Prepared in Cooperation with the 

U.S. Army Corps of Engineers

Mercury in Waters, Soils, and Sediments of the 

New Jersey Coastal Plain: A Comparison of Regional 

Distribution and Mobility with the Mercury Contamination 

at the William J. Hughes Technical Center, 

Atlantic County, New Jersey

Scientific Investigations Report 2012–5115

U.S. Department of the Interior

U.S. Geological Survey

Mercury in Waters, Soils, and Sediments of 

the New Jersey Coastal Plain: A Comparison of Regional Distribution and Mobility 

with the Mercury Contamination at the 

William J. Hughes Technical Center, 

Atlantic County, New Jersey

By Julia L. Barringer, Zoltan Szabo, and Pamela A. Reilly

Prepared in cooperation with the 

U.S. Army Corps of Engineers

Scientific Investigations Report 2012–5115

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Barringer, J.L., Szabo, Zoltan, and Reilly, P.A., 2012, Mercury in waters, soils, and sediments of the New Jersey 

Coastal Plain: A comparison of regional distribution and mobility with the mercury contamination at the William 

J. Hughes Technical Center, Atlantic County, New Jersey: U.S. Geological Survey Scientific Investigations Report 

2012–5115, 34 p.
iii

Acknowledgments

The authors thank Gregory Goepfert, Tracy Dorgan, and James Kelly of the U.S Army Corps 

of Engineers for providing the funding for this overview of the mercury studies in New Jersey. 

Thanks go to Ryan Brown of Weston Solutions for supplying documentation of the studies at the 

William J. Hughes Technical Center site.

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................1

Description of Regional Study Area ..................................................................................................3

Regional Levels and Distribution of Mercury in the New Jersey Coastal Plain .................................3

Groundwater..........................................................................................................................................3

Soils and Streambed Sediments ........................................................................................................6

Surface Water.......................................................................................................................................8

Possible Sources of Inorganic Mercury in the New Jersey Coastal Plain........................................13

Anthropogenic Sources.....................................................................................................................13

Atmospheric Deposition ...........................................................................................................13

Agricultural Chemicals .............................................................................................................14

Household Sources ...................................................................................................................14

Other Anthropogenic Sources.................................................................................................15

Natural Sources..................................................................................................................................16

Factors Affecting Mobility..........................................................................................................................17

Mercury Forms....................................................................................................................................17

Other Constituents .............................................................................................................................19

Methylmercury....................................................................................................................................22

Summary of Mercury Found at the William J. Hughes Technical Center .........................................23

 Site Description and History ............................................................................................................23

Area Hydrology....................................................................................................................................25

Mercury in Soils and Sediments ......................................................................................................25

Mercury in Groundwater and Streamwater...................................................................................28

Methylmercury in Sediment and Water .........................................................................................29

Comparison of Mercury Levels at the William J. Hughes Technical Center with Levels Found 

Regionally in Southern New Jersey ...........................................................................................29

Summary and Conclusions ........................................................................................................................30

References Cited..........................................................................................................................................31
iv

Figures

1. Map showing outcrop areas of the sediments of Miocene age that compose the 

Kirkwood-Cohansey aquifer system, overlying Pleistocene sediments of the Cape 

May Formation, and location of the William J. Hughes Technical Center, the 

Burlington County site, the Franklin Township site, the Squankum Branch 

watershed, and domestic well SUSCP30 in the New Jersey Coastal Plain............................2

2. Map showing location of regional study area, extent of Pine Barrens in New Jersey, 

now referred to as Pinelands, and an idealized vertical section through the 

Kirkwood-Cohansey aquifer system showing regional groundwater flow.........................4

3. Map showing location of Squankum Branch, tributary to the Great Egg Harbor River, 

and its watershed, showing 1930s land use, recent (2008–09) streamwater and 

sediment sampling sites, and site of residential area where groundwater from the 

Kirkwood-Cohansey aquifer system was found in the 1990s to contain contaminant 

levels of mercury ..........................................................................................................................6

4. Map showing land use (2002) within the non-tidal part of the Great Egg Harbor River 

watershed and Hammonton Creek watershed in New Jersey, with sampling sites 

from the U.S. Geological Survey 2006–08 investigations of mercury and 

methylmercury in the watersheds .............................................................................................9

5. Graph showing concentrations of total mercury in unfiltered and filtered water 

collected throughout the day from domestic well 051789 completed in the 

Kirkwood-Cohansey aquifer system, Burlington County, New Jersey, June, 2009.........18

6. Graphs showing concentrations of (a) nitrate, (b) dissolved oxygen, (c) mercury, (d) 

iron, and (e) dissolved organic carbon, and (f) pH in groundwater samples from the 

Kirkwood-Cohansey aquifer system, collected at discrete intervals with a screened 

augur, showing increase of iron and mercury concentrations with onset of reducing 

conditions downgradient from an abandoned septic leach field, Franklin Township, 

Gloucester County, New Jersey ..............................................................................................21

7. Map showing location of Atlantic City International Airport, which encompasses 

the William J. Hughes Technical Center and Area U, from TRC, 2005, with overlay 

of residential areas with mercury-contaminated groundwater from the KirkwoodCohansey aquifer system, shown in Barringer and others, 1997 .......................................24

8. Graph showing time line indicating various events at and in the vicinity of the 

William J. Hughes Technical Center site, New Jersey........................................................25

9. Map showing concentrations of mercury in groundwater from domestic wells 

completed in the Kirkwood-Cohansey aquifer system at a residential area (site 2) to 

the southwest of the William J. Hughes Technical Center site, Atlantic County, New 

Jersey, and direction of the horizontal component of groundwater flow determined 

from water-level data.................................................................................................................26

10. Map showing area surrounding the Atlantic City International Airport in New Jersey, 

which encompasses the William J. Hughes Technical Center site, groundwaterflow directions in the Kirkwood-Cohansey aquifer system, and six residential sites 

where domestic wells yielded water containing total mercury at concentrations that 

approached or exceeded the New Jersey maximum contaminant level of 

2 micrograms per liter................................................................................................................27
v

Tables

1. Contents of selected trace elements determined by total digestion and organic 

carbon in core samples of Kirkwood-Cohansey aquifer-system sediments from 

wells installed along rights-of-way in Williamstown, in the Great Egg Harbor River 

watershed, Gloucester County, New Jersey ...........................................................................7

2. Contents of trace elements in aquifer sediments from core samples from 

Squankum Branch, Gloucester County, New Jersey, 2009 ...................................................8

3A. Contents of recoverable mercury, streambed sediments from Hammonton Creek 

and the Great Egg Harbor River and tributaries, Gloucester and Atlantic Counties, 

New Jersey, 2006–07. ...............................................................................................................10

3B. Values of pH and concentrations of total mercury and methylmercury in 

unfiltered and filtered samples of streamwater from Hammonton Creek and the 

Great Egg Harbor River and tributaries, Gloucester and Atlantic Counties, 

New Jersey, 2006–07. ................................................................................................................11

4. Concentrations of selected constituents and values of pH in backwash brines 

from household water-treatment systems at three domestic wells in Burlington 

County, New Jersey, 2008–09...................................................................................................15

5. Field properties, concentrations of total mercury, and dissolved major and trace 

constituents in well water from domestic well SUSCP30 in cranberry bog area in 

New Jersey, 1998 and 2006. .....................................................................................................16

6. Concentrations of particulate mercury and mercury in unfiltered and filtered 

samples of domestic-well water collected throughout a day to simulate normal 

household water use, Burlington County, New Jersey, 2008–09. ......................................19

7. Contents of selected constituents in B-horizon soils from Burlington County, 

New Jersey, and concentrations of mercury and selected constituents and pH 

in leaching solutions and leachate from column experiments. ..........................................20

8. Summary of similarities and dissimilarities between mercury levels at the 

William J. Hughes Technical Center and regionally in the Coastal Plain of 

New Jersey..................................................................................................................................30
vi

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.305 meter (m)

mile (mi) 1.609 kilometer (km)

yard (yd) 0.914 meter (m)

Area

square mile (mi2) 2.59 square kilometer (km2) 

Volume

barrel (bbl), (petroleum, 1 barrel = 42 gal) 0.159 cubic meter (m3) 

ounce, fluid (fl. oz) 0.030 liter (L) 

pint (pt) 0.473 liter (L) 

quart (qt) 0.946 liter (L) 

gallon (gal) 3.785 liter (L) 

Flow rate

cubic foot per second (ft3/s) 0.028 cubic meter per second 

(m3/s)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Vertical coordinate information is referenced either to the North American Vertical Datum of 

1988 (NAVD 88), or, for the earliest studies cited, to the National Geodetic Vertical Datum of 1929. 

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L), 

which is equivalent to parts per million; or micrograms per liter (μg/L), which is equivalent to 

parts per billion.

Concentrations of chemical constituents in soils are given in milligrams per kilogram (mg/kg), 

which is equivalent to parts per million. 
vii

Chemical Abbreviations

As Arsenic

Ca Calcium

Cl- Chloride

DO Dissolved oxygen

DOC Dissolved organic carbon

Fe Iron

Hg Mercury

K Potassium

MBAS Methylene blue active substances

Mg Magnesium

Mn Manganese

N Nitrogen

Na Sodium

NH4+ Ammonium

NO3- Nitrate

NO2- Nitrite

P Phosphorus

Pb Lead

SC Specific conductance

SO4

2- Sulfate

T Temperature

137Cs Cesium-137

210Pb Lead-210

Acronyms

CKKD Kirkwood-Cohansey aquifer system 

FAA Federal Aviation Administration

NBAC North Branch Absecon Creek

NJDEP New Jersey Department of Environmental Protection

SBAC South Branch Absecon Creek

USGS U.S. Geological Survey

WHJTC William J. Hughes Technical Center

Mercury in Waters, Soils, and Sediments of the 

New Jersey Coastal Plain: A Comparison of Regional 

Distribution and Mobility with the Mercury Contamination 

at the William J. Hughes Technical Center, 

Atlantic County, New Jersey 

Julia L. Barringer, Zoltan Szabo, and Pamela A. Reilly 

Abstract

Mercury in soils, surface water, and groundwater at 

the William J. Hughes Technical Center , Atlantic County, 

New Jersey, has been found at levels that exceed established 

background concentrations in Coastal Plain waters, and, in 

some cases, New Jersey State standards for mercury in various 

media. As of 2012, it is not known whether this mercury is 

part of regional mercury contamination or whether it is related 

to former military activities. Regionally, groundwater supplying about 700 domestic wells in the New Jersey Coastal 

Plain is contaminated with mercury that appears to be derived 

from anthropogenic inputs, such as agricultural pesticide use 

and atmospheric deposition. High levels of mercury occasionally are found in Coastal Plain soils, but disturbance during 

residential development on former agricultural land is thought 

to have mobilized any mercury applied during farming, a 

hypothesis borne out by experiments leaching mercury from 

soils. In the unsewered residential areas with mercury-contaminated groundwater, septic-system effluent is believed to create 

reducing conditions in which mercury sorbed to subsoils is 

mobilized to groundwater. 

In comparing the levels of mercury found in soils, sediments, streamwater, and groundwater at the William J. Hughes 

Technical Center site with those found regionally, mercury 

concentrations in groundwater in the region are, in some 

cases, substantially higher than those found in groundwater 

at the William J. Hughes Technical Center site. Nevertheless, 

concentrations of mercury in streamwater at the site are, in 

some instances, higher than most found regionally. The mercury contents in soils and sediment at the William J. Hughes 

Technical Center site are substantially higher than those found 

to date (2012) in the region, indicating that a source other than 

regional sources may be present at the site.

Introduction

Mercury (Hg) has been found at the William J. Hughes 

Technical Center (WJHTC) Superfund site in Atlantic County, 

New Jersey (fig. 1), at levels that exceed the background 

concentrations in Coastal Plain waters, soils, and sediments; 

past and recent investigations by the U.S. Geological Survey 

(USGS) and the New Jersey Department of Environmental 

Protection (NJDEP) illustrated the likely ranges of naturally occurring and background levels of mercury in these 

media. Streamwater concentrations at this site have, in some 

instances, exceeded the State Surface Water Quality Standard 

of 0.05 microgram per liter (μg/L; New Jersey Department 

of Environmental Protection, 2010). Groundwater in parts of 

the site contains Hg at concentrations that exceed the State 

maximum contaminant level (MCL) of 2 μg/L (New Jersey 

Department of Environmental Protection, 2005). Whether the 

mercury is associated with contamination dating from the use 

of the site by the U.S. Navy, whether it represents part of a 

southern New Jersey regional problem with Hg contamination, 

or some combination of both, is currently (2012) being investigated. As part of the investigation, by the U.S. Army Corps of 

Engineers, the USGS has summarized results of regional studies of mercury and the findings for the WJHTC, and compared 

the latter with findings from the previous studies of mercury in 

the New Jersey Coastal Plain.

Purpose and Scope

The purpose of this report is to (1) review the existing 

data on mercury in water, soils, and sediments of the New Jersey Coastal Plain, (2) summarize the interpretations of those 

data with respect to mercury sources and causes of mobility, and (3) discuss the findings of mercury at the William J. 

Hughes Technical Center, Atlantic County, New Jersey, in 

light of the existing Coastal Plain area studies. 
2 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

DELAWARE

NEW JERSEY

DELAWARE BAY

A

T L

A

N T I

C

O

C E A

N

FALL LINE

Base from U.S. Geological Survey digital line graph files, 1:24,000,

Universal Transverse Mercator projection, Zone 18, NAD 83

0 5 10 MILES

0 5 10 KILOMETERS

PENNSYLVANIA

Beacon Hill Gravel

Bridgeton Formation

Cohansey Formation

Kirkwood Formation

EXPLANATION

New Jersey coastal plain boundary

Squankum Branch watershed

Pleistocene sediments

Cape May Formation

Miocene sediments

Site locations

Burlington County site

Franklin Township site

Well SUSCP30

William J. Hughes Technical Center

75° 74°

40°

39°

D E L AW A R E

R I V E R

CSL site Williamstown

Atlantic City

Figure 1. Outcrop areas of the sediments of Miocene age that compose the Kirkwood-Cohansey aquifer system, overlying Pleistocene 

sediments of the Cape May Formation, and location of the William J. Hughes Technical Center, the Burlington County site, the Franklin 

Township site, the Squankum Branch watershed, and domestic well SUSCP30 in the New Jersey Coastal Plain.
Regional Levels and Distribution of Mercury in the New Jersey Coastal Plain 3

The report is composed of five main sections. The first 

section is a summary of the levels and distribution of Hg in 

the Coastal Plain region. The second section is a summary 

of likely sources determined from existing regional and local 

studies. The third section presents a discussion of factors 

affecting Hg mobility. The fourth section presents the available data on methyl mercury (MeHg) in the New Jersey 

Coastal Plain, and the fifth section is a brief summary of major 

findings from the WJHTC and a comparison of those results 

with results from previous regional and local studies.

