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Land Risk Management Research

Sediments Impacted by Contaminated Groundwater Discharge – Assessing Exposure and Restoration Alternatives

Introduction

Contaminated Soil and Sediments
Contaminated Soil and Sediments

To manage watersheds in a manner that preserves ecosystem services, it is necessary to understand the functions and interactions of all components of the hydrologic system. In most cases, the surface waterbody within a watershed is intimately connected to the associated subsurface groundwater system. The groundwater system serves two important functions within a watershed. First, it supplies some of the water that is conveyed through surface waterbodies. Second, it is a source of nutrients and contaminants that influence the health of the supported ecosystem. Sediments in the transition zone between the groundwater and surface water (GW/SW) transition zone, serve a critical function in supporting organisms at the base of food webs that characterize ecosystems within a watershed. In short, sediments serve as a gatekeeper for the flux of nutrients and contaminants that move through the GW/SW transition zone.

Environmental Issue or Problem

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

  • 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

Groundwater can act as a conduit for dissolved pollutants and sediment constituents. With a better understanding of groundwater discharge to surface water systems, scientists can improve estimates of long-term contamination in sediments to better control human and ecosystem exposure to this contamination.

Research

Contaminated Soil and Sediments
Researcher examining results of groundwater contaminated with metal such as arsenic and iron (red color) at a field site in Massachusetts.

This research entails characterization of water and solids within the GW/SW transition zone to explain processes that occur during contact between groundwater and sediments. EPA land risk management researchers conduct this field-based research to:

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

Outcomes and Impact

Field and laboratory studies conducted by the research team have enabled EPA to better predict the mobility, bioavailability, and fate of contaminants in sediments. Research has helped to develop cost-effective and sustainable strategies to restore ecosystem and human health.  Impact of this research on EPA’s ability to manage ecosystem resources at historically impacted sites is seen through the:

  • Catalytic role of EPA/ORD to stimulate progress on politically and technically intractable sites in Massachusetts
  • Explicit recognition outside of EPA/ORD from both the EPA program and regional offices via multiple regional and national awards, including:
      • EPA/OSWER National Notable Achievement Award - Regional Science Award: Fort Devens Superfund Site - Red Cove Team, 2009
      • Science Achievement Award - EPA New England Regional Honor Award - Aberjona River Study – Sound Science and Superfund Remedy, 2006
      • Exceptional/Outstanding ORD Technical Assistance to the Regions or program Offices, 2006

Publications

Developing Rapid and Cost-Effective Tools for Assessing Groundwater Impacts on Contaminated Sediments (2 pp, 247 KB) (EPA/600/F-12/533) May 2012

Risk Mangement Research | Air and Climate Change Research | Water Research | Ecosystems Restoration Research | Land Risk Management Research | Technology: Sustainable Technologies Research, Environmental Technology Verification Program (ETV), and Technology Assessments

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