addressed to move into the modeling phase of contaminant

transport in the Bay watershed.

< Better define the uncertainties in the magnitudes of the fall line load estimates. The

Susquehanna and/or Potomac Rivers should be used as model basins to more precisely

define the factors which affect the loading estimates and to systematically quantify the

uncertainties in loadings estimates.

< Better link the contaminant release information with fall line loadings. For example,

contaminant release data should support the fall line loading estimates by determining

pesticide application rates within river basins rather than within the states or counties. 

< To more fully understand the effects of extremely high flow events in the major

tributaries. Many contaminants are stored in sediments up in the watersheds, and

extremely high flow events may promote the transport of these contaminants to the Bay in

very large quantities over short time frames. These low frequency events may have

profound implications to the biological effects of contaminants in the Bay.

< Establish one or more long-term contaminant-loading stations. We have established that

the majority of the loadings occur through the rivers if we look at the nutrient model.

Long-term data is essential for resolving management issues. We recommend that each

state in the watershed select one site, such as:

PA - Conowingo Dam (Susquehanna River) 

Washington, D.C. - Chain Bridge (Potomac River)

VA - Cartersville (James River)

MD - Choptank or Nanticoke Rivers (Eastern Shore)

We recommend combining funds from EPA, USGS, and the states to start long-term

monitoring using our low-level techniques.
Fall Line Loadings

6-12

Table 6.6. Annual loads (kg/yr) of organonitrogen and organophosphorus pesticides above the fall line

(AFL) of the Susquehanna River.

Organonitrogen &

Organophosphorus Pesticides

Estimation

Method

3/92-2/93

AFL

2/93-1/94

AFL

2/94-1/95

AFL

Simazine I-I 580-610 - 2010-2020

Prometon I-I 110-160 - 1030

Atrazine I-I 1700 - 2970

Diazinon I-I 8-98 - 220-260

Alachlor I-I 97-106 - 710

Metolachlor I-I 920 - 2450

Malathion I-I 8-86 - 20-180

Cyanazine I-I 430-480 - 3010

Hexazinone I-I 170-180 - 130-250

Table 6.7. Annual loads (kg/yr) of organonitrogen and organophosphorus pesticides above the fall line

(AFL) of the Potomac River.

Organonitrogen &

Organophosphorus Pesticides

Estimation

Method

3/92-2/93

AFL

2/93-1/94

AFL

2/94-1/95

AFL

Simazine I-I 340 - -

Prometon I-I 56-66 - -

Atrazine I-I 780 - -

Diazinon I-I 3-27 - -

Alachlor I-I 25-44 - -

Metolachlor I-I 390 - -

Malathion I-I 3-25 - -

Cyanazine I-I 220-230 - -

Hexazinone I-I 6-14 - -

cis- and trans-Fenvalerate I-I - - -

cis- and trans-Permethrin I-I - - -
Fall Line Loadings

6-13

Table 6.8. Annual loads (kg/yr) of organonitrogen and organophosphorus pesticides above the fall line

(AFL) of the James River.

Organonitrogen &

Organophosphorus Pesticides

Estimation

Method

3/92-2/93

AFL

2/93-1/94

AFL

2/94-1/95

AFL

Simazine I-I 130-140 - -

Prometon I-I 18-26 - -

Atrazine I-I 220 - -

Diazinon I-I 20-30 - -

Alachlor I-I 15-28 - -

Metolachlor I-I 89-92 - -

Malathion I-I 3-18 - -

Cyanazine I-I 32-43 - -

Hexazinone I-I 18-26 - -

Table 6.9. Annual loads (kg/yr) of polycyclic aromatic hydrocarbons above the fall line (AFL) of the

Susquehanna River.

Polycyclic Aromatic Hydrocarbon Estimation

Method

3/92-2/93

AFL

2/93-1/94

AFL

2/94-1/95

AFL

Naphthalene I-I 300 - -

2-Methylnaphthalene I-I - - 220

2,6-Dimethylnaphthalene I-I - - 140

Acenaphthylene I-I - - 50

Acenaphthene I-I - - 57

Fluorene I-I - - 120

Phenanthrene I-I 98-120 - 450

Fluoranthene I-I - - 1130

Pyrene I-I - - 1030

Benz[a]anthracene I-I 55-120 - 380

Chrysene I-I - - 330

Benzo[a]pyrene I-I 14-120 - 440

Perylene I-I - - 480
Fall Line Loadings

6-14

Table 6.10. Annual loads (kg/yr) of polycyclic aromatic hydrocarbons above the fall line (AFL) of the

Potomac River.

Polycyclic Aromatic Hydrocarbon Estimation

Method

3/92-2/93

AFL

2/93-1/94

AFL

2/94-1/95

AFL

Naphthalene I-I 60-75 - -

2-Methylnaphthalene I-I - - -

2,6-Dimethylnaphthalene I-I - - -

Acenaphthylene I-I - - -

Acenaphthene I-I - - -

Fluorene I-I - - -

Phenanthrene I-I 19-23 - -

Fluoranthene I-I - - -

Pyrene I-I - - -

Benz[a]anthracene I-I 29-48 - -

Chrysene I-I - - -

Benzo[a]pyrene I-I 11-49 - -

Perylene I-I - - -

Table 6.11. Annual loads (kg/yr) of polycyclic aromatic hydrocarbons above the fall line (AFL) of the

James River.

Polycyclic Aromatic Hydrocarbon Estimation

Method

3/92-2/93

AFL

2/93-1/94

AFL

2/94-1/95

AFL

Naphthalene I-I 43-67 - -

2-Methylnaphthalene I-I - - -

2,6-Dimethylnaphthalene I-I - - -

Acenaphthylene I-I - - -

Acenaphthene I-I - - -

Fluorene I-I - - -

Phenanthrene I-I 140 - -

Fluoranthene I-I - - -

Pyrene I-I - - -

Benz[a]anthracene I-I 26-35 - -

Chrysene I-I - - -

Benzo[a]pyrene I-I 61-82 - -

Perylene I-I - - -
Fall Line Loadings

6-15

Table 6.12. Annual loads (kg/yr) of organochlorines above the fall line (AFL) of the Susquehanna River.

Organochlorines Estimation

Method

3/92-2/93

AFL

2/93-1/94

AFL

2/94-1/95

AFL

alpha-HCH I-I - - 11

beta-HCH I-I - - 6

gamma-HCH I-I - - 18

Oxychlordane I-I 26-32 - 10

trans-Chlordane I-I 11-17 - 12

cis-Chlordane I-I 21-28 - 6

trans-Nonachlor I-I - - 13

Dieldrin I-I 7-14 - 12

p,p'-DDE I-I - - 16

o,p'-DDD I-I - - 20

Endrin I-I - - 4-11

p,p'-DDD I-I - - 13

p,p'-DDT I-I 6-29 - 12

Methoxychlor I-I - - 1-8

PCBs I-I 170-198 - 160-190

Hexachlorobenzene I-I - - 4

cis- and trans-Fenvalerate I-I 14-44 - -

cis- and trans-Permethrin I-I 4-95 - -
Fall Line Loadings

6-16

Table 6.13. Annual loads (kg/yr) of organochlorines above the fall line (AFL) of the Potomac River.

Organochlorines Estimation

Method

3/92-2/93

AFL

2/93-1/94

AFL

2/94-1/95

AFL

alpha-HCH I-I - - -

beta-HCH I-I - - -

gamma-HCH I-I - - -

Oxychlordane I-I 14-15 - -

trans-Chlordane I-I 4-6 - -

cis-Chlordane I-I 13-15 - -

trans-Nonachlor I-I - - -

Dieldrin I-I 13-15 - -

p,p'-DDE I-I - - -

o,p'-DDD I-I - - -

Endrin I-I - - -

p,p'-DDD I-I - - -

p,p'-DDT I-I 3-10 - -

Methoxychlor I-I - - -

PCBs I-I 22-48 - -

Hexachlorobenzene I-I - - -

cis- and trans-Fenvalerate I-I - - -

cis- and trans-Permethrin I-I - - -
Fall Line Loadings

6-17

Table 6.14. Annual loads (kg/yr) of organochlorines above the fall line (AFL) of the James River.

Organochlorines Estimation

Method

3/92-2/93

AFL

2/93-1/94

AFL

2/94-1/95

AFL

alpha-HCH I-I - - -

beta-HCH I-I - - -

gamma-HCH I-I - - -

Oxychlordane I-I 6-10 - -

trans-Chlordane I-I 11-12 - -

cis-Chlordane I-I 16-19 - -

trans-Nonachlor I-i - - -

Dieldrin I-I 3-4 - -

p,p'-DDE I-I - - -

o,p'-DDD I-I - - -

Endrin I-I - - -

p,p'-DDD I-I - - -

p,p'-DDT I-I 0.1-6 - -

Methoxychlor I-I - - -

PCBs I-I 18-32 - -

Hexachlorobenzene I-I - - -

cis- and trans-Fenvalerate I-I - - -

cis- and trans-Permethrin I-I - - -
Fall Line Loadings

6-18

Table 6.15. Annual loads (metric tons per year) of trace metals above the fall line (AFL) of the

Susquehanna River.

Trace Metals Estim.

Method

1992

Loads

3/92-2/93

AFLa

Estim.

Method

1993

Loads

2/93-1/94

AFLa

Estim.

Method

1994

Loads

2/94-1/95

AFLb

Al AMLE 828-994 AMLE 1,111-1,388 II 67,400

As II 0-32 II 12-49 -

Cd II 0-32 II 0-46 II 29

Cr II 64-74 II 80-94 II 115-116

Cu AMLE 60-71 AMLE 111-135 II 199

Fe AMLE 17-29 AMLE 76,448- II 44,100

Pb AMLE 42-53 AMLE 119-163 II 45

Mn - - II 4,830

Hg II 0.3-3 - -

Ni AMLE 147-190 - II 186

Zn AMLE 349-453 AMLE 992-1,314 II 438

aLoads determined from total recoverable concentrations except for A1 loads for 1992 and 1993 in which they were determined

from dissolved (only) concentrations.

bLoads determined from the sum of dissolved and particulate concentrations.

Table 6.16. Annual loads (kg/yr X 10-3) of trace metals above the fall line (AFL) of the Potomac River.

Trace Metals Estim.

Method

1992

Loads

3/92-2/93

AFLa

Estim.

Method

1993

Loads

2/93-1/94

AFL

Estim.

Method

1994

Loads

2/94-1/95

AFL

Al - - -

As II 0-58 - -

Cd II 0-19 - -

Cr II 31-50 - -

Cu II 44-60 - -

Fe (dissolved only) II - - -

Pb II 41-77 - -

Mn - - -

Hg - - -

Se II 0-76

Ni II 60-167 - -

Zn II 241-327 - -

aLoads determined from total recoverable concentrations.
Fall Line Loadings

6-19

Table 6.17. Annual loads (metric tons per year) of trace metals above the fall line (AFL) of the James

River.

Trace Metals Estim.

Method

1992

Loads

3/92-2/93

AFLa

Estim.

Method

1993

Loads

2/93-1/94

AFL

Estim.

Method

1994

Loads

2/94-1/95

AFL

Al AMLE 729-949 - -

As II 0-4 - -

Cd II 0-6 - -

Cr AMLE 31-44 - -

Cu AMLE 22-28 - -

Fe (dissolved only) AMLE 1,490-1,940 - -

Pb AMLE 24-34 - -

Mn - - -

Hg II 0.02-0.6 - -

Ni AMLE 25-38 - -

Zn AMLE 93-118 - -

aLoads determined from total recoverable concentrations except for A1 which was determined from dissolved (only)

concentrations.

Table 6.18. Instantaneous loads (mg/s) of organonitrogen and organophosphorus pesticides above the

fall lines or head of tide of the nine major tributaries of Chesapeake Bay from March 26 through May 5,

1994.

Pam Mat Jam Rap Pot Chop Nant Pat Sus

Simazine 0.50 0.010 2.40 0.58 18.2 0.81 0.82 0.005 154

Prometon 0.17 0.083 0.52 0.27 4.31 0.18 0.085 0.005 13.8

Atrazine 0.51 0.12 1.02 0.61 17.8 2.98 0.24 0.004 172

Alachlor 0.009 0.051 0.064 0.016 0.90 0.15 0.13 0.003 8.46

Metolachlor 0.056 0.005 0.045 0.011 5.40 0.84 0.041 0.002 39.9

Cyanazine 0.020 0.016 0.14 0.036 1.93 0.11 0.017 0.007 1.43

Hexazinone 0.38 0.29 0.52 0.66 28.8 2.14 0.37 0.002 174
Fall Line Loadings

6-20

Table 6.19. Instantaneous loads (mg/s) of organonitrogen and organophosphorus pesticides above the

fall lines or head of tide for the nine major tributaries of Chesapeake Bay from November 8 through

November 18, 1994.

Pam Mat Jam Rap Pot Chop Nant Pat Sus

Simazine 0.209 0.30 0.59 0.51 3.67 0.031 0.019 0.27 0.077

Prometon 0.049 0.031 0.32 0.088 1.38 0.008 0.009 0.076 1.37

Atrazine 0.085 0.055 0.15 0.25 3.20 0.013 0.011 0.26 4.51

Alachlor 0.007 0.002 0.034 0.007 0.047 0.000 0.001 0.095 0.27

Metolachlor 0.002 0.001 0.013 0.003 0.107 0.005 0.045 0.015 0.65

Cyanazine 0.054 0.005 0.040 0.011 0.057 0.001 0.001 0.003 0.81

Hexazinone 0.028 0.017 0.061 0.22 1.35 0.026 0.047 0.19 2.83

Table 6.20. Instantaneous loads (mg/s) of polycyclic aromatic hydrocarbons above the fall line or head

of tide of the nine major tributaries of Chesapeake Bay from March 26 through May 5, 1994.

Pam Mat Jam Rap Pot Chop Nant Pat Sus

MNa0.12 0.076 18.9 0.011 24.3 1.13 0.15 0.002 85.2

DMN 0.31 0.015 0.67 0.028 0.74 0.014 0.011 0.007 1.43

ACE 0.037 0.012 0.23 0.023 1.18 0.008 0.004 0.000 5.84

CAN 0.020 0.002 0.46 0.056 6.09 0.004 0.007 0.007 9.93

FLU 0.003 0.003 0.080 0.003 0.74 0.002 0.002 0.001 1.30

PHEN 0.005 0.006 0.25 0.003 0.56 0.011 0.004 0.001 1.52

FLR 0.011 0.008 0.32 0.018 1.39 0.010 0.005 0.003 3.66

PYR 0.028 0.032 0.68 0.051 3.70 0.023 0.010 0.027 10.2

CHR 0.025 0.019 0.76 0.030 13.2 0.013 0.018 0.11 56.1

BAA 0.014 0.009 0.49 0.015 9.46 0.008 0.017 0.091 42.9

BAP 0.001 0.001 0.26 0.003 4.49 0.000 0.001 0.032 6.95

PER 0.001 0.001 0.18 0.001 3.15 0.000 0.001 0.032 7.31

a

 Refer to Table 3 for PAH abbreviations.
Fall Line Loadings

6-21

Table 6.21. Instantaneous loads (mg/s) of polycyclic aromatic hydrocarbons above the fall line or head of tide of

the nine major tributaries of Chesapeake Bay from November 8 through November 18, 1994.

Pam Mat Jam Rap Pot Chop Nant Pat Sus

MN 0.002 0.001 5.69 0.003 6.12 <0.001 <0.001 0.001 7.005

DMN 0.12 0.053 0.33 0.009 0.14 0.003 0.003 0.041 0.120

ACE 0.018 0.013 0.26 0.034 0.20 0.006 0.003 0.020 0.598

ACN <0.001 <0.001 0.005 0.001 0.11 0.007 <0.001 0.001 0.312

FLU 0.008 0.003 0.028 0.004 0.079 0.001 0.001 0.009 0.136

PHEN 0.002 0.001 0.001 0.001 0.043 <0.001 <0.001 <0.001 0.078

FLR <0.001 <0.001 <0.001 <0.001 0.010 <0.001 <0.001 0.001 0.292

PYR 0.019 0.006 0.088 0.005 0.27 0.001 <0.001 0.017 0.807

CHR 0.016 0.007 0.093 0.005 0.45 0.001 0.001 0.033 1.548

BAA <0.001 <0.001 0.021 <0.001 0.24 <0.001 <0.001 0.020 1.384

BAP <0.001 0.003 0.052 0.001 0.29 0.001 0.001 0.019 0.679

PER <0.001 <0.001 0.009 <0.001 0.11 <0.001 <0.001 0.007 0.820

Table 6.22. Instantaneous loads (mg/s) of organochlorines above the fall line or head of tide of the nine major

tributaries of Chesapeake Bay from March 26 through May 5, 1994.

Pam Mat Jam Rap Pot Chop Nant Pat Sus

PCBs 0.0002 0.0002 0.37 0.0004 6.13 0.0001 0.0001 0.057 5.04

HCB 0.0870 0.19 0.42 0.0012 5.56 0.0043 0.0001 0.037 7.27

p,p'-DDE 0.0399 0.0047 0.31 0.0435 1.62 0.0048 0.0026 0.013 3.07

p,p'-DDT 0.0024 0.0001 0.015 0.0017 0.084 0.0002 0.0001 0.0001 0.017

"-BHC 0.0002 0.0002 0.0068 0.0045 0.25 0.0021 0.0024 0.0013 0.311

$-BHC <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4

(-BHC 0.0005 0.0009 0.0061 0.0067 0.0658 0.0010 0.0009 0.0002 0.311

Oxychlor 0.0018 0.0015 0.0060 0.0092 0.0408 0.0003 0.0002 0.0011 0.19

(-Chlordane 0.0025 0.0032 0.038 0.014 0.1793 0.0016 0.0043 0.0002 0.97

"-Chlordane <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4

t-Nonachlor 0.0002 0.0002 0.0087 0.0078 0.14 0.0009 0.0009 0.0014 0.052

Dieldrin 0.0015 0.0005 0.0041 0.0024 0.0056 0.0002 0.0004 0.0001 0.0156

o,p'-DDD 0.0002 0.0002 0.0017 0.0021 0.0128 0.0001 0.0002 0.0012 0.0345

Endrin 0.0023 0.0006 0.0170 0.0066 0.033 0.0030 0.0002 0.0020 0.1036

p,p'-DDD 0.0007 0.0004 0.0034 0.0021 0.138 0.0001 0.0003 0.0040 0.225
Fall Line Loadings

6-22

Table 6.23. Instantaneous loads (mg/s) of organochlorines above the fall line or head of tide of the nine

major tributaries of Chesapeake Bay from November 8 through November 18, 1994.

