期刊
ENVIRONMENTAL SCIENCE & TECHNOLOGY
卷 51, 期 6, 页码 3307-3317出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.6b04873
关键词
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资金
- Genomes to Watershed Scientific Focus Area at Lawrence Berkeley National Laboratory - U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research [DE-AC02-05CH11231]
- United States Department of Energy [DE-AC05-76RL01830]
- Office of Biological and Environmental Research
Three-dimensional variably saturated flow and multicomponent biogeochemical reactive transport modeling, based on published and newly generated data, is used to better understand the interplay of hydrology, geochemistry, and biology controlling the cycling of carbon, nitrogen, oxygen, iron, sulfur, and uranium in a shallow floodplain. In this system, aerobic respiration generally maintains anoxic groundwater below an oxic vadose zone until seasonal snowmelt-driven water table peaking transports dissolved oxygen (DO) and nitrate from the vadose zone into the alluvial aquifer. The response to this perturbation is localized due to distinct physico-biogeochemical environments and relatively long time scales for transport through the floodplain aquifer and vadose zone. Naturally reduced zones (NRZs) containing sediments higher in organic matter, iron sulfides, and non-crystalline U(IV) rapidly consume DO and nitrate to maintain anoxic conditions, yielding Fe(II) from FeS oxidative dissolution, nitrite from denittification, and U(VI) from nitrite-promoted U(IV) oxidation. Redox cycling is a key factor fbr sustaining the observed aquifer behaviors despite Continuous oxygen influx and the annual hydrologically induced oxidation event. Depth-dependent activity of fermenters, aerobes, nitrate reducers, sulfate reducers, and chemolithoautotrophs (e.g., oxidizing Fe(II), S compounds, and ammonium) is linked to the presence of DO) which has higher concentrations near the water table.
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