BY-PRODUCTS OF ANAEROBIC ALKYLBENZENE METABOLISM USEFUL AS INDICATORSOF IN-SITU BIOREMEDIATION

Based on the concordance of laboratory studies of anaerobic bacteria a nd field observations from an aquifer in Seal Beach, CA, a group of co mpounds including benzylsuccinic acid, benzylfumaric acid (or a closel y related isomer), and the o-, m-, and p-methyl homologs of these comp ounds are proposed as biogeochemical indicators of in situ anaerobic a lkylbenzene metabolism in gasoline-contaminated aquifers. Under the co ntrolled conditions of tile field study, a strong correspondence was o bserved between the disappearance of alkylbenzenes from groundwater ov er time and the appearance of associated metabolic byproducts. This co rrespondence was both qualitative (i.e., only products specific to the metabolism of toluene, o-xylene, and m-xylene were observed, and only these three hydrocarbons were depleted) and quantitative (i.e., meta belie byproduct concentrations tended to increase as the associated al kylbenzene concentrations decreased). These metabolites may prove usef ul for distinguishing biotic losses of BTEX (benzene, toluene, ethylbe nzene, and xylenes) from abiotic losses when monitoring gasoline-conta minated, typically anaerobic, aquifers that are not being actively rem ediated or that are being remediated by stimulation of anaerobic bacte ria.