Pam Mat Jam Rap Pot Chop Nant Pat Sus

PCBs <1e-4 <1e-4 0.0005 0.0001 0.093 <1e-4 <1e-4 0.0080 1.2

HCB 0.039 0.048 0.22 0.062 0.17 0.0081 0.0050 0.020 2.2

p,p'-DDE 0.0074 0.0030 0.12 0.044 0.045 0.0005 0.0002 0.0020 0.32

p,p'-DDT <1e-4 <1e-4 0.0025 0.0007 0.0041 <1e-4 <1e-4 <1e-4 0.0072

"-BHC <1e-4 <1e-4 0.0005 0.0001 0.0012 0.0002 <1e-4 0.0002 0.046

$-BHC <1e-4 <1e-4 <1e-4 0.0003 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4

(-BHC 0.0001 0.0019 0.018 0.0045 0.0068 <1e-4 <1e-4 0.0008 0.035

Oxychlor 0.0008 0.0018 0.022 0.0039 0.0019 <1e-4 0.0002 0.0005 0.0087

(-Chlordane 0.0001 0.0011 0.026 0.0028 0.023 <1e-4 <1e-4 0.0083 0.062

"-Chlordane <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4 <1e-4

t-Nonachlor <1e-4 0.0003 0.0039 0.0010 0.013 <1e-4 <1e-4 0.0006 0.010

Dieldrin <1e-4 <1e-4 0.0013 <1e-4 0.0006 <1e-4 <1e-4 0.0002 0.0013

o,p'-DDD <1e-4 <1e-4 0.0005 0.0001 0.0007 <1e-4 <1e-4 0.0004 0.0014

Endrin <1e-4 0.0004 0.0046 0.0007 0.0102 <1e-4 <1e-4 0.0003 0.0043

p,p'-DDD 0.0001 0.0005 0.0069 0.0002 0.016 <1e-4 0.0001 0.0004 0.0072

Table 6.24. Instantaneous loads (mg/s) of trace metals above the fall line or head of tide of the nine

major tributaries of Chesapeake Bay from March 26 through May 5, 1994.

Pam Mat Jam Rap Pot Chop Nant Pat Sus

Al 3350 4630 23000 3780 210000 1650 806 3700 336000

Cd 4.8 1.4 12.9 0.94 29.9 0.36 1.4 1.3 242

Cr 10.5 17.5 197 19.1 1200 5.8 3.3 21.5 9590

Cu 59.1 15.2 326 36.1 1620 11.2 9.8 22.2 4090

Fe 14500 31800 28300 7980 236000 8050 3400 6810 88700

Mn 667 1270 1430 290 13300 819 222 614 102000

Ni 1.46 15.2 105 0.12 1130 15.1 17.0 21.6 4350

Pb 10 11.3 20.5 8.20 81.4 2.9 1.2 4.5 395

Zn 122 72.1 367 22.1 2972 44.2 103 58.8 19800
Fall Line Loadings

6-23

Table 6.25. Instantaneous loads (mg/s) of total trace metals above the fall line or head of tide of the nine

major tributaries of Chesapeake Bay from November 8 through November 18, 1994.

Pam Mat Jam Rap Pot Chop Nant Pat Sus

Al 3860 548 966 390 17800 14.6 46.6 186 126000

Cd naa0.74 4.19 0.51 5.57 0.11 0.22 0.56 929

Cr 2.95 3.22 21.4 2.84 68.9 0.26 1.00 1.97 4550

Cu 12.8 3.88 22.6 8.29 72.2 0.15 0.24 2.75 2180

Fe 6350 5980 6100 1130 12400 548 161 1420 651000

Mn 550 175 313 40.4 648 11.9 13.4 381 94300

Ni 9.19 5.85 37.5 7.55 64.4 0.93 2.12 5.85 3230

Pb 2.71-

2.92

2.45 3.05-

4.51

1.28 10.7 0.02-

0.05

0.00-

0.04

0.45 1270

Zn 67.6 10.6 24.2-

25.1

7.92 115 0.94 18.7 20.6 5670

a

not available

.
7-1

CHAPTER 7 - Pesticide Usage and Occurrence in Surface

and Ground Water

Eric Maurer 

Chesapeake Bay Program Office

Environmental Protection Agency

410 Severn Avenue, Suite 109

Annapolis, MD 21403

INTRODUCTION

The use of pesticides for agricultural and non-agricultural purposes and the potential for

these chemicals to adversely affect both surface and ground water as well as the Bay’s living

resources is a concern of the Chesapeake Bay Program. Although the use of pesticides is a

necessary aspect of pest control, Integrated Pest Management (IPM) techniques can be utilized to

potentially reduce the use of pesticides and possible risks associated with these chemicals. 

Additionally, the utilization of IPM practices improves the overall management of farm inputs. 

Some examples of IPM techniques include scouting, planting resistant varieties, crop rotation,

and utilizing biological controls.

Current data show that more than 30 percent of the cropland acreage within the watershed

is under some level of IPM. These data, however, are inconsistent between the states and may

not capture the total number of acres under IPM. The Pesticide Workgroup (workgroup) of the

Toxics Subcommittee is currently initiating efforts to capture data on the adoption of IPM

techniques within the Chesapeake Bay watershed to determine the level of education and

outreach efforts necessary to increase IPM. 

To determine the potential impacts to the Bay, a current pesticide usage analysis must be

completed to determine what pesticides are actually being used. This will allow IPM managers

to focus efforts on those pesticides with the highest risk as well as determine a baseline from

which to measure any decrease in pesticide use.

PESTICIDE USAGE ANALYSIS

Pesticide use in the Chesapeake Bay watershed in terms of pounds of active ingredient

(AI) applied is targeted mainly toward weed control on agronomic crops. The control of

competitive weed populations in corn, soybeans, alfalfa, and small grains through pesticide

inputs allows farmers to minimize labor, equipment, and time constraints associated with specific

farm economics.

This chapter summarizes usage estimates from 1990 - 1996 for those pesticides that are
Pesticide Use

7-2

used most frequently on the four major crops within the Chesapeake Bay watershed: corn, alfalfa,

soybeans, and small grains (wheat, oats/rye, and barley). These crops represent approximately

80-90 percent of all cropland within the watershed, excluding other hay and land used for

pasture. The data for the remaining crops that represent 10-20 percent of the cropland will not

likely be as reliable at the state level. Thus, these data were not presented. Data gathering

techniques utilized for this usage analysis are explained later in this chapter.

Although this analysis quantifies only the most frequently used pesticides on each of the

four crops, there are also several others which were listed that show relatively minor usage across

all three states. For example, although only 10,000 pounds AI of aldicarb were applied to

soybeans in 1996, it was the only insecticide that displayed any quantifiable usage. Thus, it was

included in the table to provide the reader with an idea of which insecticide was typically chosen. 

If these pesticides were not unique in some fashion, they were not included in the table.

Figures 7.3 and 7.4 provide a trend analysis of pesticide usage from 1990-1996 in terms

of pounds AI applied to agricultural lands and multiple acres treated within the Bay watershed. 

These tables provide context to the chemical specific analysis provided in Tables 7.1-7.5. The

differences between the aggregated 1996 estimates presented in Table 7.1 and those presented in

Figures 7.3 and 7.4 can be explained by the number of chemicals accounted for in each of the

analyses. The number of chemicals accounted for in Tables 7.1-7.5 is a subset of the total range

of pesticides presented in Figures 7.3 and 7.4.

Additionally, Figures 7.3 and 7.4 show that pesticide usage is variable from year to year

due to several factors including weather, pest pressure, product availability, price, and regulatory

concerns. Other limitations of these data will be discussed later in this chapter as well as steps

necessary to better quantify usage within this region.

Table 7.1 provides aggregated totals and Tables 7.2-7.5 provide a summary of the major

pesticides usage for the aforementioned crops. Usage on Tables 7.2-7.5 is shown for each crop,

by chemical and state. Pesticides that showed relatively minor usage are listed at the bottom in

the “Notes” section. It is important to note that all of these tables present the data as total pounds

AI on multiple acres treated. Multiple acre treatments occur when a given pesticide is applied

more than once to the same acre in a particular year. This allows us to present the total pounds

AI applied annually of a given pesticide.

The herbicides that were used most frequently (atrazine and metolachlor) in the Bay

watershed constitute the bulk of overall pesticide usage and are applied at relatively stable rates

of application from year to year. Atrazine and metolachlor represent two families of herbicides

which account for the majority of groundwater concerns in this country. IPM approaches could

potentially reduce these risks.
Pesticide Use

7-3

Corn

Table 7.2 shows that in 1996, about 6.5 million pounds AI were applied to about 5.5

million acre treatments. Atrazine is the largest contributor to this total with about 35 percent of

the total pounds AI and multiple acres treated. Atrazine (35 percent), metolachlor (26 percent),

pendimethalin (8 percent), and alachlor (7 percent) represent more than 75 percent of the total

pounds AI applied. Herbicides account for nearly 95 percent of the total pounds AI applied to

corn.

Alfalfa

Based on historical estimates, pesticide usage was relative low for alfalfa in 1996. 

Previous year estimates show that it would not be uncommon for usage to exceed 1996 estimates

fourfold. Table 7.3 shows that approximately 112,000 acre treatments were treated with 70,000

pounds AI in 1996. Dimethoate (33 percent) and chlorpyrifos (14 percent) represent the largest

pesticides used in terms of pounds AI. Dimethoate (32 percent), carbofuran (13 percent), and

chlorpyrifos (12 percent) represent the largest usage in terms of multiple acre treatments. All of

these chemicals are considered insecticides and accounted for two thirds of all pesticides applied

to alfalfa.

Soybeans

Pesticide usage was relatively low for soybeans in 1996 compared to other years. 

However, it was still in the range of other years which was not the case for alfalfa. Table 7.4

shows that approximately 1.4 million pounds AI were applied to more than 1.7 million acre

treatments. Metolachlor (42 percent), alachlor (14 percent), and glyphosate (13 percent)

accounted for nearly 70 percent of the total pounds AI applied. Aldicarb, which accounted for

less than 1 percent of total usage, was the sole insecticide that made the list.

Small Grains

Table 7.5 presents usage on small grains (wheat, oats/rye, and barley) and shows that

more than one million acre treatments received a pesticide application in 1996. 2,4-D accounted

for 31 percent of the 183,000 pounds AI applied to these sites. In addition to 2,4-D, glyphosate

(17 percent) and disulfoton (15 percent) represented more than 60 percent of pesticides applied. 

Small grains received the lowest typical rates of any of the crops with an average rate of less than

0.2 pounds AI/acre/year for all of the pesticides combined. Small grains were the only crops in

which a fungicide (mancozeb, propiconazole, and tridimefon) made the list of major chemicals

used.

Corn accounted for 79 percent of the total pounds AI applied to the four crops within the

Bay watershed in 1996. Soybeans accounted for 18 percent of total pesticide usage, small grains
Pesticide Use

7-4

accounted for 2 percent, and alfalfa received less than one percent of all pesticides applied. 

1,985,000 acres of corn (42 percent), 1,140,000 acres of soybeans (23 percent), 990,000 acres of

small grains (20 percent), and 740,000 acres of alfalfa (15 percent) were planted in the Bay

watershed in 1996. Atrazine (28 percent) and metolachlor (28 percent) accounted for over half of

all pesticides applied to these four sites.

Additionally, Pennsylvania, Maryland and Virginia accounted for 49%, 28%, and 23%,

respectively, of the total pounds AI applied and multiple acres treated. Herbicides accounted for

approximately 95 percent of the total pounds AI applied to these four crops.

DISCUSSION OF DATA GATHERING TECHNIQUES AND LIMITATIONS

It is vitally important to note that pesticide usage is variable and may or may not represent

an average year for any specific site analyzed. Several factors can influence pesticide usage in

any given year. Some of these factors include pest pressure, economics, weather, regulatory

concerns, etc. Thus, this analysis provides only a snapshot of chemical specific pesticide usage

in 1996. The trend analysis attempts to provide a more general overview of pesticide usage.

The pesticide usage estimates are based on proprietary and non-proprietary data sources. 

Some of the non-proprietary sources include U.S. Department of Agriculture’s 1992 National

Agricultural Statistics Service, National Agricultural Chemical Association’s 1992 Industry

Profile, 1992 pesticide usage analysis for the National Center for Food and Agricultural Policy,

state surveys, and state pesticide experts. These data were compared to those in the proprietary

data sources to derive more reliable estimates.

To establish usage estimates for the watershed, a multiplier was applied to the state usage

estimates. This multiplier was derived by dividing the crop specific acreage within the watershed

portion of the state by the total acreage of that crop within the entire state. This allowed for the

use of state pesticide usage estimates which are more reliable than county estimates because the

data is derived from a much larger sample size. Reliable data showing crop acreage within

counties that lie within the Bay watershed are available from the states’ agricultural statistics

service.

Since all data sources have unique limitations, it is preferable to derive pesticide usage

estimates from as many sources as possible. Although this analysis did utilize several sources,

additional data sets would improve the quality of these data.

Due to agreements with companies that provide proprietary data, point estimates from

these sources can not be disclosed. This is another reason several sources are utilized. 

Proprietary sources provide more validity to those estimates that are publicly available because

these sources tend to be more statistically valid. Thus, they are an integral component of this

analysis.
Pesticide Use

7-5

PESTICIDES IN SURFACE AND GROUND WATER

As stated earlier in the introduction, the use of pesticides for agricultural and nonagricultural purposes and the potential for these chemicals to adversely affect both surface and

ground water as well as the Bay’s living resources is a concern of the Chesapeake Bay Program. 

Many pesticides are soluble in water and may enter the Bay or its tributaries in a dissolved state

through storm water and ground water flows.

Ground water delivers more than half of the fresh water that enters the Bay. This water is

transported to the Bay as base flow to non-tidal tributaries or upwelled directly to the mainstem

and tidal tributaries. Although the Bay is not utilized for drinking water, excessive pesticide

exposure could have negative impacts on the overall ecosystem.

Pesticides and/or their metabolites are typically persistent in the environment. This

characteristic can result in undesirable loads to surrounding ground and surface water. Estimates

of these loads for select pesticides are reported in the fall line and atmospheric deposition chapter

of this inventory. 

Additionally, this section provides a summary of ambient levels of high use pesticides

found in surface and ground water. The United States Geological Survey (USGS) recently

released two reports entitled “Pesticides in Surface Water of the Mid-Atlantic Region” and

“Nitrate and Selected Pesticides in Ground Water of the Mid-Atlantic Region.” Along with the

pesticide usage data, these reports provide a comprehensive view of where these chemicals are

being detected in ground water and surface water samples. 

Table 7.6 and Figure 7.1 summarize data for the high use pesticides detected in surface

water. Four pesticides (atrazine, metolachlor, simazine, and 2,4-D) were detected in over 50

percent of the sites sampled. The remaining six pesticides were only detected at 7-30 percent of

the sites sampled. Chlorpyrifos concentrations in surface water exceeded the federal acute

ambient water quality criterion once (0.14 percent of analyses) and the chronic criterion twice

(0.28 percent of analyses). There are no chronic or acute criteria for the other high use

pesticides. Atrazine was detected in over 90 percent of the sites sampled and 86 percent of

analyses. Concentrations ranged from 0.002-25 ug/l, well below the level judged to be

ecologically significant (50 ug/l; Solomon et al., 1996).

Table 7.7 and Figure 7.2 provide a summary of data related to pesticides detected in

ground water. The number of detections in ground water was significantly less than what was

found in surface water. Atrazine was the only pesticide detected in greater than 50 percent of the

sites sampled. It should be noted that both Tables 7.6 and 7.7 present data for only those high

use pesticides listed in Table 7.1 and for which USGS screened for.
Pesticide Use

7-6

RECOMMENDATIONS

< The link between pesticide usage, ambient levels in the Bay and the potential for negative

impacts to the ecosystem is unclear. This area should be the primary focus for additional

research efforts. Additionally, these efforts should not focus solely on pesticides but

include heavy metals and nutrients as well. 

< In order to ensure that ambient concentrations of the high use pesticides in the

Chesapeake Bay are below levels that cause adverse impacts on aquatic life, ambient

water quality criteria must be developed.
Table 7.1. Pesticide Usage on the Four Major Crops Grown Within the Chesapeake Bay Watershed by Chemical Name, 19961

.

Chemical Name

Pounds Active Ingredient (AI) (000) Multiple Acres Treated2

(000)

Typical Rate

Pounds AI/Acre/Year

MD PA VA TOTAL3 MD PA VA TOTAL3 MD PA VA AVERAGE

2,4-D (H) 49 111 43 203 109 186 56 351 0.5 0.6 0.8 0.6

Alachlor (H) 96 261 296 653 48 136 134 318 2.0 1.9 2.2 2.1

Atrazine (H) 610 1,241 419 2,270 447 1,061 305 1,813 1.4 1.2 1.4 1.3

Carbofuran (I) 30 60 24 114 32 64 25 121 0.9 0.9 1.0 0.9

Chlorpyrifos (I) 39 116 50 205 36 112 67 215 1.1 1.0 0.7 1.0

Cyanazine (H) 79 248 15 342 56 144 9 209 1.4 1.7 1.7 1.6

Dicamba (H) 37 56 8 101 186 180 27 393 0.2 0.3 0.3 0.3

Glyphosate (H) 154 170 101 425 196 164 119 479 0.8 1.0 0.8 0.9

Metolachlor (H) 640 1,046 586 2,272 379 643 373 1,395 1.7 1.6 1.6 1.6

Metribuzin (H) 40 17 21 78 150 58 82 290 0.3 0.3 0.3 0.3

Paraquat (H) 110 40 79 229 230 60 153 443 0.5 0.7 0.5 0.5

Pendimethalin (H) 26 542 45 613 36 514 49 599 0.7 1.1 0.9 1.0

Simazine (H) 131 74 39 244 108 54 35 197 1.2 1.4 1.1 1.2

TOTAL32,041 3,982 1,726 7,749 2,013 3,376 1,434 6,823 N/A N/A N/A N/A

1

 -The acreage of these crops across the three states are as follows: corn - 1,985,000, soybeans - 140,000, small grains - 990,000, and alfalfa - 740,000.

2

 - Includes multiple applications of a given pesticide on the same acre in the same year.

3

 - Totals may not add down or across due to rounding.

Notes:

C H = Herbicide, I = Insecticide, N/A = Not Applicable, - = Unknown

C Please see Tables 1 - 4 for those pesticides which showed relatively insignificant usage across all three states.

C Data based on several proprietary and non-proprietary sources.
7-8

Table 7.2. Pesticide Usage on Corn in the Chesapeake Bay Watershed by Chemical Name, 19961.

