Comparative plant uptake and microbial degradation of trichloroethylene in the rhizospheres of five plant species : implications for bioremediation of contaminated surface soils

Author

Todd Alan Anderson

Date of Award

12-1991

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Life Sciences

Major Professor

Walter R. Farkas

Committee Members

David White, Donita Frazier, John Graveel, Barbara Walton

Abstract

The objective of this study was to collect data that would provide a foundation for the concept of using vegetation to enhance in situ bioremediation of contaminated surface soils. Soil and vegetation (Lespedeza cuneata, Paspalum notatum, Pinus taeda, and Solidago sp.) samples from the Miscellaneous Chemicals Basin (MCB) at the Savannah River Site were used in tests to identify critical plant and microbiological variables affecting the fate of trichloroethylene (TCE) in the root zone. Microbiological assays including phospholipid fatty acid analyses, and ¹⁴C-acetate incorporation were conducted to elucidate differences in rhizosphere and nonvegetated soil microbial communities from the MCB. The microbial activity, biomass, and degradation of TCE in rhizosphere soils were significantly greater than corresponding nonvegetated soils. In addition, vegetation (both indigenous and nonindigenous) had a positive effect on microbial degradation of ¹⁴C-TCE in whole-plant experiments. Soils from the MCB containing Lespedeza cuneata, Pinus taeda, and Glycine max mineralized greater than 25% of the ¹⁴C-TCE added compared with less than 20% in nonvegetated soils. Collectively, these results provide evidence for the positive role of vegetation in enhancing biodegradation. Furthermore, biodegradatlon of TCE may be slower than degradation rates for less persistent waste chemicals such as nonhalogenated aromatics. Therefore, the data are likely to be conservative estimates of the potential for enhanced degradation of waste chemicals in the rhizosphere. In most of the whole plant experiments conducted, total uptake was minimal, ranging from 1%-21%, and was related to water use and plant species. Because the experiments were designed to maximize plant uptake, these data may be overestimates of the potential TCE residues in plants grown in TCE-contaminated soil. This dissertation represents a systematic approach to answering initial fundamental questions on the soil-plant-microbe-chemical relationship. The results presented provide strong evidence for the potential role of vegetation in remediation of surface soils contaminated with hazardous organic compounds. In addition, the reviewed literature on rhizosphere microbiology, accelerated degradation of agrochemicals in the root zone, and recent research on the fate of nonagricultural chemicals in the rhizosphere, all provide additional impetus for exploring the use of vegetation in bioremediation of contaminated surface soils.

Recommended Citation

Anderson, Todd Alan, "Comparative plant uptake and microbial degradation of trichloroethylene in the rhizospheres of five plant species : implications for bioremediation of contaminated surface soils. " PhD diss., University of Tennessee, 1991.
https://trace.tennessee.edu/utk_graddiss/11054