U.S. Departrnent ot the Intedor

U.S. Geological Survey

NITRATE, VOLATILE ORGANIC COMPOUNDS, AND

PESTICIDES IN GROUND WATER-.A SUMMARY OF SELECTED

STUDIES FROM NEW JERSEY AND TONG ISLAND, NEW YORK

Wqle r- Resou rc es I nvesfi go tio ns Repo rl 99 - 4027

l,lqfionol Wofer-Quolity Assessmenl Progrom
I

I

i

I

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NITRATE, VOLATITE ORGANIC COMPOUNDS, AND

PESTICIDES IN GROUND WATER..A SUMMARY OF SELECTED

STUDIES FROM NEW JERSEY AND LONG ISLAND, NEW YORK

By Rick M. Clowges, Poul E. Stockelberg, Mork A. Ayers, ond Eric F. Vowinkel

U.S. GEOLOGICAT SURVEY

Wqter- Resou rces I nvesti gof ions Rep orl 99 - 4027

Notionol Woler-Quolity Assessmenl Progrom

Wesl Trenlon, New Jersey

-

-

rciencefor a 

USGS

changing world
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretory

U.S. GEOLOGICAT SURVEY

Chorles G. Groot, Director

For additional information Copies of this report can be

write to: purchased from:

Distict Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

810 Bear Tavern Road" Suite 206 8ox25286

West Trenton, NJ 08628 Denver, CO 80225-0286

Information regarding research and data-collectionprograms of the U.S. Geological Survey is available on

the Intemet via the World Wide Web. You may connect o the Home Page for the New Jersey District

Office using the Universal Resources Locator (URL) at:

htp ://wwwnj. er.usgs.gov/index.hnnl

The URL for the New York District Office can be found at:

httr //wwwdnyalb. er.usgs. gov/index. htnl

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CONTENTS

Page

Population and land-use history.. .......................2

Occurrence and movement............ ........4

Imporlance .........8

Contamination............ ..........8

Nitrate in ground water ..................1I

Relation to aquifer conditions. .............13

Relation to depth in the aquifer...... ......14

Relation to land use............ ..................15

Predicting vulnerability to nitrate contamination ............ ........17

Volatile organic compounds inground water ....................17

Relation to aquifer conditions ..............19

Relation to depth in the aquifer...... ......19

Relation to land use............ ..................20

Predicting vulnerability to volatile-organic-compound contamination............ ...........22

Pesticides inground water .............22

Long Is1and............... .........25

New Jersey .......26

Predicting vulnerability to pesticide contamination ................27

Summary and conclusions......... ......................28

ILLUSTRATIONS

Figurel. Map showing average population density in New Jersey and on Long Island, New York,

1990 ......... .....................3

2. Graph showing population of New Jersey, 1900-90 ...............3

3. Graph showing population of Long Island, New York, 1900-90..... .........3

4. Map showing land use in New Jersey and on Long Island, New York, 1990 ..............................4

5. Diagram of the hydrologic cyc1e......... ..................5

6. Diagram showing patterns of ground-water flow and relative age in a Coastal Plain

aquifer system...... .........6

7-9. Maps showing:

7. Location of sections and generalized diagram of the four types of aquifers in New Jersey

and on Long Island, New York......... ................7

8. Ground-water withdrawals in New Jersey and on Long Island, New York, in 1990, by

county .........8

9. Percentage of the population in New Jersey and on Long Island, New York, that used

ground water in 1990, by county ......................8

10. Graph showing number of permits issued in New Jersey for soil borings, gas vents,

monitoring wells, piezometers, and recovery wells, 1983-90 ............10

ll-15. Maps showing:

1 l. Number of reported ground-water-contamination cases in New Jersey as of April l992,by

county .......10

12. Number of claims received for ground-water contamination in New Jersey in 1994, by

county .......10
ILLUSTRATIONS-Continued

page

13. Amount of nitrogen fertilizer applied in New Jersey and on Long Island, New York, in

1991, by county ..........12

14. Amount of nitrogen input from animal manure in New Jersey and on Long Island, New

York, in 1992, by county ..............12

15. Outcrop areas of the Potomac-Raritan-Magothy and Kirkwood-Cohansey aquifer

systems in New Jersey ..................13

16. Graph showing the frequency of detection of nitrate in water from wells in unconfined and

confined parts of the Potomac-Raritan-Magothy aquifer system, New Jersey .....13

17. Map showing five areas of differing land use and sewering practices in Nassau and Suffolk

Counties, Long Island, New York ......... .........15

18-22. Graphs showing:

18. Median concentration of nitrate in water from shallow and deep wells in Nassau and

Suffolk Counties, Long Island, New York.......... ..............15

19. Frequency of detection of nitrate in water from 645 wells in the Coastal Plain of New ,t;

Jersey, by predominant land use............ .........16

20. Median concentration of nitrate in water from 645 wells in the Coastal Plain of New F

Jersey, by predominant land use............ .........16 f

2l . Frequency of detection of nitrate in water from wells in five areas of differing land use I

I

and sewering practices in Nassau and Suffolk Counties, Long Island, New York.................17 t

f'

22. Median concentration of nitrate in water from wells in five areas of differing land use and i

I

sewering practices in Nassau and Suffolk Counties, Long Island, New York .......................17

23. Map showing estimated probability of detecting nitrate in a concentration greater than

3 milligrams per liter in water from wells in Nassau and Suffolk Counties, Long Island,

New York. ...................18

24. Map showing location of detections of nitrate in water from 268 wells in Nassau and

Suffolk Counties, Long Island, New York.......... ..............18

25. Graph showing frequency of detection of volatile organic compounds in water from wells

in unconfined and confined parts of the Potomac-Raritan-Magothy aquifer systern,

New Jersey ..................19

26. Section showing relation of depth and pumpage to detection of volatile organic compounds

in water from wells in the Potomac-Raritan-Magothy aquifer system, New Jersey ..............20

27-30. Graphs showing:

27. Frequency of detection of volatile organic compounds in water from wells in outcrop

areas of the Potornac-Raritan-Magothy andKirkwood-Cohansey aquifer systems,

New Jersey, by predominant land use............ ...................20

28. Frequency of detection of volatile organic compounds in concentrations greaterthan

I microgram per liter in water from wells in five areas of differing land use and

sewering practices in Nassau and Suffolk Counties, Long Island, New York .......................21

29. Frequency of detection of 1,1,1-trichloroethane (TCA) in water from wells in five areas

of differing land use and sewering practices in Nassau and Suffolk Counties, Long

Island, New York ........21

30. Frequency of detection of trichloroethylene (TCE) in water from wells in five areas of

differing land use and sewering practices in Nassau and Suffolk Counties, Long Island,

New York. ...................21

IV
31.Map showing estimated probability of detecting a total volatile-organic-compound

concentration greater than I microgram per liter in water from wells in Nassau

and Suffolk Counties, Long Island, New York.......... .......23

32.Map showing location of detections of volatile organic compounds in concentrations

greater than 1 microgram per liter in in water from 248 wells in Nassau and Suffolk

Counties, Long Island, New York......... .........23

33-36.Graphs showing:

33.Reported pesticide use in New Jersey, by land use and type of pesticide ......... .......24

34.Frequency of detection of five groups of pesticides in water from wells in five areas of

differing land use and sewering practices in Nassau and Suffolk Counties, Long Island,

New York. ...................25

35.Frequency of detection of five groups of pesticides in water from wells in the PotomacRaritan-Magothy and Kirkwood-Cohansey aquifer systems, New Jersey ...........26

36.Percentage of New Jersey public-supply wells in each of three wlnerability groups, by

major aquifer type.......... ...............28

37.Map showing vulnerability of public-supply wells in New Jersey to contamination by

pesticides.. ...................28

ILLUSTRATIONS-Continued

Page
coNvERsIoN FACTORS AltD WATER-QUALITY ABBRBVIAIONS

Multiply Bv To obtain

Length

inch (in.)

inch (in.)

foot (ft)

mile (mi)

25,400

25.4

0.3048

1.609

micron

millimeter

meter

kilometer

Area

square mile (mil)

square mile (miz)

2s9.0

2.s90

hectare

square kilometer

Velocity

inch per day (in/d)

foot per day (ff/d)

2.54

0.3048

centimeter per day

meter per day

Water-quality abbreviations :

mglL 

pgL 

VOC 

- milligrams per liter - micrograms per liter - volatile organic compound


previous studies provide the initial understanding

upon which the design of the remainder of the

study-unit investigation is based.

This report summarizes the results of

selected studies on factors'such as aquifer

characteristics and land-use patterns that affect

ground-water quality in New Jersey and on Long

Island, New York. It describes the ground-water

systems in the study area; sunmarizes current

knowledge about the presence and distribution of

nitrate, VOCs, andpesticides in these systems; and

explains why some ground-water systems are

more vulnerable to contamination than others.

Many of the findings summarized in this

report are the results of the USGS Toxic

Substances Hydrology Program, which was begun

in 1984 to assess the quality of the Nation's

ground-water resources and the nature and extent

of ground-water contamination (Helsel and

Ragone, 1984). Long Island and the Coastal Plain

of New Jersey were two of the areas selected to

study regional ground-water quality and its

relation to local hydrologic and human influences

(Barton and others, 1987; Eckhardt and others,

1 989; Stackelberg, 1995; Eckhardt and

Stackelberg,19951' Vowinkel and Battaglin, in

press). Additional information is provided from

studies conducted by the USGS in cooperation

with the following Federal, State, and local

agencies: U.S. Environmental Protection Agency;

New Jersey Departrnent of Environmental

Protection; Rutgers, The State University of New

Jersey, Department of Environmental Sciences;

New York State Department of Environmental

Conservation; New York State Department of

Environmental Services; Long Island Regional

Planning Board; Nassau County Department of

Health; Suffolk County Department of Health

Services; and Suffiolk County Water Authority.

POPULATION AND LAND.USE

HISTORY

New Jersey and Long Island contain a broad

mixture of land uses defined by a long history of

diverse settlement patterns. The early European

settlers established their homes along the easily

navigable rivers and tributaries of the Coastal

Plain. Industrial growth was spuffed by the

availability of waterpower for milling operations

and the proximity to the major ocean ports ofNew

York City and Philadelphia (flg. l). The building

of canals and railroads in the 1820's and 1830's in

New Jersey linked its expanding towns and

villages and connected them to the ocean ports.

Many investors became interested in the trade tlat

took place in the l5-mi-wide corridor of New

Jersey between New York City and Philadelphia.

In 1900, more than 75 percent of New Jersey's

population lived within this corridor (New Jersey

Department of Labor, 1984). On Long Island, the

population was concentrated in the western tip of

the island.

By the 1920's, the increasing availability of

automobiles led to residential and commercial

suburbanization. As the population of New York

City continued to increase, many people began

moving into the cities and towns of northeastem

New Jersey and western Long Island. Also, the

area of southern New Jersey adjacent o

Philadelphia grew substantially. After World War

II, development and settlement shifted from the

cities to suburban areas. Land that was once

agricultural or undeveloped was converted to

residential, commercial, and industrial uses. The

construction of major roads and highways

accelerated the suburbanization. Extensive

migration from New York City into Nassau

County caused a sharp population increase on

Long Island. From the 1950's to the 1970's, the

population of Long Island continued to grow, and

eastward migration quadrupled the population of

rural Suffolk County.