Description of Regional Study Area

The New Jersey Coastal Plain is a seaward-thickening 

wedge of sediments deposited during parts of the Mesozoic 

and Cenozoic Eras; sediments range in age from the Cretaceous through the Miocene periods with a spatially scattered veneer of younger (Pleistocene and Holocene) deposits 

(fig. 1). The uppermost part of the wedge is composed of 

quartzose sands and gravels of the Cohansey and Kirkwood 

Formations, deposited in near-shore and deltaic environments 

during the Miocene Epoch. Scattered outcrops of the Late 

Miocene Beacon Hill Gravel and Bridgeton Formation overlie 

the Cohansey Formation in some upland areas. Together, these 

four formations form the most areally extensive (3,000 square 

miles (mi2)), and mostly unconfined, aquifer system of the 

New Jersey Coastal Plain—the Kirkwood-Cohansey aquifer 

system (CKKD; Zapecza, 1989). This system is about 250 to 

300 feet (ft) thick in the WJHTC study area.

Recharge to the system is provided by precipitation, 

of which about 50 percent is returned to the atmosphere by 

transpiration and evaporation (Rhodehamel, 1979). Recharge 

in upland areas near topographic divides tends to move deeply 

into the aquifer system (fig. 2); groundwater at depth may be 

recharge that is hundreds to several thousands of years old. 

Streams and wetlands typically are in groundwater discharge 

areas, with small streams receiving local, relatively young 

water and major streams receiving deeper, older water. In 

the 1970s, Rhodehamel (1979) estimated that 89 percent of 

streamflow is derived from groundwater discharge (base flow). 

With recent development leading to greater groundwater withdrawals, this estimated percentage likely has decreased. 

Groundwater typically is acidic, with a median pH of 

4.4 found in 13 samples collected from wells in undeveloped 

areas. With increasing agricultural and (or) residential development, groundwater pH tends to change, often increasing 

(see Table III, Barringer and Szabo, 2006), particularly as 

agricultural chemicals (primarily lime, in the form of dolomite 

(CaMg (CO3)2) enter the aquifer system. Streamwater also 

is acidic. In the streamwater, pH values vary, particularly in 

wetlands areas; pH is higher during dry periods when base 

flow is dominant and lower during wet periods when acidic 

water from the wetlands is flushed into the streams (Barringer 

and others, 2010a).

The sandy soils developed on the CKKD sediments are 

acidic to strongly acidic and are well drained to excessively 

drained in upland areas; they typically contain little organic 

matter (Markley, 1979). Natural, undisturbed upland soils 

comprise several soils series with similar characteristics; these 

typically contain an organic-rich surface layer (O horizon) 

underlain by a strongly leached, sandy, mineral soil layer (A 

horizon) underlain by a layer that, in some series, is an E horizon. The A (and E) horizons, in turn, are underlain by thick 

zones where leached materials accumulate (B horizon); the 

B-horizon soils are mainly composed of iron-hydroxide-coated 

sands and clays. The B horizon grades into the C horizon, 

which is composed of barely altered geologic substrate. Along 

streams and in wetlands areas, an illuviated sediment layer 

may be found at the water table, and soils tend to be relatively 

rich in organic matter and generally are poorly drained.

With displacement of native populations and settlement 

by people of English and European origin in the 17th and 18th 

centuries, southern New Jersey became a largely agrarian 

economy (Schmidt, 1973), although glass-blowing, lumbering, 

charcoal-roasting, and iron-smelting and forging industries 

were present (Wacker, 1979) in areas that are now mostly 

part of the Pinelands (formerly known as the Pine Barrens 

(fig. 2; Rhodehamel, 1979)). Although cities grew, agriculture 

remained an important industry through the 19th and into the 

20th centuries (Schmidt, 1973). With the end of World War II, 

however, residential development increasingly began to supplant agriculture as an important land use. Much of southern 

New Jersey currently (2012) is a mosaic of land uses and land 

covers. The region still includes areas of forests and wetlands, 

some of which are protected in State Forests and Preserves and 

some of which are now adjacent to residential areas.

Most areas of the Coastal Plain underlain by CKKD sediments have been investigated in USGS and NJDEP mercury 

studies, with the exception of the lower Cape May peninsula. 

There the CKKD does not have direct connection to land surface because it is confined by the younger sediments overlying it. The WJHTC site is located in Atlantic County; about 

6 miles (mi) from the Atlantic coast (fig. 1).

Regional Levels and Distribution of 

Mercury in the New Jersey Coastal 

Plain

The following section reviews the existing data on Hg 

in the environment of southern New Jersey. Concentrations 

in groundwater and streamwater, and contents of soils and 

streambed sediments, are presented and discussed. 

Groundwater

Regional Hg contamination in southern New Jersey 

primarily affects potable water sources. In the Coastal Plain 

of southern New Jersey, groundwater is a major source of 

drinking water; about 62,000 private domestic wells (Jennifer 
4 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

NOT TO SCALE

Pre-Kirkwood Strata

Regional Flow System

Cohansey

Kirkwood

Sand

Formation

Regional Flow System

Local Flow System

Upland Area

NW SE

Silt

and Clay

Layers

Local Flow System

75 30' 75 30' 74 

A

T

L

A

N

T I C 

O

C E A

N

DELAWARE

PENNSYLVANIA

40

30'

40

39

30'

0

0

10 MILES 

10 KILOMETERS 

NEW JERSEY NEW YORK

Study area

EXPLANATION

boundary

Pine Barrens

boundary

Atlantic

Salem

Cumberland

Burlington

Cape

May

Ocean

Gloucester

Camden

Figure 2. Location of regional study area, extent of Pine Barrens in New Jersey, now referred to as Pinelands, and an idealized 

vertical section through the Kirkwood-Cohansey aquifer system showing regional groundwater flow. (Bridgeton Formation and Beacon 

Hill Gravel are not shown. Vertical section from Rhodehamel, 1970)
Regional Levels and Distribution of Mercury in the New Jersey Coastal Plain 5

Bonin, U.S. Geological Survey, written commun., 2011) 

supply much of the water to residential areas. Since the early 

1980s, water from some of the domestic wells completed 

in the CKKD (fig. 1) has been found to contain total mercury (THg)—inorganic and, if present, organic forms—at 

levels that exceed 1 μg/L but not 2 μg/L (herein referred to 

as “elevated” levels); more importantly, there are numerous 

examples of mainly unfiltered well-water samples containing 

THg at concentrations that exceed the MCL of 2 μg/L (herein 

referred to as “contaminant levels” (see Barringer and others, 

1997)). Since the discovery of contaminant levels of THg in 

groundwater in the New Jersey Coastal Plain, Hg-contaminated groundwater in a Coastal Plain aquifer has been found at 

a site in Delaware (Koterba and others, 2006). 

Although the number of wells that have or are producing 

Hg-contaminated water in southern New Jersey is not known 

with accuracy, estimates place the number at about 700. To 

date (2012), this number appears to represent from 0.5 to 

1 percent of the wells tested for Hg levels in southern New 

Jersey; the rest have yielded water with THg concentrations 

less than the MCL. For those wells that produced water with 

THg concentrations at or greater than the MCL, concentrations in unfiltered water samples have been as high as 81 μg/L 

(Dr. Judith Louis, New Jersey Department of Environmental 

Protection, oral commun., 2010), although concentrations 

have been found to change over time (see table 8 in Barringer 

and others, 1997). One well in Atlantic County yielded unfiltered water with THg concentrations that ranged from 19.0 

to 72.0 μg/L over nearly a year of sampling; the penultimate 

sample with 72 .0 μg/L was succeeded on the following day 

by a sample containing 2.2 μg/L of THg (Barringer and others, 

1997). In general, for wells sampled over months to years, 

the THg concentrations can vary widely. For those wells that 

yielded water with concentrations less than the MCL or not 

detected at 0.2 or 0.1 μg/L (the common detection limits of the 

commercial laboratories used during the 1980s and 1990s), it 

seldom has been known whether concentrations increased over 

time because those wells were not repeatedly sampled as part 

of the routine followed by State or county agencies. Recent 

sampling of wells by NJDEP at a residential area in Burlington 

County has included re-sampling of wells yielding water with 

THg at concentrations less than the MCL; however, for a few 

wells, the data indicate that concentrations have risen (Robert 

A. Gallagher, New Jersey Department of Environmental Protection, written commun., 2009).

In water from the CKKD, THg concentrations of 1 μg/L 

were much greater than background concentrations of THg, 

which have been found to be 0.010 μg/L or less in studies 

where analytical detection limits of less than 0.01 μg/L were 

available (Windom and Smith, 1992; Barringer and others 

2005; Barringer and Szabo, 2006). Anthropogenic effects 

on water quality (greater than background concentrations of 

chloride (Cl-

) and nutrients, for example) were seen in wellwater samples with THg concentrations that were greater than 

0.10 μg/L (Barringer and others, 2005). Where THg concentrations exceeded 0.010 μg/L but were less than the MCL, THg 

probably did not occur naturally but likely was the result of 

anthropogenic inputs and (or) mobilization through changes to 

the geochemical environment by human activities and chemical inputs.

Concentrations of THg as high as 72 or 81 μg/L in 

domestic well water apparently occurred rarely, but numerous concentrations greater than 10 μg/L are reported in the 

compilation of analytical results from the 1980s and 1990s in 

Barringer and others (1997). Concentrations of 2 to 10 μg/L 

represent the most common range of MCL exceedences in that 

database.

The sampling protocols used by county agencies and the 

NJDEP for domestic wells involve running the water for at 

least 15 minutes and collecting the sample directly into acidified bottles at untreated taps (either inside or outside taps) if 

the house had a water-treatment system. (The preferred site 

for sampling by USGS personnel is a tap before the pressure tank.) County agencies and the NJDEP did not filter the 

sample, thereby minimizing the potential for sample contamination during collection. Because repeat samples and split 

samples analyzed by separate laboratories returned similar 

results (Barringer and others, 1997), there is reason to believe 

that the high concentrations are not from contamination during sampling or during analysis but represent what is actually 

present in the aquifer. Samples collected from domestic and 

observation wells by the USGS since the 1990s, using ultraclean sampling techniques, confirm the existence of contaminant levels of THg in groundwater of the CKKD (see Barringer and others, 2005, 2006 and Barringer and Szabo, 2006). 

THg at contaminant levels in pre-treatment water from two 

public supply wells further strengthens this assessment.

Most of the domestic-well samples collected by county 

agencies and the NJDEP were not filtered; the USGS collected both filtered and unfiltered samples. In general, for 

those samples with greater than background concentrations of 

THg, there were slight differences in concentrations between 

unfiltered and filtered samples that indicate filtering (using 

0.45 micrometer (mm) pore-size filters) removed THg-bearing 

particles (Barringer and Szabo, 2006); therefore, some of the 

THg in groundwater was sorbed to particles.

The spatial distribution of affected wells in a given 

residential area is heterogeneous; a well that yielded THgcontaminated water could be adjacent to several that yielded 

water with undetectable THg levels, as shown by Barringer 

and others, 1997; Barringer and others, 2005; and Barringer and Szabo, 2006. Thus, the contamination appears to be 

contained in “plumelets” that move through the aquifer system 

over time. A study of groundwater discharge at a tributary 

(Squankum Branch; fig. 3) to the Great Egg Harbor River 

(Barringer and others, 2010b) indicated that THg-rich groundwater discharge to the stream occurred only in discrete areas 

along the banks of the stream, supporting the existence of the 

plumelets. Although attenuation of plumelets probably occurs 

within the aquifer, no data are currently (2012) available that 

conclusively support this speculation. The only supporting 
6 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

01410865

01410863

01410862

01410861

01410860

01410850

0141086050

01410855

01410865

01410863

01410862

01410861

01410860

01410850

0141086050

01410855

Mercury-contaminated

wells

74°59' 74°58'

39°

41'

39°

40'

New Jersey

Squankum

Branch

Basin

0 500 1,000 1,500 2,000 FEET

0 200 400 600 METERS

Williamstown

EXPLANATION

Watershed boundary

Abandoned Reading Railroad track

Streamwater sampling site and identifier

S q u a n k u m

B r a n c h

01410850

Figure 3. Location of Squankum Branch, tributary to the Great Egg Harbor River, and its watershed, showing 1930s land use, recent 

(2008–09) streamwater and sediment sampling sites, and site of residential area where groundwater from the Kirkwood-Cohansey 

aquifer system was found in the 1990s to contain contaminant levels of mercury.

evidence is the observation of decreases in THg concentrations 

over time in water from numerous wells.

Mercury at contaminant levels (defined as > 2 μg/L), for 

the most part, has not been found in water from public supply 

wells, which draw water from a much larger volume of aquifer 

than do domestic wells. Nevertheless, a new public supply 

well in Cumberland County was found to yield water with 

THg concentrations that exceeded the MCL (Szabo and others, 

2005, p. 74). Water from a public supply well in Gloucester 

County contained contaminant levels of THg; the water from 

that well is treated to remove the Hg (Richard Westergaard, 

Gloucester County Department of Planning, written commun., 

1997). In groundwater of the New Jersey Coastal Plain, the 

THg has been found mainly in inorganic form, but studies of 

MeHg in groundwater in the affected areas are few. 

Soils and Streambed Sediments

Although analyses are limited, the THg contents (by total 

digestion) of CKKD sediments were found to be less than 

0.15 milligram per kilogram (mg/kg), with the highest contents present in clays, not in sands (Barringer and others, 1997; 

table 1). For soils developed on the CKKD sediments, background contents of THg in undisturbed forested soils probably 

are about 0.10 to 0.15 mg/kg; the samples collected by the 

USGS presumably contain atmospherically deposited Hg, in 

addition to Hg derived from the geologic substrate. In contrast, 

the THg contents in disturbed residential soils generally were 

about 0.05 mg/kg or less, which is less than background levels 

(Barringer and others, 1997; Barringer and Szabo, 2006). In 

residential-area soils, THg contents were positively related 
Regional Levels and Distribution of Mercury in the New Jersey Coastal Plain 7

Table 1. Contents of selected trace elements determined by total digestion and organic carbon in core samples of KirkwoodCohansey aquifer-system sediments from wells installed along rights-of-way in Williamstown, in the Great Egg Harbor River 

watershed, Gloucester County, New Jersey.

