نتایج جستجو برای: sulfur isotopes
تعداد نتایج: 56644 فیلتر نتایج به سال:
Anaerobic oxidation of methane (AOM) coupled to sulfate reduction has been shown to consume up to 90% of the greenhouse gas methane produced within the subseafloor environment; however, the mechanism of this process has remained enigmatic. Here, we provide geochemical evidence based on sulfur, oxygen, and carbon isotopes for the involvement of iron oxides in sulfate-driven AOM inmethane seeps. ...
[1] Ice core measurements (H2O2 and CH4/HCHO) and modeling studies indicate a change in the oxidation capacity of the atmosphere since the onset of the Industrial Revolution due to increases in fossil fuel burning emissions [e.g., Lelieveld et al., 2002; Hauglustaine and Brasseur, 2001; Wang and Jacob, 1998; Staffelbach et al., 1991]. The mass-independent fractionation (MIF) in the oxygen isoto...
Sabkha deposits in the geologic record are commonly used to interpret the environmental conditions of deposition. Implicit in this use is the assumption that the solute system is chemically closed, that is, the authigenic minerals represent the composition of the fluids in their environment of origin. Thermodynamic and mass-balance calculations based on measurements of water and solute flux of ...
Life originated in Archaean oceans, almost 4 billion years ago, in the absence of oxygen and the presence of high dissolved iron concentrations. Early Earth oxidation is marked globally by extensive banded iron formations but the contributing processes and timing remain controversial. Very few aquatic habitats have been discovered that match key physico-chemical parameters of the early Archaean...
Geochemical and microbial evidence points to anaerobic oxidation of methane (AOM) likely coupled with bacterial sulfate reduction in the hypersaline groundwater of the Dead Sea (DS) alluvial aquifer. Groundwater was sampled from nine boreholes drilled along the Arugot alluvial fan next to the DS. The groundwater samples were highly saline (up to 6300 mm chlorine), anoxic, and contained methane....
Abstract. The ?74 ka Toba eruption was one of the largest volcanic events Quaternary. There is much interest in determining impact such a large event, particularly on climate and hominid populations at time. Although has been identified both land marine archives as Youngest Tuff, its precise place ice core record ambiguous. Several sulfate signals have Antarctic Greenland cores span 40Ar/39Ar a...
In PNAS, Leavitt et al. (1) describe the shared dependence of cell-specific sulfate reduction rate and sulfur isotope fractionations on the availability of a single electron donor for the model sulfate reducer, Desulfovibrio vulgaris Hildenborough. These authors then use their findings in a unique way to calibrate past sedimentary sulfate reduction rates (SedSRR) using sulfur isotope data from ...
The marine sulfate inventory represents the largest standing pool of electron acceptors, which, via microbial reduction, is responsible for roughly half organic matter mineralization globally in sediments. In addition to oxidation buried matter, reduction can be coupled methane migrating upward. Multiple sulfur isotope ratios were measured porewater sulfate, sulfide, elemental and pyrite from c...
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