This pattern of increased population in

suburban areas has continued from the 1970's to

the present, but at a slower rate. In fact, some

urban-industrialized counties in northeastem New

Jersey lost population during the 1980's, as people

left urban centers and relocated to suburban, rural,

and coastal areas in the State. Similarly, on Long

Island, Nassau County's population decreased

slightly during the 1970's, largely as a result of,

eastward migration to rural Suffolk County.

Average population density in New Jersey and on

Long Island in 1990 is shown in figure 1. The

populations of New Jersey and Long Island from

1900 through 1990 are shown in figures 2 and3,

respectively.
Ia" ruew York

EXPLANATION

Average population density,

in people per acre

ffi < o.ss

S r -+.ss

! s-s.ss

o*lorvrrr-es I >to

O 20 KILOMETERS

Figure 1. Average population density in New Jersey

and on Long lsland, New York, 1990. (Data from

U.S. Bureau of the Census, 1991a and b)

The distribution of population growth in

New Jersey and on Long Island has created a

complex assemblage of land uses ranging from

urban around the major cities of New York and

Philadelphia to the relatively pristine forests of the

Pine Barrens in southern New Jersey and eastern

Long Island (fig.4). The urban and suburban area

are dominated by residential, industrial,

commercial, and transportation-related land uses.

Agriculture is still a major land use in eastern

Long Island and the western part of New Jersey.

Additionally, large tracts of undeveloped land still

exist in eastern Long Island and in southern and

northwestern New Jersey. These include wetlands

forests, highland ridges, and parklands.

Development of some of these areas is restricted

by State agencies.

GROUND WATER

Water is constantly being recycled all over

the Earth in a process called the hydrologic cycle

(fig. 5). Major components of the hydrologic cycle

include evapotranspiration, precipitation, surface

runoff, and ground water. That part of

precipitation that infiltrates the soil and drains to

the water table is called ground-water recharge.

Ground water is water saturating interconnected

pores in a geologic unit or layer beneath the land

surface. This section describes the occurrence and

movement of ground water, its importance for

water supply, and the processes that can result in

its contamination.

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Figure 2. Population of New Jersey, 1900-90.

(Data from N.J. Department ofLabor, 1984, and

U.S. Bureau of the Census, 1991a)

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,

Figure 3. Population of Long lsland, New York,

1900-90. (Data from U.S. Bureau of the Census,

1 991 b)
t,

er

s

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g.

EXPLANATION

LAND USE

I Urban-nonresidential

I Urban-residential

I Agricultural

I water

LJ Undevetoped i.l'i'

,Pt:)

t

\,ri",l

O 20 MILES

l---T -

O 20 KILOMETERS

Figure4. Land use in NewJerseyand on Long lsland, NewYork, 1990. (Modified

from Fegeas and others, 1983, by using the method of Hitt, 1994)

Occurrence and Movement

In the Coastal Plain of New Jersey, annual

precipitation averages about 44 in. Of this amoun

24 in. is lost to the air by evaporation and

transpiration. About 17 in. becomes ground-wat

recharge (Vowinkel and Foster, 1981). Most of thi

recharge water eventually moves into lakes and

streams, and combines with surface runoff to mak

up the average 20 in. of streamflow each year.

Contrary to popular belief, ground water does not

form "underground rivers." Instead, it fills and

slowly flows through tiny spaces between

sediment grains or within fractures in bedrock.

An aquifer is a water-bearing unit that will

yield water in a usable quantity to a well or sprin

Aquifers consist of either unconsolidated deposits

or consolidated rocks. Most unconsolidated

deposits consist of material that can range in size

from tiny fractions ofa inch (clay size) to several

feet (boulders), but most commonly are sand and

gravel size. Water in unconsolidated aquifers is

found in the voids between particles. Generally,

unconsolidated aquifers composed of coarsegrained particles, such as sand and gravel, yield

more water than those composed of fine-grained

particles, such as silt and clay.

Consolidated rocks are composed of mineral

particles of different sizes and shapes that are

fused together by the effects ofheat and pressure

or chemical reactions. Consolidated-rock aquifers
r-\ \-,-\

Clouds forming 

<-

)

___-)"

/

1)t / /

, Evaporation

,,

Figure 5. Diagram of the hydrologic cycle. (Modified from Heath, 1983)

are commonly referred to as bedrock aquifers.

Water in bedrock aquifers is found chiefly in

fractures within the rock. These.fractures vary

greatly in size and are more cofilmon near the

land surface than at depth. The larger the fracture,

the more water it can hold. Some bedrock aquifers

are composed of a rock, such as sandstone, that

is itself permeable. Aquifers of this type contain

water both in fractures within the bedrock and

in spaces between the individual sand particles

that make up the bedrock.

Ground water is present in aquifers under

one of two conditions--unconfined or confined

(fig. 6). Unconfined conditions exist where water

only partly fills an aquifer. The water surface is

free to rise and fall, and fluctuates with changes in

atmospheric pressure, rainfall, and other factors.

Aquifers in these areas are referred to as

unconfined, or water-table, aquifers. Water in

unconfined aquifers is recharged by precipitation

or by leakage from surface-water bodies such as

lakes and streams. Confined conditions exist

where water completely fills an aquifer that is

overlain by a confining layer--that is, a layer of

less permeable clay or rock that slows the

vertical movement of water. These aquifers

are called confined aquifers. Water reaches

confined aquifers either by flow from an

unconfined part of the aquifer, called the

recharge or outcrop area, by leakage through

adjacent or bordering confining units, or by

recharge into an unconfined part ofthe aquifer

from adjoining surface water bodies, such as

a lake, a stream, or the ocean. Water in confined

aquifers can be very old and may have moved

from distant areas of recharge centuries or even

millennia ago. General patterns of ground-water

flow in a Coastal Plain aquifer system are

illustrated in figure 6.

The composition of an aquifer and presence

or absence of overlying confining layers influence

the rate of movement of water and contaminants.
EXPLANATION

f___l CLAY CONFINING UNIT

I COruTIruED AQUIFER

d

1

b

s

t

t

fr

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s

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a

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L

b

v

d

s

Figure 6. Diagram showing patterns of ground-water

flow and relative age in a Coastal Plain aquifer system.

(Modified from U.S. Geological Survey, 1985)

Water can move relatively quickly from land

surface to the water table in a cavernous limestone

or a highly fractured sandstone, for example, but

will move more slowly in a tight, sparsely

fractured shale or basalt. In fractured-rock

aquifers, water moves within fractures and

contaminants can be transported with this water.

The rate of movement of ground water in a clay

confining layer may be only a fraction of an inch

per day whereas, in an aquifer composed of sand,

the rate of movement may be several feet per day.

The rates of movement in limestone caverns, lava

tubes, and large rock fractures can approach those

observed in surface streams (thousands of feet per

day). The total distance that water travels

underground between recharge and discharge

areas can range from several feet to hundreds of

miles. Total distance and depth of ground-water

movement typically increase with the distance

between recharge and discharge areas.

New Jersey and Long Island are underlain by

several different aquifer types (fig. 7) (Cohen and

others, 1968;U.S. Geological Survey, 1985, 1988;

Zapecza,1989). New Jersey is underlain by both

unconsolidated aquifers and bedrock aquifers. The

area north of the Fall Line in New Jersey is

underlain by bedrock aquifers composed of many

ifferent rock types (U.S. Geological Survey,

985, p. 309-316). Some of the more important

edrock aquifers in this region consist of

andstone, siltstone. limestone, and shale. Water in

hese aquifers is generally unconfined. Significant

hicknesses of unconsolidated sediments derived

om the melting of the great Ice Age glaciers

verlie the fractured-bedrock aquifers in some

reas of northern New Jersey. The glacial

ediments are thickest in river valleys. These

valley-fill" aquifers are composed mostly of sand

nd gravel layers. In some valleys, thick, areally

xtensive silt and clay layers form confining units.

ess permeable bedrock bounds the sides and

ottom of the valley-fill deposits. Ground water in

alley-fill aquifers can be confined or unconfined,

epending on the presence or absence of overlying

ilt and clay confining layers.

The Coastal Plain of New Jersey lies

southeast of the Fall Line and differs sharply from

northern New Jersey. It is underlain by a wedgeshaped mass of unconsolidated sediments made up

of alternating layers of clay, silt, sand, and gravel

(U.S. Geological Survey, 1985, p. 309-316). This

wedge is less than 50 ft thick at the Fall Line and

thickens to more than 6,500 ft at the southern tip

of Cape May County. Five principal and several

minor unconsolidated aquifers are found in the

Coastal Plain. Four of the five principal aquifers

are confined, except in small areas where they

crop out (where the aquifer is exposed at land

surface). The fifth major aquifer, the KirkwoodCohansey aquifer system, is unconfined. Beneath

these unconsolidated sediments lies relatively

impermeable bedrock.

The aquifers of the Coastal Plain of Long

Island are very similar in composition to those of

the New Jersey Coastal Plain. Long Island is

underlain by bedrock, which in turn is overlain by

a wedge-shaped mass of unconsolidated

sediments, made up of alternating layers of clay,

silt, sand, and gravel (U.S. Geological Survey,

1985, p. 323-328). The total thickness of overlying

sediments is approximately 2,000 ft in southcentral Suffolk County and decreases toward the

north shore, where bedrock is exposed on the far

northwestern corner of the island. Two major and

two minor unconsolidated aquifers are found on

Long Island. One of the major aquifers, the upper

glacial aquifer, is unconfined. The underlying
VERTICAL SCALE GREATLY EXAGGERATED

EXPLANATION

WEATHERED ROCKS-Unconsolidated sediments

EXTENSIVELY FRACTUBED ROCK LAYER--

Water-bearing unit

SPARSELY FBACTURED ROCK LAYER--

Conlining unit

VALLEY-FILL AOUIFER

O 20 MILES

O 20 KILOMETERS

LONG ISLAND LONG ISLAND

EXPLANATION

D cnnvel

L ] SAND

f] CLAYEY SAND, SILT, AND SANDY CLAY

f l cLAY

NEW JERSEY COASTAL PLAIN AOUIFERS LONG ISLAND COASTAL PLAIN AQUIFERS

Figure 7. Location of sections and generalized diagram of the four types of aquifers in New Jersey

and on Long lsland, New York. (Modified from U.S. Geological Survey, 1985)
Magothy aquifer generally is unconfined;however, minor clay layers within the upper part of the

Magothy aquifer can restrict flow locally.The

Gardiners Clay confining unit, which is present

along the south shore, inhibits flow between the

upper glacial and Magothy aquifers.

Importance

Ground water is used for many domestic

purposes, such as drinking, food preparation,

bathing, washing clothes and dishes, flushing

toilets, and watering lawns and gardens. In

addition, people use water for commercial,

industrial, agricultural, mining, and other

purposes. Most of these uses require water of high

quality--that is, water that is not salty, highly

mineralized, or contaminated with toxic

substances.