[Location of Williamstown shown in figure 1. Site names are those of streets along which the wells are installed. ft bls, feet below land surface; Hg, mercury; 

As, arsenic; Pb, lead; Org. C, organic carbon; mg/kg, milligrams per kilogram; %, percent]

Site name/

depth interval 

(ft bls)

Description Hg

(mg/kg)

As

(mg/kg)

Pb

(mg/kg)

Org. C

(%)

Academy/50.9–51.5 Fine quartz sand, ilmenite 0.05 1.20 2.06 0.07

Academy/95.1–95.5 Quartz sand, clay, ilmenite 0.10 5.40 10.4 0.28

Denise/29.5–29.9 Fine quartz sand, gray clay 0.01 3.80 2.27 0.09

Denise/84.0–84.3 Brown/black clay 0.08 3.40 10.0 1.97

Denise/108.2–108.6 Black clay 0.13 7.70 17.1 2.85

Oak/51.2–51.5 Medium quartz sand, silt, mica 0.01 5.90 2.24 0.14

Oak/83.3–84.0 Quartz sand, clay, lignite 0.11 4.90 19.7 2.06

Oak/130.6 Coarse quartz sand 0.01 0.50 5.64 0.19

Oak/130.9–131.6 Black sand, lignite 0.01 1.30 2.74 0.33

Church/88.3–88.6 Gray clay, mica 0.06 3.40 13.3 0.16

Church/88.9–89.2 Quartz sand, ilmenite 0.01 0.50 9.83 0.08

to total organic carbon contents of the A-horizon samples; 

however, THg contents were related to iron (Fe) contents in 

B-horizon samples, indicating Hg is complexed with organic 

carbon in surficial soils but apparently is sorbed to the Fe 

hydroxides that coat soil particles in the B horizon (Barringer 

and Szabo, 2006)

Isolated instances of THg contents that exceed background levels (0.10 to 0.15 mg/kg) in soils have been found. In 

Franklin Township, Gloucester County at the site of a former 

thermometer-manufacturing facility (fig. 1), THg contents in 

soil ranged from 0.127 to 0.258 mg/kg (Barringer and others, 1997). The THg content was 0.153 mg/kg in a subsoil 

sample (orange, Fe-rich sandy B horizon) from a presumed 

dump area on a former farm now residentially developed in 

Gloucester County (the CSL site; fig.1; Barringer and others, 

2006). Although the THg contents of the Gloucester County 

soils appear to be relatively high, they are within reported 

average soil Hg contents worldwide (0.022–0.625 mg/kg; 

Andersson, 1979). Grigal (2003) reports that an arithmetic 

mean of 0.150 mg/kg of Hg is found for soil in the United 

States, which agrees with background levels determined for 

the New Jersey Coastal Plain. Currently (2012), discoveries of THg contents of regional New Jersey soils that greatly 

exceed background levels or the average reported by Grigal 

(2003) are limited and instances of high levels generally 

remain elusive. The THg and acid-leachable Hg contents of 

organic-rich bankside soils of a tributary (Squankum Branch) 

to the Great Egg Harbor River (GEHR) near its headwaters 

were as high as 12.2 mg/kg, however (table 2; Barringer and 

others, 2010b). During the 1930s, the area around the headwaters of Squankum Branch was agricultural land (fig. 3) with 

fields and orchards that extended to within a few hundred feet 

of the stream. Residential development replaced much of the 

agricultural land during the 1960s into the 1990s; remaining 

land, as of 2012, is no longer farmed and is being developed. 

Streambed sediments contain weathered material from 

the geologic substrate, as well as soil particles brought in by 

runoff. Because the Coastal Plain soils, in general, are highly 

permeable, runoff from soils likely contributes fewer particles 

to the streams in the Coastal Plain than in regions with less 

permeable geologic substrates. Runoff from man-made impervious surfaces, however, can contribute metal-bearing particles 

to streams (see, for example, Barringer and others, 2010a; Barringer and others, 2011, and references therein). On the basis 

of existing data, the THg contents (from both total-digestion 

and recoverable (acid-leachable) analyses) of Coastal Plain 

streambed sediments generally are low. In the Great Egg Harbor River watershed (fig. 4), the THg contents of streambed 

sediments in forested areas were found to be about 0.03 mg/kg 

or less, but contents were greater (as much as 0.099 mg/kg) in 

several areas with urban land (Barringer and others, 2010a). 

In the streambed sediments at Hammonton Creek (HAMM) 
8 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

Table 2. Contents of trace elements in aquifer sediments from core samples from Squankum Branch, Gloucester County, 

New Jersey, 2009.

[Arsenic and lead contents determined using total digestion; mercury content determined as recoverable (acid-leachable) mercury. Site numbers are shown in 

figure 3. USGS, U.S. Geological Survey; ft bss, feet below streambed surface; mg/kg, milligrams per kilogram; As, arsenic; Hg, mercury; Pb, lead]

USGS site 

location Sample number Depth interval (ft bss)

As 

(mg/kg)

Hg 

(mg/kg)

Pb 

(mg/kg)

01410862

Left bank MA1 0-1.0 4.4 1.52 115

Left bank MA2 1.0-3.3 <1 0.29 3.83

Mid-stream MB1 0-3.3 <1 1.59 11.5

Right bank MC1 0-1.0 12.4 6.39 337

Right bank MC2 1.0-3.3 1

6.2 12.2 229

01410863

Left bank DA1 1.3-2.3 12.7 1.87 245

Left bank DA2 2.3-3.3 3.3 1.08 65.6

Mid-stream DB1 0-1.0 2

<1 0.66 16.7

Mid-stream DB2 2.0-3.0 3

<1 0.27 3.3

Right bank DC1 0-1.0 13.3 2.64 386

Right bank DC2 1.0-2.6 9.5 1.02 404

1

Recoverable As content was 11.4 mg/kg.

2

Recoverable As content was 0.34 mg/kg.

3

Recoverable As content was 0.23 mg/kg.

in Atlantic County (fig. 4), recoverable Hg contents were less 

than 0.035 mg/kg, except for site H3 (Hammonton Creek at 

Hammonton, USGS site number 01409414) where trace elements and phosphorus (P) from upstream sources tended to 

accumulate. There, the Hg content was 0.238 mg/kg (table 3). 

At the Squankum Branch site (fig. 3) where THg contents 

were high (as much as 12.2 mg/kg; table 2) in bankside soils, 

contents of recoverable Hg in the midstream bed sediment 

were higher (0.11 to 1.59 mg/kg) than those in sediments from 

other streams in the watershed.

Surface Water

Of the major streams that are underlain by sediments of 

the CKKD and that drain to the Atlantic Ocean, the GEHR and 

its tributaries are the most extensively studied with respect to 

Hg levels (both THg and MeHg). HAMM, a nearby stream, is 

a tributary to the Mullica River, another major Coastal Plain 

river (fig. 4). The upper reaches of the GEHR are surrounded 

by old and new urban land, whereas the lower reaches run 

mainly through forests and wetlands. The headwaters of 

HAMM are in old urban land that gives way to agricultural 

land farther downstream.

THg concentrations in unfiltered streamwater from 

the GEHR watershed, with the exception of streamwater in 

Squankum Branch, ranged from about 0.005 to 0.063 μg/L 

(Barringer and others, 2010a). For a variety of flow conditions, 

Hg concentrations tended to be higher in the more urbanized areas, and a greater proportion of the Hg was present on 

particles (unfiltered concentration minus filtered concentration) than in the forested wetlands areas. THg concentrations 

in unfiltered HAMM streamwater were generally lower (0.002 

to 0.015 μg/L) than those in most of the GEHR watershed 

(table 3B). In the course of this study, no measurements could 

be found for Hg evasion (a process where Hg is lost to the 

atmosphere) from New Jersey Coastal Plain streams, so the 

effect of this process on streamwater concentrations is not 

known.

THg concentrations in streamwater from Squankum 

Branch, in contrast to streamwater in the rest of the GEHR 

watershed that has been sampled during the past decade, 

have generally ranged from about 0.050 μg/L to 0.250 μg/L; 

the latter concentration is substantially higher than the New 

Jersey Surface Water Quality Standard of 0.050 μg/L. Squankum Branch flows next to a residential area where domestic 

well water has been found to be contaminated with Hg and is 

within an area that formerly contained fields with row crops 

and orchards. A recent study by Barringer and others (2010b) 
Regional Levels and Distribution of Mercury in the New Jersey Coastal Plain 9

Lake Hammonton

EXPLANATION

74°50'

75°

39°40'

39°30'

0 2 4 MILES

0 2 4 KILOMETERS

Great Egg Harbor River

watershed

Hammonton Creek

watershed

Lake

Hammonton

74°40'

74°44'

74°48'

39°36'

39°38'

0 1 2 MILES

0 1 2 KILOMETERS

Watershed boundary

Stream

Sampling site and identifier

Sewage treatment plant

Water

Barren land

Wetlands

Forest

Urban

Agriculture

G5

Land use (2002)

Delaware River

Hammonton Creek

watershed

Great Egg Harbor River

watershed

New Jersey

COASTAL PLAIN

Mullica River

watershed

G6

GB

GG

GF

GE

G7

GD

G5

GC

GA

G3

G1,2

G8

G4

G10 G9

H3

H2

H1 H4

H5

G6

GB

GG

GF

GE

G7

GD

G5

GC

GA

G3

G1,2

G8

G4

G10 G9

Figure 4. Land use (2002) within the non-tidal part of the Great Egg Harbor River watershed and Hammonton Creek watershed in New 

Jersey, with sampling sites from the U.S. Geological Survey 2006–08 investigations of mercury and methylmercury in the watersheds. 
10 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J. Table 3A. Contents of recoverable mercury, streambed sediments from Hammonton Creek and the Great Egg Harbor River and tributaries, Gloucester and Atlantic Counties, New Jersey, 2006–07. [Sites are shown in figure 4. USGS, U.S. Geological Survey; mg/kg, milligrams per kilogram; Hg, mercury; <, less than. Land use: U, predominantly urban land use; M, mixed urban, forested and agriculture; A, predominantly agriculture; F/W, predominantly forested wetland] USGS station number USGS station name (short site name) Land use Date of sampling Recoverable Hg (mg/kg) 140941198 Hammonton Creek at Hammonton Lake Dam (H1)

U 03/14/07 0.007

39375907446031 Hammonton sewage treatment plant outfall (H2)

U 03/14/07 0.010

01409414 Hammonton Creek at Hammonton (H3)

M 03/14/07 0.238

01409416 Hammonton Creek at Wescoatville (H4)

A 03/14/07 0.035

01409418 Hammonton Creek at Nesco (H5)

A 03/14/07 0.015

01410789 Tributary 2 at Winslow Crossing (GA)

U 10/26/06 0.017

01410810 Fourmile Branch at New Brooklyn (GC)

M 10/16/06 0.025

01410865 Squankum Branch at Malaga (GD)

U 10/16/06 0.028

01410135 Hospitality Branch at Blue Bell (GE)

M 10/16/06 0.099

01411071 Hospitality Branch near Folsom (GF) F/W 10/26/06 0.01001411140 Deep Run at Weymouth (GG) F/W 10/16/06 <0.007201410770 Great Egg Harbor River above pond at Berlin (G1)

U 12/06/06 0.046

01410784 Great Egg Harbor River near Sicklerville (G3)

M 12/06/06 0.033

01410788 Great Egg Harbor River at Winslow Crossing (G4)

M 12/06/06 <0.0072

01410820 Great Egg Harbor River near Blue Anchor (G5) F/W 12/06/06 0.02401411000 Great Egg Harbor River at Folsom (G7) F/W 12/06/06 <0.007201411110 Great Egg Harbor River at Weymouth (G10) F/W 12/06/06 0.008
Regional Levels and Distribution of Mercury in the New Jersey Coastal Plain 11

Table 3B. Values of pH and concentrations of total mercury and methylmercury in unfiltered and filtered samples of streamwater from Hammonton Creek and the Great Egg Harbor River and tributaries, Gloucester and Atlantic Counties, New Jersey, 2006–07.[Sites are shown in figure 4. USGS, U.S. Geological Survey; UTHg, total mercury in unfiltered water; FTHg, total mercury in filtered water; UMeHg, methylmercury in unfiltered water; FMeHg, methylmercury in filtered water; <, less than; μg/L, micrograms per liter, ng/L, nanograms per liter; --, no data; *, collected by New Jersey Department of Environmental Protection. Land use: U, predominantly urban land use; M, mixed urban, forested, and agriculture; A, predominantly agriculture; F/W, predominantly forested wetland]

USGS station 

number USGS station name (short site name) Land use Date of sampling pH UTHg (ng/L) FTHg (ng/L) UMeHg (ng/L) FMeHg (ng/L)

140941198 Hammonton Creek at Hammonton Lake Dam (H1)

U 12/05/06 6.87 0.011 0.010 0.371 0.320

05/09/07 6.95 0.014 0.005 -- --09/20/07 7.13 0.002 0.001 -- --

10/23/08* -- -- -- 0.10 --

02/11/09* -- -- -- 0.22 --

39375907446031 Hammonton sewage treatment plant outfall (H2)

U 03/14/07 6.50 0.028 0.006 -- --

05/09/07 7.33 0.009 0.003 -- --09/20/07 7.11 0.000 0.000 -- --

01409414 Hammonton Creek at Hammonton (H3)

M 12/05/06 6.26 0.015 0.012 0.172 0.140

05/02/07* -- -- -- 0.22 --

05/09/07 -- 0.008 0.016 -- --

08/16/07* -- -- -- 0.97 --

09/20/07 5.92 0.013 0.006 -- --

11/02/07* -- -- -- 0.12 --

03/19/08* -- -- -- 0.18 --10/23/08* -- -- -- 0.15 --

02/11/09* -- -- -- 0.22 --

01409416 Hammonton Creek at Wescoatville (H4)

A 12/05/06 6.51 0.009 0.007 0.139 0.110

09/20/07 6.66 0.012 0.005 -- --

01409418 Hammonton Creek at Nesco (H5)

A 12/05/06 5.91 0.006 0.005 0.121 0.100

05/09/07 5.92 0.003 0.005 -- --09/20/07 6.39 <0.010 <0.010 -- --
12 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J. Table 3B. Values of pH and concentrations of total mercury and methylmercury in unfiltered and filtered samples of streamwater from Hammonton Creek and the Great Egg Harbor River and tributaries, Gloucester and Atlantic Counties, 2006–07.—Continued [Sites are shown in figure 4. USGS, U.S. Geological Survey; UTHg, total mercury in unfiltered water; FTHg, total mercury in filtered water; UMeHg, methylmercury in unfiltered water; FMeHg, methylmer- cury in filtered water; <, less than; μg/L, micrograms per liter, ng/L, nanograms per liter. Land use: U, predominantly urban land use; M, mixed urban, forested and agriculture; A, predominantly agriculture; F/W, predominantly forested wetland] USGS station number USGS station name (short site name) Land use Date of sampling pH UTHg (μg/L) FTHg (μg/L) UMeHg (μg/L) FMeHg (μg/L) 01410789 Tributary 2 at Winslow Crossing (GA)

U 10/26/06 6.37 0.002 0.001 0.17 0.14

01410810 Fourmile Branch at New Brooklyn (GC)

M 10/16/06 5.93 0.026 0.024 0.37 0.34

01410865 Squankum Branch at Malaga (GD)

U 10/16/06 6.03 0.187 0.159 0.37 0.31

01410135 Hospitality Branch at Blue Bell (GE)

M 10/16/06 5.71 0.005 0.005 0.24 0.22

01411071 Hospitality Branch near Folsom (GF) F/W 10/26/06 5.74 0.007 0.006 0.43 0.3901411140 Deep Run at Weymouth (GG) F/W 10/16/06 4.49 0.007 0.006 0.54 0.4601410770 Great Egg Harbor River above pond at Berlin (G1)

U 11/02/06 6.58 0.020 0.013 0.35 0.22

07/03/07 5.79 0.063 0.017 2.94 0.75

01410784 Great Egg Harbor River near Sicklerville (G3)

M 11/02/06 5.59 0.009 0.007 0.18 0.16

01410788 Great Egg Harbor River at Winslow Crossing (G4)

M 11/02/06 5.50 0.008 0.007 0.50 0.48

01410820 Great Egg Harbor River near Blue Anchor (G5) F/W 11/02/06 5.63 0.010 0.009 0.32 0.30

07/03/07 5.92 0.011 0.010 0.29 0.21

01411000 Great Egg Harbor River at Folsom (G7) F/W 11/02/06 4.78 0.012 0.011 0.43 0.42

07/03/07 5.96 0.016 0.013 1.19 1.02

01411110 Great Egg Harbor River at Weymouth (G10) F/W 11/02/06 4.79 0.009 0.008 0.20 0.18

07/03/07 5.71 0.012 0.009 0.87 0.70
Possible Sources of Inorganic Mercury in the New Jersey Coastal Plain 13

has shown that (unfiltered) shallow groundwater containing 

high concentrations of THg (1.80 to 5.65 μg/L) discharges 

to Squankum Branch where it flows past the site with Hgcontaminated groundwater. It is plausible that, where other 

Coastal Plain streams flow past sites of Hg-contaminated 

groundwater, the streamwaters also receive Hg-rich groundwater discharge; potential instances of local groundwater effects 

on surface-water quality, other than at Squankum Branch, 

have not been investigated to date (2012) by the NJDEP or the 

USGS.