Chemical Name

Pounds Active Ingredient (AI) (000) Multiple Acres Treated2

(000)

Typical Rate

Pounds AI/Acre/Year

MD PA VA TOTAL3 MD PA VA TOTAL3 MD PA VA AVERAGE

2,4-D (H) 37 72 38 147 93 128 46 267 0.4 0.6 0.8 0.6

Alachlor (H) 56 240 152 448 28 128 68 224 2.0 1.9 2.2 2.0

Atrazine (H) 605 1,240 418 2,263 442 1,060 304 1,806 1.4 1.2 1.4 1.3

Carbofuran (I) 28 56 23 107 28 56 23 107 1.0 1.0 1.0 1.0

Chlorpyrifos (I) 37 112 46 195 33 108 61 201 1.1 1.0 0.8 1.0

Cyanazine (H) 79 248 15 342 56 144 9 209 1.4 1.7 1.7 1.6

Dicamba (H) 37 56 8 101 186 180 27 393 0.2 0.3 0.3 0.3

Glyphosate (H) 60 128 15 204 79 112 19 210 0.8 1.1 0.8 1.0

Metolachlor (H) 465 880 319 1,664 279 560 209 1,048 1.7 1.6 1.5 1.6

Paraquat (H) 79 32 49 160 163 44 91 298 0.5 0.7 0.5 0.5

Pendimethalin (H) <1 500 4 505 <1 460 4 465 - 1.1 1.0 1.1

Simazine (H) 130 72 38 240 107 52 34 193 1.2 1.4 1.1 1.2

Terbufos (I) 56 40 15 111 37 32 11 81 1.5 1.3 1.3 1.4

TOTAL31,670 3,676 1,140 6,486 1,531 3,064 906 5,501 N/A N/A N/A N/A

1

 - 1,985,000 acres of corn were grown in the watershed in 1996 (MD - 495,000; PA - 1,150,000; VA - 340,000)

2

 - Includes multiple applications of a given pesticide on the same acre in the same year.

3

 - Totals may not add down or across due to rounding.

Notes:

C H = Herbicide, I = Insecticide, N/A = Not Applicable, - = Unknown

C Acetochlor, bromoxynil, butylate, dimethenamid, EPTC, esfenvalerate, icosulfuron, methyl parathion, permethrin, phorate, primisulfuron, and tefluthrin all

showed relatively insignificant usage across all three states.

C Data based on several proprietary and non-proprietary sources.
7-9

Table 7.3. Pesticide Usage on Alfalfa in the Chesapeake Bay Watershed by Chemical Name, 19961.

Chemical Name

Pounds Active Ingredient (AI) (000) Multiple Acres Treated2

(000)

Typical Rate

Pounds AI/Acre/Year

MD PA VA TOTAL3 MD PA VA TOTAL3 MD PA VA AVERAGE

2,4-DB (H) <1 4 1 6 <1 8 1 10 - 0.5 0.5 0.5

Carbofuran (I) 2 4 1 7 4 8 2 14 0.5 0.5 0.5 0.5

Chlorpyrifos (I) 2 4 4 10 3 4 6 13 0.7 1.0 0.8 0.8

Dimethoate (I) 2 20 1 23 4 28 4 36 0.5 0.7 0.3 0.7

EPTC (H) <1 2 1 4 <1 <1 1 3 - 1.6 2.0 1.5

Hexazinone (H) 2 2 <1 5 2 2 <1 5 1.0 1.0 - 1.0

Paraquat (H) 1 4 1 6 2 8 1 11 0.5 0.5 0.5 0.5

Permethrin (I) <1 4 <1 6 4 12 <1 17 0.3 0.3 - 0.4

Simazine (H) 1 2 1 3 1 2 1 3 1.0 1.0 1.0 1.0

TOTAL313 45 12 70 22 72 18 112 N/A N/A N/A N/A

1

 - 740,000 acres of alfalfa were grown in the watershed in 1996 (MD - 60,000; PA - 600,000; VA - 80,000)

2

 - Includes multiple applications of a given pesticide on the same acre in the same year.

3

 - Totals may not add down or across due to rounding.

Notes:

C H = Herbicide, I = Insecticide, N/A = Not Applicable, - = Unknown

C 1996 was a relatively low year for pesticide usage on alfalfa.

C 2,4-D, methyl parathion, metribuzin, pendimethalin, phosmet, sethoxydim, and terbacil all showed relatively insignificant usage across all three states.

C Data based on several proprietary and non-proprietary sources.
7-10

Table 7.4. Pesticide Usage on Soybeans in the Chesapeake Bay Watershed by Chemical Name, 19961.

Chemical Name

Pounds Active Ingredient (AI) (000) Multiple Acres Treated/2

(000)

Typical Rate

Pounds AI/Acre/Year

MD PA VA TOTAL3 MD PA VA TOTAL3 MD PA VA AVERAGE

Acifluorfen (H) 5 2 12 19 10 4 37 51 0.5 0.4 0.3 0.4

Alachlor (H) 40 21 144 204 20 8 66 94 2.0 2.5 2.2 2.2

Aldicarb (I) <1 <1 8 10 <1 <1 8 10 - - 1.0 1.0

Dimethanamid (H) 65 <1 <1 67 55 <1 <1 57 1.2 - - 1.2

Fomesafen (H) <1 <1 16 18 <1 <1 45 47 - - 0.4 0.4

Glyphosate (H) 80 37 74 191 105 46 90 241 0.8 0.8 0.8 0.8

Imazaquin (H) 5 2 7 13 30 8 16 55 0.2 0.2 0.4 0.2

Imazethapyr (H) 5 4 4 13 50 50 61 161 0.1 0.1 0.1 0.1

Linuron (H) 15 14 21 50 30 29 45 104 0.5 0.5 0.5 0.5

Metolachlor (H) 175 166 267 608 100 83 164 347 1.8 2.0 1.6 1.8

Metribuzin (H) 40 17 21 77 150 58 82 290 0.3 0.3 0.3 0.3

Paraquat (H) 30 4 29 63 65 8 61 135 0.5 0.5 0.5 0.5

Pendimethalin (H) 25 42 41 108 35 54 45 134 0.7 0.8 0.9 0.8

TOTAL3487 311 643 1,441 652 352 723 1,726 N/A N/A N/A N/A

1

 - 1,140,000 acres of soybeans were grown in the watershed in 1996 (MD - 490,000; PA - 240,000; VA - 410,000).

2

 - Includes multiple applications of a given pesticide on the same acre in the same year.

3 - Totals may not add down or across due to rounding.

Notes:

C H = Herbicide, I = Insecticide, N/A = Not Applicable, - = Unknown

C 2,4-D, 2,4-DB, bentazone, chlorimuron, clethodim, clomazone, fenoxaprop, fluazifop, flumetsulam, sethoxydim, permethin, and trifluralin all showed

relatively insignificant usage across all three states.

C Data based on several proprietary and non-proprietary sources.
7-11

Table 7.5. Pesticide Usage on Small Grains in the Chesapeake Bay Watershed by Chemical Name, 19961.

Chemical Name

Pounds Active Ingredient (AI) (000) Multiple Acres Treated2

(000)

Typical Rate

Pounds AI/Acre/Year

MD PA VA TOTAL3 MD PA VA TOTAL3 MD PA VA AVERAGE

2,4-D (H) 12 39 5 56 16 58 10 84 0.8 0.7 0.5 0.7

Atrazine (H) 5 <1 <1 7 5 <1 <1 7 1.0 - - 1.0

Disulfoton (I) <1 <1 25 27 <1 <1 33 35 - - 0.8 0.8

Glyphosate (H) 14 5 12 31 12 6 10 28 1.2 0.8 1.3 1.1

Lambda-cyhalothrin 1 <1 2 4 74 <1 62 138 0.0 - 0.0 0.0

MCPA (H) 2 12 <1 14 7 31 <1 38 0.3 0.4 - 0.4

Mancozeb (F) <1 7 <1 9 <1 5 <1 7 - 1.5 - 1.3

Propiconazole (F) 9 2 4 15 74 15 33 123 0.1 0.1 0.1 0.1

Thifensulfuron (H) 5 2 2 8 140 27 108 274 0.0 0.1 0.0 0.0

Triadimefon (F) 5 1 <1 6 28 5 <1 34 0.2 0.1 - 0.2

Tribenuron (H) 5 2 1 7 140 27 100 266 0.0 0.1 0.0 0.0

TOTAL359 70 55 183 497 177 360 1,034 N/A N/A N/A N/A

1

 - 990,000 acres of small grains were grown in the watershed in 1996 (MD - 300,000; PA - 380,000; VA - 310,000)

2

 - Includes multiple applications of a given pesticide on the same acre in the same year.

3 - Totals may not add down or across due to rounding.

Notes:

C F = Fungicide, H = Herbicide, I = Insecticide, N/A = Not Applicable, - = Unknown.

C 2,4-DB, aldicarb, bromoxynil, carbaryl, carbofuran, dicamba, diclofop, dimethoate, paraquat, malathion, methomyl, and thiodicarb all showed relatively

insignificant usage across all three states.

C Data based on several proprietary and non-proprietary source.
7-12

Table 7.6. High Use Pesticides in Surface Water Sampled in the Chesapeake Bay Watershed (1993-1996).

Pesticide Number of Number of Percent of Number of Number of Percent of Acute Number of Chronic Number of

Analyses * Detections Analyses Sites Sites with Sites with Criterion Acute Criterion Chronic 

with Sampled Detections Detections (ug/l) Exceedences (ug/l) Exceedences

Detections

2,4-D 264 39 14.8 17 9 52.9

ALACHLOR 1012 398 39.3 279 73 26.2

ATRAZINE 1013 875 86.4 279 252 90.3

CARBOFURAN 713 47 6.6 272 24 8.8

CHLORPYRIFOS 732 113 15.4 271 27 10.0 0.0830 1 0.0410 2

CYANAZINE 781 252 32.3 279 83 29.7

METOLACHLOR 1012 832 82.2 279 231 82.8

METRIBUZIN 732 62 8.5 271 21 7.7

PENDIMETHALIN 709 112 15.8 271 19 7.0

SMAZINE 1012 821 81.1 279 228 81.7

* The number of analyses refers to the number of samples for a pesticide that are unique for a station, date, time, and medium. 

Note: These data are from USGS's Mid-Atlantic Assessment (MAIA) project: pesticide concentrations from 463 surface water sites. Only data from 1993-1996 within the Chesapeake 

Bay Watershed were used for this analysis. These data are referenced in the USGS Water-Resources Investigations Report 97-4280 entitled “Pesticides in Surface Water of the Mid-Atlantic Region.”
7-13

Table 7.7. High Use Pesticides in Ground Water Sampled in the Chesapeake Bay Watershed (1993-1996).

Pesticide Number of Number of Percent of Number of Number of Percent of 

Analyses Detections Analyses Sites Sites with Sites with 

with Sampled Detections Detections

Detections

2,4-D 261 1 0.4 259 1 0.4

ALACHLOR 322 20 6.2 309 20 6.5

ATRAZINE 323 184 57.0 310 178 57.4

CARBOFURAN 315 7 2.2 304 6 2.0

CHLORPYRIFOS 314 0 0.0 303 0 0.0

CYANAZINE 314 12 3.8 303 12 4.0

METOLACHLOR 323 140 43.3 310 134 43.2

METRIBUZIN 322 3 0.9 309 3 1.0

PENDIMETHALIN 314 1 0.3 303 1 0.3

SIMAZINE 323 119 36.8 310 115 37.1

* The number of analyses refers to the number of samples for a pesticide that are unique for a station, date, time, and medium. 

Note: These data are from USGS's Mid-Atlantic Assessment (MAIA) project: nitrogen and pesticide concentrations for 937 

ground water sites. Only data from 1993-1996 within the Chesapeake Bay Watershed were used for this analysis.
Pesticide Use

7-14

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High Use Pesticides in Ground Water

Sampled in the Chesapeake Bay Watershed

(1993-1996)

Note: These data are from USGS's Mid-Atlantic Assessment (MAIA) project: nitrogen and pesticide concentrations for

937 ground water sites. Only data from 1993-1996 within the Chesapeake Bay Watershed were used for this analysis.

High Use Pesticides

2,4-D

ALACHLOR

ATRAZINE

CARBOFURAN

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CYANAZINE

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METRIBUZIN

PENDIMETHALIN

SIMAZINE

N

U Ground Water Sites - No Detections

% Ground Water Sites - Detections

Figure 7.1. Surface water pesticide detection sites.
Pesticide Use

7-15

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Sampled in the Chesapeake Bay Watershed

(1993-1996)

Note: These data are from USGS's Mid-Atlantic Assessment (MAIA) project: nitrogen and pesticide concentrations for

937 ground water sites. Only data from 1993-1996 within the Chesapeake Bay Watershed were used for this analysis.

High Use Pesticides

2,4-D

ALACHLOR

ATRAZINE

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% Ground Water Sites - Detections

Figure 7.2. Ground water pesticide detection sites.
Pesticide Use

7-16

0

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1990 1991 1992 1993 1994 1995 1996

Year

Multiple Acres Treated (000)

Pennsylvania

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1990 1991 1992 1993 1994 1995 1996

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Pennsylvania

Maryland

Virginia

Figure 7.3. Multiple Acres Treated With Pesticides Within the Watershed.

Figure 7.4. Pounds of Pesticide Active Ingredients Applied to Agricultural Lands Within the Watershed.
8-1

CHAPTER 8 - Relative Importance of Point and Non-Point

Sources of Chemical Contaminants to Chesapeake Bay

David Velinsky Joel Baker

Patrick Center for Environmental Research Chesapeake Biological Laboratory

The Academy of Natural Sciences University of Maryland

1900 Benjamin Franklin Parkway P.O. Box 38

Philadelphia, PA 19103-1195 Solomons, MD 20688

INTRODUCTION

This chapter compares the loadings of selected contaminants from point and nonpoint

sources to assess the relative importance of each source in contributing loads to the tidal Bay and

its major tidal rivers. This comparison of loadings from each source category will enable

managers to determine where to focus limited resources for source reductions in specific areas of

the Chesapeake Bay watershed. Specific objectives of this chapter are to: 1) combine loading

estimates from individual sources (as described in the previous chapters) to yield annual loadings

of selected contaminants to the mainstem Chesapeake Bay and tributaries; 2) compare the

magnitudes of individual loadings to assess the relative importance of each source type; 3)

examine the errors and uncertainties in the current estimated loadings; and 4) recommend further

actions to reduce the uncertainty in loadings to the Bay. Sources such as atmospheric deposition,

urban runoff, point sources, and fall line inputs to the tidal Bay are examined and augmented

with shoreline erosion rates, where possible. Loads for selected contaminants are presented for

the mainstem tidal area as well as major sub-tributaries of Chesapeake Bay such as the Potomac,

James, and Patuxent rivers. In addition, estimates are made for the Anacostia watershed which

was designated by the Chesapeake Executive Council as one of three Regions of Concern. The

Anacostia had the most complete data set of the three areas.

METHODOLOGY

Specific chemicals that were investigated for this comparative analysis include selected

trace elements arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), mercury (Hg), and zinc (Zn). 

Loading information was also compiled for organic contaminants including total polychlorinated

biphenyls (PCBs) and specific polycyclic aromatic hydrocarbons (PAHs) such as chrysene,

phenanthrene, pyrene, and benzo(a)pyrene. These chemicals were chosen due to their inclusion

in the Chesapeake Bay Toxics of Concern List (CBP, 1998) and availability of data for the

various sources. 

The data for this analysis and the limitations of each data set are presented in previous

chapters of this report. In general, the sources chosen for these estimates include point sources
Comparative Loadings in the Bay

8-2

(municipal, industrial, and federal), non-point sources (shoreline erosion and urban runoff),

riverine runoff from upstream sources (loads from the non-tidal portion of the watershed entering

tidal waters at the fall line), and atmospheric deposition (Figure 8.1). For this comparative

loadings analysis, loadings to the tidal portion of the Chesapeake Bay rivers are fall line loadings,

representing the total loadings from upstream sources, and below fall line loadings from point

sources, atmospheric deposition, urban runoff and shoreline erosion. The fall line is the zone

between tidal and non-tidal waters of each tributary. For this report, fall line inputs are the

integrated sum of the various sources within the watershed. They include point source and nonpoint sources upstream of the fall line. Below are brief descriptions of the methods used for each

source category for this chapter.

Point Source

Loadings from the Point Source chapter (Chapter 1) for the chemicals indicated above

were used for this analysis, and unless otherwise noted, the high and low estimates were

averaged. For the trace metals, dissolved, total recoverable, or total loads are reported in Chapter

1. This was due to the reporting method and type of chemical analysis by each facility. In this

chapter, the highest load from these three categories was used for comparison. Lastly, loads for

total PCBs were estimated from Arochlor 1260 only. All loads are reported in pounds per year

(lb/yr).

Urban Stormwater Runoff

Data were obtained from Chapter 2 of this document. In brief, runoff volumes were

calculated from relationships between rainfall, land use, and impervious area. Chemical loads

were determined from the runoff volume and literature-derived event-mean concentrations of

specific chemical contaminants. All loads are reported in pounds per year (lb/yr).

Shoreline Erosion 

To provide a rough estimate of loads of chemical eroding from shoreline sediments, data

presented in Helz et al. (1985) and Bryne and Anderson (1973) were used. From these studies,

the average mass erosion rates (kg sediment/yr) were obtained directly or calculated from volume

erosion rates (m3 sediment /yr) and estimates of bulk sediment density. Metal fluxes were

calculated using the average concentrations for shoreline material derived from Helz et al. (1985)

and are reported as lb/yr. Errors inherent in these calculations include the use of average rates

and concentrations throughout the Bay given the geochemical variability of shoreline material. 

In addition, shoreline material is generally more coarse and would only be transported during

storm events. However, these estimates do provide an order of magnitude estimate from

shoreline sources. All loads are reported in pounds per year (lb/yr).
Comparative Loadings in the Bay

8-3

Atmospheric Deposition

Atmospheric deposition samples were collected from three stations located around the

edge of the Bay starting in late 1990 or early 1991 to 1993 from the Chesapeake Bay

Atmospheric Deposition Program. Wet deposition samples were collected weekly or bi-weekly,

while dry deposition was estimated from measured aerosol concentrations and particle deposition

rates (See Chapter 3 for details). Estimates are to the tidal waters of the Bay and tributaries only. 

The loading rates in Chapter 3 were modified to include an urban source effect using data

from Baltimore Harbor and the amount of urban area in the Bay region. Additionally, loads are

direct to the surface waters (i.e., gross absorptive fluxes) and are not corrected for gas or aerosol

exchange back into the overlying air mass unless noted. This is especially important for organic

contaminants such as PCBs and aromatic hydrocarbons, and for mercury for which gas exchange

from the water to the atmosphere can be substantial. All loads are reported in pounds per year

(lb/yr).

Fall Line (i.e., Upstream Sources)

Fall line inputs are those directly delivered to the tidal waters of the specific tributary and

Bay. The fall line, for this report, is the boundary between tidal and non-tidal waters. Fall line

estimates provide a measure of the amount of material discharged or released from all sources in

a watershed above the fall line and delivered to the upper reaches of the Bay’s tidal tributaries

(i.e., James River) or the upper mainstem Bay (i.e., Susquehanna River). Estimates are derived

from the data presented in Chapter 6 for the mainstem Bay and various tributaries and from

Gruessner et al. (1997) for the Anacostia River. All loads are reported in pounds per year (lb/yr).