About half of the 14.6 million people who

live in New Jersey and on Long Island, New York,

used ground water as their source of drinking

water in 1990 (figs. 8 and 9). In the southern and

northwestern parts of New Jersey, and in Nassau

and Suffolk Counties, Long Island, nearly all of

the population depends on ground water for

drinking and everyday use. Unquestionably, the

quality of ground water is a major concern for

residents of these areas. Ground-water quality is

influenced by the composition of the aquifer

material and the quality of water recharging the

aquifer; the latter is highly influenced by human

activities at or near the land surface, commonly

referred to as land use.

Contamination

The degradation of ground-water quality is a

major concern for those whb use the water and for

water managers and health officials responsible for

ensuring a safe drinking-water supply for public

use. The composition of aquifer material and the

presence or absence of confining layers can be

important in determining the vulnerability of

ground water to contamination. Ground water

tends to be most vulnerable to contamination in

areas that have well-drained soils and are

underlain by unconsolidated sand and gravel

aquifers where no protective confining layer is

present. These highly permeable systems allow

contaminants to move easily from the land surface

to the water table. In contrast, the presence of fineI

EXPLANATION I

Groundwater withdrawals, 1

in million gallons per day

n oto15

l15to30

I 30to45

I greaterthan 45

O 20 MILES

O 20 KILOMETERS

Figure 8. Ground-water withdrawals in New Jersey

and on Long lsland, New York, in 1990, by county.

(Data on file at U.S. Geological Survey otfices in

West Trenton, N.J., and Troy, N.Y.)

A

EXPLANATION

Population, in perc€nt

! oto2s

I 2stoso

I 50to75

I 7s to too

0 20 MTLES I

O 20 KILOMETERS

Figure 9. Percentage of the population in

New Jersey and on Long lsland, New York,

that used ground water in 1990, by county.

(Data on file at U.S. Geological Suruey

offices in West Trenton, N.J., and Troy, N.Y.)
grained materials such as clay and silt in soils and

confining layers can restrict the downward movement of water and contaminants. Clay and silt also

enhance chemical sorption, thereby decreasing the

availability of chemicals that might have moved

through the soil to the ground water. The potenfial

for contamination of bedrock aquifers varies

greatly depending on soil and rock type and the

degree of fracturing of the rock.

Chemicals introduced at or near the land

surface can affect the quality of underlying ground

water in New Jersey and Long Island for many

years. Land use generally reflects the types and

amounts of chemicals that are introduced at or

near the land surface. Present and past land uses

such as agricultural, industrial, and urban

development have had major effects on the quality

of ground water because chemicals used or spilled

at the land surface are carried to the water table in

ground-water recharge. The quality of ground

water both beneath and downgradient from these

land uses can be affected because of ground-wate

movement.

Contamination of ground water from the

land surface can be derived from point and

nonpoint sources (Heath, 1983). Point sources of

contamination are localized, generally are a few

acres or smaller in size, and include injection

wells, landfills, hazardous-waste sites, pipelines,

leaky storage tanks, and surface impoundments.

Nonpoint sources of contamination extend over

broad geographic areas, ranging from a few acres

to hundreds of square miles. Examples of nonpoint

sources of contamination include agricultural and

residential land to which fertilizers and pesticide

are applied, mining areas, animal feedlots, and

roadways and right-of-way areas on which deicing

salts and pesticides are applied. Multiple, closely

spaced point sources, such as on-site septic

systems in residential areas and leaky undergroun

storage tanks in industrial areas, can be considere

nonpoint sources of contamination (Vowinkel and

Siwiec, 1991,p.2).

In addition to the size of the geographic

areas from which they originate, point and

nonpoint sources differ with respect to the volume

of water they affect and the resulting constituent

concentations. Point sources generally affect

small volumes of water but typically result in

r

s

d

d

hi gher contaminant concentrations than nonpoint

sources. Contamination from nonpoint sources

typically affects large volumes of water over larger

areas (Vowinkel and Siwiec, l99l) and results in

lower contaminant concentrations than

contamination from point sources.

Contamination of the shallow ground-water

system on Long Island by fertilizers and

detergents was first documented in the 1940's

(Flynn and others, 1958; Perlmutter and Koch,

1964, l97 l; Perlmutter and Guerrara, 197 0; Smith

and Myott, 1975). Reports of the detection of

VOCs and pesticides on Long Island and New

Jersey began in the early 1970's, coincident with

the advent of improved laboratory methods to

detect hese compounds. The first detection of

VOCs in ground water in Nassau and Suffolk

Counties, Long Island, was documented in 1975

(Koppelman, 1978). Reports of incidents of

contaminati on with VOCs resulting from chemical

production, waste storage, disposal, or spills were

reaching the New Jersey Department of

Environmental Protection regularly by the late

1970's (U. S. Geological Survey, 1988, p. 369).

Trace concentrations of several VOCs were

detected in a 1978-81 survey of private and public

wells in New Jersey (Tuckeq l98l; Fusillo and

Hochreiter, 1982). In many cases, contamination

with VOCs probably had been occurring years

before a laboratory technique was developed and

(or) applied to determine whetherthese substances

were present in the ground water.

The increasing incidence of ground-water

contamination in New Jersey has led waterrnanagement agencies to conduct soil borings and

to install gas vents, piezometers, monitoring wells,

and recovery wells throughoutthe State. The sharp

increase in the number of permits issued for these

types of monitoring devices, from 2,108 in 1983 to

15,333 in 1990 (Principi, l99l), is indicative of

the growing concem over existing and potential

ground-water contamination (fig. I 0). Installation

ofthese types ofdevices has increased in large

part because of the implementation of the

Environmental Cleanup Responsibility Act by the

New Jersey Department of Environmental

hotection (NJDEP) in 1983. The Actprohibits the

sale of industrial properties beneath which

contaminant concentrations exceed NJDEPdesignated limits. To ensure that these limits are
a

o

z

o

115

T

z

a

F10

trut

olr

o

tr5

IU

d)

=

f

z

1983 1984 1985 1986 1987 1988 1989 1990

YEAR

Figure 10. Number of permits issued in New Jersey

for soil borings, gas vents, monitoring wells,

piezometers, and recovery wells, 1983-90.

(Data from Principi, 1991)

not exceeded, monitoring devices are required for

the collection of ground-water, soil, and soil-vapor

samples. Because of the frequency of industrial

property sales in New Jersey, the installation of

monitoring devices has increased substantially

since the Act was adopted. In addition, the

NJDEP's underground storage tank program

requires the installation of monitoring devices

whenever an underground storage tank is

removed, contaminated soil or water is discovered

near an existing tank, or new tanks are installed at

gas stations (Principi, 1991, p. 6).

According to the New Jersey Department of

Environmental Protection and Energy (1993, p.

IV-15), nearly 5,000 cases of ground-water

contamination had been reported in New Jersey as

of April 1992 (frg.11). Substances identified as

contaminants included VOCs, metals,

radionuclides, pesticides, dioxin, and bacteria.The

number of cases was greatest in the counties

adjacent to the large urban centers of New York

City and Philadelphia. Some of the major sources

of ground-water contamination are underground

storage tanks, landfills, surface spills, and waste

EXPLANATION

Number of cases

n oto too

I tot tozoo

I zor to soo

I GreaterlhanS0o

O 20 MILES

O 20 KILOMETERS

Figure 11. Number of reported ground-watercontamination cases in New Jersey as of

April 1992, by county. (Data from New Jersey

Department of Environmental Protection and

Energy,1993)

EXPLANATION

Number of claims

! 0to49

I 50 to 149

I 150 to 249

T Greater than 249

O 20 MILES

O 20 KILOMETERS

Figure 12. Number of claims received for groundwater contamination in New Jersey in 1994, by

county. (Data from Ann McOlung, New Jersey

Department of Environmental Protection, written

commun., 1995)

10
lagoons. In many cases, however, the source of

contamination is unknown.

Ground-water contamination is a common

problem on Long Island as well as in New Jersey

TheNew York State Department of Environment

Conservation (NYSDEC) maintains a data base of

information pertaining to ground-water

contamination in New York State. In 1994. this

data base included more than 260 contaminated

public-supply wells and more than 30 groups of

contaminated private wells on Long Island. In

addition, the data base contained 1,349 oil-spill

recovery sites, 142 hazardous-waste rmediation

sites, and 70 pollution-discharge elimination sites

(William O'Brien, New York State Department of

Environmental Conservation. written commun..

ree6).

In some instances, contaminated ground

water can be treated to remove potentially harmful

substances before the water is distributed to users.

In 1995, 96 public water-supply facilities in New

Jersey were removing VOCs from contaminated

wells (Sandra Kreitzman, New Jersey Deparftnen

of Environmental Protection, wriffen commun.,

1995). The New Jersey Spill Compensation Fund,

set up by the New Jersey Legislature in 1985, is

administered by the NJDEP to handle claims by

well owners concerning ground-water

contamination. The program provides money to

compensate well owners for the cost of sealing

wells, installing treatment systems for VOCs and

(or) mercury near the wellhead, and establishing

hookups orwater-main extensions for well owners

near public-supply systems. From 1985 through

l994,the Spill Fund handled more than 6,000

claims (fig. 12) and paid more than $35 million to

well owners and water companies to ensure a safe

supply of drinking water for New Jersey resident

(Ann McClung, New Jersey Department of

Environmental Protection, written commun.,

1995). Many residents of New Jersey depend on

water pumped from shallow domestic wells.

Increasingly, these wells are becoming

contaminated with VOCs and mercury associate

with industrial, residential, and agricultural land

uses. In Ocean County, VOC contamination has

led many domestic users to switch to public water

supply. For example,in 1976 about 88 percent of

Ocean County residents used domestic water and

12 percent used publicly supplied water. In 1996,

.

al

t

s

d

these percentages were reversed (Joseph

Przyw-ara, Ocean County Health Department, oral

commun., 1994).

Treatment of water before use to remove

contaminants is a temporary solution to a longterm problem. Regional remediation of

contaminated ground water over a large area is

difficult and expensive.In some cases, purge wells

can be installed to pump ground water to the

surface, where it is treated. The treated ground

water is either reinjected into the ground, allowed

to seep back into the ground through spreading

lagoons, or discharged into a stream or other

surface-water body. In other cases, ground-water

contamination can be remediated naturally by

physical, chemical, and biological processes in

soil, rock, and water (Chapelle, 1995). In cases

where contaminated ground water is not

remediated by human treatment or natural

processes, however, it will continue to move along

a flow path to a discharge point such as a stream,

river, lake, or well. Depending on the length of the

flow path and the composition of the aquifer

material, movement of contaminated ground water

to a discharge point could take tens, hundreds, or

even thousands of years.

The diversity of land use in the study area

creates a variety of potential effects on groundwater quality that vary with duration and type of

land use. The effects of nonpoint-source

contamination by nitrates, VOCs, and pesticides

on ground-water quality in New Jersey and Long

Island are described below.

NITRATE IN GROUND WATER

Although nitrate is not a highly toxic

compound, it can be reduced to nitrite by bacteria

in the intestines of infants, which may result in the

disease methemoglobinemia, more commonly

known as "blue-baby syndrome." Infant mortality

from this disease is rare when concentrations of

nitrate (as nitrogen fNl) in drinking water are less

than l0 mg/L, but its incidence increases with

increasing concentration (Walton, 1951). The U.S.