Effects of mercury in the Coastal Plain acidic surfacewater bodies are seen in the biota. Fish-consumption advisories have been posted for most streams and lakes because 

fish tissues commonly have MeHg concentrations that exceed 

1.0 milligram per kilogram (mg/kg) wet weight (Academy 

of Natural Sciences, 1994). A USGS nationwide study of 20 

watersheds ranked the GEHR as one of the top six watersheds in the country with the highest concentrations of MeHg 

(wet weight) in fish and with MeHg and THg in streamwater 

(Brumbaugh and others, 2001).

Possible Sources of Inorganic Mercury 

in the New Jersey Coastal Plain

It was concluded early in the investigations of Hg in the 

New Jersey Coastal Plain that a natural (geologic) source of 

Hg was unlikely (Dooley, 1992); however, no chemical analyses of aquifer sediments were available, only mineralogical 

analyses. Given the former (mainly agricultural) and existing 

(residential) land use in the areas of contaminated groundwater, numerous anthropogenic sources were considered likely.

Anthropogenic Sources

Because of the common use of many Hg-bearing products and the abundance of Hg in coal used at power-generating 

stations, numerous anthropogenic sources can contribute Hg to 

the environment. In addition to emissions from power plants, 

some sources of Hg are emissions from other industrial plants, 

incinerators, and crematories and, as of 2012, agricultural 

chemicals (pesticides and fungicides). Hg, as phenyl mercuric acetate, was used as a fungicide in house paint during the 

1950s through 1980s, and was thereafter voluntarily removed 

by paint manufacturers. Mercury may still be present in some 

household chemicals such as bleach and drain cleaner as a 

result of its use as a catalyst at the chlor-alkali plants that produce these chemicals; the industry has attempted to reduce Hg 

in these materials (The Chlorine Institute, Inc., 2000), and the 

process is by now (2012) outmoded. 

Atmospheric Deposition

Atmospheric deposition of Hg has been studied extensively since the 1970s; much of the Hg deposited from the 

atmosphere came from emissions from industry and coal-fired 

power plants (Glass and others, 1986; Lindberg, 1987; Nriagu 

and Pacyna, 1988; Glass and others, 1991; Slemr and Langer, 

1992). In New Jersey, a NJDEP study found that background 

Hg concentrations in air ranged from 0.8 to 20 nanograms 

per cubic meter of air (ng/m3); Hg in air near a municipal 

solid waste incinerator, with a median value of 2.5 ng/m3, was 

within global background levels (Greenberg and others, 1992). 

In the 1990s, Hg concentrations in precipitation ranged from 

5 to 60 nanograms per liter (ng/L) with an apparent trend of 

decreasing concentrations with distance from highly urbanized 

areas (Barringer and others, 1997); these concentrations were 

measured during a time in which the 1990 Amendments to 

the Clean Air Act of 1970 (http://epa.gov/air/caa/caa_history.

html—accessed 2/13/12) would have begun to take effect. 

Studies have shown that the levels of Hg in soils and surface waters tend to increase with the percentage of land cover 

that is wetlands. This increase occurs because atmospherically 

deposited Hg has been sequestered by organic matter in wetlands soils and is transported in porewaters and surface waters 

with organic carbon (Mierle and Ingram, 1991; Krabbenhoft 

and others, 1995; Hurley and others, 1995; Kolka and others, 

1999; Wu and others, 2004). In the Atlantic Coastal Plain, 

the extensive wetlands areas can act as sinks for atmospherically deposited Hg. The levels of THg in various media of the 

Coastal Plain of South Carolina tend to be higher than those in 

upland areas of the Piedmont Physiographic Province, which 

are farther inland (Guentzel, 2009). In the New Jersey Coastal 

Plain (GEHR watershed), an increase in the percentage of the 

THg as MeHg was associated with an increase in the percentage of wetlands (Barringer and others, 2010a).

Although there is retention of atmospherically deposited 

THg in wetlands soils in the New Jersey outer Coastal Plain, 

the Hg concentrations in groundwater underlying developed 

areas clearly exceed the background concentrations (less than 

0.01 μg/L) in undeveloped areas (Barringer and Szabo, 2006). 

Therefore, sources other than just atmospheric THg need 

to be sought in the residentially developed areas. Obvious 

point sources, such as landfills, industrial operations, military 

installations, cemeteries, and golf courses, have been investigated as potential sources of the THg that contaminates the 

groundwater (Barringer and others, 1997). These potential 

sources have not, in most cases, been conclusively linked to 

the residential areas where the THg-contaminated groundwater is found (Barringer and others, 1997). Although the point 

sources listed above have yet to be identified as important 

sources of the widespread domestic well-water contamination 

by Hg, groundwater at or near various landfills (not associated 

with the residential areas) has, in some cases, been affected 

(Barringer and others, 1997). 
14 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

Agricultural Chemicals

Given that many of the residential areas where THg-contaminated groundwater has been found are on former agricultural land, the possibility of mercurial pesticide applications as 

a source was explored (Barringer and others, 1997). THg-contaminated domestic-well water was first observed in 1982, and 

discoveries of THg in well water has continued throughout 

the 1980s to the present (2012). The age of the water reaching 

domestic wells that ranged in depth from about 50 to 120 ft 

was estimated in 1997 on the basis of model simulations to be 

about 10 to 35 years (Barringer and others, 1997); more recent 

age dating and groundwater modeling (Modica and others, 

1998; Barringer and MacLeod, 2001; Kauffman and others, 

2001; Cauller and Carleton, 2006) indicate that these ages are 

young by a few years at most. The housing developments generally were completed in the late 1970s; at that time and later, 

the aggregate of pumping domestic wells likely would have 

altered flow paths and groundwater velocities. The appearance 

of the THg in domestic-well water less than 10 years after 

the developments were completed indicates that the THg was 

most likely already present in the soils and, perhaps, already 

leaching to groundwater. The leaching process probably was 

being accelerated by the disturbance of soils during the residential development. Thus former mercurial pesticide applications appeared to be a viable source of THg to groundwater. 

Mercuric chloride (HgCl2) at 7.4 x 107 μg/L is highly 

soluble in water (Merck, 1983). HgCl2 was commonly used as 

an agricultural pesticide during the mid-20th century; recommended application rates were as great as 1 x 109

 mg per acre 

per year (Murphy and Aucott, 1999; Barringer and others, 

1997 and references therein). Pesticides containing Hg were 

recommended for use on lawns for crabgrass control during 

the mid 20th century (Wolf and Engel, 1948). Also, pesticides with Hg were used on row crops during the same time 

period (Murphy and Aucott, 1999). Therefore, soils in agricultural areas later to become residential areas could well have 

received THg from both types of application. Additionally, 

fertilizers could contribute Hg to soils; analysis of a commercial 20-20-20 fertilizer solution (mixed according to manufacturer’s directions) identified 282 μg/L of Hg in the solution 

(Barringer and MacLeod, 2001).

Although soils may have received substantial amounts of 

THg through pesticide applications, leaching of soluble HgCl2

over time, particularly during soil disturbance, may have substantially reduced any residual evidence of these applications 

to soils. Leaching experiments indicate that Hg can be readily 

removed from the sandy sediments (from the Bridgeton and 

Cohansey Formations) by water, road-salt solutions, and fertilizer solutions (Barringer and MacLeod, 2001). Volatilization at 

the soil surface also may have removed Hg, although experiments have shown that volatilization of HgCl2 from sandy soils 

resulted in relatively small losses to the atmosphere (Poelstra 

and others, 1974; Hogg and others, 1978). In any case, little 

if any trace of pesticide Hg has been observed in residential 

soils examined as part of USGS studies as of 2005 to 2006. 

As discussed above, results of analyses indicate that the THg 

concentrations in soil samples from residential developments 

(typically less than 0.050 mg/kg) were substantially less than 

the THg concentrations in soils from undisturbed forested 

areas (about 0.10–0.15 mg/kg), where inputs of THg would 

be from geologic sources and atmospheric deposition only 

(Barringer and others, 1997; Barringer and Szabo, 2006). The 

disparity between Hg contents of undisturbed and disturbed 

soils (where the Hg content in undisturbed soils is higher than 

that of disturbed soils) is attributed to mobilization of Hg 

during disturbance created by a change in land use (Barringer 

and Szabo, 2006). The assumption here is that Hg originally 

present in the agricultural soils was lost to evasion and to 

leaching and transport on particles to the water table when the 

soils were disturbed (horizons overturned and mixed) during 

residential development.

A recent (2008–09) investigation by the USGS and the 

NJDEP at Squankum Branch in a former agricultural area of 

Gloucester County, New Jersey, found that high concentrations 

of THg are present in bankside soils. As mentioned above, 

samples of soil and sediment from the banks of Squankum 

Branch, a small headwaters stream (fig. 3; table 2) contained 

as much as 12.2 mg/kg of recoverable (HCl-leachable) Hg—a 

content about two orders of magnitude greater than the content 

of undisturbed forested soils reported by Barringer and others 

(1997). The Squankum Branch soils with the high Hg contents 

were rich in organic carbon, but organic-rich soils in the area 

did not universally contain such high Hg contents. Moreover, 

elevated contents of arsenic (As) and lead (Pb) in some of the 

soil samples from Squankum Branch watershed (table 2) indicate that the organic soils may have retained agricultural pesticide residues, such as lead arsenate that was used on orchards 

(Barringer and others, 1998, Murphy and Aucott, 1998), or 

trapped residues transported in runoff to the stream. Further, 

shallow groundwater entering the stream from the banks 

contained THg in concentrations as great as 5 μg/L (Barringer 

and others, 2010b), a concentration that substantially exceeds 

the New Jersey MCL. Additionally, shallow groundwater also 

contained greater than background concentrations of nitrate 

(NO3

-

), which may have derived from the former use of fertilizers or from septic tanks, which are common in rural agricultural areas. These findings are the first evidence that shallow 

groundwater can contain high concentrations of THg in a 

former agricultural area. 

Household Sources

Attempts to identify anthropogenic inputs of Hg in deep 

groundwater (> 60 ft below land surface) have been complicated by the presence of NO3

- and chloride (Cl-

), which are 

common to both agricultural fertilizers and septic-system 

effluents. In several unsewered residential areas, elevated concentrations of NO3

- , some exceeding the New Jersey MCL of 

10 mg/L as nitrogen (N), were present in domestic well water 

(data in Barringer and MacLeod, 2001). For some of these 

wells, strong positive relations between NO3

- and magnesium 
Possible Sources of Inorganic Mercury in the New Jersey Coastal Plain 15

(Mg) and barium (Ba) appear indicative of agricultural inputs 

of lime (dolomite) and fertilizer, as indicated in the study 

by Kozinski and others (1995). Domestic well waters also 

contained concentrations of Cl- that were much greater than 

background levels of 3 to 5 mg/L (Yuretich and others, 1981; 

Kozinski and others, 1995; Barringer and others, 2006); in one 

study of a residential area (the CSL site; fig. 1) near Squankum 

Branch, methylene blue active substances (MBAS), which 

include surfactants, were found in well water (Barringer and 

others, 2006), indicating likely inputs to shallow groundwater 

from the septic systems.

A household septic system in the 1980s and 1990s could 

have received Hg present as a contaminant in bleach and in 

sodium hydroxide (NaOH) used as drain cleaner. Calculations 

for bleach use show that other household water use (presumed 

to not contain Hg) would be sufficient to dilute such Hg to 

negligible concentrations (Barringer and others, 1997), and the 

same can be shown to be true for NaOH, which would be used 

far less often than bleach. On the basis of limited analyses 

of leach-field-effluent samples collected by the USGS (Barringer and others, 2006), septic-system effluent in the leach 

fields sampled did not contribute extensive amounts of Hg to 

subsoils. Low effluent inputs of Hg support the earlier calculations of likely septic-system inputs of Hg from household 

chemicals (Barringer and others, 1997). Septic-system effluent 

primarily appears to create a geochemical environment in 

which Hg is mobilized, rather than representing a major source 

of Hg in the New Jersey Coastal Plain (Barringer and Szabo, 

2006). Nevertheless, samples of backwash brines (table 4) 

were collected from several common household water-treatment systems; these were water-softening cation-exchange 

units or pH-adjustment units, not the Hg-removal point-ofentry-treatment systems supplied by NJDEP to households. 

These samples were collected in 2008 at a site in Burlington 

County with Hg-contaminated well water. The brines contained as much as 9 μg/L of THg. (Most homeowners use 

tanks filled with limestone chips for pH neutralization; these 

typically use NaCl for backwashing the units.) In the case of 

utility treatment systems, where the unit may use NaOH as a 

neutralizer, this chemical could have been contaminated with 

Hg if it was initially produced in a chlor-alkali plant (where 

Hg is used in the production process). Voluntary efforts on 

the part of the chlorine industry (The Chlorine Institute, Inc., 

2000) have presumably lowered the amount of Hg in NaOH, 

and the chlor-alkali process that used Hg is very nearly phased 

out; thus any Hg in NaOH used in a utility treatment unit 

has presumably declined over time. However, for the recent 

samples of household backwash brines reported in table 4, 

the THg is predominantly contributed by the contaminated 

groundwater that has passed into the system because domestichousehold treatment systems do not use NaOH. The backwash 

THg is routinely cycled back to subsoils along with other 

components of the backwash brine such as Cl-. The backwash 

is released in some cases to septic systems and, in others, 

through dry wells to the subsoils. As evidenced by high Clconcentrations in groundwater in residential areas and further 

studies of brine wastes (Szabo and others, 2008; Szabo and 

others, 2010a), such backwash solutions can reach the water 

table and move farther into the aquifer.

Pesticide application appears to be a likely anthropogenic 

source of THg in CKKD water because most wells contaminated by THg were installed on former agricultural land (Barringer and others, 1997). The findings at Squankum Branch 

help to support this contention. In the latter part of the 20th 

century, household inputs of THg-bearing substances, such as 

bleaches and paints, appear to have been a minor source (Barringer and others, 1997), although the recent backwash-brine 

data do indicate an additional and perhaps more substantial 

household source. 

