MERCURY IN GROUND MERCURY IN GROUND WATER, SOILS, AND WATER, SOILS, AND

SEPTAGE, NEW JERSEY SEPTAGE, NEW JERSEY COASTAL PLAINCOASTAL PLAIN

Julia L. Barringer and Zoltan SzaboJulia L. Barringer and Zoltan SzaboU.S. Geological Survey, West Trenton, NJU.S. Geological Survey, West Trenton, NJ

In cooperation with the New Jersey Department In cooperation with the New Jersey Department of Environmental Protection (NJDEP)of Environmental Protection (NJDEP)

Our objectives: information Our objectives: information about--about--

►Occurrence of mercury (Occurrence of mercury (HgHg) ) contamination in groundwater in contamination in groundwater in southern New Jersey—an ongoing southern New Jersey—an ongoing problem (rarely studied elsewhere);problem (rarely studied elsewhere);

►Likely and unlikely Hg sources;Likely and unlikely Hg sources;►Processes that are believed to lead Processes that are believed to lead

to the contamination;to the contamination;►The environments that seem The environments that seem

conducive to causing the conducive to causing the contamination.contamination.

OCCURRENCEOCCURRENCE

The Problem:The Problem:

►Total Hg exceeds the MCL (2 Total Hg exceeds the MCL (2 g/L) in g/L) in water from a major NJ aquifer system. water from a major NJ aquifer system.

►More than 600 domestic wells in more More than 600 domestic wells in more than 70 residential areas in 8 counties than 70 residential areas in 8 counties affected;affected;

►Hg concentrations as high as 72 Hg concentrations as high as 72 g/L;g/L;►Concentrations of sodium, chloride and Concentrations of sodium, chloride and

nitrate elevated in domestic-well water;nitrate elevated in domestic-well water;►VOCs may be detected.VOCs may be detected.►Hg found in ground water in Delaware, Hg found in ground water in Delaware,

too.too.

The aquifer and affected residential The aquifer and affected residential areas are shown below. Aquifer areas are shown below. Aquifer characteristics arecharacteristics are

►Quartz-rich sand and Quartz-rich sand and gravel; scattered clay gravel; scattered clay lenses;lenses;

►Acidic ground water Acidic ground water (pH ~ 4.5 – 6.0)(pH ~ 4.5 – 6.0)

►Background Hg Background Hg concentrations <0.01 concentrations <0.01 g/L in waterg/L in water

►Vulnerability to Vulnerability to contamination from contamination from the land surface.the land surface.

SOURCESSOURCES

None of the potential point sources None of the potential point sources (below) of Hg investigated by USGS (below) of Hg investigated by USGS and NJDEP could be conclusively and NJDEP could be conclusively linked to the Hg-contaminated linked to the Hg-contaminated ground water in the residential ground water in the residential areas.areas.

►LandfillsLandfills► Industrial sitesIndustrial sites►Commercial Commercial

operationsoperations►Dentists’ officesDentists’ offices

►Military Military InstallationsInstallations

►CemeteriesCemeteries►Hospital septic Hospital septic

systemssystems►LaboratoriesLaboratories

Likely Hg sources to land Likely Hg sources to land surface:surface:

►Atmospheric deposition;Atmospheric deposition;

►Mercurial pesticides used on Mercurial pesticides used on crops and turf (most crops and turf (most residential areas were built on residential areas were built on former agricultural land);former agricultural land);

►Fertilizers containing HgFertilizers containing Hg..

Hg in soils and aquifer Hg in soils and aquifer materials:materials:

► More Hg in undisturbed soils (up to More Hg in undisturbed soils (up to 150 150 g/kg) than in g/kg) than in (1)(1) disturbed disturbed residential soils (<50 residential soils (<50 g/kg) and g/kg) and (2)(2) most aquifer materials (<50 most aquifer materials (<50 g/kg);g/kg);

► Hg higher in aquifer clay lenses (50-Hg higher in aquifer clay lenses (50-110 110 g/kg);g/kg);

► Hg in ground water above and Hg in ground water above and below clay lenses at background below clay lenses at background levels.levels.

Hg in topsoils was associated with Hg in topsoils was associated with organic materials, but, in subsoils, organic materials, but, in subsoils,

with iron and aluminum hydroxides.with iron and aluminum hydroxides.

We studied Hg in several We studied Hg in several residential septic systems to residential septic systems to discover whether they were discover whether they were

sources of Hg to ground sources of Hg to ground water, or part of the process water, or part of the process of Hg mobilization, or both.of Hg mobilization, or both.

At an unsewered residential At an unsewered residential area, evidence of septic-system area, evidence of septic-system effects oneffects on domestic-welldomestic-well water water were:were:►Presence of detergents;Presence of detergents;►High concentrations of ammonia, High concentrations of ammonia,

boron, chloride, nitrate, and sodium;boron, chloride, nitrate, and sodium;►Undetectable sulfate and detected Undetectable sulfate and detected

sulfide, which indicate likely sulfide, which indicate likely presence of sulfate-reducing presence of sulfate-reducing bacteria that methylate Hg. bacteria that methylate Hg.

