Phytoremediation of chlorinated solvents: laboratory and pilot-scale results

Laboratory and field tests have shown that, unlike bacteria, poplar trees are able to carry out complete degradation of fully chlorinated hydrocarbons to carbon dioxide and chloride. CO 2 was produced from the degradation of trichloroethylene (TCE), carbon tetrachloride (CT), and perchloroethylene (PCE) by axenic tissue cultures of poplar cells. Chloride ion accumulated in the media when poplar plants growing hydroponically were exposed to TCE or 1,1,1-trichloroethane (TCA). Pilot scale experiments in the field with TCE-exposed poplar demonstrated mass removal of TCE and CT from an artificial groundwater exceeding 95%. There was no enhancement of TCE and CT degradation in the rhizosphere soils and air emissions from leaves were less than 5% of the total removal. Chloride ion accumulated in the soils, suggesting that significant dechlorination occurred. Poplars have the potential for destructive removal of TCE and CT without harmful air emissions or accumulation of a hazardous solid waste.