Environmental Protection Agency (USEPA) has

set the maximum contaminant level (MCL) for

nitrate (as N) in drinking water at l0 mg/L (U.S.

Environmental Protection Agency, I 988).

l l
Nitrate enters ground water from natural and

human sources. Natural sources of nitrate are

atmospheric deposition and organic matter in soil.

Soil particles, plant roots, and certain bacteria

within the soil use nitrate and other nitrogen

compounds and slow their movement downward

to ground water. Sources of nitrate related to

human activities vary by land-use type. In urban

areas, sources of nitrate include lawn fertilizers,

septic-system wastes, leakage from sewer pipes,

and industrial wastes. Sources of nitrate in

agricultural areas include crop fertilizers, animal

manure, and septic-system wastes. Some of the

nitrate deposited from the atmosphere is related to

human activities such as releases of nitrogen-rich

materials from automobile exhausts and industrial

smokestacks.

Estimated values of nitrogen deposition

from the atmosphere to the land in the eastern

United States are greater than those in the western

states, primarily because emissions of nitrogen

oxides are larger in urban areas (Puckett, 1995, p.

411A). Available data on nitrate concentrations in

precipitation in New Jersey are limited. Median

concentrations of nitrate (as N) at four

precipitation collectors in an undeveloped area of

the New Jersey Coastal Plain ranged from 0.3 to

0.4 mglL (Lord and others, 1990, p. 120). Most

plants require some nitrogen to grow The amount

of nitrogen entering the soil from the atmosphere

generally is adequate to support natural

vegetation; however, additional nitrogen from

fertilizers and manure is required to maintain and

increase agricultural crop yields (figs. 13 and 14),

particularly in the New Jersey and Long Island

Coastal Plain. where soils contain less nitrogen

than do soils in northern New Jersev.

Although the loading of nitrogen to the land

surface from atmospheric deposition can be

estimated (Puckett, 1995), the actual quantity of

nitrate in ground water in New Jersey and Long

Island that is derived from soil nitrogen and

atmospheric deposition is unknown. In an analysis

of nitrate concentrations in ground water from 85

wells on Long Island, Perlmutter and Koch (L972)

suggest that concentrations exceeding I mglL are

the result of human activities.

EXPLANATION

Nitrogen fertilizer applied,

in tons per square mile

n otoz.s

W e.s to s.o

W s.o to z.s

I Greater than 7.5

0 20 MTLES

Figure 13. Amount of nitrogen fertilizer applied in

New Jersey and on Long lsland, New York, in 1991,

by county. (Data from Anderson and Smith, 1990)

EXPLANATION

Nitrogen input, in tons

per square mile

n otoo.s

m o.s to 1.0

W 1.oto1.s

I Greater than 1.5

0 20 MTLES

O 20 KILOMETERS

Figure 14. Amount of nitrogen input from animal

manure in New Jersey and on Long lsland,

New York, in 1992, by county. (Data from

Anderson and Smith, 1990)

T2

-.j
Relation to Aquifer Conditions

Because confining units restrict the vertical

movement of contaminants into deep parts of the

aquifer system, the presence or absence of a

confining unit between the land surface and an

aquifer can determine whether or not contaminants

are found in the ground water. In a study of 301

wells in the Potomac-Raritan-Magothy aquifer

system, nitrate concentrations were found to be

significantly greater in unconfined than in confined

parts of the aquifer system (Vowinkel and

Battaglin, in press). The Potomac-RaritanMagothy aquifer system crops out in a naffow

band extending from Raritan Bay southwest

through central New Jersey and along the eastern

bank of the Delaware River (fig. 15). It is

unconfinedin its outcrop area,but extends beneath

other hydrogeologic units to the southeast, where

Potomac-Raritan-Magothy

aquifer system

EXPLANATION

A-A' Line of section shown in

figure 26

Figure 15. Outcrop areas of the Potomac-RaritanMagothy and Kirkwood-Cohansey aquifer systems

in New Jersey. (Modified from Vowinkel and

Battaglin, in press)

it is confined. The outcrop area underlies a highly

urbanized area of New Jersey and, therefore, is

highly vulnerable to contamination by nitrate and

other substances associated with human activities.

The median nitrate concentration in ground water

in the unconfined areas was 0.3 mglL, whereas the

median concentration in the confined areas was

less than the laboratory reporting level of 0.1 mglL.

About 4l and 4 percent of samples from wells

in the unconfined and confined areas, respectively,

contained concentrations of nitrate equal to or

greater than I mglL (fig. 16). About 54 and9

percent of samples from wells in the unconfined

and confined areas, respectively, contained

concentrations greater than the laboratory

reporting level of 0.I mglL. About 6 percent of

nitrate concentrations in samples from wells in

unconfined areas exceeded the MCL of 10 mg/L

(fig. 16); however, none of the nitrate

concentrations in samples from wells in confined

areas exceeded the MCL (Vowinkel and Battaglin,

in press).

bg

gs Z J

CONCENTRATION OF

<o NITRATE (AS NITROGEN)

a !.tl

t-F fr6 r Greaterthan 1.0

r milligram per liter

O o

1 Z Greaterthan 10.0 ry '- 

()O milligrams per liter

? * otlJ (U.S. Environmental

l-, Ul Protection Agency

39r[rJ Maximum Contaminant

zu Level)

aZ-J ttl

rrr- 

>o

(5

oZltF

u.l 

33

,^ 1 0

iyur< o(r (rFE= UNCONFINED CONFINED

AOUIFER TYPE

Figure 16. Frequency of detection of nitrate in

water from wells in unconfined and confined

parts of the Potomac-Raritan-Magothy aquifer

system, New Jersey. (Data from Vowinkel and

Battaglin, in press)

1 3
Concentrations of nitrate in the PotomacRaritan-Magothy aquifer system are smaller in the

confined areas than in the unconfined areas

because of the effect of the overlying confining

unit. The confining unit slows the movement of

water to the lower aquifer so that it is older than

waterin theunconfined areas and, therefore, is les

likely to have been affected by human activities.

Also, as water flows downward through confinin

units, dissolved oxygen is depleted. Under these

conditions, oxygen in the nitrate compound is use

as an oxygen source by bacteria, resulting in the

depletion of nitrate (Vowinkel and Battaglin, in

press).

Relation to Depth in the Aquifer

Concentrations of nitrate and other

constituents generally decrease with depth becaus

(1) the age of ground water generally increases

with depth in the flow system and, therefore,

deeper water is less likely to be affected by huma

activities; (2) physical and chemical reactions that

remove constituents from ground water have had

more time to occur; and (3) constituents are

diluted as they move through the flow system. In

the Potomac-Raritan-Magothy aquifer system,

concenfrations of nitrate in the unconfined areas

generally decreased with depth (Vowinkel and

Battaglin, in press).

Ground-water withdrawals can affect the

quality of ground water by accelerating the

downward movement of water from shallow

water-bearing zones that have been affected by

nitrate contamination. In the Potomac'RaritanMagothy aquifer system, concentrations of nitrate

were elevated (3.0-9.9 mgL) in deep groundwate

(more than 200 ft below land surface) in a part of

the aquifer where withdrawals have caused a

regional depression of ground-water levels and

have increased rates of downward ground-water

flow (Vowinkel and Battaglin, in press).

In a 1991 study to determine the vertical

distribution of agricultural chemicals in the

unconfined Kirkwood-Cohansey aquifer system,

water samples were collected from observation

wells installed at different depths (nested wells) in

five areas that were farmed in or prior to 1991

(Szabo and others, 1994). The well nests were

located near topographic divides, where the

s

g

d

e

n

r

veftical component of flow is greatest.

Concentrations of nitrate were l0 ormore times as

great in water from shallow and medium-depth

wells than in water from deep wells. Nitrate

concentrations were greatest in water from the

medium-depth wells at four of the five sites, and

equalled or exceeded the USEPA MCL in water

from two sites. The detection of elevated

concentrations of nitrate in ground water at most

depths at all five sites indicates that most of the

water in the Kirkwood-Cohansey aquifer system

directly underlying agricultural areas probably

contains elevated concentrations of nitrate. The

fact that nitrate concenfrations were smallest in the

deep wells, however, indicates that nitrate has not

penetrated to the deep parts ofthe aquifer in areas

where ground-water withdrawals are small or

absent (Szabo and others, 1994,p. 107).

In the same study, ground-water flow in the

Kirkwood-Cohansey aquifer system was

simulated with a computer model to investigate

the horizontal and vertical movement of persistent

agricultural chemicals within the aquifer system

along paths of ground-water flow. Results of these

simulations indicated that travel time (that is, the

time it takes for water to travel from a recharge

area to a discharge area) of water and

contaminants increases with depth in the aquifer,

except nearthe discharge area, where older ground

water overlies yormger ground water. Simulated

tavel times to shallow, medium, and deep wells

ranged from about 1.5 to 5 years, l0 to 25 years,

and 30 to 50 years, respectively. The maximum

simulated travel time of ground water within the

modeled area was about 125 years (Szabo and

others, 1994). The age of water samples fromthe

nested observation wells was approximated from

tritium concentrations. Tritium is an isotope of

hydrogen that is more prevalent in water that

entered the aquifer system during the 1950's and

1960's, when many above-ground atomicweapons tests were being conducted. The tritiumapproximated ground-water ages corroborated the

travel times calculated with the flow model.

Similar studies of the relation between water

quality and depth have been conducted on Long

Island. In an analysis of water-quality data from a

network of 207 wells in five areas of differing land

use and sewering practices in Nassau and Suffolk

Counties on Long Island (fig. 17), the median

t4
40'

37',

30" O 20 KILOMETERS

EXPLANATION

! unanrrr, LoNG-TERM sEWERED

llTl:l unenN, uNSEWERED

I unenrrr, REcENTLY sEWERED

f-l uruoevELoPED

nontcuLTURAL ! 

Figure 17. Five areas of differing land use and

sewering practices in Nassau and Suffolk Counties,

Long lsland, New York. (Modified from Stackelberg,

1 995)

concentration of nitrate in three suburban areas

(fig. 18) was found to be higher in water from

shallow wells (5.6 mg/L) than in water from deep

wells (2.3 mglL) (Stackelberg,7995, p. 31). The

shallow water is younger and has been affected by

recent human activities, whereas the quality of

deeper water, which is older, is indicative of a time

when nitrate loading to the water table was

smaller.

Relation to Land Use

Results of several studies have indicated a

strong relation between land use and nitrate

concentrations in water from wells in the study

area (Leamond and others, 1992; Stackelberg,

1995;Vowinkel and Battaglin, in press). In an

analysis of data from 645 wells in the Coastal

Plain of New Jersey (data on file at U.S.

