Research Project 4
| EPA Grant Number: | R828771-0-01 |
|
Title:
|
Co-Contaminant
Effects on Risk Assessment and Remediation Activities Involving Urban
Sediments and Soils |
|
Investigators: |
William P. Ball, Ph.D., Principal Investigator Edward J. Bouwer, Ph.D., Co-Principal Investigator |
|
Institution: |
The Johns Hopkins University, Department of Geography and Environmental Engineering |
| Project Period: | October 1, 2001 to September 30, 2004 |
| Description: |
| The release of hazardous organic contaminants at sites of chemical disposal, processing, storage, or release has led to the contamination of surface water, ground water, and associated solids. These latter include harbor sediments, urban surface soils and subsurface geologic materials adjacent to and downstream of the chemical source. Contaminated sites typically involve complex mixtures of contaminants, the fate of which is affected by both biochemical interactions that impact microbial attenuation (e.g., cometabolic effects, competitive inhibition and toxicity), as well as competitive adsorption on solid phases. Because sediment- or soil-bound contaminants are usually not bioavailable (from either a remediation or biotoxicity viewpoint), successful prediction and assessment of fate and transport require a full accounting and integration of the sorption effects. The proposed research will evaluate the need and means to achieve improved modeling as applied to risk assessment and management for contaminated sediments and soils. The focus will be on organic contaminant mixtures, with emphasis on improved approaches for modeling the combined effects of both sorption and biodegradation. |
| Objectives/Hypotheses: |
| In the
first year, we will focus on one of the following two objectives,
dependent upon the interests and abilities of the doctoral student: (1)
To experimentally evaluate sources and mechanisms of competitive
sorption in environmentally relevant soils and sediments; (2) To develop
and evaluate alternative (mechanistically based) approaches for
quantifying rates of biodegradation in complex mixtures of organic
chemicals. |
| Approach: |
| Our experimental approach will be based on laboratory evaluation of field samples, including harbor sediments, brownfield soils, and other sites of contamination in urban settings. In addition to characterizing solids for organic matter and black carbon (charcoals, soot, and coal), we intend to obtain screening –level sorption equilibrium and rate data using nonpolar organic chemical probes. Modeling efforts will apply postulated numerical models to evaluate the sensitivity of overall degradation rates to the biochemical issues and competitive adsorption effects identified above. Using selected waste mixtures, we intend to develop guidance about magnitudes of “correction” factors to account for bioavailability and co-contaminant interaction. |
| Expected Results: |
| Overall, this work will contribute toward better assessment and management of risk in urban settings by providing both characterizations and modeling approaches applicable to the processes that most strongly control the transport and persistence of organic pollutants. |
| Supplemental Keywords: |
| chlorinated organic chemicals, toxic chemicals, cleanup, restoration, hydrogeology |