globalchange  > 影响、适应和脆弱性
DOI: 10.1016/j.epsl.2018.05.041
Scopus记录号: 2-s2.0-85048076958
论文题名:
Chain formation as a mechanism for mass-independent fractionation of sulfur isotopes in the Archean atmosphere
作者: Harman C.E.; Pavlov A.A.; Babikov D.; Kasting J.F.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 496
起始页码: 238
结束页码: 247
语种: 英语
英文关键词: Archean ; atmospheric chemistry ; elemental sulfur ; Great Oxidation Event ; mass independent fractionation
Scopus关键词: Atmospheric optics ; Chains ; Fractionation ; Isotopes ; Photolysis ; Sulfur ; Sulfur compounds ; Archean ; Atmospheric parameters ; Elemental sulfur ; Fractionation patterns ; Great Oxidation Event ; Isotopic signals ; Mass-independent fractionation ; Reaction chambers ; Atmospheric chemistry
英文摘要: The anomalous abundances of sulfur isotopes in ancient sediments provide the strongest evidence for an anoxic atmosphere prior to ∼2.45 Ga, but the mechanism for producing this ‘mass-independent’ fractionation pattern remains in question. The prevailing hypothesis has been that it is created by differences in the UV photolysis rates of different SO2 isotopologues. We investigate here a recently proposed additional source of fractionation during gas-phase formation of elemental sulfur (S4 and S8). Because two minor S isotopes rarely occur in the same chain, the longer S4 and S8 chains should be strongly, and roughly equally, depleted in all minor isotopes. This gives rise to negative Δ33S values and positive Δ36S values in elemental sulfur—just the opposite of (and much larger than) what is predicted from SO2 photolysis itself. Back-reactions during chain formation, specifically photolysis of S2 and S3, pass sulfur having the opposite fractionation back to atomic S, and thence to other sulfur species, causing H2S, SO2, sulfate, and short-chain elemental sulfur to have positive Δ33S and negative Δ36S. Positive Δ33S values in elemental sulfur produced in laboratory SO2 photolysis experiments could be caused by the initial fractionation during photolysis, combined with rapid condensation of short-chain sulfur species on the walls of the reaction chamber, along with a scarcity of back-reactions. The simulated fractionations produced by the chain formation mechanism do not directly match fractionations from the rock record. The mismatch might be explained if the isotopic signals leaving the atmosphere were significantly modulated by life, by uncertainties in the rates of reactions of both major and minor isotopic sulfur species, or by the relatively large potential range of atmospheric parameters. Further work is needed to better constrain these uncertainties, but this novel mechanism suggests new avenues to explore in our search for a explanation for the S-MIF record. © 2018 The Authors
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109806
Appears in Collections:影响、适应和脆弱性
气候变化事实与影响

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作者单位: Department of Applied Physics and Applied Mathematics, Columbia University, 500 W. 120th St., New York, NY 10027, United States; NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, United States; NASA Astrobiology Institute, Virtual Planetary Laboratory, United States; NASA Nexus for Exoplanet System Science, United States; Planetary Environments Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States; Department of Chemistry, Marquette University, Milwaukee, WI 53021, United States; Geosciences Department, Pennsylvania State University, University Park, PA 16802, United States; Center for Exoplanets and Habitable Worlds, Pennsylvania State University, University Park, PA 16802, United States; Pennsylvania State Astrobiology Research Center, 2217 Earth and Engineering Sciences Building, University Park, PA 16802, United States

Recommended Citation:
Harman C.E.,Pavlov A.A.,Babikov D.,et al. Chain formation as a mechanism for mass-independent fractionation of sulfur isotopes in the Archean atmosphere[J]. Earth and Planetary Science Letters,2018-01-01,496
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