Elucidating pathways of benzene biodegradation in subsurface environments using isotope analysis

The pathways of benzene biodegradation in subsurface environments were studied using isotope analysis. Characterization of isotopic fractionation during anaerobic benzene biodegradation using enrichment cultures under sulfate-reducing, nitrate-reducing, and methanogenic conditions, suggested that the initial steps in the benzene biodegradation pathway might determine the extent of isotopic fractionation. Enrichment factors calculated for carbon and hydrogen isotopic fractionation showed significant differences between cultures using the three terminal electron accepting processes. The kinetic isotope effects value for the nitrate-reducing culture was consistent with a Friedel-Crafts alkylation reaction, where benzene was methylated to toluene in the initial degradation steps. Distinct carbon and hydrogen enrichment factors suggested at least two distinct pathways exist for anaerobic biodegradation of benzene. This is an abstract of a paper presented at the 8th International In Situ and On-Site Bioremediation Symposium (Baltimore, MD 6/6-9/2005).