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|a Lyons, J. R.
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|a Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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|a Ono, Shuhei
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|a Whitehill, Andrew Richard
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|a Ono, Shuhei
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|a Whitehill, Andrew Richard
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|a Contribution of isotopologue self-shielding to sulfur mass-independent fractionation during sulfur dioxide photolysis
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|c 2014-03-10T20:52:11Z.
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|z Get fulltext
|u http://hdl.handle.net/1721.1/85603
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|a Signatures of sulfur mass-independent fractionation (S-MIF) are observed for sulfur minerals in Archean rocks, and for modern stratospheric sulfate aerosols (SSA) deposited in polar ice. Ultraviolet light photolysis of SO[subscript 2] is thought to be the most likely source for these S-MIF signatures, although several hypotheses have been proposed for the underlying mechanism(s) of S-MIF production. Laboratory SO[subscript 2] photolysis experiments are carried out with a flow-through photochemical reactor with a broadband (Xe arc lamp) light source at 0.1 to 5 mbar SO[subscript 2] in 0.25 to 1 bar N[subscript 2] bath gas, in order to test the effect of SO[subscript 2] pressure on the production of S-MIF. Elemental sulfur products yield high δ[superscript 34]S values up to 140 ‰, with δ[superscript 33]S/δ[superscript 34]S of 0.59 ± 0.04 and Δ[superscript 36]S/Δ[superscript 33]S ratios of −4.6 ± 1.3 with respect to initial SO[subscript 2]. The magnitude of the isotope effect strongly depends on SO[subscript 2] partial pressure, with larger fractionations at higher SO[subscript 2] pressures, but saturates at an SO[subscript 2] column density of 10[superscript 18] molecules cm[superscript −2]. The observed pressure dependence and δ[superscript 33]S/δ[superscript 34]S and Δ[superscript 36]S/Δ[superscript 33]S ratios are consistent with model calculations based on synthesized SO[subscript 2] isotopologue cross sections, suggesting a significant contribution of isotopologue self-shielding to S-MIF for high SO[subscript 2] pressure (>0.1 mbar) experiments. Results of dual-cell experiments further support this conclusion. The measured isotopic patterns, in particular the Δ[superscript 36]S/Δ[superscript 33]S relationships, closely match those measured for modern SSA from explosive volcanic eruptions. These isotope systematics could be used to trace the chemistry of SSA after large Plinian volcanic eruptions.
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|a Exobiology Program (U.S.) (Grant NNX10AR85G)
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|a en_US
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|a Article
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|t Journal of Geophysical Research: Atmospheres
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