Departments of ¹Chemical Engineering, ²Chemistry and ³Biochemistry, Kansas State University, Manhattan, KS, 66506
Alfalfa plants were grown in sandy silt soil (silt<10%) in a laboratory chamber with two channels, each with dimensions 35 cm in depth, 1.8 m in axial length, and 10 cm in width. The daily water feeding operation to the growing plants was accomplished by introducing either pure distilled water or water contaminated with organics of interest. Experiments were conducted to investigate the influence of these alfalfa plants in bioremediating soil and ground water contaminated with 1,1,1-trichloroethane (TCA) and trichloroethylene (TCE). From July '93 to October '93, TCA and TCE were fed at 50 and 200 µL/L, respectively. The contaminants were introduced into the channel that had been previously fed with phenol at 500 mg/L. The fate of these volatile chlorinated compounds in the saturated zone was monitored using the gas chromatographic headspace analysis technique. Methane at a concentration of about 14 mg/L was observed in the saturated zone of the channel. Measurements of the gas phase samples in the enclosed chamber using FT-IR indicated the presence of TCA and small quantities of TCE. No intermediates of biodegradation were observed during the gas phase measurements. After subsequently washing out the contaminants for 2 months, TCA and TCE were reintroduced into the plant growth chamber. One channel was fed with TCA and chloroform in the entering ground water at a concentration of 100 µL/L of water; the other channel was fed with TCE at a concentration of 200 µL/L of water. Daily phenol additions in the second case were accomplished through recharging wells. The results obtained from this study were compared to earlier experiments with TCA and TCE as contaminants where phenol had been previously fed into the channel as the inflow contaminated ground water. Recent studies indicate the presence of some biodegradation intermediates and the absence of methane in the ground water samples; however, using FT-IR, no intermediates were detected in the gas phase. The fate of these chlorinated compounds was also monitored for nearly two months in the absence of alfalfa plants.
vegetation, volatile chlorinated compounds, headspace analysis, ground water
This paper is from the Proceedings of the 10th Annual Conference on Hazardous Waste Research 1995, published in hard copy and on the Web by the Great Plains/Rocky Mountain Hazardous Substance Research Center.