CHARACTERISATION OF MICROBIAL IN SITU DEGRADATION OF AROMATIC HYDROCARBONS

摘要

Carbon isotope fractionation was studied in a soil percolation column. The soil microbial community was able to degrade toluene generating a stable concentration gradient within the column. The carbon isotope composition of the residual non-degraded toluene fraction showed a significant increase in the ~(13)C/~(12)C ratio. The extent of biodegradation in this soil column was calculated using the measured isotope ratios (R_t) and an isotope fractionation factor (αC = 1.0017) obtained from a sulfate-reducing batch culture. The calculated residual substrate concentrations (C_t) were in good accordance with to the measured toluene concentrations in the column. The isotopic composition of BTEX compounds was studied in contaminated anoxic aquifers. Along the contamination plume, decrease of contaminant concentrations was associated with a distinct increase of δ ~(13)C values, suggesting in situ biodegradation. The contribution of microbial degradation to the total contaminant removal was calculated based on laboratory-derived carbon isotope fractionation factors using the Rayleigh equation. The results show that microbial degradation was the most important contaminant removal process in the aquifer.