Chemicals in fall line transport are derived from many upstream sources, both natural and

anthropogenic. As such, above fall line (AFL) inputs include point sources, urban runoff, stream

bank erosion, agricultural sources, acid mine drainage, and atmospheric deposition, among

others. It is not possible at this time to subdivide the total fall line loads by specific contributing

sources. While most sources discharge or are calculated to discharge to the free-flowing river,

atmospheric inputs are deposited to all surface areas (land and water) within the watershed and

need to be transported to the river. There are many attenuating processes that can sequester a

portion of the atmospherically-derived metals or organic compounds before they reach the

adjacent creek, stream or river, and many of these processes are chemical specific due to different

geochemical reactions. Also, once a chemical is introduced into the free-flowing river, similar

geochemical processes can act on the contaminant and can alter the amount of material

eventually transported over the fall line into tidal waters. Therefore, it is difficult to allocate the

above fall line sources noted in the previous chapters into what is actually measured at the fall

line. 
Comparative Loadings in the Bay

8-4

Other Sources

This updated inventory, although more complete than the 1994 inventory, is not a

comprehensive accounting of all loads of all chemical contaminants to the Bay and its tidal

rivers. The load for only a subset of all chemical contaminants entering the Bay were measured

or estimated, and some sources of chemical contaminants loads are not quantified or separated

from the total load. For example, the load to the Bay that is measured at the fall line is the sum

of all sources in the non-tidal watershed including atmospheric deposition to the watershed,

natural weathering of rock and soils, agricultural sources from chemical applications, point

sources, and stormwater runoff. However, due to the lack of adequate data, it is not possible to

allocate the total load into its components. Other sources of loads that have not been fully

accounted for or separated from the various loads are the following:

C Point source loads from over 3,700 minor facilities that discharge with a flow of less than

0.5 million gallons per day,

C The fraction of the atmospheric deposition load that is carried off the watershed (i.e., the

land) into the Bay by stream or river runoff,

C The fraction of the agricultural load that is carried off agricultural land by atmospheric

deposition and subsequent stream runoff,

C Groundwater loads both direct to the tidal Bay and the fraction of the fall line load to the

tidal waters and,

C Natural background loads of chemicals (i.e., trace metals) entering the Bay from natural

process such as mechanical or chemical weathering of rock.

Some of these loads are captured through fall line load estimates and possibly urban

runoff estimates, while others (e.g., direct agricultural loads) were not estimated due to a lack of

accurate data. Therefore, in the figures in this chapter, another category has been added called

“other sources” to remind the reader that this is not a comprehensive inventory and there are

some sources that are not completely accounted for or separated from other source categories.

Uncertainty Analysis of Loads

The determination and quantification of the important input fluxes to Chesapeake Bay are 

complex tasks. Many problems are inherent in these types of calculations including: 1) a general

lack of quality data; 2) incomparability of chemical measurements and forms from each source

category; and 3) incomplete reporting of the various sources as discussed in the previous loading

chapters. There is some level of uncertainty in all loads estimates that are due to a number of

factors (i.e., both systematic and random) ranging from uncertainty in measurements, spatial

extrapolation, temporal variation in rainfall or streamflow, and the method used to estimate

loads. While it would be best to have a consistent method to estimate the uncertainty in each

source category, this may not be possible given the available data. In many cases the level of

uncertainty can be fairly accurately calculated while in some cases the level of uncertainty can
Comparative Loadings in the Bay

8-5

only be estimated. The major cause of error and temporal variation was provided in each chapter

and was incorporated into the comparative loadings analysis. Below is a summary of the

uncertainty analysis that was provided within each source category:

Atmospheric loads 

Baker (Chapter 3) estimated that sources of random error in wet deposition loading

estimates include the measurement errors associated with quantifying chemical concentrations in

precipitation and the rainfall amount. For atmospheric wet deposition, the propagated

uncertainties to the metals and organics fluxes were estimated at ±10% and ±20%, respectively. 

It was estimated that dry aerosol deposition loadings are likely precise to within a factor of 2-3. 

In addition, the overall random error of a typical instantaneous gas exchange flux was calculated

as ± 40%. Lastly, a potentially larger source of uncertainty in deposition loadings results from

the spatial extrapolation from the few regional and single urban deposition sites to the Bay. 

Point Source loads 

A formal uncertainty analysis for point source loads has not been calculated due to the

nature of the data set (Chapter 1). While there are random errors in the calculation of the load,

systematic errors in reporting may also be large. Current methods for estimating organic loads

from point sources are highly uncertain and of limited use, particularly for the organic

contaminants. Reporting programs in which data were collected were not set up with the

objective of calculating loads, but rather for determining compliance with regulated parameters

in discharge permits. For certain chemicals -- all PCBs, pesticides, and most PAHs -- most or all

values were reported at below the detection limits. In addition the detection limit used or

provided may be unduly high relative to the regulatory-based method used for analysis. 

Therefore loading estimates for these contaminants may be as low as zero or as high as the

detection limit multiplied by the flow. However, this uncertainty is not the case for most of the

trace metal data since many measurements were above the detection limit. The range of

estimates based upon the detection limit and flow were used to estimate the likely bounds for the

loads and can be very large dependent on the number of samples that are below the detection

limit. 

As eluded to above, one of the largest uncertainties in this inventory is the point source

load estimate for organic contaminants. In most cases no organic contaminants were detected

and the detection limit was high. For measurements of organic contaminants and some trace

metals that are below the detection limit, using typical pollutant concentrations (TPC) from the

literature (instead of the detection limit) may be a better approach for estimating loads from point

sources. Below is an illustration of the use of a typical pollutant concentration (TPC) to help

constrain the load estimates, using PCBs as an example. For this example, a TPC is used as a

default for point sources that do not have accurate measurements and where detection limits are

high. TPCs are simply “typical” concentrations of a chemical for similar industrial activities or

processes. The TPC provides a planning level estimate that helps understand the possible

relative importance of point sources, and this illustration will help to interpret the point source
Comparative Loadings in the Bay

8-6

organics data presented in this chapter.

Total average PCB loads (i.e., Arochlor 1260) were estimated for the tidal Potomac River

to illustrate the uncertainty of the point source estimates. Atmospheric deposition loads are the

sums of wet and dry deposition, while removal from the surface water via volatilization was not

considered. Fall line loads from the non-tidal watershed were measured over multiple years as

part of the Chesapeake Bay Program Fall Line monitoring program (see Chapter 6). As can be

seen from Figure 8.2, point source load estimates for PCBs are highly uncertain relative to the

other sources. In this regard, virtually all measurements of PCBs are below the detection limit. 

Therefore concentrations could range between zero and the detection limit (e.g., high μg/L),

resulting in loads ranging from 0-210,000 lb/yr. 

To get an idea of what the actual PCB loads are within this large range, one method

would be to assume a typical concentration for total PCBs in point source effluent (based on

values in the literature) for those facilities where PCBs would be expected to be present. Loads

would be calculated by multiplying the concentration by the point source flows in the tidal

portion of the watershed. Recent studies by Durell and Lizotte (1998) and DRBC (1998) showed

wastewater treatment plants (WWTP) effluent concentrations of total PCBs much lower

compared to the detection limits used for Chesapeake Bay point sources. In 26 WWTP effluents

in the NY/NJ Harbor Estuary (Durell and Lizotte, 1998), total PCBs ranged from 0.010 to 0.055

μg/L (sum of 71 target congeners) with an overall average of 0.025 μg/L. Concentrations of total

PCBs from 7 WWTP in the tidal freshwater Delaware River (DRBC, 1998), ranged from

approximately 0.0014 to 0.045 μg/L with an overall average of 0.013 μg/L. 

Assuming a low and high concentration of 0.0014 μg/L and 0.05 μg/L, respectively,

approximately 170 lb/yr of PCBs, on average, are entering the tidal Potomac waters from point

sources (Figure 8.3). This estimate is three orders of magnitude lower than the estimate made

using the given detection limit to calculate loads (200,000 lb/yr). Using literature derived typical

pollutant concentrations, the estimated point source loads of PCBs to the tidal Potomac indicate

that approximately 60% of the total load is derived from point sources and the fall line loads are

comparable to the point source loads, with a very small load originating from atmospheric

deposition. Overall, the use of a TPC for point sources in which most or all of the measured

concentrations are at the detection limit and the limit appears to be unduly high, may be

warranted so that planning level estimates can be derived.

Fall line loading estimates

Uncertainties have not been rigorously evaluated for fall line loading estimates (see

Chapter 6). The level of uncertainty is related to the variability in the measured concentration

and discharge. In addition, estimates of contaminant loadings above the river fall lines are

extremely dependent on river flows, which vary widely throughout the year. While loads for the

Susquehanna, Potomac and James rivers were averaged over multiple years, loads for many

tributaries were obtained for only a single year from only two sampling events. Estimates of
Comparative Loadings in the Bay

8-7

contaminant loadings are dependent on river flow, which can vary substantially from year to

year. Also, due to the extreme cost and time for fall line monitoring and chemical analysis, the

contaminant concentration data used to estimate loads were sparse. The most accurate loadings

exist for the Susquehanna River for which multiple years of data have been collected. For this

analysis, four years of loadings data from the Potomac, James and Susquehanna Rivers were used

to estimate the overall level of uncertainty. The trace metals, copper, cadmium, and lead, were

used as it appears that they had the most complete data set. On average the relative standard

deviation was approximately ± 20%, and this value was applied to all fall line loadings.

Shoreline erosion loads

Variations in the shoreline erosion estimate was based on the range of estimates between

the 1994 estimate from the 1994 Reevaluation Report (CBP, 1994b) and the estimate from the

1982 Technical Synthesis Report (CBP, 1982). These were independently determined and

provide some idea as to the range of loads from shoreline sediments.

Urban runoff loads

The uncertainty in the urban runoff load estimates were not rigorously determined, but a

rough estimate of the quantifiable uncertainty was presented (see Chapter 2). Three main sources

of quantifiable error have been identified: modeling error in the average annual runoff estimates,

interannual variability in the estimates (i.e., runoff), and variability in the measured chemical

contaminant concentrations. A comparison of the basinwide urban land use data that was used in

the Chesapeake Bay Watershed Model suggested an estimate of about ± 10% error in the amount

of urban land and the percentage of impervious surface associated with those urban areas

(Mandel et al., 1997), both of which affect the average annual runoff estimates. There was some

additional uncertainty or variation associated with the average annual runoff estimates due to

interannual variability in rainfall amounts. To develop an estimate of this uncertainty, 95%

confidence intervals were calculated around the mean annual runoff estimates from 1986-1993. 

The magnitudes of the confidence intervals in either direction, expressed as the percent of the

mean, ranged from 9 to 26% and the average was 16%. Combining the ±10% estimate of

modeling error due to land use with the ±16% error from the interannual runoff variability, the

uncertainty in the calculated runoff values is likely to be about ±25%. A similar approach was

taken to determine order of magnitude estimates in the uncertainty of the EMC values. 

Gruessner et al. estimated a conservative error of ±54% as an estimate of the uncertainty in the

EMC values and since the load estimates are calculated from the product of the runoff and EMC

values, the combined quantifiable uncertainties suggest that the average annual loads are

approximately ± 60%. This level of uncertainty was applied to all urban runoff estimates.

INPUTS TO THE TIDAL CHESAPEAKE BAY

The loads of selected chemical contaminants to the tidal Chesapeake Bay were calculated

by taking the sum of all estimates of loadings entering the tidal rivers of the Bay for atmospheric
Comparative Loadings in the Bay

8-8

deposition, fall line loads, urban runoff, shoreline erosion, and point sources that are described in

previous chapters of this inventory.

Trace Elements

Summary: The highest estimated metals load comes from upstream sources (fall line) to

the tidal waters of the Bay. 

Point source loads are important for copper and mercury. 

Loads from shoreline erosion and urban runoff account for up to 13% of the

total metals loads to the tidal Bay.

In Figures 8.4-8.9, the various inputs of cadmium, copper, lead, mercury, zinc, and

arsenic are summarized along with the total load (in lb/yr) to the tidal waters of Chesapeake Bay. 

The trace metals copper and zinc had the greatest average total load to the tidal Bay of 710,000

lb/yr and 3,300,000 lb/yr, respectively, while mercury had the least, 9,500 lb/yr. 

Fall Line

All metal loads are dominated by upstream inputs (fall line loads). These loads are likely

underestimated because not all Bay tributaries were sampled and quantified; however, this

would be a small load since the total flow is dominated by the tributaries that were monitored. 

Point Sources

Point source inputs are important for mercury and copper. The level of uncertainty in the

copper loads estimates is very low because the majority of measurements were above the

detection limit. However, there was more uncertainty in the mercury loads estimates because

many of the values were below detection limit (see previous discussion of uncertainty for point

sources)

Shoreline Erosion

Erosion of shoreline material accounts for less than approximately 13% of the total load,

with the greatest loads to the tidal Bay for zinc and lead.

Urban Runoff

Urban runoff accounts for between 6 and 13% of the total load for these trace elements,

the greatest being for lead and zinc.

Atmospheric Deposition

Atmospheric inputs of metals directly to tidal waters are a small percentage of the total

load and range from approximately 3% for copper and cadmium to 7% for lead. Atmospheric
Comparative Loadings in the Bay

8-9

inputs of lead are approximately twice as high as point source inputs. The importance of this is

not just that the load is higher but also that it is spread out over the entire tidal water area, while

point source inputs are usually in small bays or tributaries. 

Organic Contaminants

Summary: Urban stormwater runoff is a substantial source of PAHs to the tidal

Chesapeake Bay.

Point sources of organic contaminants (PAHs, and PCBs) are highly uncertain

and therefore loads are largely unknown.

Total PCBs loads are approximately equally divided between atmospheric and 

fall line loads to the tidal waters of the Bay.

Estimates for organic contaminant loads to the mainstem tidal Bay are presented in

Figures 8.10-8.13 for four polycyclic aromatic hydrocarbons (PAHs, benzo[a]pyrene, chrysene,

phenanthrene, and pyrene) and total PCBs (no figure provided). No data for PAH loads from

shoreline erosion were available. 

For specific aromatic hydrocarbons, average loads range from 130,000 lb/yr for

phenanthrene to 64,000 lb/yr for benzo[a]pyrene and chrysene (Figures 8.10-8.13). Total PCB

loads to the tidal waters of the Bay, without point source estimates are nearly equally divided

between fall line inputs (650 lb/yr) and atmospheric deposition (wet and dry) to the tidal waters

(540 lb/yr).

Point Sources

Point source loads estimates of PAHs are highly uncertain as indicated by the large

uncertainty bars in Figures 8.10-8.13. Virtually all of the measurements of PAHs were below the

detection limit. Therefore the loads could range anywhere between zero to the product of the

detection limit and flow. Therefore, the point source loads of PAHs are unknown and the data

presented in the figures are of limited use.

Urban Runoff

Given that point source loads estimates are highly uncertain, the urban stormwater runoff

is the most substantial known source of PAH loads to the tidal Bay. Urban runoff accounts for

approximately 12% of the total input of PAHs to the tidal Bay. Since the point source loads

estimates are so uncertain, the relative contribution of urban runoff is probably much greater than

initially estimated. Urban stormwater runoff would include power plant combustion, automobile

emissions, both gas/oil combustion and oil drippings, and tire wear. 
Comparative Loadings in the Bay

8-10

Fall Line/Atmospheric Deposition

Inputs from the non-tidal watershed (as measured at the fall line) account for less than 3%

of the total load while total atmospheric deposition (i.e., wet, dry, and gas exchange into the

water) ranges from < 0.5% for benzo[a]pyrene (77 lb/yr) to 5% for phenanthrene (6,400 lb/yr). 

INPUTS TO TRIBUTARIES OF CHESAPEAKE BAY

A comparison of the point and nonpoint source loads was conducted for some of the

major tributaries of the Bay: the James, Potomac and Patuxent rivers below the fall line. The

organic contaminant data used to make these comparisons for many of the tributaries have a large

amount of uncertainty (i.e., point source data), therefore only trace elements (copper, cadmium,

and lead) and a subset of the organic data (i.e., PAHs only) will be discussed below for all areas. 

Total PCB loadings data are not presented due to the uncertainties in the point source data. An

illustration of this uncertainty was presented above. In addition, loadings estimates were

compiled for one of the three Regions of Concern with the most complete loadings data set

(Anacostia River) and compared to the three larger rivers. 

Inputs of Chemical Contaminants to the James, Potomac, and Patuxent Rivers

Summary: Sources of metals to the major tidal rivers are variable.

Urban runoff is the dominant source of metals loads to the Patuxent River.

Upstream sources of metals loads are dominant in the Potomac and James

Rivers.

Urban runoff is a substantial source of PAHs to the tidal James, Patuxent, and

Potomac Rivers.

Point sources of organic contaminants (PAHs, and PCBs) are highly uncertain

and therefore loads to the James, Patuxent, and Potomac Rivers are largely

unknown.

James River

Metals

Trace element loads to the tidal James River range from 9,400 lb/yr for cadmium to

110,000 lb/yr for copper (Figures 8.14-8.16). Fall line loads are the dominant source of metals to

the tidal James River. Point sources loads for copper and cadmium account for 11,000 lb/yr

(11% of the total load) and 1,600 lb/yr (17% of the total load), respectively. Urban runoff

sources for all metals account for approximately 11 to 16% of the total load to the tidal river. 
Comparative Loadings in the Bay

8-11

Polycyclic Aromatic Hydrocarbons (PAHs)

For the PAHs, benzo[a]pyrene and phenanthrene, urban runoff and to a lesser degree,

either atmospheric deposition or fall line inputs, are major sources of PAHs to the river (Figures

8.17-8.18). Point source loads estimates of PAHs are highly uncertain as indicated by the large

uncertainty bars in the figures. Virtually all of the measurements of PAHs were below the

detection limit. Therefore the point source loads could range anywhere between zero to the

product of the detection limit and flow. Therefore, the point source loads of PAHs are unknown

and the data presented in the figures are of limited use. Urban runoff accounts for approximately

4 to 6% of the total input of PAHs to the tidal Bay. Given that point source loads estimates are

highly uncertain, the relative contribution of urban runoff is substantially greater than initially

estimated. 

Potomac River

Metals

Loads of trace metals to the tidal Potomac River range from 2,300 lb/yr for cadmium to

approximately 160,000 lb/yr for lead (Figures 8.19-8.21). Fall line loads are the dominant source

to the tidal river, comprising greater than 75% of the total load. Average point source loads for

copper, 17,000 lb/yr, account for 11 % of the total load with lesser amounts for cadmium and

lead. Urban runoff from the tidal watershed to the river accounts for between 7% for cadmium

and 14% of the total load for lead. Atmospheric inputs, direct to the tidal water, are small and

generally less than 3% for all metals with the largest load of 3,400 lb/yr for lead (2% of the total

load). 

Polycyclic Aromatic Hydrocarbons (PAHs)

As with the James River, the PAH (benzo[a]pyrene and phenanthrene) loads are

dominated by point sources although the data is very uncertain (Figures 8.22-8.23). Urban runoff

and to a lesser degree, either atmospheric deposition or fall line inputs, are major sources of

PAHs to the river.