Other Anthropogenic Sources

During the Hg investigations by USGS and NJDEP in the 

1990s, it was noted that many of the residential areas with Hgcontaminated well water were distributed along defunct railroad rights-of-way. Use of Hg-rich coal in steam engines may 

have affected atmospheric THg, but no data on other railroad 

uses of Hg were available at the time (Barringer and others, 

1997). A study in France, however, (Bollen and others, 2008) 

showed that groundwater was contaminated with Hg at a site 

where wood was preserved (kyanized) with the highly soluble 

HgCl2. Railroad ties once presented a major use of such wood, 

and it may be that kyanized wood was used in the New Jersey 

railroads. If so, such use may represent another anthropogenic 

source of Hg to Coastal Plain soils and waters. As yet, this 

possibility has not been explored.

The possibility that leachate from landfills affected 

groundwater was considered, but it appears that groundwater 

in landfill areas does not flow toward the nearby residential 

areas studied in the 1980s and 1990s (Barringer and others, 

Table 4. Concentrations of selected constituents and values 

of pH in backwash brines from household water-treatment 

systems at three domestic wells in Burlington County, 

New Jersey, 2008–09.

[USGS, U.S. Geological Survey; μg/L, micrograms per liter; mg/L, milligrams per liter; THg, total mercury; DO, dissolved oxygen; Cl-, chloride; 

na, not analyzed]

Type of well/ 

USGS well 

number

THg,

unfiltered

(μg/L)

THg,

filtered

(μg/L)

DO

(mg/L)

pH

(units)

Cl-

(mg/L)

Domestic/well 

051764 6.9 na 5.09 6.44 5,300

Domestic/well 

051766 9.4 0.260 11.8 5.89 9.13

Domestic/well 

051789 5.4 0.091 na na 10.5
16 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

1997). Landfills do emit Hg in gases that vent to the atmosphere (Kim and Kim, 2002; Feng and others, 2004; de la 

Rosa and others, 2006). Thus, in parts of southern New Jersey, 

atmospheric deposition may contain some Hg acquired locally 

from landfill emissions.

Natural Sources

An early investigation by Dooley (1992) concluded that 

the mineralogy of CKKD sediments precluded a viable geologic source of THg, so the aquifer sediments were unlikely 

to supply Hg to the groundwater. At the time of Dooley’s 

study (1992), no data on the Hg contents of aquifer sediments, 

particularly clay, were available. As of 2012, several studies 

have shown that organic-rich clays that are present in lenses 

throughout the aquifer system can contain substantial contents 

of Hg (Barringer and others, 1997; table 1). Data obtained 

since 1992 (discussed below) indicate that, in the absence of 

evidence of anthropogenic inputs of Hg to the CKKD sediments, a natural source cannot be completely ruled out.

Concentrations of Hg in groundwater in undeveloped 

areas, as of 2012, have been found to be low (less than 

0.01 μg/L), indicating that under conditions that are not 

affected by human activities, Hg in aquifer sediments (particularly clays) is not extensively released to groundwater. 

To test whether proximity to clay lenses could affect Hg 

concentrations in groundwater, clusters of observation wells 

were screened above and below clay lenses (Barringer and 

others, 2005). Results of analyses of water from these wells 

did not, in most cases, indicate higher Hg concentrations in 

water samples collected near the clay lenses (Barringer and 

others, 2005). Lenses of kaolinitic light-colored clays abound 

throughout the CKKD and likely contain little Hg because 

they contain little organic matter. For the dark, organic-rich 

clays in which Hg contents are relatively high (as much as 

0.13 mg/kg based on data in table 1), the mechanism by which 

the Hg is released to groundwater has yet to be determined. 

Previously conducted studies (Barringer and others 1997; 

Barringer and Macleod, 2001; Barringer and others, 2005; 

Barringer and others, 2006; Barringer and Szabo, 2006) 

indicate that where concentrations of Hg are elevated (greater 

than background levels) or at contaminant levels (2 μg/L or 

greater), anthropogenic sources of Hg are likely to be present and that mobilization of Hg by anthropogenic chemicals 

from soils to groundwater, as of 2012, appears to be the major 

mechanism by which groundwater becomes contaminated with 

Hg (Barringer and Szabo, 2006). 

None of the studies has shown conclusively that high 

levels of Hg are released from aquifer materials; however, 

there are no data that conclusively rule out this possibility. 

Although the sediments that compose the CKKD do not contain common Hg-bearing minerals such as sulfides, the limited 

chemical analyses of CKKD sediments indicate that the Hg 

contents of gray to black, organic-rich clays, which range from 

0.060 to 0.13 mg/kg (table 1), are substantially greater than the 

contents of sand samples (less than 0.010 mg/kg). The higher 

Hg content of clay relative to that of sand also was reported in 

Barringer and others (1997).

Although a mechanism for release of Hg from aquifer 

sediments (clays) has not been determined, recent sampling 

indicates that Hg might be released from geologic materials. 

A domestic well at a relatively isolated house amid cranberry 

bogs was sampled in 1998 during a time when the house 

was occupied and the well was pumped on a regular basis. 

The well (number SUSCP30, fig. 1) was completed at 101 ft 

below land surface in the CKKD below four clay layers. At 

that time, the THg concentration in filtered well water was 

0.56 μg/L, substantially greater than background levels but 

not considered to be at contaminant levels (that is, in excess of 

2 μg/L). In 2006, the well was resampled after the house had 

been unoccupied for several months. Multiple water samples 

were collected during the well purging; all contained concentrations of THg substantially greater than the MCL, ranging 

from about 9.7 to 11 μg/L (Szabo and others, 2010b). Other 

constituents showed virtually no change from 1998 levels 

(table 5). The only substantial chemical difference was in the 

Table 5. Field properties, concentrations of total mercury, and dissolved major and trace constituents in well water from domestic 

well SUSCP30 in cranberry bog area in New Jersey, 1998 and 2006. 

[Values are for filtered water, except for field properties (T, SC, DO, pH), which were measured in unfiltered water. T, temperature; oC, degrees Celsius; SC, 

specific conductance; μS/cm at 25oC, microsiemens per centimeter at 25 degrees Celsius; DO, dissolved oxygen; mg/L, milligrams per liter; Ca2+, calcium, 

Mg 2+, magnesium; Na+, sodium, K+, potassium, Cl-, chloride; SO4

2-, sulfate; NO2

- +NO3-, nitrite + nitrate; NH4

+

, ammonium; THg, total mercury; Fe, iron; 

Mn, manganese; μg/L, micrograms per liter]

Date T 

(

o

C)

SC 

(μS/cm 

at 25oC)

DO 

(mg/L) pH Ca2+(mg/L)

Mg2+

(mg/L)

Na+

(mg/L)

K+

(mg/L)

Cl-

(mg/L)

SO4

2-

(mg/L)

NO2

-

+NO3

-

(mg/L 

as N)

NH4

+

(mg/L 

as N)

THg

(μg/L)

Fe

(μg/L)

Mn

(μg/L)

1998 13.60 53.0 1.34 4.13 1.00 1.00 5.70 0.60 13.0 0.40 0.080 0.050 0.56 10.0 11.0

2006 13.80 69.0 0.52 4.96 1.14 1.05 7.87 0.68 15.9 0.70 0.076 0.007 10.7 8.07 12.6
Factors Affecting Mobility 17

dissolved oxygen (DO) concentration, which had declined 

from 1.34 to 0.52 mg/L. In both samplings, anthropogenic 

chemicals, such as pesticides and volatile organic compounds 

(VOCs), were not detected in the well water, and no clear 

effects of anthropogenic activities on the water chemistry were 

apparent. The clay lenses reported in the log for this domestic 

well are probably laterally extensive because cranberry bogs 

are developed only in areas where drainage is restricted by 

clays beneath the land surface because flooding of the bogs is 

needed for harvest. Therefore, it is unlikely that any surficial 

applications of anthropogenic chemicals would have been 

transported to depth at this site, and there is no evidence from 

the groundwater chemistry that this has occurred. It appears 

that water withdrawals had, in 1998, moved water with 

relatively low (1.34 mg/L) but measureable concentrations of 

oxygen to the well. After the water withdrawals ended, less 

oxygenated water flowed toward the well screen; without the 

pumping, water would have been under ambient flow conditions, and flowpaths probably would have been more local 

than when the well was being pumped. This change in flow 

conditions apparently caused a shift to more reducing conditions in the volume of aquifer surrounding the well, in turn, 

leading to a substantial increase in the THg concentration in 

the water locally. In the absence of an obvious anthropogenic 

source, the source of the THg could be geologic in nature. The 

clays are described as “yellow” and “white” in the driller’s log 

and, thus, are probably low in organic matter, but organic-rich 

materials could be present that were not recorded in the driller’s log. Indeed, the increasingly reducing conditions when 

pumping ceased indicates the likelihood that, at depth, organic 

material is being microbially degraded. Clearly a source of Hg 

is present at depth (possibly lignite, which is present locally 

in the deeper aquifer sediments (Eric Jacobsen, U.S. Geological Survey, oral commun., 2010)) that appears to be near the 

well. There is no evidence for an anthropogenic source of Hg. 

The data that exist for the entire region, as of 2012, indicate 

that THg is partitioned selectively into aquifer materials, such 

as the organic-rich clays. Lignite fragments could be enriched 

in Hg, as lignites are known to contain Hg concentrations 

that range from less than 0.006 mg/kg to 15 mg/kg (Yudovich 

and Ketris, 2008); as of 2012, no analyses are available for 

lignite from the CKKD. Such Hg-enriched materials (clays 

and, possibly, lignites) are distributed unevenly throughout the 

aquifer, occurring wherever low energy environments, such 

as lagoons and swamps, existed in the near-shore and deltaic 

Miocene Epoch landscape in which the CKKD sediments were 

deposited.

Factors Affecting Mobility

Several major factors affect how THg is mobilized in 

soils, within the aquifer, and in streamwater. Determining 

whether the Hg is mainly particulate or dissolved is important; 

if Hg is dissolved, then a determination of its chemical form 

(ionic or elemental) can be used to predict its chemical behavior through the soil column or along groundwater flowpaths. 

Because streams in the Coastal Plain during base flow receive 

most of their water from groundwater discharge, mobile 

mercury in groundwater could be delivered to streams where 

chemical reactions can change the form of mercury and, thus, 

its partitioning behavior and mobility. Other important factors 

affecting mercury mobility are the chemical constituents that 

accompany the THg.

Mercury Forms

As of 2012, studies conducted by the USGS and NJDEP 

have not included sampling to determine whether some of the 

THg present in Coastal Plain streamwaters and groundwater 

is in dissolved form or whether the THg that passes 0.45-mm 

filters is largely colloidal. Studies (Ryan and Gschwend, 1994; 

Szabo and others, 2002) have shown that colloids are present in CKKD groundwater, and it has been hypothesized that 

some THg is transported within the aquifer on colloids (Barringer and Szabo, 2006). (Recent sampling (2009–10) at the 

William J. Hughes Technical Center (WJHTC) indicates that 

THg-bearing colloids are present, as discussed below.) There 

is ample evidence that some well-water samples contain THg 

on particles larger than 0.45 mm. The presence of particulate 

THg in domestic well water was first found in samples collected by NJDEP in 1991; roughly one-third to one-half of 

the THg apparently was particulate (unfiltered THg – filtered 

THg = particulate THg; Barringer and others, 1997; Barringer and MacLeod, 2001). Particulate THg also was found 

in groundwater samples collected by the USGS (Barringer 

and Szabo, 2006), though this form was rarely predominant. 

During recent (2012) sampling at the Burlington County site 

(fig. 1) several domestic wells (051789, 051765, and 051766) 

produced water with greater than background or contaminant 

levels of THg. The first-draw samples from the domestic 

wells tended to contain particulate THg, and concentrations 

of THg tended to decline in subsequent samples collected 

during purging (Szabo and others, 2010b). The data do not 

clearly indicate whether changes in DO concentrations during 

purging affected the concentrations of particulate Hg. Ryan 

and Gschwend (1994) showed that greater concentrations of 

colloids were present under reducing conditions, but in the 

USGS study, the DO concentrations measured in first-draw 

and subsequent samples from the domestic wells differed only 

slightly and did not indicate changes from anoxic or suboxic 

conditions to oxic conditions as pumping proceeded. Samples 

were collected from these wells at household taps throughout the day, without purging, to simulate householder use. 

Particulate THg was present in the samples (fig. 5; table 6), 

but the percentage of particulate THg was different at each 

well. In addition, samples of shallow groundwater discharging 

to Coastal Plain streams also were found to contain particulate 

THg; the particulate form was especially prevalent in urban 

areas (Barringer and others, 2010a), which probably indicates 
18 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

EXPLANATION

Unfiltered mercury

Filtered mercury

1.40

1.20

1.00

.80

.60

.40

.20

.00

6:006:307:007:308:008:309:009:30

10:0010:3011:0011:3012:0012:3013:0013:3014:0014:3015:0015:3016:0016:3017:0017:3018:00

Time of sampling

Concentration of mercury in

unfiltered and filtered samples,

in micrograms per liter

Well 051789

Figure 5. Concentrations of total mercury in unfiltered and filtered water collected throughout the day from domestic well 051789 

completed in the Kirkwood-Cohansey aquifer system, Burlington County, New Jersey, June, 2009. (Particulate mercury is the difference 

between unfiltered and filtered concentrations.)

the presence of reducing conditions in the aquifer in urban 

areas. Such reducing conditions, which appear to be randomly 

distributed spatially, have been shown to be associated with 

plumes of septic-system effluent in some instances (Barringer 

and others, 2006).

In a cooperative study with NJDEP during 2010–11, 

leaching experiments were performed by the USGS on 

subsoils (B horizon or zone of accumulation) from a forested 

area near the Burlington County residential site (fig. 1) where 

Hg-contaminated groundwater was present. The B-horizon 

soils, which were orange and rich in Fe hydroxides, contained 

0.01 mg/kg of THg. These soils were composited from several 

cores, mixed well, and loaded into columns that were irrigated 

from the column base (to avoid gravity-affected collection 

of particles at the bottom screen) with 4 liters of solution at a 

rate of 5.9 to 6.5 milliliters per minute, simulating conditions 

of rapid recharge following a storm. Three leaching solutions 

consisted of a 0.1 molar NaCl solution to simulate roadsalt 

leaching, a 20-20-20 fertilizer solution, and de-ionized water 

(Reilly and others, 2012). In all cases, the THg that was 

removed by the leaching solutions was particulate THg at 

concentrations of about 0.28 to 0.45 μg/L (table 7). A substantial amount of particulate Fe also was removed in the leachate 

from the NaCl and de-ionized water experiments, probably 

indicating that the THg removed was sorbed to Fe hydroxide 

particles. In the fertilizer experiments, the 20-20-20 fertilizer 

solution contained a substantial concentration of Fe, some of 

which was particulate. The Fe removed in the leachate also 

was predominantly particulate; these particles may have been 

the dominant vehicle for THg removal from soil to water table 

as indicated by Barringer and Szabo (2006). Illuviated layers 

of clays and hydroxides form naturally at the water table of the 

CKKD in undeveloped areas (Richard Walker, U.S. Geological Survey, oral commun., 2010) so it is reasonable to expect 

that Hg-rich particles in soils will be leachable and mobile, 

particularly when the soils are disturbed.

