Fate of Volatile Chlorinated Organic Compounds in a Laboratory Chamber with Alfalfa Plants

摘要

The fate of two volatile organo phlorinated compounds, 1,1,1-trichloroethane (TCA) and trichloroethylene (TCE), was studied in rhizosphere soil. Laboratory experiments were performed with alfalfa (Medicago sativa) growing in sandy silt soil fed continuously with groundwater contaminated with TCA and TCE at 50 and 200 μL/L, respectively. Methane generated in the groundwater provided evidence for anaerobic biodegradation. Groundwater samples indicated that the concentration of TCE decreased with axial position during the steady-state period. The flow rate of the effluent was significantly less than the inlet flow because of active evapotranspiration. Thus, a significant fraction of TCA and TCE disappeared. Headspace analysis of the gas in the enclosed chamber using a FT-IR spectrophotometer showed that small quantities of TCA and TCE migrated into the gas phase above the alfalfa plants; no chlorinated intermediates or methane were found in this gas phase.