Patuxent River

Metals

In contrast to the James and Potomac rivers, loads to the tidal Patuxent River for all

metals are dominated by urban runoff. Inputs of metals ranged from 390 lb/yr for cadmium to

4,200 lb/yr for copper (Figure 8.24-8.26). Urban runoff accounts for between 44 to 51% of the

total tidal input for copper and cadmium, respectively to 66% for lead. Inputs from the non-tidal

portion of the watershed (i.e., fall line) are substantial for copper (37% of the total) and smaller 9
Comparative Loadings in the Bay

8-12

to 23% of the total load for cadmium and lead, respectively (Figures 8.24-8.26). Deposition to

the tidal waters of the river accounts for between 10% for Cu and Zn to approximately 20% for

lead. Point source inputs account for a small percentage of the total load (5 to 10% of the total

load for all metals).

Polycyclic Aromatic Hydrocarbons (PAHs)

For the PAHs, benzo[a]pyrene and phenanthrene, the loads are dominated by urban runoff

with average loads of 320 and 720 lbs/yr respectively, although there is a large degree of

uncertainty as indicated by the range of the estimates (Figure 8.27-8.28). Total and atmospheric

deposition and point source loads are a small but important component of the total load to the

Patuxent River. Atmospheric deposition loads range from < 1 to 22% of the total load for

benzo[a]pyrene and phenanthrene, respectively, and from 4 to 8% of the total load for point

source loads of benzo[a]pyrene and phenanthrene.

Inputs of Trace Elements to the Anacostia River

Summary: Upstream sources of metals are dominant in the Anacostia River, with the

second highest load coming from urban runoff and combined sewer overflows.

The load of contaminants to the Anacostia River, a Region of Concern, was complied

from various sources including the data from the previous chapters, MW COG (1997), Velinsky

et al. (1996) and Gruessner et al., (1997). These documents describe loadings to the Anacostia

River and are part of the Regional Action Plan assessment. It should be noted that upstream

sources (i.e., fall line loads) were measured directly over a 1-yr period while the other source

categories were estimated from various land use/hydrologic models. Due to the limited data set,

as compared to the other, larger tributaries, uncertainties in the loads were not estimated for the

Anacostia.

Loads to the tidal Anacostia River were estimated for cadmium, copper, lead, zinc

(Figures 8.29-8.32). Since there were insufficient data for other contaminants from all sources,

only trace metal loads are presented. Total loads to the tidal waters range from 340 lb/yr for

copper to more than 23,000 lb/yr for zinc. Upstream sources dominate the input of these metals,

with more than 77% of the total input derived from the non-tidal watershed. Urban runoff or

combined sewer overflows (CSO) inputs to the tidal Anacostia River can also be a major source

of trace elements. For zinc and lead, combined sewer loads account for between 18% and 23%

of the total load to the tidal waters. Urban stormwater runoff loads are variable for these metals

(Figures 8.29-8.32). While previous calculations by Velinsky et al. (1996) suggest that urban

runoff was a major source of aromatic hydrocarbons to the tidal river, the recent data by

Gruessner et al. (1997) indicates that upstream sources could be more substantial. Uncertainties,

or ranges, were not reported for Anacostia River loads due to a lack of data from the different

data sources. For example, reports for point source and urban runoff loads did not include ranges
Comparative Loadings in the Bay

8-13

and therefore they could not be calculated in this inventory.

Watershed Yields

Summary: The Anacostia River watershed, a highly urbanized area, produces 3 and 12

times more copper and lead, respectively, per watershed area than any of the

major rivers in the Bay watershed. 

Landuse characteristics in a watershed influences the chemical loadings from a

watershed. 

Loadings are not proportional to the size of the watershed. 

The total watershed yield for specific trace metals was calculated by dividing the total

load (lb/yr) for a watershed by its total drainage area (above and below the fall line) for four trace

metals (units: lb/km2-yr; Table 8.1). This calculation can be used to evaluate if specific

watershed characteristics are more important in determining the overall load to the tidal Bay. 

Land use (i.e., amount of urban area) and point sources could be two important characteristic

affecting the yield of a chemical from a watershed area. 

Table 8.1. Trace metal total watershed yields for selected tributaries of the Bay.

Susquehanna Potomac James Patuxent Anacostia

Cu 4.05 3.90 3.95 1.75 13.1 

Cd 0.61 0.61 0.35 0.16 0.46 

Pb 2.44 4.17 3.15 1.54 42.9 

Hg 0.052 0.084 0.055 0.018 0.026 

Units: lb/km2-yr.

The watershed yield information suggests that there is no trend between watershed size

and area and the load of specific trace metals. For example, the Susquehanna River watershed,

the largest in the Bay watershed, did not show the greatest areal yields indicating that watershed

area was not directly related to the loads. The copper yield for the Anacostia watershed was

higher than other watersheds by a factor ranging between 3 and 6. The Anacostia’s lead yield

was approximately 12 times higher than the other watersheds. This indicates a higher

concentration of copper and lead sources in the Anacostia watershed which most likely originate

from urban runoff, illustrating the higher per unit area loads in urban environments. Landuse

characteristics are probably more important in determining the load of a contaminant to the Bay. 

The higher yields for the Anacostia, may be the result of higher urban stormwater sources for

many contaminants. 
Comparative Loadings in the Bay

8-14

Copper yields were very similar between the Susquehanna, Potomac, and James Rivers,

the three largest watersheds in the Bay, while the copper yield for the Patuxent watershed was

slightly lower (Table 8.1). Cadmium yields for most watersheds were in good agreement except

for the Patuxent watershed in which the total cadmium yield was lower by a factor of 4. 

Similarly, lead yields for the Susquehanna, Potomac and James watersheds agreed, while the

yield for the Patuxent watershed was slightly lower. Mercury yields were similar for the

Susquehanna and Potomac watersheds, while slightly lower for the both the Patuxent and

Anacostia watersheds. The good agreement for watershed yields for many metals between

watersheds suggests a fairly accurate accounting of sources and loads, however, systematic error

in data gathering can not be discounted at this time. 

DISCUSSION AND RECOMMENDATIONS

Sources of contaminants to the tidal Bay and specific tributaries varied substantially. Fall

line loadings are a substantial source of metals to the tidal Bay and individual rivers such as the

Potomac, James, and Anacostia rivers. Point sources are substantial sources for select metals in

the tidal Bay. Urban runoff is a substantial source of organic contaminants to the tidal Bay and

many of its rivers and a substantial source of metals to the Patuxent river. Point source loads of

organic contaminants are largely unknown due to limitations of the data. In the Anacostia, a

highly urbanized Region of Concern, watershed yields of metals were much higher than in the

Susquehanna, Potomac, James, and Patuxent rivers.

To better define the load from point sources specific monitoring efforts are needed

throughout the Bay area and specific targeted areas, such as the Regions of Concern. This is due

to the fact that point sources may be under or overestimated (i.e., detection limits, lack of data). 

While it would be prohibitively expensive to accurately determine the concentration of specific

metals and organic contaminants in every outfall of the Bay, representative discharges could be

sampled to provide a Baywide database of typical pollutant concentrations (i.e., TPCs) for

specific industrial/municipal facilities. This database could then be used to help augment the

statewide monitoring efforts and provide a better information to make loadings summaries. 

Additionally, more accurate chemical analysis and reporting within the National Pollutant

Discharge Elimination System (NPDES) and Permit Compliance System (PCS) programs need to

be initiated. Information within the NPDES database is difficult to obtain, not accurately

reported (i.e., missing units, decimal points, etc.), and are not accurately analyzed (i.e., laboratory

analysis). Historically, the NPDES data was used mainly to determine water quality violations at

a facility, not loads. However, with the advent of TMDLs, the NPDES data is now being used to

determine loads to specific waterbodies. Unless the laboratory analysis of the NPDES programs

and reporting aspects of the PCS improved, loads obtained from this data will be questionable.

Overall, better basic monitoring information is needed for almost all sources identified in

this inventory and in each chapter specific recommendations are provided to better quantify each

source. To improve upon the loading analysis for future loadings studies, additional information
Comparative Loadings in the Bay

8-15

is needed. The purpose of many of these recommendations is to help provide site specific data

that can be applied to other areas of the tidal and non-tidal Bay. As such, studies should focus on

representative areas in which the data can be applied to other areas. Recommendations include: 

< For all sources determine a consistent chemical fraction (e.g., total, total recoverable,

dissolved).

< Explore alternate methods such as the typical pollutant concentration method for

subsequent updates to the point source inventory for organic contaminants.

< Use lower detection limit methods for dissolved, particulate or total analyses for point

sources and other sources as needed.

< Improved analysis for organic contaminants for many source functions.

< Include urban agricultural stations in the atmospheric deposition network as well as

stations within specific watersheds.

< Conduct comprehensive sampling of representative major point source dischargers for

specific contaminants using clean methods.

< Conduct site specific studies (i.e., sampling, analysis, and modeling) to better estimate the

urban flux of chemical contaminants.

< Characterize and determine the source of chemical contaminants within the measured fall

line loads (i.e., source allocation, watershed retention). 

< Develop confidence levels and measures of uncertainty for each source category and

incorporate into the final loadings analysis.

Comparative Loadings in the Bay

8-17

Sources

AD FL UR SE PS Other

PCBs (lb/yr)

0

20000

40000

60000

PCBs

Total Input: 27,000 lb/yr

?

Figure 8.2. Total loads of PCBs to the tidal Potomac River from atmospheric deposition (AD);

fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples of

“Other Sources” not fully quantified may include loads from smaller point sources, agricultural

runoff, atmospheric deposition, groundwater, and natural sources. The variability in the

atmospheric deposition and fall line estimates is smaller than the symbol representing the

average.

AD FL UR SE PS Other

PCBs (lb/yr)

0

20

40

60

80

100

120

140

160

Sources

TPC Estimate

Total Input: 170 lb/yr

?

Figure 8.3. Total estimated loads of PCBs to the tidal Potomac River based on typical pollutant

concentrations (TPC) from the literature from atmospheric deposition (AD); fall line (FL); urban

runoff (UR); shoreline erosions (SE); and point sources (PS). Examples of “Other Sources” not

fully quantified may include loads from smaller point sources, agricultural runoff, atmospheric

deposition, groundwater, and natural sources.
Comparative Loadings in the Bay

8-18

Sources

AD FL UR SE PS Other

Cadmium (lb/yr X 1000)

0

10

20

50

75

100

?

Cadmium

Total Input: 94,000 lb/yr

Sources

AD FL UR SE PS Other

Copper (lb/yr X 1000)

0

50

100

300

400

500

600

?

Copper

Total Input: 710,000 lb/yr

Figure 8.4. Total loads of cadmium to the tidal waters of the Chesapeake Bay from atmospheric

deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources

(PS). Examples of “Other Sources” not fully quantified may include loads from smaller point

sources, agricultural runoff, atmospheric deposition, groundwater, and natural sources.

Figure 8.5. Total loads of copper to the tidal water of the Chesapeake Bay from atmospheric

deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources

(PS). Examples of “Other Sources” not fully quantified may include loads from smaller point

sources, agricultural runoff, atmospheric deposition, groundwater, and natural sources. The

variability in the shoreline erosions estimate is smaller than the symbol representing the average.
Comparative Loadings in the Bay

8-19

Sources

AD FL UR SE PS Other

Mercury (lb/yr X 1000)

0

2

4

6

8

Mercury

Total Input: 9,500 lb/yr

?

AD FL UR SE PS Other

Lead (lb/yr X 1000)

0

100

200

300

400

500

?

Lead

Sources

Total Input: 560,000 lb/yr

Figure 8.6. Total loads of lead to the tidal water of the Chesapeake Bay from atmospheric

deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources

(PS). Examples of “Other Sources” not fully quantified may include loads from smaller point

sources, agricultural runoff, atmospheric deposition, groundwater, and natural sources. The

variability in the shoreline erosions estimate is smaller than the symbol representing the average.

Figure 8.7. Total loads of mercury to the tidal water of the Chesapeake Bay from atmospheric

deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources

(PS). Examples of “Other Sources” not fully quantified may include loads from smaller point

sources, agricultural runoff, atmospheric deposition, groundwater, and natural sources.
Comparative Loadings in the Bay

8-20

AD FL UR SE PS Other

Arsenic (lb/yr X 1000)

0

10

20

80

120

160

?

Arsenic

Sources

Total Input: 140,000 lb/yr

Sources

AD FL UR SE PS Other

Zinc (lb/yr X 1000)

0

500

1000

1500

2000

2500

3000

Zinc

Total Input: 3,300,000 lb/yr

?

Figure 8.8. Total loads of zinc to the tidal water of the Chesapeake Bay from atmospheric

deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources

(PS). Examples of “Other Sources” not fully quantified may include loads from smaller point

sources, agricultural runoff, atmospheric deposition, groundwater, and natural sources. The

variability in the point source estimate is smaller than the symbol representing the average.

Figure 8.9. Total loads of arsenic to the tidal water of the Chesapeake Bay from atmospheric

deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources

(PS). Examples of “Other Sources” not fully quantified may include loads from smaller point

sources, agricultural runoff, atmospheric deposition, groundwater, and natural sources.
Comparative Loadings in the Bay

8-21

Sources

AD FL UR SE PS Other

Benzo[a]pyrene (lb/yr X 1000)

0

5

10

15

20

50

100

150

Benzo[a]pyrene

Total Input: 64,000 lb/yr

?

Sources

AD FL UR SE PS Other

Chrysene (lb/yr X 1000)

0

10

20

50

100

150

Chrysene

Total Input: 64,000 lb/yr

?

Figure 8.10. Total loads of benzo[a]pyrene to the tidal water of the Chesapeake Bay from

atmospheric deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point

sources (PS). Examples of “Other Sources” not fully quantified may include loads from smaller

point sources, agricultural runoff, atmospheric deposition, groundwater, and natural sources. The

variability in the atmospheric deposition and fall line estimates is smaller than the symbol

representing the average.

Figure 8.11. Total loads of chrysene to the tidal water of the Chesapeake Bay from atmospheric

deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). 

Examples of “Other Sources” not fully quantified may include loads from smaller point sources,

agricultural runoff, atmospheric deposition, groundwater, and natural sources. The variability in the

atmospheric deposition and fall line estimates is smaller than the symbol representing the average.
Comparative Loadings in the Bay

8-22

Sources

AD FL UR SE PS Other

Phenanthrene (lb/yr X 1000)

0

25

100

200

300

Phenanthrene

Total Input: 130,000 lb/yr

?

Sources

AD FL UR SE PS Other

Pyrene (lb/yr X 1000)

0

10

20

80

120

160

200

Pyrene

Total Input: 88,000 lb/yr

?

Figure 8.12. Total loads of phenanthrene to the tidal water of the Chesapeake Bay from

atmospheric deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and

point sources (PS). Examples of “Other Sources” not fully quantified may include loads from

smaller point sources, agricultural runoff, atmospheric deposition, groundwater, and natural

sources. The variability in the fall line estimate is smaller than the symbol representing the

average.

Figure 8.13. Total loads of pyrene to the tidal water of the Chesapeake Bay from atmospheric

deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources

(PS). Examples of “Other Sources” not fully quantified may include loads from smaller point

sources, agricultural runoff, atmospheric deposition, groundwater, and natural sources.
Comparative Loadings in the Bay

8-23

Sources

AD FL UR SE PS Other

Copper (pounds/yr X 1000)

0

25

50

75

100

125

?

Copper

Total Input: 110,000 lb/yr

Sources

AD FL UR SE PS Other

Cadmium (lb/yr X 1000)

0

2

4

6

8

10

?

Cadmium

Total Input: 9,400 lb/yr

Figure 8.14. Total loads of cadmium to the tidal James River from atmospheric deposition (AD);

fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples of

“Other Sources” not fully quantified may include loads from smaller point sources, agricultural

runoff, atmospheric deposition, groundwater, and natural sources.

Figure 8.15. Total loads of copper to the tidal James River from atmospheric deposition (AD);

fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples of

“Other Sources” not fully quantified may include loads from smaller point sources, agricultural

runoff, atmospheric deposition, groundwater, and natural sources. The variability in the point

source estimate is smaller than the symbol representing the average.
Comparative Loadings in the Bay

8-24

AD FL UR SE PS Other

Lead (lb/yr X 1000)

0

20

40

60

80

?

Lead

Sources

Total Input: 84,000 lb/yr

Sources

AD FL UR SE PS Other

Benzo[a]pyrene (lb/yr X 1000)

0.0

2.5

5.0

25.0

50.0

75.0

Benzo[a]pyrene

Total Input: 30,000 lb/yr

?

Figure 8.16. Total loads of lead to the tidal James River from atmospheric deposition (AD); fall line

(FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples of “Other

Sources” not fully quantified may include loads from smaller point sources, agricultural runoff,

atmospheric deposition, groundwater, and natural sources. The variability in the point source

estimate is smaller than the symbol representing the average.

Figure 8.17. Total loads of benzo[a]pyrene to the tidal James River from atmospheric deposition

(AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples

of “Other Sources” not fully quantified may include loads from smaller point sources, agricultural

runoff, atmospheric deposition, groundwater, and natural sources. The variability in the atmospheric

deposition and fall line estimates is smaller than the symbol representing the average.
Comparative Loadings in the Bay

8-25

Sources

AD FL UR SE PS Other

Phenanthrene (lb/yr X 1000)

0.0

2.5

5.0

50.0

100.0

150.0

Phenanthrene

Total Input: 63,000 lb/yr

?

Sources

AD FL UR SE PS Other

Cadmium (lb/yr X 1000)

0.0

2.5

5.0

20.0

30.0

?

Cadmium

Total Input: 23,000 lb/yr

Figure 8.18. Total loads of phenanthrene to the tidal James River from atmospheric deposition

(AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). 

Examples of “Other Sources” not fully quantified may include loads from smaller point sources,

agricultural runoff, atmospheric deposition, groundwater, and natural sources. The variability in

the fall line estimate is smaller than the symbol representing the average.

Figure 8.19. Total loads of cadmium to the tidal Potomac River from atmospheric deposition

(AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). 

Examples of “Other Sources” not fully quantified may include loads from smaller point sources,

agricultural runoff, atmospheric deposition, groundwater, and natural sources.
Comparative Loadings in the Bay

8-26

Sources

AD FL UR SE PS Other

Copper (lb/yr X 1000)

0

10

20

30

60

90

120

150

?

Copper

Total Input: 150,000 lb/yr

AD FL UR SE PS Other

Lead (lb/yr X 1000)

0

20

40

90

120

150

180

?

Lead

Sources

Total Input: 160,000 lb/yr

Figure 8.20. Total loads of copper to the tidal Potomac River from atmospheric deposition (AD);

fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples of

“Other Sources” not fully quantified may include loads from smaller point sources, agricultural

runoff, atmospheric deposition, groundwater, and natural sources.

Figure 8.21. Total loads of lead to the tidal Potomac River from atmospheric deposition (AD);

fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples of

“Other Sources” not fully quantified may include loads from smaller point sources, agricultural

runoff, atmospheric deposition, groundwater, and natural sources.
Comparative Loadings in the Bay

8-27

Sources

AD FL UR SE PS Other

Phenanthrene (lb/yr X 1000)

0

5

10

15

20

25

30

Phenanthrene

Total Input: 18,000 lb/yr

?

