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Scientific Investigations Report 2013-5107

Prepared in cooperation with the New Jersey Department of Environmental Protection

Arsenic in New Jersey Coastal Plain Streams, Sediments, and Shallow Groundwater: Effects from Different Geologic Sources and Anthropogenic Inputs on Biogeochemical and Physical Mobilization Processes

By Julia L. Barringer, Pamela A. Reilly, Dennis D. Eberl, Adam C. Mumford, William M. Benzel, Zoltan Szabo, Jennifer L. Shourds, and Lily Y. Young

Thumbnail of and link to report PDF (2.9 MB)Abstract

Arsenic (As) concentrations in New Jersey Coastal Plain streams generally exceed the State Surface Water Quality Standard (0.017 micrograms per liter (µg/L)), but concentrations seldom exceed 1 µg/L in filtered stream-water samples, regardless of geologic contributions or anthropogenic inputs. Nevertheless, As concentrations in unfiltered stream water indicate substantial variation because of particle inputs from soils and sediments with differing As contents, and because of discharges from groundwater of widely varying chemistry.

In the Inner Coastal Plain, streams draining to lower reaches of the Delaware River traverse As-rich glauconitic sediments of marine origin in which As contents typically are about 20 milligrams per kilogram (mg/kg) or greater. In some of these sedimentary units, As concentrations exceed the New Jersey drinking-water maximum contaminant level (5 µg/L) in shallow groundwater that discharges to streams. Microbes, fueled by organic carbon beneath the streambed, reduce iron (Fe) and As, releasing As and Fe into solution in the shallow groundwater from geologic materials that likely include (in addition to glauconite) other phyllosilicates, apatite, and siderite. When the groundwater discharges to the stream, the dissolved Fe and As are oxidized, the Fe precipitates as a hydroxide, and the As sorbs or co-precipitates with the Fe. Because of the oxidation/precipitation process, dissolved As concentrations measured in filtered stream waters of the Inner Coastal Plain are about 1 µg/L, but the total As concentrations (and loads) are greater, substantially amplified by As-bearing suspended sediment in stormflows.

In the Outer Coastal Plain, streams draining to the Atlantic Ocean traverse quartz-rich sediments of mainly deltaic origin where the As content generally is low (<8 mg/kg). In unfiltered and filtered water samples, As concentrations typically are less than 1 µg/L in the acidic stream water and groundwater of the Outer Coastal Plain, but are greater in waters from urban areas. Despite the generally small geologic contributions to Outer Coastal Plain groundwater, where wastewater inputs were indicated, concentrations of As in unfiltered shallow groundwater discharging to small urban streams exceeded the maximum contaminant level.

With a history of agriculture in the New Jersey Coastal Plain, anthropogenic inputs of As, such as residues from former pesticide applications in soils, can amplify any geogenic As in runoff. Such inputs contribute to an increased total As load to a stream at high stages of flow. As a result of yet another anthropogenic influence, microbes that reduce and mobilize As beneath the streambeds are stimulated by inputs of dissolved organic carbon (DOC). Although DOC is naturally occurring, anthropogenic contributions from wastewater inputs may deliver increased levels of DOC to subsurface soils and ultimately groundwater. Arsenic concentrations may increase with the increases in pH of groundwater and stream water in developed areas receiving wastewater inputs, as As mobilization caused by pH-controlled sorption and desorption reactions are likely to occur in waters of neutral or alkaline pH (for example, Nimick and others, 1998; Barringer and others, 2007b). Because of the difference in As content of the geologic materials in the two sub-provinces of the Coastal Plain, the amount of As that is mobile in groundwater and stream water is, potentially, substantially greater in the Inner Coastal Plain than in the Outer Coastal Plain. In turn, streams within the Inner and Outer Coastal Plain can receive substantially more As in groundwater discharge from developed areas than from environments where DOC appears to be of natural origin.

First posted April 18, 2014

  • Appendix 3 XLSX (26 KB)
    Replicates and blanks for water samples from five watersheds in the New Jersey Coastal Plain.
  • Appendix 4 XLSX (36 KB)
    Total and recoverable contents, major and trace elements, streambed sediments, five Coastal Plain streams, 2007–2009.
  • Appendix 5 XLSX (28 KB)
    Field properties and concentrations of selected constituents in groundwater discharging to streams in five watersheds in the New Jersey Coastal Plain.
  • Appendix 6 XLSX (69 KB)
    Field properties, discharge, and concentrations of constituents in stream waters of five watersheds in the New Jersey Coastal Plain.

For additional information, contact:
Director, New Jersey Water Science Center
U.S. Geological Survey
3450 Princeton Pike, Suite 110
Lawrenceville, NJ 08648
http://nj.usgs.gov/

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Suggested citation:

Barringer, J.L., Reilly, P.A., Eberl, D.D., Mumford, A.C., Benzel, W.M., Szabo, Zoltan, Shourds, J.L., and Young, L.Y., 2013, Arsenic in New Jersey Coastal Plain streams, sediments, and shallow groundwater: Effects from different geologic sources and anthropogenic inputs on biogeochemical and physical mobilization processes: U.S. Geological Survey Scientific Investigations Report 2013–5107, 37 p., http://dx.doi.org/10.3133/sir20135107.

ISSN 2328-0328 (online)



Contents

Acknowledgments

Abstract

Introduction

Methods

Sediment and Soil Chemistry, Mineralogy, Microbiology, and Arsenic Content

Groundwater Chemistry, Microbiology, and Arsenic Concentrations

Stream-water Chemistry and Arsenic Concentrations

Effects of Geologic Sources and Anthropogenic Inputs on Arsenic Mobilization Processes

Summary and Conclusions

References Cited

Appendix 1. Short site names, U.S. Geological Survey site numbers and age, and description of underlying geologic formations for three Inner Coastal Plain streams

Appendix 2. Composition of anaerobic medium used in microcosm experiments using Crosswicks Creek groundwater and streambed sediments

Appendix 3. Replicates and blanks for water samples from five watersheds in the New Jersey Coastal Plain

Appendix 4. Total and recoverable contents, major and trace elements, streambed sediments, five Coastal Plain streams, 2007–2009

Appendix 5. Field properties and concentrations of selected constituents in groundwater discharging to streams in five watersheds in the New Jersey Coastal Plain

Appendix 6. Field properties, discharge, and concentrations of constituents in stream waters of five watersheds in the New Jersey Coastal Plain


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