Geological Survey office in West Trenton, N.J.),

nitrate concentrations were higher in samples from

wells in agricultural areas than in samples from

wells in urban or undeveloped areas. Nitrate

concentrations exceeded 3 mg/L in about 30

percent of wells; that is, nearly one-third of wells

sampled were affected by human inputs. Nitrate

concentrations in more than 7 percent of the wells

z

tu

t

- 3

z

c/)

s

rll cc

ktr 4

tr --'i

t-- -fY- zfr

oois 3

^<

6*

a v

= J u l

L-Z o'

zz

F

t 1

z

ul

O

z

()v

SHALLOW DEEP

WELL DEPTH

Figure 18. Median concentration of nitrate in water

from shallow and deep wells in Nassau and Suffolk

Counties, Long lsland, New York. (Modified from

Stackelberg, 1995)

sampled exceeded the MCL of 10 mg/L. The

number of samples in which these limits were

exceeded was largely a function of the land use

surrounding the well (figs. 19 and20). Nitrate

concentrations in water from almost 70 percent of

the wells in agricultural areas exceeded 3 mglL

(median concentration 5.5 mglL), whereas those in

water from only l0 percent of the wells in

undeveloped areas exceeded 3 mglL (median

concentration 0. 1 mglL). Furthermore,

concentrations of nitrate in water from 35 percent

of the wells in urban-residential areas and 21

percent of the wells in urban-nonresidential

(industrial/commercial/transportation) areas

(median concentrations 1.4 and 0.9 mglL,

respectively) exceeded 3 mg/L. Nitrate

concentrations in water from less than 3 percent of

the wells in urban-residential, urbannonresidential, and undeveloped areas exceeded

10 mg/L; however, those in water from more than

22 percent of the wells in agricultural areas

exceeded 10 mg/L.

l 5
CONCENTRATION OF

NITRATE (AS NITROGEN)

I Greaterthan 3.0

mil[grams per ilrer

f___l Greaterthan 10.0

- milligrams per liter

(U.S. Environmental

Protection Agency

Maximum Contaminant

Level)

e\

o <

o >

tro

- -

=z OR

t=z E

o?,

J:.i.'i d6=il

SFs3F - =2

o xm6

-o$* -o$W -,$$Fv -."r""

.o.9otcp' .oegtot 

"a.r*" 

u*rBuu*

$€9N -r$$oN'

$Sto'

PREDOMINANT LAND USE

Figure 19. Frequency of detection of nitrate in

water from 645 wells in the Coastal Plain of

New Jersey, by predominant land use. (Data

on file at U.S. Geological Survey office in

West Trenton, N.J.)

.nrFv

oeud$* ".ee'f$w ."u$d ^oud

,lesF"et- -*$$o$'$ 

-t.*- 'J$cio

$sp'

PREDOMINANT LAND USE

tlJ rf

FIl <tr (E..1

zfi

! o

a>

9ff

@4.

o i

2=

?; #Utro z EulF

o -

= a X <

Figure 20. Median concentration of nitrate in water

from 645 wells in the Coastal Plain of New Jersey,

by predominant land use. (Data on file at U.S.

Geological Survey office in West Trenton, N.J.)

A study on Long Island showed that

sewering practices, as well as land use, affect

concentrations of nitrate in ground water

(Leamond and others, 1992). Water samples were

collected during 1987-88 from 90 wells

completed at depths within 50 ft below the water

table in the unconfinedupper glacial aquifer in five

study areas on Long Island. The study areas were

delineated according to land use and historical

sewering practices. The areas included (1) a longterm sewered suburban area (20 wells), (2) a

recently sewered suburban ^rea (20 wells), (3) an

unsewered suburban area (20 wells), (4) an

agricultural area (15 wells), and (5) an

undeveloped area (15 wells). Concentrations of

nitrate exceeded I mglL in more than 80 percent

of samples from wells in the three suburban areas

and the agricultural area and in 40 percent of

samples from wells in the undeveloped area (fig.

2l). Concentrations of nitrate exceeded 10 mg/L

in 40 percent of samples from wells in the

agricultural area (median concentration 8.9 mglL)

and in 25 percent of samples from wells in both

the recently sewered area (median concentration

5.8 mg/L) and the unsewered area (median

concentration 6.6 mglL) (fig.22). Only 10 percent

of samples from wells in the long-term sewered

area (median concentration 5.1 mg/L) contained

nitrate concentrations greater than 10 mglL, and

no concentrations in the samples from wells in the

undeveloped areas (median concentration

0.2 mglL) exceeded the MCL (Leamond and

others, 1992).

In general, concentrations of nitrate in

ground water were lowest in the undeveloped

areas, highest in the agricultural areas, and

intermediate in the three suburban areas. The data

indicate that sewering has resulted in decreased

nitrate concentrations (Leamond and others,

1992). Stackelberg (1995) found that

concentrations of nitrate and other chemicals

indicative of human effects have decreased in

areas that have been sewered for more than2

decades. Median concentrations of nitrate in

young, shallow ground water were highest in

samples from the unsewered suburban area and the

recently sewered area, where the effects of sewers

were not yet apparent.

t6
I Greaterthan 1..0

mililoram oer ilrer

l:.-St$"$x$"

PREDOMINANT LAND USE

100 r--r------------

*useoe]"se*l]n,,

i15;5n""'

PREDOMINAN

trt u

E ]IJ

#fi

F r.rj

z Y

Q 2

IoUr =tr?

z>< _i->

a'2 o

fuJUl HH3

xoo v^z

wzouJ

< o

iPUJE

3=uJu) o-s

$

EXPLANATION

CONCENTRATIONF NITRATE (AS NITROGEN)

p,1 Greaterthan 10.0 milligrams

* per liter (U.S. Environmental

Protection Agency Maximum

Contaminant Level)

"

f

X$

Figure 21. Frequency of detection of nitrate in water

from wells in five areas of differing land use and

sewering practices in Nassau and Suffolk Counties

Long lsland, New York. (Modified from Leamond

and others, 1992)

,

E 1om

Ei ", il HH.I

==

"g::lrffirr,$$: - PREDOMINANT LAND USE

Figure 22.Median concentration ofnitrate in water

from wells in five areas of differing land use and

sewering practices in Nassau and Suffolk Counties,

Long lsland, New York. (Modified from Leamond

and others, 1992)

Predicting Vulnerability to Nitrate

Contamination

Ground-water-quality studies to predict the

vulnerability of ground water to contamination

from the land surface have been undertaken in

New Jersey and on Long Island. The results of

these studies have been useful to Federal. State.

and local water-management and regulatory

agencies as a scientific basis for the development

of plans and programs to identify and mitigate

existing ground-water contamination and to

prevent future contamination.

*

For example, the likelihood of contamination

in parts of Long Island was predicted by using

regression equations, statistical tools that express

the relations between the presence of contaminants

and land-use variables that represent potential

contaminant sources (Eckhardt and Stackelberg,

1995). These regression equations were developed

by using data from the 90 wells in the five land-use

areas of Long Island described previously. One of

these regression equations was applied to a

gridded map of Nassau and Suffolk Counties to

estimate the probability of nitrate concentrations

in ground water exceeding 3 mglL. The resulting

estimates were used to construct a predictive map

(fig. 23) that was compared to a map of nitrateconcentration data from 268 wells in the twocounty area (fig.24).The measured nitrate

concentrations 

determined 

high 

are 

greater 

probability 

observed 

(Eckhardt 

VOLATILE 

GROUND 

used 

VOCs "d

fi

corroborate the statistically

estimates. The data show that areas of

predicted probability of nitrate contamination

related to observed nitrate concentrations

than 3 mglL and that areas of low predicted

of nitrate contamination are related to

nitrate concentrations less than 3 mglL

and Stackelberg, 1995).

ORGANIC COMPOUNDS IN

WATER

Volatile organic compounds (VOCs) are

for many household and industrial purposes.

are widely used as cleaning agents, solvent

degreasers, refrigerants, and fumigants. Some

VOCs are components of gasoline, oil, and heating

fuels. VOCs are a concern because exposure to

them has been associated with avariety of adverse

health effects, including cancer,liver and kidney

damage, nervous- system disorders, and re s ptratory

t1
EXPLANATION

Probability of nitrate (as nitrogen) concentration

greater than 3 milligrams per liter

< Less than or equal to > Greater than

W <0.+o f >0.+o-0.60 fl >0.60-0.80 I >0.e0

Figure 23. Estimated probability of detecting nitrate in a concentration greater than 3 milligrams per liter

in water from wells in Nassau and Suffolk Counties, Long lsland, New York. (Modified from Eckhardt and

Stackelberg, 1995)

410

Detection limit is 3 milligrams per liter

3-":

-1.^> - .O O O' .

o .at o ^o ^

o^ oo oo

*' ;51 : " d;8.'t"^t" 

'

. .....o..o1 o.?. o" o.,

han o

oo-'o 

o o o

lii'.".fiii

.q:3'.';l-::

Figure 24. Location of detections of nitrate in water from 268 wells in Nassau and Sutfolk Counties, '1995) Long lsland, New York. (Modified from Eckhardt and Stackelberg, 

1 8
problems. Ground water has been and is presently

contaminated by VOCs from a variety of sources,

including industrial discharges, landfills, municipal-wastewater discharges, leaks and spills, and

domestic septic-system effluent. Because VOCs

are associated with urban land use, they are likely

to be found more frequently in aquifers beneath

urban areas than in aquifers beneath nonurban

areas.

VOCs differ from each other with respect to

density, solubility in water, and tendency to

vaporize. Some VOCs are less dense than water

and are water-insoluble; these compounds tend to

float on the water table as a separate liquid phase.

Other VOCs are heavier than water and are waterinsoluble; these compounds tend to sink

downward within the aquifer system to clay lenses

or bedrock that retard further vertical movement.

Still others are water-soluble and tend to move

within the aquifer system as part of ground-water

flow.

Chemical, physical, and microbial

mechanisms can prevent or slow the movement of

VOCs from the land surface or the soil zone into

the ground-water system. Because VOCs, by

definition, are volatile (easily escape from water to

the atmosphere), air purging is a method

commonly used to treat ground water that has been

contaminated by VOCs. Air purging involves

bubbling air through contaminated water to

convert the volatile compounds from the liquid

(dissolved) state to the vapor state, thereby

removing them from the water.

Relation to Aquifer Conditions

Concentrations of VOCs, like those of

nitrate, differ depending on whether the aquifer is

confined or unconfined. Water samples from24I

wells in the Potomac-Raritan-Magothy aquifer

system in New Jersey were analyzed for the

presence of 11 VOCs at concentrations equal to or

greater than 3 pg/L (Vowinkel and Battaglin, in

press). VOCs were present in 17 percent of the

samples from unconfined areas and 3 percent of

the samples from confined areas (fig. 25).The

most commonly detected VOCs were

trichloroethylene (TCE), tetrachloroethylene

(PCE), l, 1, I -trichloroethane (TCA), benzene, and

chloroform. Concentrations of VOCs exceeded 10

u,g/L in samples from only one well in a confined

ffi ourcnoPAREA (uNcoNFrNED)

r---------r DOWNDIP FBOM THE OUTCROP

LJ AREA (CONFINED)

3 10 50 100

CONCENTRATION, INMICROGRAMS PER LITER

25

1 5

1 0

TU

l

J

tL<

o >

z QA U

Y F

D A

r u2 z

tlJ ^

z x

vul

o x

T _

= a > o

z z

a =

il>

3 R

o 9

w z (ry<

>16

F(r fro

HK

Figure 25. Frequency of detection of volatile organic

compounds in water from wells in unconfined and

confined parts of the Potomac-Raritan-Magothy

aquifer system, New Jersey. (Data on file at U.S.

