Removal of Trichloroethylene from Aquifers Using Trees

Abstract

Poplars are deep rooted, fast growing trees with high transpiration rates and are well suited for removal of pollutants from shallow and moderately deep aquifers. Laboratory experiments have shown that poplars can remove trichloroethylene (TCE) from soil and oxidize it to carbon dioxide. Seedlings were placed in bioreactors with the root zone separated from the shoot zone (headspace). {sup 14}C-labeled carbon dioxide was recovered from the headspace after the soil zone was dosed with radiolabeled TCE. Additional products of TCE oxidation were found in plant tissue and in axenic plant tissue cultures: trichloroethanol and di- and trichloroacetic acid. A model is presented showing how a poplar plantation planted down-gradient of a contaminated site could intercept a TCE plume from a dense nonaqueous phase liquid source. Costs for plant bioremediation are estimated to be about 20% of that for a conventional pump and treat system. Planned field experiments with poplars for TCE removal and degradation are described.