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Research Activities
Research Activities
Contaminated Sediments Research
At sites with contaminated sediments, EPA’s Superfund program must decide how best to protect the environment and public health. Decisions to remediate a site are based, in part, on the relative risks to the environment and health posed. In some cases, a site is left alone to avoid further contamination and in others a site can be effectively remediated with available technology and tools.
The Superfund program must have an understanding of the potential risks posed by the remedial action itself, and an understanding of how best to monitor effectiveness of the cleanup activities over time.
The Land Research Program (LRP) in EPA’s Office of Research and Development is conducting research to answer key scientific questions that will improve the scientific basis for making decisions about contaminated sediments.
Research includes:
- Modeling fate and transport of contaminants under different remedial alternatives
- Defining critical sediment and tissue residue criteria for aquatic biota, wildlife, and humans
- Developing alternative sediment remedies that are cost-effective
Modeling Activities
When assessing what to do to remove contaminated sediments from property, decision makers must forecast changes in nature and the extent of contamination under various management, temporal, and hydrodynamic scenarios. This research is therefore addressing fate and transport (F&T) questions such as:
What is the most appropriate framework for modeling F&T of contaminants under different remedial alternatives?
Existing contaminated sediment transport models and bioaccumulation models were evaluated to determine their capabilities and limitations. Public domain F&T models that ranked highest in the model evaluation (Environmental Fluid Dynamic Code, or EFDC) are being augmented to include:
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A sediment consolidation–contaminant transport model to simulate consolidation due to sediment self-weight and cap overburden, and the resulting contaminant flux
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A model to simulate wave-induced resuspension of highly organic sediments and associated contaminants.
The sediment transport, eutrophication, and diagenesis modules will be linked to account for resuspension of inorganic sediment and organic carbon, and for the settling and deposition of both inorganic sediment and organic matter. The upgraded EFDC was tested in several types of water bodies to improve the capability of the site-specific models to support management decisions. The final step will be to develop the framework for modeling remedial alternatives. The framework will include:
- A watershed loading model
- The enhanced EFDC model
- A bioaccumulation model
- Protocols for applying the component models
- Software for evaluating uncertainties in a modeling study.
Sediment Residue Criteria Activities
Understanding the toxic properties of contaminants is essential to understanding the risks. The LRP) is focused on contaminants that tend to be persistent and bioaccumulate within organisms, since they pose the most evident long-term risk.
Since the risk to humans is primarily from exposure to contaminants accumulated up the aquatic food chain or from contact with exposed aquatic organisms research on residue criteria is largely on ecological receptors.
The research will establish and improve understanding of causal relationships between sediment contamination and chemical residues and exposure to aquatic organisms. This research also will provide tools for use in defining critical sediment and tissue residue thresholds between acceptable and unacceptable effects for aquatic and aquatic dependent organisms.
Key research foci include the following:
Determining the critical tissue residues to use as screening levels for aquatic organisms exposed to PBTs. Research consists of assembling and evaluating a residue–effects database for polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) for aquatic and aquatic-dependent organisms.
Determining how to extrapolate field-measured bioaccumulation data across species, ecosystem, and/or time through development of a hybrid empirical/modeling approach.
Determining the impact of incomplete removal or resuspension of contaminated sediments on the aquatic organisms.
Determining the conditions under which different approaches to measuring the integrity of benthic organism communities at sites are most suited.
Alternative Sediment Remedies Activities
Current remediation approaches to addressing contaminated sediments include dredging, capping, and monitored natural attenuation (MNA) techniques. LINK EPA’s Superfund program must decide which of these options best suits a particular site.
Development of new treatment approaches is desirable, considering the costs, strengths, and limitations of these approaches in the context of the wide variety of sites to which they must be applied. The LRP provides the science and technology needed to better understand the traditional risk management options and to investigate alternative treatment options.
The LRP continues to evaluate post-dredging residuals models through case study and field evaluation. Field studies will be conducted to evaluate post-dredging residuals and implement innovative monitoring tools, such as core profiling techniques, semi-permeable membrane devices, volatilization chambers, and innovative techniques for evaluating capping technologies yet to be applied for monitoring dredging operations.
The LRP is investigating several alternative sediment remedies with the potential to be more cost-effective than conventional dredging or capping remedies. An emphasis will be placed on bioremediation of organics, electrochemical degradation, and conventional and reactive caps. In coordination with the U.S. Army Corps of Engineers, and in association with the Strategic Environmental Research and Development Program (SERDP), the LRP will complete a number of research projects to evaluate the field performance of dredging and capping and to improve understanding of the best management practices.
The LRP is developing and testing the applicability of a number of tools for monitoring contaminated sediment and associated risks, which can then be applied to monitoring remedy performance. The tools include sampling devices suitable to investigate contaminant migration into natural or constructed sediment caps and migration from the sediment into the overlying water column and atmosphere as well as monitoring techniques used in developing and evaluating potential remedies. The models of sediment transport and uptake by organisms will provide insight into the time scale appropriate for implementing the monitoring techniques to measure progress toward the cleanup goal.