Geological Survey office in West Trenton, N.J.)

area. The lower frequency of occurrence and

smaller concentrations of VOCs in ground water

in confined areas can be attributed to the greater

age of the water and to the presence of overlying

confining units, which restrict the vertical movement of contaminants from unconfined areas.

Three of the four wells in confined areas that contained water with detectable concentrations of

VOCs are within about 0.6 mi of an unconfined

area (Vowinkel and Battaglin, in press).

Relation to Depth in the Aquifer

In the same study, VOCs were detected at

depths greater than 200 ft below land surface

mainly in the central and southwestern parts of the

Potomac-Raritan-Magothy aquifer system

outcrop area (fig. 26), in a region of heavy

pumping. Because the primary direction of

ground-water flow in a heavily pumped area is

downward, the transport of VOCs into deep parts

of the aquifer system is enhanced (Vowinkel and

Battaglin, in press).

l 9
ffi:

;. '; qjli"J.l t : 

'

Ssoo

oq o oIB" o o 

:?lIE^cfgD^_-^

NOTToSCALE 

- ONOTDETECTED

F

[j 2oo

LL

z

j

lrJ

do

<

uJU)

3

I -zoo

uJ

dl

I

-

S -+oo

A 40

930

LU

=

u-

!! ,i

I

F

z

uJ

TE

lrl (L10

.-$sW .-d$W "$$Fv ..,?9o

^N\\se.\Qv .^*FNo n"Nut u**€-

$$9"' ^r$$t'

$so'

PREDOMINANT LAND USE

EXPLANATION

CONCENTRATION OF VOLATILE ORGANIC COMPOUNDS

GREATER THAN 3 MICROGRAMS PER LITER IN WATER

FROM WELLS IN THE OUTCROP AREA OF THE

t POTOMAC-RARTTAN-MAGOTHYAQUTFERSYSTEM

Figure 26. Relation of depth and pumpage to

detection of volatile organic compounds in water

from wells in the Potomac-Raritan-Magothy

aquifer system, New Jersey. (Data on file at U.S.

Geological Survey office in West Trenton, N.J.;

location of section shown in fig. 15)

Relation to Land Use

An analysis of water-quality data from the

Potomac-Raritan-Magothy and KirkwoodCohansey aquifer systems (fig. 15) conducted as

part of the same study, showed that of the 11

VOCs for which samples were analyzed, none was

detected in shallow ground water in agricultural

areas in either aquifer system (fig.27). These

VOCs generally are not used in agricultural areas.

VOCs were detected most frequently in water

from wells in the unconfined part of the PotomacRaritan-Magothy aquifer system with overlying

urban-nonresidential (commercial/industrial) land

use. Possible sources of VOCs in this area include

leaking oil-refinery storage tanks and waste

lagoons or landfills containing industrial solvents.

The frequency of detection of VOCs in samples

from undeveloped areas was greater than

expected, most likely because although the area

immediately surrounding the well was

undeveloped, urban land generally was present

near the well. Urban land, in fact, is found within

0.25 mi of 24 of the 2l wells in the study area that

contained VOCs. Benzene and TCE were the most

frequently detected VOCs (Vowinkel and

Battaglin, in press).

Water samples collected during 1987-88

from the 90 wells in the five study areas on Long

Island also were analyzed for VOCs (Leamond

Figure 27. Frequency of detection of volatile organic

compounds in water from wells in outcrop areas of

the Potomac-Raritan-Magothy and KirkwoodCohansey aquifer systems, New Jersey, by

predominant land use. (Data on file at U.S.

Geological Survey office in West Trenton, N.J.)

and others, 1992). VOCs were detected at

concentrations at or above the reporting limit of 1

pg/L in samples from 37 percent of the wells and

most commonly in samples from wells in the

recently sewered suburban area (74 percent),

followed by the long-term sewered suburban area

(50 percent) and the unsewered suburban area (40

percent) (fig.28). VOCs were detected in only 1 of

15 samples from wells in the undeveloped area

and in none of the samples from wells in the

agricultural area (Leamond and others, 1992).

The most commonly detected VOCs in

samples from the three suburban areas were TCA

20
260

tr

=

uo

U+o

F

z

ul

truJrL 20

^"*.1[l?'1[11.*

. 'o$t'-. $9o"'.".J$9'

.uuuouN.iuuouN' 

e\

PREDOMINANT LAND USE

$*"

Figure 28. Frequency of detection of volatile organic

compounds in concentrations greater than 1 microgram per liter in water from wells in five areas of

differing land use and sewering practices in Nassau

and Suffolk Counties, Long lsland, New York.

(Data from Leamond and others, 1992)

and TCE, which are common industrial and

commercial organic solvents. TCA was detected in

39 percent of samples and was detected most

frequently in samples from the recently sewered

suburban area (68 percent) (fig.29), where the

highest concentration was 12,000 pgll-. Frequent

detection of TCA in samples from unsewered

suburban areas was expected because use of this

compound as a septic-system degreaser was

widespread before its ban in 1981. Concentration

of TCA exceeded the USEPA MCL of 50 pglt- in

one well each in the recently sewered and

unsewered areas. TCE was detected in22percent

of samples and also was detected most frequently

in samples from the recently sewered suburban

area (26 percent) (fig. 30), where the highest

concentration was 390 v,gtL, Like TCA,

concentrations of TCE exceeded the USEPA MCL

of 50 pg/L in one well each in the recently sewered

and unsewered areas (Leamond and others, 1992\.

s

;]ll"s

T--l Greater than 50 micrograms

* per liter (U.S. Environmental

Protection Agency Maximum

Contaminant Level)

I Greater than 1 microoram

per ilrer (oerecton ilmrl)

.o$9'.o?GP'ou?.9r """-::Yfh"Sl"lS:"::$

-9uoun)uuu"un*' ?"a=oo",NANT LAND usE

EXPLANATION

CONCENTRATION OF l.l.l.TRICHLOROETHANE

Figure 29. Frequency of detection of 1 ,1 ,1-trichloroethane (TCA) in water from wells in five

areas of ditfering land use and sewering

practices in Nassau and Suffolk Counties, Long

lsland, New York. (Data from Leamond and

others, 1992)

llr

I Greater than 1 microoram

per ilrer (oereqron ilmrr)

.o*'.tef,ioe{iou"$''' 

Fs\' \}n"

^oF$." .ogFs' 9u-

..ro$* eogt' PREDoMTNANT LAND usE

EXPLANATION

9

tr

=20

IL

L!

F

z

uJ 10

uJ

CONCENTRATION OF TRICHLOROETHYLENE:

f---l Greater than 50 micrograms

* per liter (U.S. Environmental

Protection Agency Maximum

Contaminant Level)

Figure 30. Frequency of detection of trichloroethylene (TCE) in water from wells in five areas

of differing land use and sewering practices in

Nassau and Suffolk Counties, Long lsland, New

York. (Data from Leamond and others, 1992)
The frequent detection of TCA and TCE in

samples fromthe sewered suburban areas support

the findings of an earlier study (Eckhardt and

others, 1989) of 903 wells in Nassau and Suffolk

Counties, in which the spatial distributions of

these two VOCs in ground water were directly

correlatedwith population density in the twocounty area. The results of the 1987-88 study of 90

wells indicate that the mitigating effects of

regional sewers in the highly developed areas of

Long Island probably are obscured by (1) the

continueduse of VOCs in these densely develope

urban areas after sewering; (2) sources of VOCs

that bypass sewers, such as leaks, spills, and

illegal disposal; and (3) the persistence in ground

water of VOCs introduced before sewering

(Eckhardt and Stackelberg, 1995). The regional

sewers have been used to dispose of industrial and

commercial VOC wastes by permitted discharge,

but such waste could contribute to ground-water

contamination wherever the sewer lines leak. For

these reasons, the frequency of detection of VOCs

in samples from the long-term sewered suburban

aroa was similar to those in samples from the other

suburban areas (Eckhardt and Stackelberg, 1995).

Predicting Vulnerability to VolatileOrganic-Compound Contamination

Eckhardt and Stackelberg (1995) develope

regression equations for predicting the presence of

VOCs in ground water in Nassau and Suffolk

Counties on Long Island. VOCs, for the most part,

are not naturally occurring compounds and,

therefore, any wells containing VOC's at

concentations above the detection limit of I pgil

can be assumed to have been affected by human

activity. The detection of VOCS was significantly

correlated to the amount of high- and mediumdensity residential and commercial and uses

within a 0.5-mi radius of the well (Eckhardt and

Stackelberg, 1995). The probability of finding

VOCs in Nassau and Suffolk Counties as

predicted fromthe equations (fig. 3l) was

correlated with the detection of VOCs in samples

from 248 wells (frg. 32). The comparison shows

that areas of high predicted probability of VOC

contamination are related to observed detections

of VOC concentrations greater than I pgil, and that

areas of low predicted probability of VOC

contamination are related to an observed absence

s

d

d

of VOCs or detections of VOCs in concentrations

less than I FelL (Eckhardt and Stackelberg, 1995).

PESTICIDES IN GROUND WATER

A pesticide is any substance or mixture of

substances used to confrol pests, such as insects

(insecticides), weeds (herbicides), and fungi

(tungicides). Although synthetic organic

pesticides were introduced in the 1940's, reliable

records on their manufacture and use were not

compiled until the 1960's. Since then, their

manufacture and use have increased steadily

(Smith and others, 1988; Barbash and Resek,

1996). Pesticides have long been used in

agricultural settings. In the last several decades,

their use in nonagricultural settings, such as urban

and undeveloped areas, has increased as well.

Pesticides are used in urban settings to control

insects, weeds, and fungi on lawns, and golf

courses, and in cemeteries, parks, and private and

public gardens; to control pests in and around

homes and commercial buildings; and to control

vegetation on railroad, transmission-line, and

roadway rights-of-way. Insecticides also are used

to control mosquito and other pest populations in

urban and undeveloped areas for the protection of

pubtic health and for nuisance reduction (Barbash

and Resek, 1996). More than 10,000 products

containing more than 400 major active ingredients

are currently registered for use as pesticides in

New Jersey (Hamilton and Meyer, 1994).

In New Jersey, agriculture accounts for the

largest use of pesticides by volume (fig. 33). In

1991, nearly 1 million acres of agricultural land in

New Jersey was treated at least once with a

pesticide (Hamilton and Meyer, 1994). More than

1.6 million pounds of active ingredients was

applied to New Jersey crops in 1994 (New Jersey

1994 Agricultural Pesticide Use Survey data on

file atNJDER Pesticide Control Prograrn" Trenton,

N.J.). Fungicides (sulfua captan, and

chlorothalonil) accounted for the largest amount

used, followed by herbicides (metolachlor,

atrazine, and alachlor) and insecticides (petroleum

oils and sodium aluminofluoride). The large

diversity of crops grown in New Jersey results in a

correspondingly large diversity in the types of

pesticides used in the State.
40"

37',

30"

EXPLANATION

Probability of total volatile-organic-compound

concentration greater than 1 microgram per liter

< Less than or equal to > Greater than

ffi <0.+o | >o.ao-o.oo ! >o.oo-o.eo ! >o.ao

20 KILOMETERS

Figure 31. Estimated probability of detecting a totalvolatile-organic-compound concentration greater

than 1 microgram per liter in water from wells in Nassau and Suffolk Counties, Long lsland, New york.

