Mass-independent fractionation of sulfur isotopes (MIF-S) has been observed in Archean sedimentary rocks and modern stratospheric sulfate aerosol (SSA). Photolysis of SO₂ is known to cause significant MIF-S and could be related to the observed MIF-S. However, previous experiments with SO₂ photolysis at room temperature, or at low temperatures and atmospheric pressure, did not quantitatively explain quadruple sulfur isotopic compositions (δ³⁴S, Δ³³S, and Δ³⁶S values) of the Archean sedimentary rocks and the modern SSA. Here we describe sulfur isotopic fractionation during SO₂ photolysis including isotopic self-shielding at low temperatures (down to 228 K) and low pressures (from 5.8 to 10 kPa) where pressure broadening of SO₂ becomes negligible. Results indicate that magnitudes of sulfur isotopic fractionation factors (³⁴ε, ³³E, and ³⁶E values, where ³³E = ³³ε – 1000 × [(1 + ³⁴ε/1000)^0.515 − 1] and ³⁶E = ³⁶ε − 1000 × [(1 + ³⁶ε/1000)^1.90 − 1]) increase with decreasing temperature, with values at 228 K being about four times those at 296 K (³⁴ε of up to +344‰). Meanwhile, ³³E/³⁴ε and ³⁶E/³³E ratios are roughly independent of temperature over the temperature range (by approximately +0.1 and − 3.1, respectively), although the ³³E/³⁴ε ratios slightly increase with decreasing temperature, ranging from ~ + 0.08 to ~ + 0.13. A two-component mixing model involving SO₂ oxidation by OH and SO₂ photolysis in the stratosphere reproduces δ³⁴S and Δ³³S values of modern SSA when the contribution ratio of SO₂ photolysis to SO₃ production is ~20%. The contribution ratio of ~20% is consistent with a previous estimation by Whitehill et al. (2015). However, Δ³³S/δ³⁴S ratios at low temperatures are far from those of Archean sedimentary rocks, calling for an additional mechanism (or mechanisms) to explain Archean MIF-S.

在太古代沉积岩和现代平流层硫酸盐气溶胶 (SSA) 中观察到与质量无关的硫同位素分馏 (MIF-S)。_{已知 SO 2}的光解会导致显着的 MIF-S，并且可能与观察到的 MIF-S 有关。然而，先前在室温或低温和大气压下进行 SO ₂光解的实验并未^定量解释太^{古代沉积岩}和现代SSA。在这里，我们描述了 SO _{2过程中的硫同位素分馏}光解包括在低温（低至 228 K）和低压（从 5.8 至 10 kPa）下的同位素自屏蔽，其中 SO ₂的压力展宽可以忽略不计。结果表明硫同位素分馏因子的大小（³⁴ ε、³³ E 和³⁶ E 值，其中³³ E =  ³³ ε – 1000 × [(1 +  ³⁴ ε/1000) ^0.515  - 1] 和³⁶ E =  ³⁶ ε - 1000 × [(1 +  ³⁶ ε/1000) ^1.90  - 1]) 随着温度的降低而增加，228 K 时的值约为 296 K 时的四倍（³⁴ ε 高达 +344‰）。同时，³³ E/ ³⁴ ε 和³⁶ E/ ³³ E 比率在整个温度范围内大致与温度无关（分别约为 +0.1 和 - 3.1），尽管³³ E/ ³⁴ ε 比率随着温度的降低略有增加，范围从 ~ + 0.08 至 ~ + 0.13。_{当SO 2}光解对SO ₃的贡献比时，由OH 氧化SO 2 和SO _2光解在平流层的双组分混合模型再现了现代SSA的δ ³⁴ S 和Δ ³³ S 值产量约为 20%。约 20% 的贡献率与 Whitehill 等人先前的估计一致。（2015 年）。然而，低温下的 Δ ³³ S/δ ³⁴ S 比值与太古代沉积岩相差甚远，需要额外的机制来解释太古代 MIF-S。