Sediment Research

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USEPA: Research Guides Remediation of Contaminated Sediments Impacted by Groundwater Discharge (PDF) (2 pp, 127KB, About PDF)

Issue

The discharge of groundwater into surface water may influence the concentrations and availability of contaminants in sediments. There are three predominant pathways by which groundwater may affect the characteristics of contaminated sediments:

Direct contribution of contaminants from the discharge of contaminated groundwater
Indirect influence on existing contaminants due to geologic and chemical processes that change the properties of sediments and contaminants
Indirect influence on existing contaminants due to the influence of groundwater discharge on biological (e.g., microbial) processes that transform or degrade contaminants

Ground water can act as a conduit for dissolved pollutants and sediment constituents. With an enhanced understanding of groundwater discharge to surface water systems, scientists can improve estimates of long-term contaminant loads in sediments and develop better management practices to control human and ecosystem exposure to contaminated sediments.

Scientific Objective

The Land Research Program in EPA’s Office of Research and Development is conducting field-based research to:

Develop methods to best characterize hydrologic and chemical processes at the groundwater / surface water (GW/SW) interface
Understand the role of groundwater flux on sediment processes governing contaminant speciation and mass

This research entails characterization of water and solids within the GW/SW transition zone to explain processes that occur during physical contact between groundwater and sediments. These measurements are conducted to capture the spatial and temporal variability that is commonly encountered in these natural systems.

The overarching research goal is to develop a framework for risk characterization at contaminated sites, which will assist risk managers in selecting remediation strategies to best manage human and ecosystem exposure to contaminated sediments impacted by groundwater discharge.

Applications and Impacts

The outcome of this research provides EPA with practical knowledge to guide site characterization and remediation at sites where groundwater discharge exerts short- and long-term influence on sediment contamination.

Field and laboratory studies conducted by the Land Research Program have enabled EPA to better predict the mobility, bioavailability, and fate of contaminants in sediments, and to develop effective remediation strategies.

Research accomplishments include:

Identification of links between groundwater discharge and sediment contamination with emphasis on arsenic, lead and zinc
Development of new approaches to identify spatial variability of groundwater discharge into surface-water systems using direct measurements and cost-effective surrogate measures
Use of research findings by EPA Region 1 to identify the impact of groundwater discharge on metal contamination in sediments, and to select cost-effective remedies to manage contaminant inputs at two Superfund sites.

Groundwater discharge may serve as a long-term source of contaminants to sediments within a watershed and/or may govern processes controlling the properties of existing contaminants. Design of appropriate remedies that account for the influences of groundwater provides the basis for more effective remedies to manage risks to human and ecosystem health.

References

Lien, B. K. 2006. Development and Demonstration of a Bidirectional Advective Flux Meter for Sediment-Water Interface. EPA Report, U.S. Environmental Protection Agency, Cincinnati, OH, EPA/600/R-06/122.
http://www.epa.gov/nrmrl/pubs/600r06122/600r06122.pdf

Ford, R. G., Wilkin, R. T., Hernandez, G. 2006. Arsenic cycling within the water column of a small lake receiving contaminated ground-water discharge. Chemical Geology, 228(1-3): 137-155.

Wilkin, R. T., Ford, R. G. 2006. Arsenic solid-phase partitioning in reducing sediments of a contaminated wetland. Chemical Geology,
228(1-3): 156-174.

Ford, R. G., Wilkin, R. T., Scheckel, K. G., Paul, C. J., Beck, F., Clark, P., Lee, T. 2005. Field Study of the Fate of Arsenic, Lead, and Zinc at the Ground-Water/Surface-Water Interface, EPA Report, U.S. Environmental Protection Agency, Cincinnati, OH, EPA/600/R-05/161.
http://www.epa.gov/ORD/NRMRL/pubs/600R05161/600R05161.pdf

Ford, R. G. 2005. The Impact of Ground Water-Surface Water Interactions on Contaminant Transport with Application to an Arsenic Contaminated Site, EPA Environmental Research Brief, U.S. Environmental Protection Agency, Cincinnati, OH, EPA/600/S-05/002.
http://www.epa.gov/ORD/NRMRL/pubs/600s05002/epa_600_s05_002.pdf

Contacts

Robert Ford (ford.robert@epa.gov), EPA’s National Risk Management Research Laboratory, 513-569-7501

Bob Lien (lien.bob@epa.gov), EPA’s National Risk Management Research Laboratory, 513-569-7443

Steven Acree (acree.steven@epa.gov), EPA’s National Risk Management Research Laboratory, 580-436-8609