Phytoremediation of 1,4-dioxane by hybrid poplar trees

1,4-Dioxane (dioxane), a suspected carcinogen, is a persistent environmental pollutant that is difficult to remove from contaminated sites. This work investigated the feasibility of vegetative uptake as a site remediation alternative. In hydroponic studies, hybrid poplar cuttings (Populus deltoides x nigra, DN 34, Imperial Carolina) removed 23 mg/L, dioxane rapidly. Within 9 days, a removal of 54.0 +/- 19.0% was achieved. This removal corresponded to a transpiration stream concentration factor of 0.72 +/- 0.07. Poplars also effectively remediated a dioxane-spiked soil (10 mg/kg). Only 18.8 +/- 7.9% of the initial dioxane spike remained in planted soil after 15 days, compared with 72.0 +/- 7.7% remaining in sterilized, unplanted soil. In both hydroponic and soil experiments, 76 to 83% of the dioxane taken up by poplars was transpired from leaf surfaces to the atmosphere, where it can be readily dispersed and photodegraded. These results suggest that phytoremediation is a viable alternative to remove dioxane from contaminated sites and should be considered for other hydrophilic contaminants.