Phytoremediation of trichloroethene (TCE) using cottonwood trees

摘要

Phytoremediation uses the natural ability of plants to degrade contaminants in ground water. A field demonstration designed to remediate aerobic shallow ground water that contains trichloroethene began in April 1996 with the planting of cottonwood trees over an approximately 0.2-hectare area at the Naval Air Station, Fort Worth, Tex. Ground water was sampled in July 1997, November 1997, February 1998, and June 1998. Analyses from samples indicate that ree roots have the potential to create anaerobic conditions in the ground water that will facilitate degradation of grichloroethene by microbially mediated reductive dechlorination. Dissolved oxygen concentrations, which varied across the site, were smallest near a mature cottonwood tree (about 20-years old) 60 meters southwest of the cottonwood plantings. Reduction of dissolved oxygen is the primary microbially mediated reaction occurring in the ground water beneath the planted trees, whereas near the nature cottonwood tree, data indicate that methanogenesis is the most probable reaction occurring. Reductive dechlorination either is not occurring or is not a primary process away from the mature tree. On the basis of isotopic analyses of carbon-13 at locations away from the mature tree, trichloroethene concentration is controlled by volatilization.