Poplar trees were found to be capable of taking up trichloroethylene (TCE) and degrading it to several known metabolic products:  trichloroethanol, trichloroacetic acid, and dichloracetic acid. Poplars were also shown to transpire TCE in measurable amounts. To eliminate the possibility that the degradation we observed was produced solely by rhizosphere organisms, axenic poplar tumor cell cultures were tested; the cultures produced the same intermediate metabolic products. When dosed with [14C]TCE, cell cultures also produced low levels of radiolabeled carbon dioxide and a labeled insoluble residue. These results show that significant TCE uptake and biotransformation occurs in poplar, which demonstrates the potential for the use of poplars for in situ remediation of TCE.

We tested the ability of hybrid poplar to absorb trichloroethylene (TCE) from groundwater. Initial studies used axenic tumor cultures of H11 -11 grown in the presence of 14 C-TCE. These cells metabolized the TCE to produce trichloroethanol, di-and trichloroacetic acid. Some of the TCE was incorporated into insoluble, non-extractable cell residue, and small amounts were mineralized to 14 C-CO 2 . Rooted poplar cuttings grown in PVC pipes produced the same metabolites when exposed to TCE. Mass balance studies indicate that the poplars also transpire TCE. In addition we are conducting one of the first controlled field trials for this technology. Trees were planted in cells lined with high density polyethylene and dosed with TCE via an underground water stream during the growing season. Cells containing trees had significantly reduced TCE levels in the effluent water stream compared to control cells containing only soil. These results show that significant TCE uptake and degradation occur in poplars, which bodes well for the future use of poplars for in situ remediation of TCE.Trichloroethylene (TCE) has been widely used since its discovery in the midnineteenth century (1) for a variety of purposes: as an anesthetic, a dry cleaning agent and, until recently, in enormous quantities as a degreasing agent. While most TCE is of anthropomorphic origin, TCE has recently been found to be produced by marine algae (2). It has contaminated ground water at many localities, and is now the most commonly found volatile organic contaminant at many of these sites (3).The fact that TCE is a suspected carcinogen (4) has lent urgency to clean-up efforts. The stability, persistence and accumulation ofTCE in non-miscible underground pools, "DNAPLs", that are not easily found or accessible render attempts at remediation

Axenic tumor cultures of poplar cells, clone H11-11, were grown in the presence of [14C]-trichloroethylene (TCE) (uniformly labeled). The cells were capable of metabolizing TCE to produce trichloroethanol, di- and trichloroacetic acid. Some of the carbon from TCE was found in insoluble, nonextractable cell residue, and small amounts were mineralized to [14C]CO2. Poplar cuttings grown in soil and exposed to TCE produced the same metabolites. In field trials, trees were planted in soil in test cells and exposed to TCE via underground water injection during the growing season. During the growing season, at least 95% of the TCE was removed from the influent water stream in cells containing trees. Mass balance studies conducted in the laboratory indicated that 70 to 90% of the TCE was transpired; however, greenhouse and field study results showed that less than 5% of the total TCE taken up by the plants is transpired. These results show that significant TCE uptake and degradation occur in poplars. Poplars appear to be useful for in situ remediation of TCE-contaminated sites under proper conditions.ImagesFigure 2