气候变化领域集成服务门户(CCPortal): Organic sulfur fluxes and geomorphic control of sulfur isotope ratios in rivers

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DOI	10.1016/j.epsl.2021.116838
	Organic sulfur fluxes and geomorphic control of sulfur isotope ratios in rivers
	Kemeny P.C.; Torres M.A.; Lamb M.P.; Webb S.M.; Dalleska N.; Cole T.; Hou Y.; Marske J.; Adkins J.F.; Fischer W.W.
发表日期	2021
ISSN	0012821X
卷号	562
英文摘要	Pyrite oxidation plays a critical role in the relationship between weathering and climate, and its impact on the global carbon cycle has previously been constrained through inversion models utilizing observations of river sulfate (SO42−) and its 34S/32S isotope ratio (δ34SSO4). However, measurements from some rivers have suggested that δ34SSO4 can be substantially impacted by processes such as microbial sulfate reduction and/or sulfur assimilation and cycling, rather than simply reflecting a weighted mixture of lithologic sulfur sources. To study the prevalence and controls on SO42− transformations, we measured dissolved major element concentrations and δ34SSO4 in river water samples from throughout western Iceland. Our analyses focused on samples from a small catchment hosting the Efri Haukadalsá river, a system with relatively uniform and isotopically constrained basaltic bedrock. We also measured sediment δ34S and sulfur speciation using sulfur K-edge X-ray absorption spectroscopy on sediment and vegetation samples from this catchment. Values of dissolved δ34SSO4 in the Efri Haukadalsá ranged from 2.5‰ to 23.7‰ and had a linear relationship with Cl−/SO42− ratios, indicating that SO42− predominantly derived from basalt weathering and meteoric precipitation. The lower δ34SSO4 values were found in fluvial valleys with V-shaped cross sections, while higher values of δ34SSO4 occurred in U-shaped, glacially eroded valleys with thick alluvial fills blanketing the valley floor. Spectroscopic observations identified organic sulfur phases in suspended river sediment, floodplain deposits, and vegetation. Mass balance calculations quantified the organic sulfur flux as less than 10% of SO42− export, and sediment δ34S values were comparable to river δ34SSO4. We interpreted these isotopic and chemical patterns as reflecting differences in the availability of unweathered bedrock across the Efri Haukadalsá catchment, with V-shaped valleys having greater access to fresh sulfide-bearing minerals than alluviated U-shaped valleys; this interpretation is in contrast to one in which the elevated δ34SSO4 values reflect fractionation during sulfur transformations along alluvial reaches. These results validated the application of river inversion models for constraining weathering fluxes and affirmed that pyrite oxidation globally, even in the presence of river sulfur cycling, modulates the abundance of atmospheric carbon dioxide. © 2021 Elsevier B.V.
关键词	chemical weathering Iceland pyrite oxidation sulfur isotopes XANES
英文关键词	Atmospheric chemistry; Carbon dioxide; Carbon dioxide process; Catchments; Climate models; Isotopes; Landforms; Pyrites; Rivers; Runoff; Suspended sediments; Vegetation; Weathering; X ray absorption spectroscopy; Atmospheric carbon dioxide; Floodplain deposits; Geomorphic controls; Global carbon cycle; Linear relationships; Mass-balance calculations; River water samples; Sulfur transformation; Sulfur dioxide; bedrock; chemical weathering; fluvial deposit; isotopic ratio; organic sulfur compound; oxidation; pyrite; river water; speciation (chemistry); sulfur isotope; water chemistry; XANES spectroscopy; Iceland
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/203159
作者单位	Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, United States; Earth, Environmental, and Planetary Sciences, Rice University, Houston, TX, United States; Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, United States
推荐引用方式 GB/T 7714	Kemeny P.C.,Torres M.A.,Lamb M.P.,et al. Organic sulfur fluxes and geomorphic control of sulfur isotope ratios in rivers[J],2021,562.
APA	Kemeny P.C..,Torres M.A..,Lamb M.P..,Webb S.M..,Dalleska N..,...&Fischer W.W..(2021).Organic sulfur fluxes and geomorphic control of sulfur isotope ratios in rivers.Earth and Planetary Science Letters,562.
MLA	Kemeny P.C.,et al."Organic sulfur fluxes and geomorphic control of sulfur isotope ratios in rivers".Earth and Planetary Science Letters 562(2021).