Speciation and Removal Mechanisms of Rhenium in Anoxic Waters: Roles of Zero-Valent Sulfur, Mineral Oxide Catalysis, and Pyrite Surfaces
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Redox heterogeneity of subsurface waters in the Mesoproterozoic ocean.
A substantial body of evidence suggests that subsurface water masses in mid-Proterozoic marine basins were commonly anoxic, either euxinic (sulfidic) or ferruginous (free ferrous iron). To further document redox variations during this interval, a multiproxy geochemical and paleobiological investigation was conducted on the approximately 1000-m-thick Mesoproterozoic (Lower Riphean) Arlan Member ...
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The effect of sequential extraction of trace metals on sulfur (S) speciation in anoxic sludge samples from two lab-scale biogas reactors augmented with Fe was investigated. Analyses of sulfur K-edge X-ray absorption near edge structure (S XANES) spectroscopy and acid volatile sulfide (AVS) were conducted on the residues from each step of the sequential extraction. The S speciation in sludge sam...
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Groundwater and sediment samples (~1 m depth) at sites representative of different groundwater pathways were collected to determine the aqueous speciation of sulfur and the fractionation of sulfur isotopes in aqueous and solid phases. In addition, selected sediment samples at 5 depths (from oxic to anoxic layers) were collected to investigate the processes controlling sulfur biogeochemistry in ...
متن کامل7.10.4 Iron Speciation and Isotope Perspectives on Palaeoproterozoic Water Column Chemistry
Ancient rocks record the redox conditions of the oceanatmosphere system through the distribution of iron (Fe) between oxidised and reduced minerals, which can be formulated into a suite of Fe palaeoredox proxies. The balance between Fe and S in a given system reflects the variance in a range of highand low-temperature sources and sinks. Iron can be delivered by hydrothermal, diagenetic or clast...
متن کاملIron Sulfide-arsenite Interactions: Adsorption Behavior onto Iron Monosulfides and Controls on Arsenic Accumulation in Pyrite
Arsenic mobility in natural systems is often linked to iron and sulfur cycling at redox boundaries, apparently due to co-precipitation reactions of arsenic with poorly crystalline iron (oxy)hydroxides, iron monosulfides, and pyrite (e.g., Edenborn et al., 1986; Moore et al., 1988). The mobility of arsenic under anoxic, sulfate-reducing conditions is expected to be governed by interactions betwe...
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