As yet, it is not known conclusively whether THg on 

particulates persists in that form once the water table is 

reached. Under certain circumstances (reducing conditions), it 

appears that Fe hydroxides in subsoils and aquifer sediments 

are reductively dissolved, and associated (presumably sorbed) 

THg is released (fig. 6; Barringer and MacLeod, 2001; Barringer and others, 2006). Under sulfate-reducing conditions, 

the released THg also may be reduced to elemental Hg (Hg0

) 

by magnetite (Wiatrowski and others, 2009), which may be 

formed along with sulfides during microbial activity (Burton 

and others, 2011). Whether the Hg remains in dissolved form 

as Hg0 or whether it is re-oxidized and becomes re-associated 

with particles is not known, but the presence of THg-bearing 

particulate material in some well-water samples indicates this 

association does occur (Barringer and Szabo, 2006). Most 

of the well-water samples collected by county agencies and 

NJDEP were unfiltered; a few filtered samples were collected. 

Nevertheless, sufficient data have accumulated over the last 

two decades to verify that some of the mobile THg in groundwater is in particulate form. 

The nature of the particles with which THg is associated in groundwater is not, as yet, clear. Water collected from 

a septic-system effluent plume (Barringer and others, 2006) 

contained aqueous sulfide, and results of geochemical speciation modeling, using the PHREEQC program (Parkhurst and 

Appelo, 1999), indicated that Hg-sulfide (metacinnabar) could 

precipitate. Mercury-bearing sulfides likely do not persist in 

oxygenated water. Consequently, THg in sulfide form may 

be present locally where conditions are reducing, such as in 

organic-rich wetlands or in substantive organic wastewater 

plumes, but is unlikely to be present throughout most parts of 

the typically oxygenated aquifer. There is evidence that THg 

can be associated with Fe hydroxides (discussed in greater 

detail farther on in the report), but as yet, there is no clear 

evidence that THg is associated with organic-matter particles 

in the aquifer. The composition of THg-bearing particles may 

vary, depending upon local geochemical conditions. 
Factors Affecting Mobility 19

Table 6. Concentrations of particulate mercury and mercury in unfiltered and filtered samples of domestic-well water collected 

throughout a day to simulate normal household water use, Burlington County, New Jersey, 2008–09.

[Particulate total mercury (PTHg) is calculated as the difference between total mercury in unfiltered water (UTHg) and total mercury in filtered water (FTHg). 

USGS, U.S. Geological Survey; μg/L, micrograms per liter]

USGS well number Date Time UTHg 

(μg/L)

FTHg 

(μg/L)

PTHg 

(μg/L)

051789 06/17/09 6:50 0.675 0.176 0.449

9:00 0.647 0.123 0.524

11:00 0.634 0.281 0.353

13:00 0.504 0.099 0.405

13:01 0.487 0.126 0.361

15:00 0.695 0.179 0.516

16:00 1.180 0.154 1.020

051765 11/18/08 7:45 0.182 0.159 0.023

7:50 0.232 0.104 0.128

9:38 0.249 0.142 0.107

11:38 0.180 0.175 0.005

13:28 0.175 0.144 0.031

15:30 0.181 0.169 0.012

17:30 0.194 0.153 0.041

051766 7/09/08 7:10 1.018 0.484 0.534

9:10 0.995 0.524 0.471

11:10 1.160 0.530 0.630

13:05 1.120 0.522 0.598

15:00 1.087 0.468 0.619

17:05 1.030 0.551 0.479

The form of THg not associated with particles greater 

than 0.45 μm or with colloids less than 0.45 μm has not been 

determined. If dissolved THg is present in the groundwater, 

speciation analysis (Barringer and others, 2006) indicates that, 

under reducing conditions, the THg could, at equilibrium, be 

present as Hg0

. Hg0 is slightly soluble in water at 56 μg/L at 25 

degrees Celsius (O’Neil, 2006), a concentration that is important with regard to drinking-water quality. As of 2012, USGS 

and NJDEP studies have not included direct measurement of 

Hg0 in groundwater samples. However, some samples of shallow groundwater and seeps to surface water collected in 2010 

at the WJHTC site were analyzed for Hg0, and it was detected 

at low concentrations, ranging from 0.00023 to 0.00929 μg/L 

(Weston Solutions, written commun., 2011). Therefore, Hg0

presence in groundwater is confirmed, but more research is 

needed to determine the range of concentrations, distribution, 

and prevalence. In oxic conditions, other dissolved forms of 

THg are possible, such as Hg–Cl or Hg–dissolved organic 

carbon (DOC) complexes; results of geochemical modeling 

efforts indicate that an HgCl2 complex would be present only 

under highly oxic conditions, and Hg–organic matter complexes would not be dominant (Barringer and others, 2006). 

All the samples collected from the domestic wells are 

representative of water that is at the end of a localized flow 

path to the well; they may or may not be of water from along 

a regional flow path. The chemistry of that water may offer 

clues to the geochemical environments through which the 

water has passed on its way to a well, but given the reactivity 

of THg, it is seldom if ever possible to determine the various 

forms of THg that have existed along either the local flowpath 

or a regional flow path from the chemistry of a domestic-well 

water sample. 

Other Constituents 

Relations between THg and various dissolved constituents in well-water samples have been variable. During 

a USGS/NJDEP cooperative study (Barringer and others, 

2005), 105 domestic wells completed in the CKKD were 

sampled; these included wells chosen specifically because of 

the land use in a buffer zone surrounding the well and wells 

chosen randomly. Positive and statistically significant relations 

between THg and Cl-

 and NO3

-

 were found for well waters 

containing THg at concentrations up to 0.10 μg/L but were 
20 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J. Table 7. Contents of selected constituents in B-horizon soils from Burlington County, New Jersey, and concentrations of mercury and selected constituents and pH in leaching solutions and leachate from column experiments. [ THg, total mercury; UTHg, total mercury in unfiltered water; FTHg, total mercury in filtered water; UFe, iron in unfiltered water; FFe, iron in filtered water; Al, aluminum; Fe, iron, Na+, sodium; Cl-, chloride; NO2

- + NO3

-, nitrite + nitrate; NH4

+, ammonium; Org. N, organic nitrogen; P, phosphorus; H2PO4

-, phosphate; Org. C, organic carbon; TOC, total organic carbon; B, boron; DI, de-ionized; 

mg/kg, milligrams per kilogram; %, percent; μg/L, micrograms per liter; mg/L, milligrams per liter; valences of major dissolved ions are indicated; na, not analyzed; <, less than; Leach 1 and Leach 2 indicate duplicate leaching experiments with a given solution]

Element contents determined by total digestion

Sample

type

THg

(mg/kg)

Al

(mg/kg)

Fe

(mg/kg)

Na+

(mg/kg)

P

(mg/kg)

Org.C

(%)

Soil 0.01 6,880 6,840 37.8 62.6 0.15

Constituents in unfiltered and filtered aqueous samples and pH

UTHg

(μg/L)

FTHg

(μg/L)

UFe

(μg/L)

FFe

(μg/L)

Na+

(mg/L)

Cl-

(mg/L)

NO2

-+NO3

-

(mg/L as N)

NH4

+

(mg/L as N)

Org. N

(mg/L)

H PO 2 4

-

(mg/L as P)

TOC

(mg/L)

B

(μg/L)

pH

(units)

NaCl solution <0.010 <0.010 12.8 <6 233 375 na na na na 0.423 na 3.87NaCl (Leach 1) 0.284 <0.010 11,900 28.5 372 635 na na na na 21.8 na 4.64NaCl (Leach 2) 0.452 <0.010 16,700 16.7 239 444 na na na na 19.8 na 4.11DI-water <0.005 <0.005 <4.6 <3.2 <0.06 0.062 0.026 <0.010 <0.050 <0.004 <0.03 <1.0 naDI-water (Leach 1) 0.452 <0.010 30,500 269 <0.10 0.670 0.043 0.017 1.29 <0.008 na na naFertilizer solution <0.005 <0.005 6,690 1,490 7.74 12.0 372 337 506 533 257 1,230 6.77Fertilizer (Leach 1) 0.438 <0.035 25,900 2,880 6.93 10.3 304 297 387 478 255 1,030 6.86Fertilizer (Leach 2) 0.305 0.043 19,200 2,350 7.16 11.4 297 292 383 466 289 944 6.75
Factors Affecting Mobility 21

0 10 20

Nitrate

concentration

(mg/L as N)

30

110

40

50

60

70

80

90

100

Borehole depth, in feet below land surface

0 5 10

Dissolvedoxygen

concentration

(mg/L)

0 20 40

Mercury

concentration

(μg/L)

0 5,000

Iron 

concentration

(μg/L)

0 2 4

Dissolvedorganic-carbon

concentration

(mg/L)

2 4 6

pH

(a) (b) (c) (d) (e) (f)

Figure 6. Concentrations of (a) nitrate, (b) dissolved oxygen, (c) mercury, (d) iron, and (e) dissolved organic carbon, and (f) pH in 

groundwater samples from the Kirkwood-Cohansey aquifer system, collected at discrete intervals with a screened augur, showing 

increase of iron and mercury concentrations with onset of reducing conditions downgradient from an abandoned septic leach field, 

Franklin Township, Gloucester County, New Jersey. (Modified from Barringer and MacLeod, 2001; mg/L, milligrams per liter; μg/L, 

micrograms per liter; N, nitrogen.).

not found where THg concentrations exceeded 0.10 μg/L. In 

several of the USGS-led studies, relations between THg and 

DOC were variable, some showing positive relations, others 

not (Barringer and others, 2005, 2006). In general, the highest concentrations of THg, including those that exceeded the 

MCL, have not shown strong relations with other dissolved 

constituents. One reason for this may be that, where THg is 

found at contaminant levels, the high concentrations are due 

mainly to THg-bearing particles. In such cases, statistical relations between concentrations of THg (mostly not dissolved) 

and concentrations of dissolved constituents are unlikely to 

be strong. Another reason for a lack of relations between high 

concentrations of THg and other constituents may be that the 

domestic well-water samples represent groundwater that is 

at the end of a flow path along which THg from subsoils and 

aquifer sediments may continue to be removed and released to 

groundwater during various biogeochemical reactions. Other 

constituents, such as Cl-, with no source in the aquifer matrix 

(Yuretich and others, 1981; Szabo and others, 2010a) may not 

be added along the flowpath but instead are gradually diluted; 

this is in contrast to THg, which may originate in the soils 

and sediments. An indication of this possible soil or sediment 

source for THg is shown in Barringer and others (2006) who 

report the observation of higher concentrations of THg at the 

water table downgradient from septic leachfields than in the 

septage within the septic tank. One reason for a lack of 

relations between THg and DOC in groundwater could be the 

effects from other constituents such as Cl-

, which interferes 

with the complexation of Hg with organic carbon (Wu and 

others, 2004). Further, Haitzer and others (2002) show binding of Hg to organic matter (OM) becomes less strong as the 

Hg/OM ratio increases to greater than 10 μg of Hg/mg OM; 

the Hg/DOC ratio is greater than 10 for some samples of 

groundwater from domestic wells (Barringer and others, 2006).
22 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

Redox transformations along flow paths affect not only 

THg, but other redox-sensitive constituents as well, such as N. 

Where differing redox conditions are encountered along a flow 

path, N species in the system may be altered, from ammonium (NH4

+

) to NO3

-

, for example. The same is true of sulfate 

(SO4

2-); because many of the domestic well-water samples 

contained low (less than 1 mg/L) to undetectable concentrations of SO4

2-, it appears that sulfate-reducing conditions may 

have been encountered along flow paths, likely within septiceffluent plumes, as found in one area study (Barringer and 

others, 2006). Septic-system effluent clearly can affect local 

geochemical environments, adding organic carbon, nitrogen, 

and sulfur, thus stimulating microbial activity and creating 

reducing conditions as organic carbon is oxidized. Additions 

of surfactants also may affect the behavior of particles in the 

aquifer (Barringer and others, 2006; Barringer and Szabo, 

2006). Additionally, the influx of septic-system effluent could 

cause mounding at the water table, possibly affecting the flow 

direction of the shallow groundwater. 

The geochemical speciation modeling (Barringer and others, 2006; Barringer and Szabo, 2006) that indicated possible 

presence of Hg0 also indicated that Hg–Cl complexes were of 

negligible importance in the waters analyzed when Hg reduction or Hg complexation with organic matter was considered. 

In some speciation modeling, Hg–organic carbon complexes 

were calculated. Nevertheless, relations between THg and 

DOC have not always been found to be strong. In the study at 

Squankum Branch, the relations between the highest THg concentrations in groundwater and ultra-violet absorbance at 254 

nanometers (UV254, an indicator of DOC aromaticity) were 

found to be negative—a relation that is opposite to that found 

for surface waters at several North American sites (Shanley 

and others, 2008). Relations between THg and organic matter 

in the Coastal Plain appear to be complex, and it is not clear 

under what geochemical conditions DOC plays a role in the 

mobility of THg in groundwater. It may be that binding of 

THg to organic carbon in the CKKD is inhibited by acidic 

conditions and the high concentrations of Cl- (Wu and others, 

2004), or binding may be inhibited because the Hg/DOC ratio 

is greater than 10 μg Hg/mg DOC (Haitzer and others, 2002) 

in water along some flowpaths. In samples of the uppermost 

mineral soils (A horizons) and aquifer sediments, however, 

there appears to be a positive relation between THg and OM 

(Barringer and Szabo, 2006).

As mentioned earlier, a positive relation between THg 

and Fe was observed for residential subsoils (B horizons), 

and the same relation occurred for leachfield effluent samples 

(Barringer and others, 2006). Although Hg (from atmospheric 

deposition and, most likely, from former pesticide and fertilizer use) is associated with OM in the A horizons of residential 

areas (Barringer and Szabo, 2006), some of the Hg is dislocated and moved to the Fe-rich B-horizon soils or deeper into 

the C horizon of barely altered sediments in the unsaturated 

zone. In these subsoils and sediments, THg apparently is 

sorbed to the ubiquitous Fe hydroxides that coat sediment 

grains.

It is hypothesized that septic-system effluent removes 

and mobilizes Hg from Fe hydroxides. In the environment of 

a recently abandoned septic-system leachfield, concentrations 

of Fe and THg increased in water as concentrations of DO 

decreased (fig. 6; Barringer and MacLeod, 2001). Further, a 

linear and positive relation was found between THg and Fe 

concentrations in filtered septic-system effluent and groundwater samples from low-oxygen environments (Barringer 

and others, 2006). These relations between THg, Fe, and DO 

are interpreted as demonstrating reductive dissolution of the 

hydroxides and release of the sorbed THg. 

Volatile organic compounds (VOCs), mainly chlorinated 

solvents, have a nearly ubiquitous presence in groundwater 

at the residential areas where well water contains Hg contamination. The VOCs occur in some cases, at concentrations 

substantially greater than the respective MCLs. Nevertheless, 

the cases in which water from a given well contains both Hg 

and VOC contamination are relatively few. This lack of direct 

association was particularly evident in the large database 

compiled for sampling of Gloucester County wells (Donald 

Schneider, Gloucester County Health Department, written 

commun., 2006). Relatively weak statistical relations between 

presence of VOCs and presence of Hg at contamination 

levels were found for six residential sites in Atlantic County 

(Barringer and Szabo, 2006). The VOCs and THg appear to 

derive from different sources; a likely source of the VOCs, 

chlorinated solvents, is septic-system cleaners used until the 

early 1970s (Robert A. Gallagher, New Jersey Department of 

Environmental Protection, oral commun., 2005); other sources 

(commercial effluents, for example) are likely in the residential areas as well. VOCs could play a role in facilitating Hg 

mobility in the CKKD, perhaps by influencing redox conditions during biodegradation. With concentrations of daughter 

products, such as 1,2-dichloroethylene, present in the groundwater, the VOC concentrations likely are affected directly by 

biodegradation over time, whereas microbial activity may lead 

to biotransformations of inorganic compounds that affect both 

THg speciation and complexation. A study of Hg in Delaware 

groundwater (Koterba and others, 2006) clearly illustrates a 

similar coincidence between VOCs and Hg occurrence.