Sources

AD FL UR SE PS Other

Benzo[a]pyrene (lb/yr X 1000)

0

2

4

6

8

10

12

14

Benzo[a]pyrene

Total Input: 8,800 lb/yr

?

Figure 8.22. Total loads of benzo[a]pyrene to the tidal Potomac River from atmospheric deposition

(AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples

of “Other Sources” not fully quantified may include loads from smaller point sources, agricultural

runoff, atmospheric deposition, groundwater, and natural sources. The variability in the atmospheric

deposition and fall line estimates is smaller than the symbol representing the average.

Figure 8.23. Total loads of phenanthrene to the tidal Potomac River from atmospheric deposition

(AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples

of “Other Sources” not fully quantified may include loads from smaller point sources, agricultural

runoff, atmospheric deposition, groundwater, and natural sources. The variability in the fall line

estimates is smaller than the symbol representing the average.
Comparative Loadings in the Bay

8-28

Sources

AD FL UR SE PS Other

Cadmium (lb/yr X 1000)

0.0

0.1

0.2

0.3

0.4

?

Cadmium

Total Input: 390 lb/yr

Sources

AD FL UR SE PS Other

Copper (pounds/yr X 1000)

0

1

2

3

?

Copper

Total Input: 4,200 lb/yr

Figure 8.24. Total loads of cadmium to the tidal Patuxent River from atmospheric deposition

(AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). 

Examples of “Other Sources” not fully quantified may include loads from smaller point sources,

agricultural runoff, atmospheric deposition, groundwater, and natural sources.

Figure 8.25. Total loads of copper to the tidal Patuxent River from atmospheric deposition (AD);

fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples of

“Other Sources” not fully quantified may include loads from smaller point sources, agricultural

runoff, atmospheric deposition, groundwater, and natural sources.
Comparative Loadings in the Bay

8-29

Sources

AD FL UR SE PS Other

Benzo[a]pyrene (lb/yr X 1000)

0.0

0.1

0.2

0.3

0.4

0.5

Benzo[a]pyrene

Total Input: 320 lb/yr

?

AD FL UR SE PS Other

Lead (lb/yr X 1000)

0

1

2

3

4

5

?

Lead

Sources

Total Input: 3,700 lb/yr

Figure 8.26. Total loads of lead to the tidal Patuxent River from atmospheric deposition (AD);

fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources (PS). Examples of

“Other Sources” not fully quantified may include loads from smaller point sources, agricultural

runoff, atmospheric deposition, groundwater, and natural sources.

Figure 8.27. Total loads of benzo[a]pyrene to the tidal Patuxent River from atmospheric

deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources

(PS). Examples of “Other Sources” not fully quantified may include loads from smaller point

sources, agricultural runoff, atmospheric deposition, groundwater, and natural sources. The

variability in the atmospheric deposition and fall line estimates is smaller than the symbol

representing the average.
Comparative Loadings in the Bay

8-30

Sources

AD FL UR CSO PS Other

Cadmium (lb/yr X 1000)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

?

Cadmium

Total Input: 340 lb/yr

Sources

AD FL UR SE PS Other

Phenanthrene (lb/yr X 1000)

0.0

0.2

0.4

0.6

0.8

1.0

Phenanthrene

Total Input: 720 lb/yr

?

Figure 8.28. Total loads of phenanthrene to the tidal Patuxent River from atmospheric

deposition (AD); fall line (FL); urban runoff (UR); shoreline erosions (SE); and point sources

(PS). Examples of “Other Sources” not fully quantified may include loads from smaller point

sources, agricultural runoff, atmospheric deposition, groundwater, and natural sources. The

variability in the fall line estimates is smaller than the symbol representing the average.

Figure 8.29. Total loads of cadmium to the tidal Anacostia River from atmospheric deposition

(AD); fall line (FL); urban runoff (UR); combined sewer overflow (CSO); and point sources

(PS). Point source loadings were not reported. Examples of “Other Sources” not fully quantified

may include loads from smaller point sources, agricultural runoff, atmospheric deposition,

groundwater, and natural sources. The variability was not calculated due to the lack of data and

reported ranges.
Comparative Loadings in the Bay

8-31

Sources

AD FL UR CSO PS Other

Copper (lb/yr X 1000)

0.0

0.5

1.0

4.0

5.0

6.0

?

Copper

Total Input: 6,000 lb/yr

Sources

AD FL UR CSO PS Other

Lead (lb/yr X 1000)

0.0

0.5

1.0

5.0

10.0

15.0

?

Lead

Total Input: 19,000 lb/yr

Figure 8.30. Total loads of copper to the tidal Anacostia River from atmospheric deposition (AD); fall

line (FL); urban runoff (UR); combined sewer overflow (CSO); and point sources (PS). Examples of

“Other Sources” not fully quantified may include loads from smaller point sources, agricultural runoff,

atmospheric deposition, groundwater, and natural sources. The variability was not calculated due to the

lack of data and reported ranges.

Figure 8.31. Total loads of lead to the tidal Anacostia River from atmospheric deposition (AD); fall line

(FL); urban runoff (UR); combined sewer overflow (CSO); and point sources (PS). Point source

loadings were not reported. Examples of “Other Sources” not fully quantified may include loads from

smaller point sources, agricultural runoff, atmospheric deposition, groundwater, and natural sources. The

variability was not calculated due to the lack of data and reported ranges.
Comparative Loadings in the Bay

8-32

Sources

AD FL UR CSO PS Other

Zinc (lb/yr X 1000)

0

5

15

20

?

Zinc

Total Input: 23,000 lb/yr

(< 0.1) (< 0.1)

Figure 8.32. Total loads of zinc to the tidal Anacostia River from atmospheric deposition (AD);

fall line (FL); urban runoff (UR); combined sewer overflow (CSO); and point sources (PS). 

Examples of “Other Sources” not fully quantified may include loads from smaller point sources,

agricultural runoff, atmospheric deposition, groundwater, and natural sources. The variability

was not calculated due to the lack of data and reported ranges.
9-1

CHAPTER 9 - Mass Balance of Chemical Contaminants

within Chesapeake Bay

David Velinsky Joel Baker

Patrick Center for Environmental Research Chesapeake Biological Laboratory

The Academy of Natural Sciences University of Maryland

1900 Benjamin Franklin Parkway P.O. Box 38

Philadelphia, PA 19103-1195 Solomons, MD 20688

INTRODUCTION

The Chesapeake Bay Basinwide Toxics Reduction Strategy Reevaluation Report

(Chesapeake Bay Program, 1994b) described the results of a multi-year effort to evaluate the

nature, extent, and magnitude of the Bay's chemical contaminant problems. Continuing these

efforts, the data within the preceding chapters present recent information regarding the various

measured and potential inputs to the Bay. While these studies continue the Bay Program's effort

to account for the sources of chemical contaminants, a more exacting examination of both the

sources (inputs) and sinks (outputs) is needed. The identification and quantification of the

different sources and sinks of anthropogenic chemicals in Chesapeake Bay is an important step

towards understanding their cycling and potential effects, and can help target strategies for

contaminant reductions.

One way to place this information into a coherent framework, or accounting system, is to

develop chemical contaminant mass balances (Velinsky, 1997). A mass balance requires that the

quantities of chemical contaminants entering the Bay, less the amount stored, transformed, or

degraded within the system, equal the amount leaving the Bay system. With a working mass

balance budget, various control strategies can be simulated to evaluate long-term changes for

each contaminant or for contaminant groups. Such simulations and predictions can be valuable

in the assessment of the effect of chemical contaminants on ecosystem health, and can help make

expensive monitoring programs within the Bay more cost-effective. Once a mass balance is

accurately verified, it could be used to answer "what if" questions such as; if specific sources are

reduced, how much reduction is needed and how long will it take to lower the concentration of a

specific contaminant in the water column or an organism to a given level?

A mass balance framework is a useful system in understanding the inputs, outputs and

flow of chemical contaminants in the Bay and tributaries. Specifically, a mass balance provides:

1) a gross check and balance on whether or not loadings estimates are consistent and realistic, 2)

an idea of the fate of contaminants in the Bay and its tributaries, 3) a management tool for

predicting results from load reductions, and 4) a consistent way to identify key data gaps and

uncertainties that need to be addressed for management/scientific purposes.
Mass Balance

9-2

1

2

3

4

5

6

7

8

9

BH

Px

AR Pt

Rp

Yk

Jm

ER

Cp

Surface Water Advection

Bottom Water Advection

Dispersion

Susquehanna

Ocean

Figure 9.1. Schematic of Chesapeake Bay Chemical

Contaminant Mass Balance Model (after Hagy, 1998).

This chapter presents an initial test of a simple chemical contaminant mass balance for

Chesapeake Bay. This mass balance utilizes data obtain from the preceding chapters and

information obtained from the Solomons Island Mass Balance Workshop (May 7&8, 1998). The

overall objective of this exercise is to help verify the loads estimated for the Bay. An inherent

problem with the current load estimates is that are of varying accuracy and precision, and are

integrated over different spatial and temporal scales. A second problem is that an independent

reality check for the loading estimates is lacking. This initial mass balance is used to help

compare and evaluate the loadings estimates in the Toxics Loadings and Release Inventory

(TLRI). However, major differences (i.e., > 10X) between inputs and outputs of a given

contaminant likely indicate problems with one or the other estimates, or both.

Model Framework 

The mass balance model used in this study is designed to be as simple as possible while

maintaining the extreme spatial variability (i.e., salinity, chemical concentrations, etc.) of the

mainstem of the Chesapeake Bay. This is a very simple model, and is not meant to represent the

state-of-the-art in water quality modeling. Rather, it is an initial attempt to organize the chemical

contaminant loading data within the context of measured ambient levels and estimated

contaminant loss processes. This effort describes the spatial variability on scales of tens of

kilometers and on an annual time scale. 

This model allows us to compare the

loadings described in the preceding chapters

to net loss processes, and also to estimate

the transport of chemicals from the

tributaries to the mainstem of the

Chesapeake Bay. The model takes the input

of contaminants from the mouth of each

tributary (i.e., the boundary between the

mainstem bay and a tributary), along with

other loadings direct to the mainstem (i.e.,

atmospheric deposition, point sources, etc.),

transports them through the Bay, allowing

for burial, degradation, volatilization

between the air/sea interface, and sediment

burial. 

The model is based on a salt-balance

model developed by Hagy (1998). The

mainstem is divided horizontally into nine

boxes (numbered 1-9 from south to north),

with all but the northern-most box further

subdivided by depth into a surface and

bottom layers (Figure 9.1). Water
Mass Balance

9-3

Wet Aerosol

Gas

Exchange

Upstream

Point

Stormwater

Runoff

Up/down-welling

Sinking

Downstream

Diffusion Resuspension Burial

Groundwater

Upstream Downstream

Surface

Bottom

Shoreline

Degradation

Figure 9.2. Flows of chemical contaminants into and from

model cells.

exchanges between these 17 model cells were calculated by Hagy by balancing water flows to

match the salinity profiles determined by the Chesapeake Bay monitoring program. Similarly,

transport of solids among the boxes depends upon the water flows and the observed suspended

solids concentrations in the mainstem. Tributary flows entering the mainstem model boxes were

determined by the long-term flow and suspended solids records at the respective tributary

gauging stations.

Tributaries are not explicitly modeled here, but rather are treated as single boxes which

process loadings and export chemicals to the mainstem at the boundary between the tributary and

mainstem boxes. It is important to remember that this model does not properly describe the

dynamics of contaminant movements within each tributary. This constraint results from the lack

of spatially-explicit concentration data within the tributaries and because the salt-balance

approach breaks down in the fresher reaches of the tributaries. There is no explicit linkage

between contaminant loadings to the tributaries (which are simply totaled and reported by the

model) and the net exports from the tributary (which are calculated as the product of the net

water outflow and the estimated ambient chemical concentrations at the mouth of each river).

Chemical contaminants enter and leave each model cell by a variety of processes (Figure

9.2). Chemical inputs to each model segment or cell include those sources cataloged in the

previous chapters of this report as well as flows of chemicals from adjacent model cells and

exchange with the sediments (resuspension and burial). Gross advective transport between

adjacent cells is calculated as the product of the estimated concentration of the chemical in the

cell (g/m3) and the water transport flux

(m3/day) estimated from the salt balance

and the tributary flows. The sinking flux

which transports chemicals from surface

to bottom model cells is calculated in two

steps. First, the concentration of particleassociated chemical contaminant in the

surface cell is calculated as a fraction of

the total (dissolved plus particulate)

concentration using an estimated

distribution coefficient and the measured

suspended solids concentration. This

particle-associated chemical contaminant

concentration (g/m3) is then multiplied by

a ‘settling velocity’ term (equal to 1

m/day in this model) and the interfacial

area (m2) to estimate the settling flux

(g/day). Long-term net rates of chemical

burial in sediments is calculated as the

product of the measured (or interpolated)
Mass Balance

9-4

chemical concentration in surficial sediments and the long-term net sediment accumulation rate

estimated from measured sediment accretion rates. The bottom of each model cell is the

boundary between bottom waters and sediments. Diffusion of chemicals from the sediments are

estimated from field and laboratory flux chamber experiments for metals; diffusional fluxes for

organic chemicals are assumed to be zero. Resuspension is considered to be a chemical recycling

process within the water column (which, therefore, does not affect the mass balance on each

model cell), and is calculated as the difference between calculated settling and long term burial

rates.

The model calculates chemical flows into and from each model cell on a monthly basis,

assuming constant daily flows within each month. All observations were either aggregated (in

the case of more frequent measurements such as tributary flows) or disaggregated (in the case, for

example, of loadings that were reported on an annual basis) to provide the average daily value for

each month. Results from the monthly budgets for each cell were aggregated to produce annual

summaries of loadings and losses to the mainstem Chesapeake Bay.

It is very important to remember that this ‘mass balance’ does not require that the

loadings and losses of each chemical ‘balance’. That is, the model does not ‘force’ a balance,

and no loading or loss term is calculated by difference in order to create a balance. In fact, there

is no reason to suspect that the Chesapeake Bay is at steady state with respect to chemical

loadings, and it is entirely reasonable to expect that loads do not equal losses. The model simply

converts all of the loading terms to the same units and temporal scale and sums them. This is

compared to our best estimate of total contaminant losses in the mainstem. Major (i.e., order of

magnitude) discrepancies between loadings and losses of a given contaminant, however, likely

indicate problems with one or the other estimates, or both.

RESULTS AND DISCUSSION

Trace Elements

Below are two examples of the model for copper (Cu) and mercury (Hg). 

Copper

Point source, fall line, urban stormwater, atmospheric deposition, and shoreline erosion

inputs to the Bay and its tributaries were derived from the information within the preceding

chapters. Sediment diffusion of copper out of the sediments was obtained from studies and 

unpublished data by Riedel et al. (1995a,b;1997; 1999a,b; unpublished data), Cornwall et al.

(unpublished data), and others. For copper as well as other metals there is a lack of sediment

diffusion data for most areas of Chesapeake Bay and its tributaries. Studies were conducted with

Baltimore Harbor, Mid-Chesapeake Bay (Site M), and Patuxent River sediments; either in the

laboratory or in-situ. The limited data were used along with best professional judgement to

derive rates for the mainstem Bay and tributaries. It should be noted that the sediment diffusion
Mass Balance

9-5

flux of copper to the bottom waters of the Bay is an internal source, and does not affect the

assessment of the overall input/output budget within the current model framework. 

Accurate concentrations of dissolved copper in the water column throughout the Bay

were limited, and there was no information for particulate copper for the mainstem or many

tributaries of the Bay. Dissolved data were obtained from the studies of Culberson and Church

(1988), Donat et al. (1994; unpublished data), Henry and Donat (1996), Donat and Henry (1997),

and for the Patuxent and Anacostia Rivers from Riedel et al. (1995a,b;1997; 1999a,b;

unpublished data), Velinsky et al. (1999), and Coffin et al. (1998). The dissolved copper

concentrations in the mainstem Bay covered a 10 year period from the work by Culberson and

Church (1988) to Donat (1994; unpublished data), Henry and Donat (1996), and Donat and

Henry (1997), however, for the current model framework total concentrations of copper are

needed. Since there was no particulate (or total) copper concentrations, an average copper

partition coefficient (i.e., Kd [L/kg = conc. in dissolved phase/conc. in particulate phase]) was

derived using the Patuxent River copper data set (Riedel and Gilmour, unpublished data) with

varying salinities. The Patuxent River copper Kd values were used for each segment of the

model. 

Concentrations of copper in the surface sediments of Chesapeake Bay and its tributaries

were obtained from the comprehensive report by Eskin et al. (1996). The data within the report

represents surface sediment concentrations from samples collected over various years. Each

segment was assigned a median or average concentration for the entire area of the segment. 

While median or average concentrations were used to calculate the burial of trace metals, there is

substantial spatial variability in the concentration of metals throughout all areas. Additionally, as

stated above, deposition rates were assumed to cover the entire area of each segment (see Officer

et al, 1984). This would tend to overestimate the total deposition to the sediment due to the

spatial variations in deposition within each box or area of the mainstem bay. 

The total copper load to the mainstem Bay is approximately 118,000 kg/yr (Table 9.1)

and indicates that approximately 60% of the total input to the tidal Bay (322,000 kg/yr) is

retained within the tributaries. In other words, a substantial portion of the total load to the entire

Chesapeake Bay is retained within the tributaries with approximately 40% of the total input

transferred to the mainstem Bay. Tributary inputs and shoreline erosion account for major input

to the mainstem Bay; approximately 90% of the total input, while direct atmospheric (wet+dry)

and point sources are small and total approximately <1% of the total mainstem load. Due to a

lack of data, the flux of sediment and associated copper from shoreline erosion was assumed to

be to the mainstem Bay, and this is probably an overestimation given the extensive shoreline in

the tributaries and potential erosion.

The main mechanism for the loss of copper from the mainstem Bay is sediment burial

with only a small fraction exchanging out the Bay mouth to the coastal waters (Table 9.2). The

total output from the mainstem was calculated to be 110,000 kg/yr which is in excellent
Mass Balance

9-6

agreement with the total input to the mainstem Bay. Given the uncertainty in the modeling

framework and assumptions for various input/output rates (i.e., flows, sedimentation rates, etc), it

is remarkable that a good balance was obtained and suggests that the inputs to the Bay are fairly

well constrained. The loss of copper via burial (105,000 kg/yr) is a net rate with sediment

diffusion re-releasing approximately 20,000 kg Cu/yr back into the mainstem Bay. 

In summary, the present mass balance estimate within Chesapeake Bay for copper

appears to be fairly well constrained. While there is a good agreement between the sources of

copper and removal of copper, better quantification of the tributary inputs (i.e., the boundary

between the tributaries and the mainstem) and sediment burial are needed. These along with the

Susquehanna River inputs are the major fluxes identified by the model. The majority of the

copper loads to the mainstem Bay is from Susquehanna River with lesser amounts from the

tributaries. As stated earlier, shoreline erosion was assumed to be direct to the mainstem Bay. 