(Modified from Eckhardt and Stackelberg, 1995)

73

) 20 MTLES ..!;? 

r

-l .ddt' " N ) ,/q^ 1 l ) 20 KTLOMETER. J1{*r ,. 

V

,-6^ 9"a,b*%\t> r L

surrorkcounty ..".2* 

.ra./"// /i{:.:"}">

- .o . o' o 7 f- - no*"

,,,8- [ ,o KrLoMErER. rr-d#sR> r\ v Jgp

sunorkcountv .--;'.f* /t{: *'V"

N-..4- .4"t." f:' a' .)\: o ;33o'o' 

" 4-* {:)/ o" o 

oooo rt )-''

..-.Oto.-OO',,?

' '_oo'.1 inZ o 

.. o.". \-tU/ 

EXPLANATIoN

o o^. ' 

. 

'.o 'o -:ri-1..:t voLATILEoRGANlccoMpouNDS .' .".o'. ^." i"_ Ftl=7' vuLAll|-tUHGAN|L;COMPOUNDT

' 

... 

..':i/--J - 

a".tt 

Detection limit is 1 microgram per liter

-.==.' . DETECTED ///-' //'/-/--,:=/ 40'

e-71

30"

a a a

t iao" 

t e

O NOT DETECTED

Figure 32. Location of detections of volatile organicompounds in concentrations greater than

1 microgram per liter in water from248 wells in Nassau and Suffolk Counties, Long lsland,

New York. (Modified from Eckhardt and Stackelberg, 1995)

L-'t
Lll

=(L

o-.'/)

< o

t zz )

g o

Oo.

tlJ,'

66z (t) - o

U Z

a <

F A

< o

IIT otr

, =

o

200

150

T-_-] FUNGICIDES

I HERelctoes

I INSECTICIDES

AGRICULTURE LAWNS GOLF RIGHTSCOURSES OF-WAY

LAND USE

Pesticide use for termite control in New

Jersey in1992 was about 147,000 pounds of active

pesticide ingredient, mostly chlorpyrifos (New

Jersey l992Termiticide Use Survey data on file at

NJDEP, Pesticide Control Program, Trenton, N.J.).

Pesticide use for mosquito control in New Jersey

in 1993 was about 63,000 pounds of active

pesticide ingredient, mostly petroleum oils,

temephos, and malathion (New lersey 1992

Mosquito Control Pesticide Use Survey data on

file at NJDEP, Pesticide Control Program, Trenton,

N.J.).

Pesticide use for the control of weeds in

right-of-way areas in New Jersey such as those

adjacent to railroad tracks, highways, and power

lines in 1992 was about 54,000 pounds of active

pesticide ingredient (New Jersey 1992 Right-ofWay Pesticide Use Survey data on file at NJDEB

Pesticide Control Program, Trenton, N.J.). Diuron

and glyphosate accounted for 80 percent ofthe

use.

Farmers, commercial applicators, and

pesticide manufacturers report the use and sales of

pesticides on Long Island to the New York State

Department of Environmental Conservation.

Because most of this information is not readily

available, little is known about the amount of

pesticide use on Long Island. Legislation enacted

in 1996 in New York required the establishment of

a statewide computer registry of pesticide use and

sales by farmers and commercial pesticide users;

therefore, these data will be available in the future.

The USEPA (U.S. Environmental Protection

Agency, 1988) indicates that the effects on human

health that can result from exposure to pesticides

depend on the toxicity of the pesticide compound,

the duration of exposure, and the dosage.

Pesticides typically are found only in trace

amounts in ground water. The USEPA has

established MCLs for more than 60 pesticides

(U. S. Environmental Protection Agency, 1 988).

MCLs are set only when sufficient information

concerning the health effects of the pesticide is

available and when it is believed that the pesticide

may find its way into water supplies.

The potential of individual pesticides to

contaminate ground water depends on their

chemical characteristics and the characteristics of

Figure 33. Reported pesticide use in New Jersey,

by land use and type of pesticide. (Data from

Hamilton and Meyer, 1994, and data on file at New

Jersey Department of Environmental Protection,

Pesticide Control Program, Trenton, N.J.)

Residential lawn care accounts for the

second largest use of pesticides in New Jersey. In

1995, more than 370,000 pounds of active

pesticide ingredient, mostly herbicides with

smaller amounts of insecticides and fungicides,

was applied (New Jersey 1995 Lawn Care

Pesticide Use Survey data on file at NJDEB

Pesticide Control Program, Trenton, N.J.). The

most commonly used pesticides for lawn care in

1995 were pendimethaLin,2,4-D, mecoprop, and

trichlorfon. The first three compounds are

herbicides; trichlorfon is an insecticide.

Maintenance of golf courses requires the use

of substantial amounts of fertilizers and pesticides

with the potential for more than 30 different

applications annually to a variety of areas, such as

greens, tees, and fairways. About 202,000 pounds

of active pesticide ingredient reportedly was used

on207 golf courses in New Jersey during 1993

(New Jersey 1993 Golf Course Pesticide Use

Survey data on file at NJDEB Pesticide Control

Program, Trenton, N.J.). Fungicides were used the

most (72 percent of total use), followed by

insecticides (16 percent) and herbicides (12

percent).

1 A
the soil and aquifer material they penetrate.

Pesticide characteristics include water solubility,

the ability to cling to soil matter (soil adsorption),

and the ability to resist decomposition or

degradation (persistence). Pesticides that are

highly water soluble, poorly sorbed, and highly

persistent pose the greatest risk of contaminating

ground water. Soil and aquifer characteristics that

affect pesticide movement include soil texture,

amount of organic matteq number and size of

pores in the soil, and depth to water from the land

surface. A coarse-textured (sandy) soil low in

organic matter will allow pesticides to move easily

from the land surface to the underlying aquifer.

Shallow depth to water from the land surface

increases the likelihood that pesticides will reach

ground water.

Pesticides can be grouped according to their

chemical composition. In the discussions that

follow, insecticides are categorized into one of

three groups (carbamate, organochlorine, or

organophosphorous), and herbicides are

categorized into one of two groups (acetanilide/

triazine or chlorophenoxy acid). Use of

organochlorine insecticides has been severely

restricted since the 1970's; however, residues of

these compounds are persistent and are sometimes

detected at low concentrations in ground water.

Many pesticides in the other groups are currently

used in New Jersey and on Long Island and have

been detected in ground water.

Long Island

Water samples collected during 1987-88

from the 90 wells in the five study areas on Long

Island were analyzedfor pesticides (fig. 3a)

(Leamond and others, 1992).Insecticides were

detected primarily in suburban and agricultural

areas. Organochlorine insecticides were the most

frequently detected class of pesticides in all five

study areas. Detectable concentrations were found

in water from 80, 71, and 50 percent of the

sampled wells in the recently sewered area, the

agricultural area, and the long-term sewered area,

respectively. Organochlorine insecticides detected

in the three suburban areas were dieldrin,

heptachlor epoxide, and chlordane. In the

agricultural area, heptachlor epoxide was detected

most frequently, followed by dieldrin, endosulfan,

and DDD. Endosulfan was the only

."*"t' -u"u**,."*"**-""""t' .,"^uun"

-..*r$'- O1v{e -.$.u$"- u*od- ngetd" ^.\do ^"&

sgl$'v- ^.rod*' u9$"

-$9.' E$oPREDOMINANT LAND USE

EXPLANATION

I cenenvATE rNsEcrcrDEs

! onenr.rocHloRtNE tNSEclctDES

[l oncnr.ropHospHoRus tNSEclcIDES

! rnrnzrruE HERBtctDES

! cnlonoPHENoxY AcrD HERBTcIDES

100

980

J

IJJ

3

b60

uJ

240

UJ

E

UJ o-20

Figure 34. Frequency of detection of five groups of

pesticides in water from wells in five areas of

differing land use and sewering practices in Nassau

and Suffolk Counties, Long lsland, New York.

(Data from Leamond and others, 1992)

organochlorine insecticide detected in the

undeveloped area (in one well adjacent o

agricultural land) (Leamond and others, 1992).

The detection of organochlorine insecticides in

water samples collected during 1987-88, a decade

after their use was restricted, confirms their

persistence in ground water.

Organophosphorus insecticides (mainly

diazinon) were detected in the recently sewered

suburban area, the unsewered suburban area, and

the agricultural area, but relatively infrequently

and at low concentrations (Leamond and others,

1992). Compared to organochlorine insecticides,

organophosphorous insecticides have a relatively

short half-life in soil and water. Organophosphorus

insecticides tend to sorb to soils or degrade before

they can be transported into the aquifer system.

25
Carbamate insecticides, primarily

carbofuran and degraded forms of aldicarb, were

detected at the highest concentrations of any

pesticide in the study and in 67 percent of the

wells sampled in the agricultural area. The high

concentrations of these compounds are directly

related to their use in Long Island agriculture as

insecticides. Carbamate insecticides also were

detected in one sample from the undeveloped area

and one sample from the unsewered suburban

area, each near small parcels of agricultural land.

Total aldicarb concentrations (the sum of aldicarb

and its degraded forms) exceeded the New York

State guideline of 7 v,glL in 60 percent of wells in

the agricultural area (Eckhardt and others, 1989).

The highest concentration of total aldicarb

detected was 104 pg/L (Leamond and others,

1992). Carbamate insecticides have a shorter life

span in soil and water than organochlorine

compounds, but they tend to be more soluble in

water.

Herbicides were detected mainly in the

suburban areas, where they were used extensively

for the control of weeds in lawns. Triazine

herbicides were detected in 15 to 25 percent of the

sampled wells in the three suburban areas, but no

triazine herbicides were detected in the

agricultural or undeveloped areas. Triazine

compounds detected include atrazine, simazine,

and prometone (Leamond and others, 1992).

Chlorophenoxy-acid herbicides were detected

infrequently and at low concentrations in the three

suburban areas and the asricultural area.

New Jersey

In a 1985 study of shallow ground water in

the Potomac-Raritan-Magothy aquifer system,

samples collected from 66 wells were analyzed for

organochlorine and organophosphorus insecticides

and triazine herbicides (Barton and others, 1987).

Pesticides were detected most frequently in

agricultural areas and least frequently in urban and

undeveloped areas. Furthermore, the frequency of

detection of pesticides in ground water within 0.25

mi of agricultural land (23 percent) was

significantly larger than that in ground water more

than 0.25 mi from agricultural land (5 percent).

Water samples collected from 81 wells in

asricultural areas of the Potomac-RaritanMagothy and Kirkwood-Cohansey aquifer

systems during 1986-87 (Vowinkel and Battaglin,

in press) were analyzedfor three insecticide

groups (organochlorine, organophosphorus, and

carbamate) and two herbicide groups

(chlorophenoxy acid and triazinelacetanilide) (fig.

