Research Project Description May 18, 1995 - September 30, 1996 Fate of Trichloroethylene (TCE) in Plant/Soil Systems W.J. Doucette, B. Bugbee and D.K. Stevens, Utah State University Goals: The goal of this research is to 1) investigate the fate of TCE and other chlorinated ethenes in plant/soil systems through a combination of laboratory experiments and mathematical modeling and 2) to evaluate the applicability of a plant-based bioreactor for the remediation of groundwater contaminated with TCE. Rationale: Chlorinated solvents, such as TCE, are among the most frequently found groundwater contaminants at military installations, due to their widespread use in degreasing operations. Understanding the fate of these contaminants is critical in performing risk assessments and evaluating remediation options. Development of less costly remediation alternatives for contaminated groundwater are also of considerable importance. The uptake into plants is a potentially important fate process that has not been adequately evaluated for TCE and other chlorinated solvents. Determination of uptake rates, plant/water and plant/air distribution coefficients and degradation rates would greatly improve fate modeling and risk assessment efforts. In addition, the literature indicates that conditions in the rhizosphere may favor co-metabolic transformation of TCE. Phytoremediation has shown promise, but its implementation has been limited in part, due to the difficulties associated with non-engineered systems. The plant-based bioreactor proposed in this study may provide a cost-effective approach for remediating groundwater contaminated with TCE and other hazardous organic chemicals. The bioreactor approach enables the control of key environmental variables, such as moisture, nutrients, pH, and oxygen in order to maximize plant growth and remediation efficiency. Approach: Laboratory studies will evaluate the fate of chlorinated ethenes in hydroponic systems. Specifically, these studies will determine plant/water/air distribution coefficients and plant uptake rates. This approach will be extended to laboratory and field plant/soil systems. Based on the results, a plant-based bioreactor for the remediation of contaminated groundwater will be constructed. Environmental conditions will be managed to optimize plant growth and microbial activity. Status: Funding for the project was received in September 1996. Investigators have started working on the construction of the closed-chamber systems and are cultivating plants to be used in the hydroponic studies. This project is in its first year. Clients/Users: Successful completion of this project will provide information of value to state and federal government agencies, environmental consulting firms and the U.S. Department of Defense. Key words: chlorinated solvents, trichloroethylene, TCE, contaminated ground water, remediation, soil systems, plant systems. Return to List