Sulfur isotope fractionation by broadband UV radiation to optically thin SO 2 under reducing atmosphere

Total Pressure Dependence of Sulfur Mass‐Independent Fractionation by SO2Photolysis

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Sulfur Mass-Independent Fractionation (S-MIF) may provide a clue to understanding Earth's early atmosphere. The pSO 2 dependence has been demonstrated by SO 2 photolysis experiments (Endo et al, 2016;Ono et al, 2013), though they yield a Δ 36 S/Δ 33 S slope from À2.4 to À5, which does not match the observed Archean S-MIF. Isotopic self-shielding is known to produce S-MIF, which could be changed by both the partial pressure of SO 2 (pSO 2 ) and by the total pressure (pTotal).

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“…The experimental system was developed by Endo et al (2016), which consists of (1) an ultraviolet (UV) light source, (2) a cylindrical reaction chamber, and (3) a monochromator for monitoring UV spectra ( Figure S2 in the supporting information).…”

Recombination reactions as a possible mechanism of mass-independent fractionation of sulfur isotopes in the Archean atmosphere of Earth

“…This relatively simple model may finally offer mechanistic explanation for striking S-MIF in the Archean atmosphere. In the future, the theoretical framework developed here can be applied to other recombination reactions potentially relevant to the MIF of sulfur, such as SO + SO → S 2 O 2 (42).…”

“…Inclusion of some of these effects into consideration is desirable. Photochemical origin of the enrichment is another viable mechanism that also gives promising results (42). It should be studied separately and added to the overall picture.…”

Use of Isotope Effects To Understand the Present and Past of the Atmosphere and Climate and Track the Origin of Life

“…[136] Tw om ajor discoveries in 2000 (the sulfur isotope mass independent composition in Martian meteorites [76] and Archean rocks [96] )r equired an additional mechanistic explanation because S 2 F 10 is not relevant and concentrations of CS 2 in the Martian and terrestrial atmospheres are too low to explain the observed effect. Thef irst series of SO 2 and H 2 S photochemistry experiments was conducted by Farquhar et al, [76,97] and confirmed that as ulfur isotope mass independent effect can be found in these photolytic reactions and qualitatively resemble observations in nature.A ll multiple sulfur isotope measurements in extraterrestrial and terrestrial samples (e.g., meteorites,rocks,ice cores,aerosols) in the first decade of the 21 st century were interpreted based on similar photochemistry.B ecause existing theoretical knowledge of sulfur isotope effect was not totally satisfied to explain observations,e xperimental investigations accelerated and broadened in the second decade of the 21 st century:T he cross sections of anumber of isotopomers ( 32 SO 2 , 33 SO 2 , 34 SO 2 , 36 SO 2 ,O C 32 S, OC 33 S, OC 34 S, O 13 CS) [137][138][139][140] were firstly determined in as eries of experiments (joint efforts by many scientists in Japan and Denmark:D anielache,H attori, Johnson, Schmidt, Ueno,a nd Yoshida) for advancing theoretical studies;U eno and colleagues expanded their experiments to SO 2 photolysis; [141] Farquhar and colleagues also revisited their early SO 2 photolysis experiment results by carrying out additional experiments; [142,143] H 2 Sp hotolysis experiments were extended to the VUV range by Chakraborty et al; [144] another series of photochemistry experiments (with am ajor focus on SO 2 [145][146][147][148] and expanded to COS [149] and phenacylphenylsulfone [150] )w as carried out by Ono and colleagues as well. Ar eview of detailed experimental results and theoretical interpretation was recently provided by Ono.…”