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TERMINAL ELECTRON ACCEPTING PROCESSES IN THE ALLUVIAL SEDIMENTS OF A HEADWATER STREAM
Citation:
Morrice, J A., C. N. Dahm, H. M. Valett, P. V. Unnikrishna, AND M. E. Campana. TERMINAL ELECTRON ACCEPTING PROCESSES IN THE ALLUVIAL SEDIMENTS OF A HEADWATER STREAM. JOURNAL OF THE NORTH AMERICAN BENTHOLOGICAL SOCIETY 19:593-608, (2000).
Description:
Chemical fluxes between catchments and streams are influenced by biochemical processes in the groundwater-stream water (GW-SW) ecotone, the interface between stream surface water and groundwater. Terminal electron accepting processes (TEAPs) that are utilized in respiration of organic carbon in anoxic environments may have a strong effect on nutrient dynamics and water chemistry. Concentrations of oxidized and reduced forms of terminal electron acceptors (dissolved O2, NO3, Fe2+, SO4, and CH4) were measured in networks of vertically nested wells installed beneath the surface stream and in the near-stream aquifer of a headwater catchment. Tracer addition experiments were conducted in surface and groundwater environments of a first-order montane stream to characterize hydrologic fluxes between the stream and aquifier, and to quantify ecosystem retention of terminal electron acceptors (nitrate and sulfate) in the GW-SW ecotone.
Sulfate retention was evident in both hyporheric and groundwater environments. Distribution of important redox sensitive solutes varied predictably with changing hydrologic residence time of water in the GW-SW ecotone. Results suggest a strong hydrologic control of TEAPs and ecosystem retention of biologically important solutes in the GW-SW ecotone related to characteristics of GW-SW mixing and residence time of water in the hyporheic zone.