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Environmental Health - Toxic Substances

Research Projects -- Oxygenated Fuel -- Laurel Bay, South Carolina, Site

Hydrogen Isotopes

Dissolved hydrogen (H2(aq)) is an important intermediate produced and consumed by microorganisms during the anaerobic decomposition of organic matter in many subsurface environments. Because H2 may undergo isotopic fractionation reactions as a result of microbial cycling, the stable hydrogen-isotope (delta symbol2H) value of ground water in equilibrium with H2 may be changed from ambient conditions. However, field-scale observations and isotopic dilution and isotopic fractionation calculations suggest that microbial cycling of H2 does not affect the delta symbol2H value of ground water, even in strongly reducing methanogenic conditions characterized by high H2 concentrations. These results imply that the widespread application of delta symbol2H and delta symbol18O values to deduce the climatic history of ground-water recharge is valid, even if applied in areas where the ground water may have received recharge from areas affected by petroleum-hydrocarbon releases or natural accumulations of organic matter, attendant anaerobic conditions, and active H2 cycling.

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