However, given the extensive shoreline and potential erosion in the tributaries the total flux

needs to be separated between tributary and mainstem Bay inputs. These areas would help

support the agreement between inputs and outputs in the Chesapeake Bay. 

Mercury 

Loadings of total mercury to the Chesapeake Bay below the fall-lines are summarized in

Table 9.3. Estimates of atmospheric deposition (wet deposition, dry aerosol deposition, and net

volatilization) and fall-line loadings are taken from the studies of Mason and co-workers (Mason

et al., 1997a,b; Lawson and Mason, 1998; Benoit et al., 1998; Mason et al., 1999; Mason and

Lawrence, 1999). Mercury loadings from point sources and urban runoff are taken from

estimates in the preceding chapters. Erosion of shoreline material is assumed to be an

insignificant source of mercury, though whether erosion is an important source of mercury to the

Bay is largely unknown. The role of groundwater as a source of mercury to the Bay is also

unknown and is assumed to be zero for this exercise. As is the case with the other chemicals

analyzed here, point source loadings of mercury were estimated as the average of the ‘high’ and

‘low’ estimates taken from Chapter 1. 

According to this analysis, tributary and point source inputs contribute the majority of the

total mercury loading to the Bay below the fall-lines. The point source loads are likely an

overestimation due to analytical methods and detection limit issues with point source effluent

analysis. Diffusion from sediments, urban runoff, and inputs from the rivers contribute about

75% of the total mercury load to the mainstem Bay if the point source loads are correct. The

majority of the mercury enters the bay in its tributaries below the fall-lines. Virtually all of the

urban runoff and point sources of mercury are discharged to the tributaries rather than the

mainstem. As was seen with other particle-reactive chemicals, the vast majority of the mercury

discharged into the tributaries is retained and not transmitted to the mainstem. Less than 10% of

the mercury that enters the tributaries is transmitted into the mainstem of the Chesapeake Bay. 

Although we do not have sufficient data from the tributaries to verify these estimates of mercury

retention, this calculation suggests that localized tributary sediments should be enriched in
Mass Balance

9-7

mercury and other particle-reactive contaminants.

Losses of mercury from the mainstem Chesapeake Bay include export to the ocean, burial

in sediments, and volatilization (Table 9.4). In this analysis, burial accounts for three quarters of

the mercury loss, with export and volatilization resulting in 20% and 3% of the annual mercury

loss, respectively. The estimated total annual losses of mercury from the mainstem Chesapeake

are four times the estimated loadings to the mainstem. Whether this discrepancy reflects a real

imbalance between loads and losses or indicates over- and/or underestimations of sources and

sinks cannot be determined from these data. 

Organic Contaminants 

Below are two examples of the mass balance calculations for organic contaminants

presented using total PCBs (sum of all measured congeners or, in the case of point source

loadings, Aroclor 1260) and the polycyclic aromatic hydrocarbon (PAH) phenanthrene.

Total PCBs 

Total PCB loadings were calculated for each source type as described in the preceding

chapters (Table 9.5). As no estimate of PCB loadings from urban runoff were made, we assumed

here that the PCB load was equal to one half of the total mercury load from urban runoff, based

on our recent observations that the concentrations of total PCBs in the water column and

sediments of an urban-runoff dominated system (i.e., Baltimore Harbor) are approximately one

half those of mercury (Ashley et al., 1999; Mason and Lawrence, 1999). Transport of total PCBs

from the tributaries to the mainstem was estimated for each tributary assuming a total PCB

concentration at the river mouths of 0.95 to 1.2 ng/L (Nelson et al., 1998).

The comparison of loadings of total PCBs to the Chesapeake Bay below the fall lines

shows that estimated point sources are three orders of magnitude greater than all other sources

(Table 9.1) and this is certainly not correct. In fact, the estimated point source loadings of PCBs

far exceed our best estimate of the amount of PCBs in the mainstem Chesapeake Bay (perhaps on

the order of 1,000 kg total in the water column and sediments). Even if the point source estimate

is 100 fold too high, however, we still conclude that point source emissions of PCBs is an

important contribution to the total loading. This was illustrated by the Potomac River point

source data described in the previous chapter. In this example, point source concentrations of

total PCBs were derived from recent studies in the Delaware and Hudson Rivers and used with

the flow from point sources to the tidal Potomac River. The resultant load indicates that

approximately 60% of the total PCB load is derived from point sources and PCB loads are

comparable to fall line estimates to the tidal Potomac. In the current analysis, virtually all of the

PCBs entering the Chesapeake Bay are loaded into the tributaries. The estimate for the total PCB

loading to the mainstem of the Chesapeake Bay is 183 kg/year, one third of which is supplied by

loading from the Susquehanna River. Urban runoff and atmospheric deposition supply

approximately equal loads of PCBs to the mainstem Chesapeake Bay.
Mass Balance

9-8

It is crucial to note that a vanishingly small fraction of the PCB loading to the tributaries

is transported to the mainstem Chesapeake Bay (< 0.5% of 410,000 kg/year,). Even excluding

the admittedly flawed point source estimate from the comparison, only 5% of the non-point

source loads to the tributaries are transported to the mainstem. This implies that tributaries are

extremely efficient traps for these particle-reactive chemicals and that dilution by downstream

transport is not an effective cleansing mechanism for the tributaries. Stated another way, these

simple calculations support the observation of higher concentrations in the Chesapeake Bay

tributaries, where local chemical loadings remain concentrated near discharge points (i.e., point

and non-point sources).

Interestingly, the estimates of PCB loadings to the mainstem are six times less than our

estimates of PCB losses from the mainstem. Losses of PCBs are distributed among ocean export

(50%), volatilization (30%) and burial (20%; Table 9.6). Some fraction of this difference may be

real, as the inventories of PCBs in the bay are likely decreasing with time (i.e., losses exceed

loadings) in response to the production and use ban on PCBs in the late 1970's. Also, these

calculations do not include any net release of PCBs from sediments. A net release on the order

of 180 μg/m2-year from the sediments would be required to balance loads and losses; this is

about 3.5 times the long-term PCB burial rate.

Phenanthrene 

Loadings of phenanthrene to the Chesapeake Bay are summarized in Table 9.7. Unlike

PCBs, where volatilization exceeds wet and dry aerosol deposition, absorption of gaseous

phenanthrene from the atmosphere is a significant source to the Bay (Nelson et al., 1998;

Bamford et al., 1999). Point sources, as estimated in this report, comprise three quarters of the

total phenanthrene loading to the Bay below the fall lines, while gas absorption and urban runoff

contribute most of the phenanthrene entering the mainstem of the Bay. Approximately 90% of

phenanthrene entering the Chesapeake Bay is loaded into the tributaries. As was the case of

PCBs, only a small fraction of the phenanthrene entering the tributaries (53,000 kg/year) is

transported to the mainstem (1250 kg/year, or 0.2%). This inefficient transmission of

phenanthrene likely reflects both burial in tributary sediments and degradation near the emission

sources. Degradation of phenanthrene in surface waters, primarily via photolytic reactions,

accounts for two thirds of the loss of phenanthrene from the mainstem, and burial and export to

the ocean are approximately equal in magnitude (Table 9.8).

The reader will note that the independent estimates of phenanthrene loading to the

mainstem (4,360 kg/year) and losses (4,310 kg/year) agree to within 2%. As with the copper

balance, whether this reflects the skill or the luck of the author remains to be determined.
Mass Balance

9-9

Table 9.1. Loadings of total copper to Chesapeake Bay.

Total Load

Below FallLines

Total Load to

Mainstem

Total Load to

Tributaries

(by difference)

Wet Deposition 4,700 330 4,400

Dry Aerosol Deposition 4,300 430 3,900

Urban Runoff 24,500 7,200 17,300

Point Sources 36,600 330 36,300

Shoreline Erosion 27,700 27,700 0

Groundwater 0 0 0

Tributaries to Bay 224,000 81,700 142,300

TOTAL 322,000 118,000 204,200

Units: kg/yr

Table 9.2. Losses of total copper from the mainstem 

Chesapeake Bay.

Export to the Ocean 2,000

Burial in Sediments 105,000

TOTAL MAINSTEM LOSSES 107,000

Units: kg/yr
Mass Balance

9-10

Table 9.3. Loadings of Mercury to Chesapeake Bay.

Total Load

Below FallLines

Total Load to

Mainstem

Total Load to

Tributaries

(by difference)

Wet Deposition 105 92 13

Dry Aerosol Deposition 21 17 4

Diffusion from Sediments 240 130 110

Urban Runoff 370 0 370

Point Sources 1,200 3 1,200

Shoreline Erosion 0 0 0

Groundwater 0 0 0

Tributaries to Bay 2,600 180 2,400

TOTAL 4,540 420 4,120

Units: kg/yr

Table 9.4. Losses of Mercury from the Mainstem 

Chesapeake Bay.

Export to the Ocean 350

Volatilization 57

Burial in Sediments 1,350

TOTAL MAINSTEM LOSSES 1,760

Units: kg/yr
Mass Balance

9-11

 Table 9.5. Loadings of total PCBs to Chesapeake Bay.

Total Load

Below FallLines

Total Load to

Mainstem

Total Load to

Tributaries

(by difference)

Wet Deposition 65 27 38

Dry Aerosol Deposition 65 27 38

Urban Runoff 180 55 129

Point Sources 410,000 0 410,000

Tributaries to Bay 130 74 72

TOTAL 410,400 183 410,300

Units: kg/yr

Table 9.6. Losses of total PCBs from the mainstem 

Chesapeake Bay.

Export to the Ocean 560

Volatilization 340

Burial in Sediments 280

TOTAL MAINSTEM LOSSES 1,180

Units: kg/yr
Mass Balance

9-12

Table 9.7. Loadings of Phenanthrene to Chesapeake Bay.

Total Load

Below FallLines

Total Load to

Mainstem

Total Load to

Tributaries

(by difference)

Wet Deposition 65 46 19

Dry Aerosol Deposition 150 110 44

Gas Absorption from the Atmosphere 3,040 1,950 1,090

Urban Runoff 7,130 2,100 5,030

Point Sources 47,000 4 47,000

Tributaries to Bay 120 150 95

TOTAL 57,510 4,360 53,300

Units: kg/yr.

Table 9.8. Losses of Phenanthrene from the Mainstem 

Chesapeake Bay.

Export to the Ocean 750

Degradation (k=0.045 day-1) 2,860

Burial in Sediments 700

TOTAL MAINSTEM LOSSES 4,310

Units: kg/yr
Mass Balance

9-13

SUMMARY AND CONCLUSIONS

The mass balance analysis for total PCBs, phenanthrene, copper and mercury reveal

different levels of agreement between the inputs to the mainstem Bay and the outputs. While

copper and phenanthrene show good agreement between the inputs and outputs, total PCBs and

mercury do not. Both total PCBs and mercury outputs from the mainstem water column are

higher than the loads to the mainstem by about a factor of 5. Unfortunately, due to the lack of

sufficient data it is impossible to quantify the uncertainty for these estimates and this is where

future monitoring efforts should be focused. Greatest uncertainty for the sources is most likely

tributary inputs to the mainstem segment of the model, while for the output of chemicals, the

greatest amount of uncertainty is probably with the export to the ocean and burial in the

sediments.

The comparison between the total load below the fall line and inputs to the mainstem Bay

reveal a common and important feature for all chemicals. In this analysis, most of the loads are

to the tributaries (i.e., Potomac, James, York Rivers) with the majority (i.e., > 90%) of these

inputs for total PCBs, phenanthrene, mercury, retained in the tributaries. Copper shows the

greatest export to the mainstem from the tributaries with approximately 60% of the total load

exported to the mainstem. However, due to the method used for this analysis and the available

data, this estimate is tentative at best.

This study suggests focusing monitoring efforts on specific sources and geographic areas

that would greatly improve and expand a mass balance and provide better check and balances

between inputs and outputs. This would enable better confidence in the loading estimates from

the previous chapters. For example, in many tributaries point sources or urban runoff are

dominant sources. The method used to calculate these sources should be updated. This is

especially true for the point source data in which there is a large range in the estimates. The best

method would be to determine, by flow, the dominant point sources and analyze their effluent

using state of the art methods with lower detection limits. Given that this would be very costly,

select point sources that represent specific industrial types (i.e., SIC) should be monitored to

provide baywide typical pollutant concentrations (TPCs) for unmonitored point sources. This

data could be used in conjunction with NOAA’s extensive TPC database and would greatly

improve the overall point source estimate to the Bay. Additionally, the water column

concentrations of many chemicals are lacking throughout the Bay with respect to the data needs

of this or future models. Transport of dissolved and particulate metals and organic contaminants

at the tributary and ocean boundaries is largely unknown and are a major source/sink in the

model for all contaminants. 

In general, basic monitoring information is needed for almost all sources and sinks

identified in this report. While these monitoring data will not provide information as to the

effects of chemical contaminants, they do provide the needed information as to where and how

much a reduction in a particular source load is needed. Until both sources and sinks are better
Mass Balance

9-14

quantified, future input-output balances will remain uncertain and of limited quantitative use. 

Once accurately verified, a mass balance model could be used to answer "what if" questions such

as; if specific sources are reduced, how much reduction is needed and how long will it take to

lower the concentration of a specific contaminant in the water column or an organism to a given

level?

For a more complete mass balance model to be useful, its development must be driven by

the objectives upon which both managers and scientists decide. Also, there are many questions

concerning the feasibility of using a mass balance approach to manage or evaluate chemical

contaminants in Chesapeake Bay. For example, if a concerted effort is applied to determine the

absolute inputs and outputs from significant sources and sinks, will enough specific information

exist to help managers of the various sources of contaminants (i.e., point source regulators or

urban planners) determine the need for potential additional regulation of these sources? Also, if

additional regulatory actions are taken, will living resources that are affected by contaminants

respond and show some improvement (i.e., fewer fish advisories)? 

As can be seen from the simple input-output model for the mainstem Bay, the data needs

for any of these tasks are enormous and would therefore be very expensive. However, it would

be useful and less expensive to focus on one tributary. This would allow a testing of specific

questions as to how contaminants are transported through a system and would help guide the data

needs for a much larger and complex system as the Chesapeake Bay. In addition, the preliminary

mass balance indicates that a majority of the contaminants, due to their particle-reactive

behavior, are trapped within the tributaries of the Bay. Therefore, it is more relevant to look at

the balances within specific tributaries to determine how much material is transported to the

mainstem Bay.

The development of a simple mass balance would provide useful information to Bay

managers. For example, current load estimations to the Bay could be evaluated and judged for

accuracy by also estimating the outputs. This would help managers and scientists determine any

unrecognized source(s) to the Bay. When an accurate assessment of the relative loading exists,

the importance of each source can be determined, and a determination can be made of the

possible measures in controlling these sources in an overall context. This information is needed

to help focus clean-up efforts and the limited dollars to areas and sources that will make the

biggest difference in the overall health of Chesapeake Bay. 

Summary Recommendations for Implementing the Mass Balance

< Determine the spatial/temporal distribution of dissolved, particulate and volatile chemical

contaminants throughout the Bay and within the tributaries.

< Obtain accurate point source loading estimates.
Mass Balance

9-15

< Obtain recent surface and subsurface sediment concentrations of chemical contaminants.

< Determine the depositional areas and rates within the mainstem and tributaries of the Bay.

< Derive relationships between sediment variables (e.g., sediment concentrations of metal

or organic, grain size, organic carbon, etc) and the diffusion to the overlying bottom

waters. 

< Water and chemical exchange rates at the ocean-bay interface.

< Focus research/monitoring efforts on a specific tributary to test specific hypothesis on

inputs and outputs fluxes.
Mass Balance

9-16

ACKNOWLEDGMENT

We would like to thank the participants of the Solomons Island Mass Balance Workshop

(May, 1998) for their assistance in gathering the data for the mass balance model. Special thanks

to Rob Mason, Fritz Riedel, and Laura McConnell for editorial help. Jim Hagy helped derive a

working salt balance for the modeling framework. 
r-1

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Poster, D.L. and J.E. Baker. 1996b. The influence of submicron particles on hydrophobic

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Press, Pensacola FL, 1-16.
Appendix A: Chemicals and default detection limits

CHEMICAL SUBSTANCES DEFAULT LIMITS(mg/l)

1,1,1-TRICHLOROETHANE 0.0038

1,1,2,2-TETRACHLOROETHANE 0.0069

1,1,2-TRICHLOROETHANE 0.005

1,1-DICHLOROETHANE 0.0047

1,1-DICHLOROETHYLENE 0.0028

1,2,4-TRICHLOROBENZENE 0.0019

1,2-CIS-DICHLOROETHYLENE 0.001

1,2-DICHLOROBENZENE 0.0019

1,2-DICHLOROETHANE 0.0028

1,2-DICHLOROPROPANE 0.006

1,2-DIPHENYLHYDRAZINE 0.000001

1,2-TRANS-DICHLOROETHYLENE 0.0016

1,3 DICHLOROPROPENE 0.000002

1,3-DICHLOROBENZENE 0.0019

1,3-DICHLOROPROPENE 0.000002

1,4-DICHLOROBENZENE 0.0044

2,3,7,8-TETRACHLORODIBENZOFURAN 0.01

2,4,6-TRICHLOROPHENOL 0.0027

2,4-DICHLOROPHENOL 0.0027

2,4-DIMETHYLPHENOL 0.0027

2,4-DINITROPHENOL 0.042

2,4-DINITROTOLUENE 0.0057

2,6-DINITROTOLUENE 0.0019

2-CHLOROETHYLVINYLETHER 0.00013

2-CHLORONAPHTHALENE 0.0019

2-CHLOROPHENOL 0.0033

2-METHYL-4-CHLOROPHENOL 0.003

2-METHYLNAPTHTHALENE 0.01

2-NITROPHENOL 0.0036

3,3'-DICHLOROBENZIDINE 0.017

3,4-BENZOFLUORANTHENE 0.0048

4,6-DINITRO-O-CRESOL 0.024

4-BROMOPHENYLPHENYLETHER 0.0019

4-CHLOROPHENYLPHENYLETHER 0.0042

4-NITROPHENOL 0.0024

ACENAPHTHENE 0.0019

ACENAPHTHYLENE 0.0035

ACETONE 1

ACROLEIN 0.0007

ACRYLONITRILE 0.0005

ALDRIN 0.0019

ALUMINUM, ACID SOLUABLE 0.02

ALUMINUM, DISSOLVED 0.02

ALUMINUM, TOTAL 0.02

ALUMINUM, TOTAL RECOVERABLE 0.02

AMMONIA+UNIONIZED AMMONIA 0.01

ANTHRACENE 0.0019

ANTIMONY, TOTAL 0.008

ARSENIC, DISSOLVED 0.0009

ARSENIC, TOTAL 0.0009

ARSENIC, TOTAL RECOVERABLE 0.0009

ASBESTOS

BARIUM, DISSOLVED 0.001

BARIUM, TOTAL 0.001

BENZENE 0.0044

BENZIDINE 0.044

BENZO[A]ANTHRACENE 0.0078

BENZO[A]PYRENE 0.0025

BENZO[GHI]PERYLENE 0.0041

BENZO[K]FLUORANTHENE 0.0025

BERYLLIUM, TOTAL 0.00002

BHC-ALPHA 0.000003

BHC-BETA 0.0042

BHC-DELTA 0.0031

BHC-GAMMA 0.000004

BIS (2-CHLOROETHYL) ETHER 0.0057

BIS (2-CHLOROISOPROPYL) ETHER 0.0057

BIS (2-ETHYLHEXYL) PHTHALATE 0.0025

BIS(2-CHLOROETHOXY) METHANE 0.0053

 A-1
Appendix A: Chemicals and default detection limits

CHEMICAL SUBSTANCES DEFAULT LIMITS(mg/l)

