Publications— Water-Resources Investigations Report

Relation of Mercury to Other Chemical Constituents in Ground Water in the Kirkwood-Cohansey Aquifer System, New Jersey Coastal Plain, and Mechanisms for Mobilization of Mercury from Sediments to Ground Water

U.S. Geological Survey Water-Resources Investigations Report 00-4230

Prepared in cooperation with the New Jersey Department of Environmental Protection

By Julia L. Barringer and Cecilia L. MacLeod

View the report in Portable Document Format (PDF) WRIR 00-4230 (1.73 MB)

Download the Appendixes (PDF 4.0 MB)

Abstract

Water from 265 domestic wells that tap the unconfined Kirkwood-Cohansey aquifer system in the Coastal Plain of New Jersey contained concentrations of mercury that are equal to or exceed the U.S. Environmental Protection Agency maximum contaminant level (MCL) of 2 μg/L (micrograms per liter). The wells range in depth from 50 to 200 feet, and are located in 32 discrete, mostly residential, areas that were developed primarily on former agricultural land during the 1950’s through the 1970’s. Concentrations in two other areas exceeded 1 μg/L. Naturally occurring mercury concentrations in ground water from the Kirkwood-Cohansey aquifer system typically are less than 0.01 μg/L, but concentrations in water from some wells were as much as 42 μg/L. No evidence currently exists that conclusively links known point sources such as landfills, industrial operations, or commercial enterprises to most of the elevated concentrations of mercury in ground water in the residential areas. Possible sources of the mercury include pesticides and atmospheric deposition.

Analysis of water from wells in 6 of the 34 areas for other constituents indicates that nitrate concentrations also commonly are elevated above background levels (which typically are undetectable at 0.01 milligrams per liter), and exceed the MCL of 10 milligrams per liter in some samples. Several volatile organic compounds (VOCs), including chloroform, also have been measured in water from wells at many of the 34 sites. Analytical results for water samples collected at several depths from boreholes at 2 of the 34 sites indicate elevated concentrations of calcium, magnesium, barium, strontium, nitrate, and chloride, which may be related to both agricultural chemical applications and septic-system effluent. Determinations of tritium and helium concentrations indicate that water containing elevated concentrations of mercury recharged the aquifer between 9.4 and 79 years ago, which includes the period during which many of the 34 sites were undergoing a change from agricultural or undeveloped to residential land use.

Batch equilibrium experiments were used to measure adsorption of dissolved mercury, mercuric chloride, and phenylmercuric acetate by aquifer sediments at pH 3.5-4.0, 4.5-5.0, and 5.5-6.0. In nearly all cases, 55 to 95 percent of the mercury added to the sediments was adsorbed. Mercury mobilization from aquifer sediments inoculated with mercury was investigated by leaching the sediments with two concentrations of nitric acid (a component of acid rain), a sodium chloride solution (simulating road salt), and three fertilizer solutions. A solution of 20-20-20 (nitrogenphosphorous-potassium) fertilizer removed virtually all of the mercury with which the sediments had been inoculated. The sodium chloride solution was moderately effective in removing applied mercury from the sediments, as was a solution of nitric acid. A more dilute nitric acid solution and two sodium nitrate fertilizer solutions were less effective.

Results of these experiments indicate that mercury adsorbs to aquifer sediments, but that varying amounts can be removed by infiltrating solutions, some of which can be related to specific land uses. Land-use history at the 34 sites generally indicates a change from agricultural or undeveloped settings to residential settings. Whatever the source of mercury to these sites, a change in the geochemical environment of the soil and aquifer brought about by land-use change probably provides mechanisms for mobilizing the mercury from soils and sediments to ground water.

Abstract
Introduction
     Purpose and scope
     Mercury in the environment
     History of mercury contamination in the Kirkwood-Cohansey aquifer system
          Concentrations
          Possible sources
     Acknowledgments
Chemistry and mobility of mercury and colloidal transport
     Chemistry and mobility of mercury
     Colloidal transport
Description of the study area
     Lithology
     Ground-water hydrology
     Soils
     Land use
     Geochemistry of water in the Kirkwood-Cohansey aquifer system in undeveloped
       and agricultural areas
          Undeveloped areas
          Agricultural areas
Study methods
     Field
     Laboratory
          Adsorption experiments
          Desorption experiments
Relation of mercury to other chemical constituents
     Vertical distribution of mercury and other constituents at boreholes in Gloucester and
      Atlantic Counties
          Borehole 1--Gloucester County
          Borehole 2--Atlantic County
     Age of water sampled at the boreholes
     Relations between concentrations of mercury and other constituents at selected sites
Mobilization of mercury from land surface or subsurface to ground water
     Adsorption to and desorption from soils
     Adsorption to and desorption from aquifer sediments
          Characteristics of aquifer sediments
          Adsorption to aquifer sediments
          Desorption from aquifer sediments
               Leaching experiments using dilute nitric acid
               Leaching experiments using a sodium chloride solution
               Leaching experiments using fertilizer solutions
     Conditions and possible mechanisms for mobilization of mercury
          Persistence of mercury in soils
          Geochemical mechanisms for mobilization
          Mechanisms associated with land-use change
Summary and conclusions
References cited
Appendix A--Chemical characteristics of and constituents in water from selected wells in
undeveloped and agricultural land-use areas, Kirkwood-Cohansey aquifer system, Atlantic,
Burlington, Camden, Gloucester, and Salem Counties, New Jersey
Appendix B--Sampling protocols, analytical methods, and raw analytical data
Appendix C--Sediment-size analysis and raw and calculated data for mercury-adsorption
experiments
Appendix D--Experimental procedures and raw and calculated data for mercury-desorption
experiments

Suggested citation:
Barringer, J.L., and MacLeod,C.L., 2001, Relation of mercury to other chemical constituents in ground water in the Kirkwood-Cohansey aquifer system, New Jersey Coastal Plain, and mechanisms for mobilization of mercury from sediments to ground water: U.S. Geological Survey Water-Resources Investigations Report 00-4230, 154 p.

If you have Adobe® Acrobat® or Adobe® Acrobat®Reader® installed on your computer, you may view and print the PDF version of this report. Acrobat Reader, is a free download from Adobe Systems Incorporated.