35). Pesticide residues were detected in water

from27 of the 81 wells (33 percent); 13

insecticides and 6 herbicides were detected,

generally at low levels. Alachlor was the most

commonly detected herbicide, but only one

sample contained a concentration of alachlor

greater than the applicable USEPA MCL of 2 v,gl-

(Vowinkel and Battaglin, in press).

The frequency of detection of each of the

five pesticide groups was similar in the Potomac-

..""t."^ooes *oNS? *.{P'o\g *t"t" ^o$v" .,o9?t- ^'$9N .r$o1' -16

^F$" .n?S- Crn' ^e$o' -r?-\F"

o$o' ^cots$" .. o$t' ^.xa\$-

O\ - O$" {r''

PESTICIDE GROUP

EXPLANATION

ffi poToMAC-RARITAN-MAGoTHY AQUIFER SYSTEM

[__l rrnrwooD-coHANSEy AeurFER sysrEM

2

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220

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Figure 35. Frequency of detection of five groups of

pesticides in water from wells in the PotomacRaritan-Magothy and Kirkwood-Cohansey aquifer

systems, New Jersey. (Data from Vowinkel and

Battaglin, in press)

26
Raritan-Magothy and Kirkwood-Cohansey aquife

systems. Herbicides of the triazine and acetanilid

groups were detected in more than20 percent of

the samples from both aquifer systems; atrazine

and alachlor were detected most frequently. No

chlorophenoxy-acid herbicides were detected.

Carbamate insecticides were detected in more than

30 percent of the samples from both aquifer

systems; carbofuran and the degraded forms of

aldicarb were detected most frequently.

Organochlorine compounds were detected in

about l0 percent of the samples from both aquifer

systems; dieldrin was detected most frequently

and lindane was detected at the largest

concenfration. Diazinon, the only

organophosphorus insecticide detected, was

present at the laboratory reporting level of

0.01 pgll, in only one water sample. The similar

frequencies of detection of the pesticide groups in

shallow ground water in the two aquifer systems

probably reflect similar pesticide-use pattems and

similar vulnerability to contamination of the two

systems (Vowinkel and Battaglin, in press).

In a 1991 study to investigate the movemen

of agricultural chemicals in the KirkwoodCohansey aquifer system, nested wells (wells

installed at different depths in the same location)

in five active or historically active agricultural

sites were sampled for pesticides and other

constituents (Szabo and others, 1994). Pesticides

were detected in shallow wells at four of the sites,

but were not detected in the deep wells. The

maximum depth at which any pesticide (bromacil

in this case) was detected was 60 ft below land

surface (40 ft below the water table). Bromacil, a

carbamate insecticide, is a particularly persistent

and mobile compound. The detection of pesticide

in shallow ground water at four of the five sites

indicates that most of the shallow ground water in

the Kirkwood-Cohansey aqui fer sy stem directly

underlying agricultural areas (where pesticides

were likely applied) probably contains low

concenffations of one or more pesticides. The fact

that pesticides were not detected in water from the

deep wells at these five sites indicates that

pesticides have degraded and (or) have not yet

penetrated to deeper parts ofthe aquifer system

(Szabo and others, 1994\.

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s

Predicting Vulnerability to Pesticide

Contamination

Beginning in 1995, New Jersey's Safe

Drinking Water Act requiredthe 626large

community water systems in the State to monitor

their 2,600 wells quarterly for 23 pesticides

(Vowinkel and others, 1994,1996). As part of a 3-

year study that began in October l992,the USGS,

in cooperation with the NJDEP, developed a

geographic information system (GIS) data base to

provide data with which to assess the vulnerability

of water from public-supply wells to

contamination by pesticides. A vulnerability rating

was determined for each well by using a numerical

rating method based on information on well

construction, land use, soils, and other

characteristics that can affect vulnerability. The

vulnerability of a well to contamination by

pesticides is defined bV (l) the sensitivity of the

aquifer to contamination and (2) the intensity of

pesticide use in areas where the aquifer is sensitive

to contamination. Three variables were used to

predict aquifer sensitivity: (1) location of a well

relative to the outcrop area, (2) soil organic-matter

content, and (3) depth from the land surface to the

top of the open interval of the well (top of the well

screen for wells in unconsolidated sediments and

top ofthe open hole for bedrock aquifers). Three

variables were used to predict pesticide-use

intensity near wells that are sensitive to

contamination: (l) predominant land use near the

well, (2) distance from the nearest agricultural

area, and (3) distance from the nearest golfcourse

(Vowinkel and others, 1994,1996). The

vulnerability rating will be used by the State to

determine the required level of monitoring for

each well and to issue waivers if a well is

determined to have low vulnerability to

contamination.

Well-construction characteristics and

location were determined for 2,100 of the 2,600

public-supply wells in New Jersey; available

information was insufficient forthe remaining 500

wells. The 2,600 wells are located in three

different aquifer types: (1) Coastal Plain

unconsolidated sand and gravel deposits, (2)

unconsolidated glacial-deposit sediments, and (3)

fracfured bedrock. By using the numerical rating

method, each of the 2,100 wells was assigned to

one of three vulnerability groups on the basis of its

27
COASTAL BEDROCK GLACIAL ALL

PLAIN WELLS

AOUIFER TYPE

EXPLANATION

I HIGH

I MODERATE

I LOW

100

U)

j80

tU3

bao

uJ

f,+o

z

ul ()

ffzo (!

Figure 36. Percentage ofNew Jersey public-supply

wells in each of three vulnerability groups, by major

aquifer type. (Modified from Vowinkel and others, 1996)

EXPLANATION

. Low

. Medium

. High

O 2 5 M I L E S

O 25 KILOMETERS

41"

Figure 37. Vulnerability of public-supply wells in

New Jersey to contamination bypesticides. (Modified

from Vowinkel and others, 1996)

sensitivity and intensity ratings (figs. 36 and37).

About 26 percent of the public-supply wells are

ranked in the low-vulnerability group. All wells in

this group are in the confined parts of Coastal

Plain aquifers. About 4 percent of all publicsupply wells are ranked in the high-vulnerability

group. These wells are in the unconfined parts of

aquifers and are in or adjacent to agricultural land.

The remaining 70 percent of all wells were

determined to be moderately vulnerable to

contamination from human activities; most are

completed in unconfined aquifers and are in or

adjacent to residential or agricultural land

(Vowinkel and others, 1994,1996).

Vulnerability ratings were validated by

analyzing water samples from a subset of 90

public-supply wells throughout New Jersey for

pesticides and nitrate. Wells were chosen from

each combination of vulnerability group and

aquifer type. Pesticides were detected in water

from 6 of the 90 wells sampled. Three of these

wells were rated in the high-vulnerability group;

the other three were rated as having moderate

vulnerability (Vowinkel and others, 1994, 1996).

Ground-water studies like those conducted

to predict nitrate and VOC contamination of

ground water on Long Island by using regression

analysis and pesticide contamination of ground

water in New Jersey by using the vulnerability

rating method can lead to substantial cost savings.

The NJDEP estimated that monitoring waivers

granted for wells determined to have low

vulnerability to contamination by pesticides will

save taxpayers almost $5 million annually for a

one-time cost of $1 million (Vowinkel and others,

1994,1996). In addition, Federal, State, and

county agencies, consulting firms, universities,

and the public make requests daily for the wateruse, water-quality, and hydrogeologic data

resulting from these and similar studies.

SUMMARY AND CONCLUSIONS

This report summarizes the results of

selected studies on factors such as aquifer

characteristics and land-use patterns that affect

ground-water quality in New Jersey and on Long

Island, New York. It describes the ground-water

systems in the study area; summarizes available

information about the occurrence and distribution

of nitrate, VOCs, and pesticides in these systems;

and explains why some ground-water systems are

more vulnerable to contamination than others.

28
The geology and hydrology of fractured

bedrock and valley-flll aquifers of northern New

Jersey are considerably more complex and locall

variable than those of the more areally extensiv

unconsolidated sand and gravel aquifers ofthe

Coastal Plain on Long Island and in New Jersey

hence, the quality of water in these aquifers is

more difficult to generalize or extrapolate from

available data. Therefore. additional data

collection and research are needed to investigat

water quality and factors controlling ground-wat

contamination in these areas.

Although the vulnerability of ground water

to contamination from the land surface is

influenced by many factors, the degree of aquifer

confinement, the depth of the well, and the

surrounding land use are key factors. For exampl

whether the well is in the unconfined or confined

part of the aquifer is important--unconfined

aquifers generally are much more vulnerable to

contamination than confined aquifers. For a well

in a confined aquifer, however, the distance of the

well from the unconfined (outcrop) area is a

factor--generally, the farther the well is from the

unconfined area, the less vulnerable it is to

contamination.The depth of the well also can be

influential, especially in an unconfined aquifcr--

generally, the deeper the well, the less vulnerable

it is to contamination.Finally, because human

activities greatly affect the quality of recharge

water to an aquifer, the amount and type of land

use in the area that contributes water to the well

is a keyfactor in determining vulnerability.

Nitrate contamination of ground water

typically occurs in agricultural and residential

areas, especially where the aquifer is very

permeable and unconfined, and nitrogen-fertiliz

use is high. In New Jersey and on Long Island,

concentrations ofnitrate exceed the U.S.

Environmental Protection Agency Maximum

Contaminant Level more often than those of

VOCs or pesticides. Nitrate contamination

generally is associated with nonpoint sources.

VOC contamination of groundwater

occurs primarily in urban areas, especially in

urban-industrial areas where chemicals are uscd.

In general, VOC concentrations are low and do not

exceed MCLs. High VOC concentrations

generally are associated with point sources.

y

e

;

e

er

e,

er

Pesticide contamination of gro und water

occurs in some agricultural and residential

sreas) where the aquifer is very permeable and

unconfined, and where chemicals are used.

Concentrations of pesticides in New Jersey and on

Long Island generally are low; however, some

have been found to exceed MCLs in agricultural

areas of Long Island. Pesticide contamination

generally is associated with nonpoint sources.

Most of the regional studies of water quality

in New Jersey and on Long Island conducted thus

far have focused on the occurrence and spatial

distribution of contaminants within the groundwater system. Although valuable information has

been learned from these studies. such as the

probability of finding a contaminant based on

location, depth, and land use, other questions have

arisen. Some of these questions include--

--What specific human activities result in

ground-water contamination and how can these

activities be minimized?

--Will the contamination eventually affect

deeper ground-water supplies? On Long Island in

particular, when and where will the deeper aquifer

systems be affected by water from the extensively

contaminated surfi cial aquifers?

--Are contaminants inground water reaching

and affecting streams, wetlands, and other surfacewater bodies?

--What other components of the hydrologic

cyclc, such as the atmosphere and unsaturated soil

zone, must be investigated in order to learn more

about he sources and movement of contaminants?

--What is the ultimate fate of these

contaminants and how do various hydrologic,

chemical, microbiological, and other processes

affect the extent of contaminant movement?

--How will the quality of water in the

contaminated parts of aquifer systems change in

25 to 50 years and how might conditions change

under various management srategies?

Finding the answers to these and other

questions will be the responsibility of watermanagement agencies and research organizations

in the vears to come.

29