BORON, TOTAL 0.003

BROMODICHLOROMETHANE 0.0022

BROMOFORM 0.0047

BUTYL BENZYL PHTHALATE 0.0025

CADMIUM, DISSOLVED 0.005

CADMIUM, TOTAL 0.005

CADMIUM, TOTAL RECOVERABLE 0.001

CARBON DISULFIDE 0.01

CARBON TETRACHLORIDE 0.0028

CHLORDANE 0.000014

CHLORIDE 1

CHLORINE, FREE AVAILABLE 0.0002

CHLORINE, FREE RESIDUAL 0.0002

CHLORINE, TOTAL RESIDUAL 0.0002

CHLOROBENZENE 0.006

CHLORODIBROMOMETHANE 0.0031

CHLOROETHANE 0.00052

CHLOROFORM 0.0016

CHLORPYRIFOS

CHROMIUM, DISSOLVED 0.004

CHROMIUM, HEXAVALENT 0.0003

CHROMIUM, HEXAVALENT DISSOLVED 0.0003

CHROMIUM, HEXAVALENT TOTAL RECOVERABLE 0.0003

CHROMIUM, TOTAL 0.004

CHROMIUM, TOTAL RECOVERABLE 0.004

CHROMIUM, TRIVALENT 0.0001

CHRYSENE 0.0025

CLAMTROL CT-1

COBALT, TOTAL 0.002

COPPER, DISSOLVED 0.003

COPPER, TOTAL 0.003

COPPER, TOTAL RECOVERABLE 0.003

CYANIDE 0.02

CYANIDE, FREE AMENABLE TO CHLORINATION 0.02

CYANIDE, FREE NOT AMENABLE TO CHLORINATION 0.02

CYANIDE, TOTAL 0.02

CYANIDE, TOTAL RECOVERABLE 0.02

CYANIDE, WEAK ACID DISSOCIABLE 0.02

DDD 0.0028

DDE 0.0056

DDT 0.0047

DI-N-BUTYL PHTHALATE 0.0025

DI-N-OCTYLPHTHALATE 0.0025

DIBENZO(A,H)ANTHRACENE 0.0025

DICHLOROBROMOMETHANE 0.0022

DICHLOROETHENE 0.0028

DIELDRIN 0.0025

DIETHYL PHTHALATE 0.0019

DIMETHYL PHTHALATE 0.0016

DIOXIN 0.000002

ENDOSULFAN - ALPHA

ENDOSULFAN - BETA

ENDOSULFAN SULFATE 0.0056

ENDRIN 0.000006

ENDRIN ALDEHYDE 0.000023

ETHION 0.0001

ETHYL BENZENE 0.0072

ETHYLBENZENE 0.0072

FLUORANTHENE 0.0022

FLUORENE 0.0019

FLUORIDE 0.1

FLUORIDE, TOTAL

HALOGENATED HYDROCARBONS 0.0019

HEPTACHLOR 0.0022

HEPTACHLOR EPOXIDE 0.0019

HEXACHLOROBENZENE 0.0009

HEXACHLOROBUTADIENE 0.0004

HEXACHLOROCYCLOPENTADIENE 0.0016

HEXACHLOROETHANE 0.02

 A-2
Appendix A: Chemicals and default detection limits

CHEMICAL SUBSTANCES DEFAULT LIMITS(mg/l)

HEXAMETHYLPHOSPHORAMINE 0.005

HYDRAZINE 0.0037

INDENO(1,2,3-CD)PYRENE 0.03

IRON, DISSOLVED 0.03

IRON, TOTAL 0.03

IRON, TOTAL RECOVERABLE 0.0022

ISOPHORONE 0.01

LEAD, DISSOLVED 0.01

LEAD, TOTAL 0.01

LEAD, TOTAL RECOVERABLE 0.02

MAGNESIUM, TOTAL 0.001

MANGANESE, DISSOLVED 0.001

MANGANESE, TOTAL 0.007

MERCURY, DISSOLVED 0.007

MERCURY, TOTAL 0.007

MERCURY, TOTAL RECOVERABLE

METALS, TOTAL 0.0012

METHYL BROMIDE 0.00008

METHYL CHLORIDE 1

METHYL ISOBUTYL KETONE 0.0028

METHYLENE CHLORIDE 0.02

MOLYBDENUM, TOTAL 0.00046

N-NITROSODI-N-PROPYLAMINE 0.00015

N-NITROSODIMETHYLAMINE 0.0019

N-NITROSODIPHENYLAMINE 0.0016

NAPHTHALENE 0.005

NICKEL, DISSOLVED 0.005

NICKEL, TOTAL 0.005

NICKEL, TOTAL RECOVERABLE 0.01

NITRITE PLUS NITRATE 0.0019

NITROBENZENE 0.01

NITROGEN, AMMONIA TOTAL 0.03

NITROGEN, KJELDAHL TOTAL 0.002

NITROGEN, NITRATE DISSOLVED 0.002

NITROGEN, NITRATE TOTAL 0.01

NITROGEN, NITRITE TOTAL 0.03

NITROGEN, ORGANIC TOTAL 0.03

NITROGEN, TOTAL

NITROGLYCERIN 0.03

PCB 1221 0.001

PCB 1232

PCB 1242 0.001

PCB 1254 0.001

PCB-1016 0.0001

PCB-1248 0.0001

PCB-1260

PENTACHLOROBIPHENYL 0.0036

PENTACHLOROPHENOL 1

PETROLEUM HYDROCARBONS

PETROLEUM OIL, TOTAL RECOVERABLE 0.0054

PHENANTHRENE 0.0015

PHENOL

PHENOLICS 0.002

PHENOLS 0.01

PHOSPHATE, ORTHO 0.06

PHOSPHOROUS 0.01

PHOSPHORUS, DISSOLVED 0.01

PHOSPHORUS, TOTAL

PHTHALATE ESTERS 0.00001

POLYCHLORINATED BIPHENYLS (PCBS) 0.0019

PYRENE 0.0006

SELENIUM, DISSOLVED 0.0006

SELENIUM, TOTAL 0.0006

SELENIUM, TOTAL RECOVERABLE 0.002

SILVER 0.002

SILVER, DISSOLVED 0.002

SILVER, TOTAL 0.002

SILVER, TOTAL RECOVERABLE 1

SULFATE 1

 A-3
Appendix A: Chemicals and default detection limits

CHEMICAL SUBSTANCES DEFAULT LIMITS(mg/l)

SULFATE, TOTAL 1

SULFIDE, TOTAL 1

SULFITE

TANTALUM, TOTAL 0.0041

TETRACHLOROETHYLENE 0.02

THALLIUM, TOTAL 0.007

TIN, DISSOLVED 0.007

TIN, TOTAL 0.05

TITANIUM, TOTAL 0.006

TOLUENE

TOTAL TOXIC ORGANICS 1

TOXAPHENE 0.00024

TRANS-1,2-DICHLOROETHYLENE 0.0016

TRICHLOROETHENE 0.0019

TRICHLOROETHYLENE 0.0019

TRICHLOROFLUOROMETHANE 0.01

TUNGSTEN, TOTAL

VANADIUM, TOTAL 0.003

VINYL CHLORIDE 0.00018

VOLATILE ORGANICS 1

XYLENE 0.005

ZINC, DISSOLVED 0.002

ZINC, TOTAL 0.002

ZINC, TOTAL RECOVERABLE 0.002

Note: No data available for empty spaces under "Default Limits."

 A-4
Appendix B: Loads of Chemical Categories by SIC Code

SIC

CODE SIC CODE DESCRIPTION AFL BFL

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

2011 MEAT PACKING PLANTS 1 1 62,636.18 62,636.18 905.27 913.79 0.00 102.45

2015 POULTRY SLAUGHTERING & PROCESS 1 62,093.43 62,093.43

2021 CREAMERY BUTTER 1 295,114.09 295,114.09

2023 CONDENSED AND EVAPORATED MILK 1 1,920.94 1,920.94

2041 FLOUR & OTHER GRAIN MILL PROD 1 55,581.24 55,581.24

2066 CHOCOLATE AND COCOA PRODUCTS 1 44,769.73 44,769.73 53,976.12 56,378.76

2221 BROAD WOVEN FABRIC MILLS, SYNT 1 28.57 28.57

2231 BROAD WOVEN FABRIC MILLS, WOOL 1 2.54 6.52

2269 FINISHERS OF TEXTILES, NEC 1 29,863.52 29,863.52 677.11 711.38

2491 WOOD PRESERVING 1 108.03 108.03

2611 PULP MILLS 2 46,607.79 46,607.79 10,961.14 11,331.57 0.00 709.51

2621 PAPER MILLS 3 2 1,275,525.08 1,278,855.56 69,369.71 72,501.93 0.07 2,707.11

2631 PAPERBOARD MILLS 2 134,858.09 156,755.67 209,841.25 248,678.59 467.39 7,088.55

2676 SANITARY PAPER PRODUCTS 1 432,937.71 432,937.71

2678 STATIONERY,TABLETS & REL PROD 1 40,920.99 40,920.99

2816 INORGANIC PIGMENTS 2 25,362.37 25,362.37 606,833.94 619,394.74

2819 INDUSTRIAL INORGANIC CHEMICALS 3 705,825.29 705,825.29 54,226.27 54,554.04 106.41 106.41

2821 PLSTC MAT./SYN RESINS/NV ELAST 1 1 92,061.85 92,061.85 9,474.48 13,085.67 302.74 31,524.13

2833 MEDICINAL CHEM/BOTANICAL PRODU 1 270,622.02 270,622.02 580,999.60 582,485.59

2834 PHARMACEUTICAL PREPARATIONS 1 22.58 25.47

2841 SOAP/DETERG EXC SPECIAL CLEANR 1 0.00 3.65 247.30 258.96 0.00 18.31

2869 INDUST. ORGANIC CHEMICALS NEC 1 1.16 1.16

2873 NITROGEN FERTILIZERS 1 158,497,740.17 158,497,740.17 5,350.91 6,475.64 943.03 943.03

2899 CHEMICALS & CHEM PREP, NEC 1 123.28 123.40

2911 PETROLEUM REFINING 1 1,531.63 1,605.62 0.00 278.84

2952 ASPHALT FELT AND COATINGS 1 79.03 79.03

3111 LEATHER TANNING AND FINISHING 2 70,894.43 70,962.91 2,648.76 3,000.31 0.00 72.36

3131 BOOT & SHOE CUT STOCK & FINDNG 1 37,298.15 37,298.15 8.25 15.24

3253 CERAMIC WALL AND FLOOR TILE 1 0.96 2.12

3312 BLAST FURN/STEEL WORKS/ROLLING 2 2 1,798,850.37 1,798,850.37 16,585.69 20,097.20

3322 MALLEABLE IRON FOUNDRIES 1 453.63 453.63 867.11 867.11

3331 PRIMRY SMELTING & COPPER REFIN 1 306.03 310.86 200.57 205.20 0.00 0.35

3334 PRIMARY PRODUCTION OF ALUMINUM 1 2,846.01 3,085.21

3351 ROLL/DRAW/EXTRUDING OF COPPER 1 526.81 534.77

3399 PRIMARY METAL PRODUCTS, NEC 1 265,689.92 265,693.27 2,650.05 2,658.02

3443 FAB PLATE WORK (BOILER SHOPS) 1 207,059.54 207,059.54 634.08 929.44 0.00 18.29

# OF 

FACILITIES

UNDER SIC

INORGANICS METALS ORGANICS
Appendix B: Loads of Chemical Categories by SIC Code

SIC

CODE SIC CODE DESCRIPTION AFL BFL

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

# OF 

FACILITIES

UNDER SIC

INORGANICS METALS ORGANICS

3469 METAL STAMPINGS, NEC 1 2,105.77 2,179.98

3471 PLATING AND POLISHING 2 476.77 476.77

3483 AMMUNIT., EXC. FOR SMALL ARMS 2 204,425.81 204,425.81 229,099.06 229,917.98 18,765.27 43,737.55

3671 ELECTRON TUBES 1 548.87 557.53

3713 TRUCK & BUS BODIES 1 33.43 33.43

3731 SHIP BUILDING AND REPAIRING 1 106.26 106.26 12,799.48 12,806.48

4513 AIR COURIER SERVICES 1 70.20 127.64

4911 ELECTRICAL SERVICES 8 12 83,409.67 142,757.40 526,131.08 535,863.29 322,494.60 2,716,910.22

4931 ELEC & OTHER SERVICES COMBINED 1 33,098.13 48,755.90 2,303.92 2,646.17 0.00 2,504.67

4941 WATER SUPPLY 2 72,518.12 72,522.33 0.00 13.79

4952 SEWERAGE SYSTEMS 90 44 69,569,562.49 69,585,466.37 1,159,406.07 1,305,645.89 23,992.89 915,444.20

5171 PETROLEUM BULK STATIONS & TERM 2 63.46 63.46 2,357.50 2,364.44 2,400.92 2,428.95

8062 GEN. MEDICAL/SURGICAL HOSPITAL 1 7.13 7.13 5.13 12.64 0.00 0.41

8733 NONCOMMERCIAL RESEARCH ORGANI 1 498,557.14 498,557.14

9199 GENERAL GOVERNMENT, NEC 1 32.36 42.86

9511 AIR & WATER RES & SOL WSTE MGT 1 3,270.60 3,323.75

9711 NATIONAL SECURITY 4 40,269.40 41,764.94 255,367.15 256,814.71

Note: Empty spaces mean no data available for facilities under the SIC code by given chemical categories. Zeros present in the loading estimates can have several 

meanings. A zero may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.
Appendix B:. Loads of Chemical Categories by SIC Code

SIC

CODE SIC CODE DESCRIPTION AFL BFL

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

2011 MEAT PACKING PLANTS 1 1 0.00 189.13 0.00 189.13 0.00 97.72

2015 POULTRY SLAUGHTERING & PROCESS 1

2021 CREAMERY BUTTER 1

2023 CONDENSED AND EVAPORATED MILK 1

2041 FLOUR & OTHER GRAIN MILL PROD 1

2066 CHOCOLATE AND COCOA PRODUCTS 1

2221 BROAD WOVEN FABRIC MILLS, SYNT 1

2231 BROAD WOVEN FABRIC MILLS, WOOL 1

2269 FINISHERS OF TEXTILES, NEC 1

2491 WOOD PRESERVING 1

2611 PULP MILLS 2 0.00 446.02 0.00 16.99 0.00 62.31

2621 PAPER MILLS 3 2 0.00 3,394.91 0.00 213.27 0.00 131.91

2631 PAPERBOARD MILLS 2 33.50 6,645.50 0.00 29,972.98 0.00 11,722.20

2676 SANITARY PAPER PRODUCTS 1

2678 STATIONERY,TABLETS & REL PROD 1

2816 INORGANIC PIGMENTS 2

2819 INDUSTRIAL INORGANIC CHEMICALS 3 31.80 31.80

2821 PLSTC MAT./SYN RESINS/NV ELAST 1 1 348.93 35,431.68 0.00 273,026.07 0.00 165,794.25

2833 MEDICINAL CHEM/BOTANICAL PRODU 1

2834 PHARMACEUTICAL PREPARATIONS 1

2841 SOAP/DETERG EXC SPECIAL CLEANR 1 0.00 13.89

2869 INDUST. ORGANIC CHEMICALS NEC 1

2873 NITROGEN FERTILIZERS 1

2899 CHEMICALS & CHEM PREP, NEC 1

2911 PETROLEUM REFINING 1 0.00 154.17 0.00 6.68 0.00 24.49

2952 ASPHALT FELT AND COATINGS 1

3111 LEATHER TANNING AND FINISHING 2 0.00 157.88 0.00 15.79 0.00 11.68

3131 BOOT & SHOE CUT STOCK & FINDNG 1

3253 CERAMIC WALL AND FLOOR TILE 1

3312 BLAST FURN/STEEL WORKS/ROLLING 2 2 100.95 774.08

3322 MALLEABLE IRON FOUNDRIES 1

3331 PRIMRY SMELTING & COPPER REFIN 1 0.00 0.41

3334 PRIMARY PRODUCTION OF ALUMINUM 1 0.10 0.21

3351 ROLL/DRAW/EXTRUDING OF COPPER 1 0.00 0.00

3399 PRIMARY METAL PRODUCTS, NEC 1

3443 FAB PLATE WORK (BOILER SHOPS) 1 0.00 14.14 0.00 1.64 0.00 0.42

PAHs PCBs PESTICIDES

# OF 

FACILITIES

UNDER SIC
Appendix B:. Loads of Chemical Categories by SIC Code

SIC

CODE SIC CODE DESCRIPTION AFL BFL

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

LOW LOAD

(lbs/year)

HIGH LOAD

(lbs/year)

PAHs PCBs PESTICIDES

# OF 

FACILITIES

UNDER SIC

3469 METAL STAMPINGS, NEC 1

3471 PLATING AND POLISHING 2

3483 AMMUNIT., EXC. FOR SMALL ARMS 2 0.00 179.89

3671 ELECTRON TUBES 1

3713 TRUCK & BUS BODIES 1

3731 SHIP BUILDING AND REPAIRING 1

4513 AIR COURIER SERVICES 1

4911 ELECTRICAL SERVICES 8 12 0.00 1,997,831.60 0.00 11,571,705.14 0.00 9,843,155.17

4931 ELEC & OTHER SERVICES COMBINED 1 0.00 2,278.08

4941 WATER SUPPLY 2 0.00 41.38 0.00 4.26 0.00 1.48

4952 SEWERAGE SYSTEMS 90 44 8,596.50 94,847.04 0.00 227,764.36 3,418.56 143,251.72

5171 PETROLEUM BULK STATIONS & TERM 2 1.01 1.02

8062 GEN. MEDICAL/SURGICAL HOSPITAL 1 0.00 0.55 0.15 0.47 0.00 0.06

8733 NONCOMMERCIAL RESEARCH ORGANI 1

9199 GENERAL GOVERNMENT, NEC 1 0.01 2.14

9511 AIR & WATER RES & SOL WSTE MGT 1

9711 NATIONAL SECURITY 4

Note: Empty spaces mean no data available for facilities under the SIC code by given chemical categories. Zeros present in the loading estimates can have several 

meanings. A zero may indicate the chemical was non-detect, or that the flow was reported as zero for a given record, or that the concentration was reported as zero for a 

given record, or that the concentration value was not recorded in the PCS database.