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STABLE CARBON ISOTOPE BIOGEOCHEMISTRY OF A SHALLOW SAND AQUIFER CONTAMINATED WITH FUEL HYDROCARBONS
Citation:
Fang, J., M. J. Barcelona, R. V. Krishnamurthy, AND E. A. Atekwana. STABLE CARBON ISOTOPE BIOGEOCHEMISTRY OF A SHALLOW SAND AQUIFER CONTAMINATED WITH FUEL HYDROCARBONS. APPLIED GEOCHEMISTRY 15:169-181, (2000).
Description:
Ground-water chemistry and the stable C isotope composition ( 13CDIC) of dissolved C (DIC) were measured in a sand aquifer contaminated with JP-4 fuel hydrocarbons. Results show that ground water in the upgradient zone was characterized by DIC content of 14-20 mg C/L and 13CDIC values of -11.3% to -13.0%. The contaminant source zone was characterized by an increase in DIC content (12.5 mg C/L to 54 mg C/L), Ca, and alkalinity, with a significant depletion of 13C in 13CDIC (-11.9% to -19.2%). That source zone of the contaminant plume was also characterized by elevated levels of aromatic hydrocarbons (0?g/L to 1490 ?g/L) and microbial metabolites (aromatic acids, 0 ?g/L to 2277 ?g/L), non-detectable dissolved O2, NO3 and SO4. Phospholipid ester-linked fatty acid analyses suggest the presence of viable SQ-reducing bacteria in ground water at the time of sampling. The ground-water chemistry and stable C isotope composition of ground-water DIC are interpreted using a chemical reaction model involving rainwater recharge, contrbutions of CQ from soil gas and biodegradation of hydrocarbons, and carbonate dissolution. The major-ion chemistry and 13CDIC were reconciled, and the model predictions were in good agreement with field measurements. It was concluded that stable C isotope measurements, combined with other biogeochemical measures can be a useful tool to monitor the dominant terminal electron-accepting processes in contaminated aquifers and to identify mineralogical, hydrological, and microbiological factors that a ect 13C of dissolved inorganic C.