Methylmercury

Data on MeHg in New Jersey Coastal Plain soils are 

limited. In residential soils, the MeHg contents of upper 

(A-horizon) soils were found to be less than 0.001 mg/kg and 

typically about 0.0001 mg/kg (Barringer and Szabo, 2006). 

The MeHg content of streambed sediments has, to these 

authors’ knowledge, been determined only for the streams that 

border the WJHTC.

Well-water samples collected from the CKKD by southern New Jersey county agencies and NJDEP are not routinely 

analyzed for MeHg. Results of analyses of water from five 

wells sampled by NJDEP in the early 1990s indicate high concentrations of MeHg (0.100–0.137 μg/L) are present (Murphy 
Summary of Mercury Found at the William J. Hughes Technical Center 23

and others, 1994), but subsequent sampling of 33 domestic 

wells by the USGS for the National Water Quality Assessment 

( NAWQA) Program have not yielded comparable concentrations. The USGS MeHg dataset for groundwater in the CKKD 

is small, but concentrations typically are less than 0.001 μg/L 

or are not detected at 0.0004 μg/L. 

The median concentration of SO4

2- in relatively pristine groundwater from the CKKD in undeveloped areas was 

5.6 mg/L, but in some residential areas, concentrations were 

either greater than those background levels or are not detectable (Barringer and others, 2006). The presence of aqueous 

sulfide (Barringer and others, 2006) and the low (less than 

1 mg/L) to undetectable concentrations of SO4

2- in some 

samples of domestic well water collected by USGS (Barringer 

and Szabo, 2006) likely are indicative of sulfate-reducing conditions in the CKKD. However, such conditions may not lead 

to the methylation of mercury, which is a reaction resulting 

from metabolic activity by sulfate-reducing bacteria (Gilmour 

and Henry, 1991). It may be that, in the CKKD, the Hg is in 

a form unavailable to the microbes (Hg0, perhaps) or that, 

where affected by septic-system effluent, the high salinity of 

some groundwater inhibits the methylation process as shown 

by Barkay and others (1997). It is also possible that the time 

spans in which conditions are conducive to sulfate reduction 

are short (transient conditions) and methylation of Hg is difficult to initiate.

In areas of the Coastal Plain underlain by the CKKD 

sediments, MeHg in streamwater has been determined only for 

the mainstem and tributaries of the GEHR in USGS/NJDEP 

cooperative studies (Barringer and others, 2010a; fig. 4). 

Concentrations of MeHg in GEHR streamwater typically were 

less than 0.001 μg/L in downstream, wetlands parts of the 

watershed, but concentrations were as high as 0.003 μg/L in 

streamwater from the upstream, urban part of the watershed 

(Barringer and others, 2010a). Given its areal extent and range 

of land uses, the GEHR watershed is likely representative of 

other Coastal Plain streams that flow over CKKD sediments. 

Thus, the MeHg concentrations measured in GEHR waters 

probably are representative of those found under ambient 

conditions elsewhere in the region, as further described by 

Brumbaugh and others (2001). 

Summary of Mercury Found at the 

William J. Hughes Technical Center 

 Site Description and History

The 5,000-acre William J. Hughes Technical Center 

(WJHTC) site is within the boundary of the Atlantic City 

International Airport in Atlantic County, New Jersey, which is 

located to the west-northwest of the two Atlantic City reservoirs (Upper Reservoir and Lower Reservoir; fig. 7). The part 

of the airport area that extends between the two branches of 

Absecon Creek was leased by Atlantic City to the U.S. Navy 

in the 1940s and 1950s. During that time, various operations 

involving aircraft and weapons were carried out that included 

use of mercury (TRC, 2005). As a result, liquid mercury was 

stored at the site; much of the Hg is thought to have been 

salvaged after the U.S. Navy left the site in 1958 and when 

the buildings were cleaned out and (or) demolished during 

1959–62 (TRC, 2005). The Federal Aviation Administration 

(FAA) now owns the site, which was placed on the National 

Priorities List (Superfund) in 1990.

The airport and the WJHTC are underlain by sediments 

of the Cohansey Formation, the upper unit of the CKKD sediments. The Cohansey Formation is predominantly sandy but 

contains clay layers, some of which are areally extensive at the 

WJHTC site (TRC, 2010), as evidenced by local area clay pits, 

highly dissected relief, and determinations of local subsurface extent from well logs, which indicate the presence of an 

extensive 15-ft-thick dark gray clay layer (TRC, 2010). Land 

at the site slopes to the North and South Branches of Absecon 

Creek (NBAC and SBAC, respectively), both of which were 

dammed in 1936 to form the reservoirs. The area within the 

watershed of these two creek branches is known as Area U 

(fig. 7). Most of the detailed Hg investigations have been carried out in Area U. Hg contamination was substantially more 

prominent in the watershed of the SBAC, which has received 

the most focused investigation. Hg contamination of the creek 

watersheds is of concern because water from the creeks flows 

into the public reservoirs.

There are residential areas on the uplands to the north of 

NBAC and to the south of SBAC; these areas are composed 

of housing developments and trailer parks built mainly in the 

1960s through the 1970s, generally on former agricultural 

land (residential sites 2, 3, 5, and 17 in Barringer and others, 

1997; figs. 7 and 8). Within these unsewered communities in 

the 1980s, water from some of the domestic wells was found 

to contain concentrations of THg that exceeded the MCL of 

2 μg/L. In the residential area to the south of the WJHTC site 

(site 2 in fig. 7; Barringer and others, 1997), THg exceeded the 

MCL in water from 4 monitoring wells at a waste-transfer station and in water from 28 of the 216 domestic wells sampled 

by NJDEP during 1988–92 (fig. 9). The domestic wells were 

completed at depths of 40 to 180 ft below land surface; most 

wells were completed at about 85 ft. Prior to sampling at 

site 2, samples collected from more than 300 wells in site 3, 

another residential area (Barringer and others, 1997) to the 

southeast, by the Atlantic County Health Department indicated 

that about 20 percent of those wells yielded water with THg 

concentrations in excess of the MCL. Wells in this residential 

development (where well-log data are available) were completed at depths of 60 to 130 ft; most were completed at about 

100 ft. During the same time period, wells withdrawing water 

with THg concentrations substantially greater than background 

levels and, in numerous cases, exceeding the MCL, were 

reported in residential areas to the north and northeast of the 

WJHTC (fig. 7), as well as several farther to the east-southeast 
24 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

2

3

5

17

Garden State Parkway

Card Road

Tilton Road

South BranchAbsecon Creek

North BranchAbsecon Creek

Amelia Earhart

Boulevard

Upper Reservoir Lower Reservoir

Residential site of mercurycontaminated groundwater(Barringer and others, 1997)

2

39°

27'

30"

74°35' 74°32'30"

39°

26'

Figure 7. Location of Atlantic City International Airport, which encompasses the William J. Hughes Technical Center and Area U, from TRC, 2005, with overlay of residential areas with mercury-contaminated groundwater from the Kirkwood-Cohansey aquifer system, shown in Barringer and others, 1997.
Summary of Mercury Found at the William J. Hughes Technical Center 25

Atlantic City

acquires land

Reservoirs

created

Site added to

Airport built FAA constructs facilities NPL

U.S. Navy occupation of site FAA moves to site

1930 1940 1950 1960 1970 1980 1990 2000

1936 1943 1958 1965

Agricultural activities Residential development on land surrounding airport

THg discovered in domestic-well water

THg uptake by trees near Tilton Road

THg uptake by trees near Upper Reservoir

THg deposited near and in Upper Reservoir sediments

(Dendrochronology study)

( Cs sediment dating study)

No Cs Bomb-related Cs 137 137

137

SBAC channelized

Figure 8. Time line indicating various events at and in the vicinity of the William J. Hughes Technical Center site, New Jersey. 

(THg, total mercury; 137Cs, cesium-137 isotope; NPL, national Priorities List (Superfund); FAA, Federal Aviation Administration; SBAC, 

South Branch Absecon Creek.)

and southeast (fig. 10). Thus, the airport and WJHTC are surrounded by residential areas where groundwater was discovered to be contaminated with THg in the mid-to-late 1980s 

and early 1990s. (To these authors’ knowledge, affected wells 

have been sealed, and no recent sampling in these areas has 

occurred; therefore, it is not known whether the groundwater 

is still contaminated more than two decades later.) 

Area Hydrology

On the basis of local topography and the water-table map 

of Clark and Paulachok (1989), flow directions of shallow 

groundwater from the residential areas were interpreted to be 

toward the NBAC, SBAC, and the reservoirs (fig. 10; Barringer and others, 1997), although the direction of deep regional 

flow likely is toward the ocean. Measurements in 2008 of 

hydraulic heads in piezometers placed along the SBAC in the 

area west of Tilton Road indicate that shallow groundwater 

from the south is draining to the deeper aquifer rather than 

discharging to the stream. Immediately downstream, however, 

shallow groundwater from the north (from the airport area) is 

discharging to the SBAC (Weston Solutions, 2009). In small 

streams of the Coastal Plain, the directions of flow between 

shallow groundwater and streams can change depending on 

antecedent conditions; following rainfall, parts of a stream 

may lose flow to groundwater for several days until infiltration 

raises the hydraulic head in the aquifer (Johnsson and Barringer, 1993). It is possible that similar changes in shallow flow 

might be observed along some parts of the SBAC if hydraulic 

heads were monitored over a long period of time. The general direction of groundwater flow at shallow to intermediate 

depths (roughly 27 to 32 ft below land surface) from north 

of the SBAC watershed in the area just east of Tilton Road 

was determined to be in a generally east-southeast to easterly 

direction, from the airport runway area towards the SBAC and 

the reservoirs (TRC, 2010).

Mercury in Soils and Sediments

Most of the investigations of Hg at the WJHTC focused 

on the area of the SBAC where contaminant levels of Hg 

were found to be the highest. Soil and sediment Hg concentrations in the watershed of the NBAC have been generally 

low but highly variable; typical concentrations were less than 

0.3 mg/kg, but occasionally much higher concentrations were 

observed during sampling in 2008 (Weston Solutions, 2009). 

During the late 1950s and early 1960s, the SBAC was 

channelized (fig. 8), and disturbance of soils and sediments 

along the once meandering stream occurred during this time, 

just prior to major land-use change from forested land and 
26 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

75 30' 75 30' 74 

A T L A N T I C O C E A N

DELAWARE

PENNSYLVANIA

40

30'

40

39

30'

0

0

10 MILES 

10 KILOMETERS 

NEW JERSEY

Site location

Location of well yielding

EXPLANATION

water with undetectable

mercury concentrations

Location of well yielding water

with mercury cpncentrations

less than 2.0 micrograms per liter

Location of well yielding water with

mercury concentrations equal to or

greater than 2.0 micrograms per liter

Direction of horizontal component of

ground-water flow determined from

water-table map (Clark and Paulachok,

1989)

Base from U.S. Geological Survey

Pleasantville, 1:24,000, 1989

39°

26'

74°36'30" 74°36' 74°35'30" 74°35'

0

0 300 600 METERS

1,000 2,000 FEET

Figure 9. Concentrations of mercury in groundwater from domestic wells completed in the Kirkwood-Cohansey aquifer system at a 

residential area (site 2) to the southwest of the William J. Hughes Technical Center site, Atlantic County, New Jersey, and direction of 

the horizontal component of groundwater flow determined from water-level data. (From Barringer and others, 1997)
Summary of Mercury Found at the William J. Hughes Technical Center 27

75 30' 75 30' 74 

A T L A N T I C 

O C E A N

DELAWARE

PENNSYLVANIA

40

30'

40

39

30'

0

0

10 MILES 

10 KILOMETERS 

NEW JERSEY

Site location

EXPLANATION

Direction of horizontal component of

ground-water flow determined from

water-table map (Clark and Paulachok,

1989)

Base from U.S. Geological Survey

Atlantic City, New Jersey, 1:100,000, 1984

39°

26'

39°

28'

74°36' 74°34' 74°32' 74°30'

0

0 1 2 3 KILOMETERS

1 2 MILES

Figure 10. Area surrounding the Atlantic City International Airport in New Jersey, which encompasses the William J. Hughes 

Technical Center site, groundwater-flow directions in the Kirkwood-Cohansey aquifer system, and six residential sites where domestic 

wells yielded water containing total mercury at concentrations that approached or exceeded the New Jersey maximum contaminant 

level of 2 micrograms per liter. (Numbers correspond to numbers in Barringer and others, 1997; map is from figure 33 of Barringer and 

others, 1997)

agricultural land to residential development on the highlands 

surrounding the airport site. THg contents were found to be 

as high as 200 mg/kg (Bopp, 2005) in soils and sediments of 

the abandoned meander of the SBAC east of Amelia Earhart 

Boulevard and, on the basis of isotope concentrations of 

cesium-137 (137Cs) and lead-210 (210Pb) found in the soils, 

the deposition of THg is thought to have occurred during the Navy occupation of the site (TRC, 2010). The THg 

contents ranged up to 555 mg/kg; levels well above regional 

background levels (0.015 mg/kg or less) were consistently 

reported during sampling in 2004 and earlier at the stream 

meander between Amelia Earhart Boulevard and Card Road 

(TRC, 2005; Weston Solutions, 2009). Later sampling in 2008 

confirmed that the THg contents of soils and sediments in this 

area were particularly high (up to 88.4 mg/kg). Soil and sediment sampling in 2008 by Weston Solutions (2009) along the 

SBAC in the area west of Tilton Road reveal THg contents of 

the sediments there were an order of magnitude or more lower 

than THg in soils at the stream meander near Amelia Earhart 

Boulevard (ranging up to 8.24 mg/kg) but much higher than 

regional background levels (0.015 mg/kg or less). Given that 

sediment contents of THg were generally highest at abandoned 
28 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

SBAC meanders, particularly in the area between Amelia Earhart Boulevard and Card Road, it is presumed that deposition 

of Hg occurred along the original channel of the SBAC before 

channelization occurred. The THg concentrations in tree rings 

of Atlantic White Cedars at this site indicate that the 1940s 

and mid-to-late 1950s were times when elevated concentrations of THg were taken up by trees in the SBAC watershed 

(TRC, 2005), although uptake of THg by trees near Tilton 

Road appears to have occurred later, during the mid-1960s to 

mid-1990s. Because Eastern Red Cedar has preserved patterns 

of Hg incorporation that correspond to timing of known emissions (Ralph Turner, RT Geosciences, Inc., written commun., 

2004), Hg uptake is presumed to be well-preserved in rings 

of the Atlantic White Cedar; therefore, the tree-ring dates 

for greater uptake of Hg by trees in the SBAC watershed are 

likely to be reliable. 