Chemical characteristics of Chemical characteristics of septage and leach-field effluent septage and leach-field effluent were--were--►Hg concentrations in septage Hg concentrations in septage

ranging from < 0.02 to 0.06 ranging from < 0.02 to 0.06 g/L;g/L;►No dilution of Hg concentrations No dilution of Hg concentrations

from septage to effluent, but from septage to effluent, but dilution of other constituents;dilution of other constituents;

►Concentrations of chloride (Cl) and Concentrations of chloride (Cl) and sodium (Na) in domestic-well water sodium (Na) in domestic-well water overlapping those in leach-field overlapping those in leach-field effluent.effluent.

Sodium and chloride concentrations in domestic-well water at the CSL site, and in leach-field effluent (CSL/DOM = CSL site

domestic well; EFF = leach-field effluent).

0

50

100

150

200

250

300

350

400

450

Co

nce

ntr

atio

n (

mg

/L) Sodium

Chloride

------------Domestic wells----------------

----Effluent------

PROCESSESPROCESSES

Potential processes for mobilizing Potential processes for mobilizing mercury are--mercury are--

►Soil disturbance moves Hg from topsoil to Soil disturbance moves Hg from topsoil to subsoil;subsoil;

►Hg adsorbs to iron hydroxides in subsoils;Hg adsorbs to iron hydroxides in subsoils;►Effluent removes Hg from subsoils as it Effluent removes Hg from subsoils as it

moves downgradient from the septic tank,moves downgradient from the septic tank,►Effluent reduces the subsoil’s iron Effluent reduces the subsoil’s iron

hydroxides,hydroxides,► Iron and adsorbed Hg go into solution in Iron and adsorbed Hg go into solution in

the effluent.the effluent.

In leach-field effluent, Hg concentrations In leach-field effluent, Hg concentrations increased with Fe concentrations.increased with Fe concentrations.

Hg concentrations decreased with Hg concentrations decreased with dissolved organic carbon (DOC) dissolved organic carbon (DOC)

concentrations; apparently, DOC is not concentrations; apparently, DOC is not transporting Hg.transporting Hg.

Concentrations of Hg in effluent Concentrations of Hg in effluent increased as pH decreased. In increased as pH decreased. In ground water, the same relation ground water, the same relation occurs.occurs.

The USGS and NJDEP also collected The USGS and NJDEP also collected both unfiltered and filtered ground-both unfiltered and filtered ground-water samples for Hg analysis;water samples for Hg analysis;►In some cases, the filtered sample In some cases, the filtered sample

contained less Hg than the contained less Hg than the corresponding unfiltered sample.corresponding unfiltered sample.

►A likely explanation for this A likely explanation for this observation is that some of the Hg observation is that some of the Hg is bound to particles that are is bound to particles that are removed by filtering.removed by filtering.

Differences in Hg in filtered and Differences in Hg in filtered and unfiltered sample pairs from 16 unfiltered sample pairs from 16 domestic and production wellsdomestic and production wells

Co-occurrence of Hg >0.1 Co-occurrence of Hg >0.1 g/L and VOCs g/L and VOCs was examined for 6 Atlantic County Hg was examined for 6 Atlantic County Hg sites.sites. o, Non-significant at p=0.10; o, Non-significant at p=0.10; **Significant at or above Significant at or above p=0.1; p=0.1; ****, Significant at or above p=0.05; , Significant at or above p=0.05; ******; Significant at or ; Significant at or above p=0.01; --, Insufficient VOC data to testabove p=0.01; --, Insufficient VOC data to test

Site number

OtherVOC

TotalVOC

Ben-zene

Chloro-form

1,1-DCA

1,1-DCE

1,2-DCE

PCE 1,1,1-TCA

TCE Tolu-ene

1 -- o -- ** -- -- -- -- -- -- --

2 -- o -- o *** ** o o o o o

4 o ** ** ** -- -- o -- -- -- --

7 -- o o * * * o o o -- --

18 -- -- o o -- -- -- -- -- -- --

31 * o -- o -- -- -- -- -- -- --

IMPORTANT IMPORTANT ENVIRONMENTSENVIRONMENTS

Some important components of the Some important components of the environment where Hg is mobilized environment where Hg is mobilized may be:may be:

►Disturbed soilsDisturbed soils►Leach-field effluent Leach-field effluent ►Localized anoxic zones where Localized anoxic zones where

iron reduction (also sulfate iron reduction (also sulfate reduction and Hg methylation?) reduction and Hg methylation?) can occur; can occur;

►Particles to transport Hg.Particles to transport Hg.

We’re still trying to find out:We’re still trying to find out:

►Whether VOCs affect Hg mobility;Whether VOCs affect Hg mobility;►Whether methyl Hg in ground water Whether methyl Hg in ground water

poses a problem;poses a problem;►How Hg accumulates to high levels How Hg accumulates to high levels

in the aquifer; in the aquifer; ►Will the problem occur elsewhere in Will the problem occur elsewhere in

similar land-use, geologic, and similar land-use, geologic, and biogeochemical settings?biogeochemical settings?

Contact: jbarring@usgs.govContact: jbarring@usgs.gov