Comparison of Trichloroethylene Toxicity, Removal, and Degradation by Varieties of Populus and Salix for Improved Phytoremediation Applications

Abstract

Trichloroethylene (TCE), a chlorinated organic solvent, is one of the three most common and widespread groundwater contaminants worldwide. Exposure to this contaminant has been linked to liver and kidney toxicity and cancer in humans and animals [1]. The Salicaceae family, which includes poplar and willow trees, has been very successful in phytoremediation efforts involving chlorinated solvents including TCE. Previous phytoremediation studies investigated removal of this contaminant using one or two genotypes, but a screening of a large number of genotypes in this family of plants had not yet been conducted. In this study, nine Populus and twelve Salix varieties were chosen for their previous success in phytoremediation efforts or local native significance, and experiments were conducted to compare toxicity, uptake, and degradation of TCE. Results from the toxicity screening demonstrated that hybrid poplar clones Crandon (Populus alba x grandidentata), Nisqually-1 (P. trichocarpa), D.Pa (P. alba) and willow clone S365 (Salix discolor) had the highest mass gain and best health at the highest TCE concentration. Percent removal of TCE in one week ranged from 19.2 to 44.9 with Crandon, P. deltoides hybrid 91x0403, poplar clone H11-11 (P. trichocarpa x deltoides), Salix sitchensis clone B, and Nisqually-1 all removing more than 40 percent of the TCE from hydroponic solution. In terms of TCE degradation, S. sitchensis clone B, poplar hybrid 91x0403, and hybrid poplar H11-11 had the most TCE metabolite, trichloroethanol, per gram of fresh plant weight, with the best performer, S. sitchensis clone B, having eight times the amount than the lowest genotype tested. These results indicated that there are significant differences in the ability of poplar and willow genotypes to remove and degrade TCE, and that many different genotypes could be successfully utilized for phytoremediation of TCE. This data set could be applied toward choosing the appropriate genotypes for the phytoremediation of TCE in a given location and climate.