The 1940s and early 1950s were times when crops were 

being grown on the highlands surrounding the SBAC and the 

airport (Barringer and others, 1997); applications of mercurial pesticides may have occurred during this period. Whether 

runoff from the agricultural land could have carried THg 

from pesticide applications to the streams is not known, nor 

is it known whether shallow groundwater from the agricultural areas would have discharged to the NBAC and SBAC, 

potentially carrying THg derived from leached mercurial 

pesticides. Residential development began on the agricultural 

land, mostly in the 1960s, and may have been instrumental 

in mobilizing Hg already in the soils. During this period and 

afterwards, Hg released to groundwater may have been transported downgradient and discharged into parts of the SBAC, 

probably after channelization was completed. In the absence 

of any groundwater data for the WJHTC site from this time 

period, this hypothesis cannot be confirmed.

THg contents of sediment samples collected in 2008 

along the channelized SBAC and in its abandoned meanders 

between Tilton Road and the Upper Reservoir indicate that 

THg was highest (up to 88.4 mg/kg) in the shallow (1- to 

6-inch depth) sediments in the meanders, whereas the THg 

contents of sediments in the channelized stream are lower 

(Weston Solutions, 2009). Because of sediment accumulation 

at road crossings, stream sediments immediately upstream 

from crossings tended to have higher contents of Hg than 

sediments in other stream reaches. In the Upper Reservoir, 

THg contents of bottom sediments, which in general are rich 

in OM, were elevated, ranging as high as 19.6 mg/kg at the 

upstream end; THg contents were substantially lower throughout much of the reservoir (Weston Solutions, 2009), however. 

Sulfide was detected in a few samples, indicating reducing 

conditions were present in some parts of the reservoir bottom.

Mercury in Groundwater and Streamwater

Groundwater samples were collected from both banks 

of the NBAC and SBAC using piezometers and from wells 

installed in and adjacent to Area U (the watersheds of the 

NBAC and SBAC). However, relatively little attention was 

given to groundwater and streamwater in the watershed of the 

NBAC because early sampling efforts indicated Hg concentrations were lower in the NBAC watershed than in the SBAC 

watershed. In the SBAC watershed, unfiltered samples of 

groundwater collected in 1996 north of the SBAC between 

Tilton Road and the Upper Reservoir contained concentrations of THg of 23.6 and 26.7 μg/L, most of which was 

particulate in form (TRC, 2010). Samples collected from 

monitoring wells both north and south of the SBAC channel, 

in some cases, contained Hg at greater than background levels, 

although not at contaminant levels of 2 μg/L or greater. Higher 

concentrations were found in some samples collected adjacent to the former meanders of the SBAC. Recently (2008) 

collected samples of groundwater from midstream seeps to 

the SBAC indicate that THg concentrations were variable, 

from background levels (less than 0.010 μg/L) to a high 

of 8.9 μg/L (Weston Solutions, 2009). In general, the THg 

concentrations in samples from the wells and piezometers 

were highly variable. The highest THg concentration in recent 

(2008) samples (6.97 μg/L) was found in filtered groundwater 

(interstitial water) from beneath the SBAC channel in the area 

west of Tilton Road (Weston Solutions, 2009). Three other 

filtered samples from the area, collected at depths of 5 to 10 ft, 

contained THg at concentrations that exceeded the MCL, and 

two other samples contained Hg at concentrations exceeding 

1 μg/L. Overall, when both unfiltered and filtered samples 

were collected, substantial differences in concentrations indicate that much of the Hg in the groundwater is in particulate 

form. Some of the particulates may be sampling artifacts, as 

sample collection using a low-flow protocol was found to produce fewer particulates (TRC, 2010). (Decreasing the amount 

of particulates present as an artifact of purging also decreases 

the amount of particulate Cu, Pb, and other trace elements 

(Gibs and others, 2000).) Nevertheless, results of ultrafiltration 

of groundwater samples from the WJHTC site (with filters of 

pore size less than 0.1 μm and less than 0.0015 μm) indicate 

that Hg was present on colloids, as well as on the larger particles filtered using 0.45-μm pore-size filters (TRC, 2010).

Concentrations of THg in SBAC streamwater also were 

variable. One sample from a 2004 round of sampling contained 2.69 μg/L of THg, and other samples contained THg at 

concentrations of 0.256 and 0.954 μg/L (TRC, 2006). Interstitial water in the SBAC streambed in the area west of Tilton 

Road contained THg at concentrations that ranged from 0.14 

to 5.45 μg/L (Weston Solutions, 2009). 

A plume of chlorinated solvents in the shallow groundwater underlies part of the SBAC channel between Tilton Road 

and Amelia Earhart Boulevard. This plume has been, and is 

currently (2012) being, remediated through extraction wells, 

water treatment, and reinjection into wells to the southeast of 

Amelia Earhart Boulevard (TRC, 2010). It is not known what 

effect this may have on the chemistry and mobility of Hg in 

the groundwater and SBAC streamwater, but it appears from 

a recent investigation of groundwater concentrations that the 
Comparison of Mercury Levels at the William J. Hughes Technical Center with Levels Found Regionally in Southern New Jersey 29

extraction wells are drawing Hg from shallow depths more 

deeply into the aquifer in this area (TRC, 2010).

Methylmercury in Sediment and Water 

Because the reservoirs supply drinking water to Atlantic 

City and the SBAC drains to the Upper Reservoir, levels of 

MeHg in sediments and water of the reservoirs were a matter 

of concern. The MeHg contents of sediment samples collected along the SBAC in 2008 were variable, ranging from 

0.00011 mg/kg to 0.0266 mg/kg. MeHg contents of sediments were higher above a depth of 1 ft, and lower in deeper 

sediments (Weston Solutions, 2009). The MeHg content of 

sediment samples from the upstream end of the Upper Reservoir was high (up to 0.0977), but the content of most of the 

reservoir sediment samples was low (less than 0.01 mg/kg). 

Concentrations of MeHg in two samples of reservoir water 

were 0.000877 and 0.00059 μg/L (Weston Solutions, 2009), 

and elevated levels in fish tissue (up to 6.5 mg/kg) have been 

found (TRC, 2010).

Comparison of Mercury Levels at the 

William J. Hughes Technical Center 

with Levels Found Regionally in 

Southern New Jersey 

The THg contents of soils and sediments at several 

identified “hotspots” in the SBAC watershed at the WJHTC 

site were substantially greater than those found in soils and 

streambed sediments during regional investigations. These 

data may be indicative of a source of THg at the WJHTC that 

is not found elsewhere in the region.

The range of concentrations of THg found to date (2012) 

in groundwater at the WJHTC covers only part of the substantial range of concentrations (0.0004–82 μg/L) found regionally in domestic well water. Both regionally and locally at the 

WJHTC, some of the Hg in groundwater is in particulate form, 

which affects the mobility of Hg. If THg is moving mainly as 

a particle or colloid, it may be less likely to participate in biogeochemical reactions while being transported by the groundwater. It appears that THg in groundwater at the WJHTC 

behaves geochemically in the same manner as it does regionally. Given the likelihood that disturbance of soils within the 

southern New Jersey region plays a role in mobilizing THg, 

the fate and transport of THg at the WJHTC is undoubtedly 

affected by channelization of the SBAC, road incisions that 

cross the stream channel, accumulation of sediments upstream 

from the reservoirs, and dams that form the reservoir system. Whether some portion of the Hg found in the reservoir 

sediments and water is contributed by groundwater discharge 

currently is not known; surface flow appears to contribute Hg 

to the Upper Reservoir.

Concentrations of THg in streamwater at the WJHTC 

were variable. In a few streamwater samples from the SBAC, 

THg was measured at concentrations as high as 2.6 μg/L. 

Concentrations exceeding 2 μg/L were not measured in 

streamwater samples elsewhere in the Coastal Plain. As of 

2012, the highest concentration, 0.25 μg/L, was present in a 

water sample collected by NJDEP from Squankum Branch in 

Gloucester County.

If the THg in the soils, sediments, surface water, and 

groundwater at the WJHTC is derived from Hg0, as is indicated by the anecdotal evidence gathered by TRC (2005), then 

initially, THg from this source could be expected to behave 

differently than the ionic Hg present in HgCl2 pesticides that 

likely were used on crops in the region. Ionic Hg would be 

easily complexed or sorbed to particles, as evidenced by data 

gathered during various USGS investigations (Barringer and 

MacLeod, 2001; Barringer and others, 2006; Barringer and 

Szabo, 2006). On the other hand, Hg0 would likely become 

oxidized in order to sorb to particles. This apparently has 

occurred, insofar as groundwater at the WJHTC has been 

shown to contain particles and colloids, and no discoveries of 

Hg in liquid elemental form have been reported for the soil 

and sediment samples. Once in ionic form, the THg at the 

WJHTC would likely behave in the environment much as the 

THg in the region is thought to behave—binding/complexing with organic matter and sorbing to Fe hydroxides, for 

example. The main similarities and differences in the levels of 

THg and MeHg at the WJHTC and regionally are summarized 

in table 8. 
30 Comparison of Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.

Table 8. Summary of similarities and dissimilarities between mercury levels at the William J. Hughes Technical Center and 

regionally in the Coastal Plain of New Jersey.

[THg, total mercury; MeHg, methylmercury; mg/kg, milligrams per kilogram; <, less than; <, less than or equal to; μg/L, micrograms per liter; μm, micrometer; SBAC, South Branch Absecon Creek; MCL, maximum contaminant level in drinking water; NJDEP, New Jersey Department of Environmental 

Protection]

William J. Hughes Technical Center New Jersey Coastal Plain Region

Soils and sediments

THg contents of disturbed soils and sediments are highly variable. 

THg contents approaching or reaching 100 mg/kg in the SBAC 

watershed are substantially greater than the THg contents found 

in regional soils and sediments. MeHg content of soils and sediments is generally < 0.001 mg/kg, but has been found as high as 

0.0977 mg/kg in reservoir sediments, and up to 0.0266 mg/kg in 

SBAC sediments.

THg contents of disturbed residential soils typically are 

< 0.50 mg/kg. Contents of undisturbed forest soils are about 

0.10–0.15 mg/kg. Former agricultural soils/sediments with possible 

pesticide residues contain about 12 mg/kg of THg. Total and recoverable Hg contents of streambed sediments generally are <0.03 mg/kg, 

but in streams affected by urban inputs, contents increase to 

0.099 mg/kg. Where inputs from former agricultural pesticides 

may be present, contents are as great as 1.59 mg/kg. Limited data 

indicate the MeHg content of residential soils is < 0.001 mg/kg.

Groundwater

Concentrations of THg in groundwater are variable. Background 

concentrations (< 0.01 μg/L) are found. In the SBAC watershed, concentrations can exceed the New Jersey MCL (2 μg/L) but have not 

been found to reach the high levels present regionally in domestic 

well water. A substantial portion of the THg is particulate, and colloidal THg (< 0.45 μm) has been found.

Concentrations of THg in water from domestic wells range from 

0.0004 μg/L to 82 μg/L. In some samples, particulate Hg is present. 

Sampling for colloidal Hg has not been carried out.

Except for a few early samples collected by NJDEP, concentrations 

of MeHg in well water have been found at <0.001 μg/L, but data are 

limited to fewer than 100 wells sampled.

Surface Water

Concentrations of THg in streamwater are variable and span the 

range of concentrations found regionally. Concentrations in a few 

samples from the SBAC substantially exceed regional concentrations. MeHg concentrations in surface water—both streamwater and 

reservoir water—have generally been found to be <0.001 μg/L.

Concentrations of THg typically are < 0.020 μg/L in streamwater 

except in urban areas, where concentrations are as high as 

0.063 μg/L. In an area apparently affected by past pesticide use, concentrations were as high as 0.250 μg/L. Much of the THg in urban 

areas was in particulate form. Concentrations of MeHg exceeded 

0.002 μg/L in some urban areas, but were < 0.001 μg/L in forested 

wetlands areas.

Summary and Conclusions 

Since the 1980s, total mercury (THg) has been found 

at contaminant levels in groundwater from the KirkwoodCohansey aquifer system in the New Jersey Coastal Plain. 

Studies of sources of the THg and its possible mobilization by 

anthropogenic inputs to the subsurface, such as discharges of 

septic-system effluent, are summarized in this report. Results 

of studies of contaminant levels of THg in soils, sediments, 

groundwater and surface water at the William J. Hughes 

Technical Center in Atlantic County, New Jersey, which may 

arise from former military activities, also are summarized. In 

comparing the levels of mercury found in various media at 

the William J. Hughes Technical Center (WJHTC) with those 

found regionally, the following conclusions can be made.

• Some total mercury (THg) concentrations in groundwater and streamwater at the WJHTC are low, similar 

to concentrations considered background levels (less 

than 0.01 μg/L and less than 0.1 μg/L, respectively) for 

waters of the Coastal Plain region underlain by sediments of the Cohansey and Kirkwood Formations.

• THg in groundwater and streamwater at the WJHTC 

site is, however, found at concentrations that are highly 

variable.

• THg in groundwater and streamwater at the WJHTC 

site has been measured at concentrations that exceed 

the MCL for drinking water (2 μg/L) and the Surface 

Water Quality Standard of 0.05 μg/L but has not been 

found at the high concentrations (greater than 10 μg/L) 

reported for some domestic-well waters in the region.

• Where THg is contributed by geologic and atmospheric 

deposition, regional levels of THg in soils and bed 

sediments are low (less than 0.1 mg/kg).

• Regionally, where agricultural or urban inputs of THg 

appear likely, the THg contents of soils and sediments 

are, in a few instances, at levels (up to 12.2 mg/kg) 

higher than those regarded as representative of background levels. 
References Cited 31

• The levels of THg (up to 555 mg/kg) found in soils 

and sediments of parts of the watershed of the South 

Branch of Absecon Creek (SBAC) greatly exceed 

those generally found in regional soil and streambed 

sediments. 

• Because of channelization and other disturbances, it is 

likely that THg in the SBAC watershed has been mobilized; the original distribution probably has changed, 

and as a result of redistribution, THg contents of soil 

and sediment may not now (2012) be as high as they 

were when deposition took place.

• The THg contents of SBAC soils and sediments that 

are found at levels greatly exceeding regional levels 

may be indicative of a source at the WJHTC site other 

than the hypothesized regional THg sources.

It is not known whether the THg-contaminated (>2 μg/L) 

groundwater from the residential areas that surround the 

WJHTC has contributed to the THg concentrations in shallow groundwater at the WJHTC. Concentrations of THg in 

groundwater at the WJHTC do not range as high as some of 

the concentrations found in domestic-well waters throughout 

the region. On the other hand, THg concentrations in several 

streamwater samples from the SBAC exceed those found, as 

of 2012, in other Coastal Plain streams. THg-rich runoff from 

contaminated soils bordering the SBAC may have led to the 

high concentrations in the streamwater. 

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Zapecza, O.S., 1989, Hydrogeologic framework of the New 

Jersey Coastal Plain: U.S. Geological Survey Professional 

Paper 1404-B, 49 p., 24 pl.
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Barringer and others—Mercury in the N.J. Coastal Plain and at the William J. Hughes Technical Center, Atlantic County, N.J.—Scientific Investigations Report 2012–5115