Toxic Substances Hydrology Program
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U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting Charleston South Carolina March 8-12, 1999--Volume 3 of 3--Subsurface Contamination From Point Sources, Water-Resources Investigations Report 99-4018C
![]() Biogeochemical Processes in a Contaminant Plume Downgradient from a Landfill, Norman, OklahomaBy Isabelle M. Cozzarelli, Joseph M. Suflita, Glenn A. Ulrich, Steve H. Harris, Martha A. Scholl, Jamie L. Schlottmann, and Jeanne B. Jaeschke ABSTRACTStudies of an alluvial aquifer contaminated with landfill leachate,
at Norman, Oklahoma, indicate that the non-uniform distribution
of electron acceptors and biogeochemical reactions in anoxic ground
water result in steep chemical gradients and the formation of distinct
reaction zones. A combined geochemical and microbiological approach
was used to delineate different biogeochemical zones along a transect
parallel to regional ground-water flow downgradient from the landfill.
The important microbially mediated reactions in the anoxic plume
are iron reduction, sulfate reduction, and methanogenesis. Dissolved
H2 measurements in ground water
at several depth intervals at one location near the edge of the
landfill indicate that sulfate reduction is a dominant respiratory
process, but near- saturation levels of methane were detected in
some intervals. Cycling of sulfur was apparent in a thin interval
at the water table where the highest rates of sulfate reduction
(13.2 micromoles per day (µM/day)) and sulfate concentrations
well above background levels (up to 4.6 millimolar (mM)) were measured.
In this zone, sulfur isotope analyses indicate that the sulfate
is enriched in 34S ( ![]() |
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