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https://doi.org/10.5194/egusphere-2023-2554
https://doi.org/10.5194/egusphere-2023-2554
20 Nov 2023
 | 20 Nov 2023

Quantifying SO2 oxidation pathways to atmospheric sulfate by using stable sulfur and oxygen isotopes: laboratory simulation and field observation

Ziyan Guo, Keding Lu, Pengxiang Qiu, Mingyi Xu, and Zhaobing Guo

Abstract. The formation of secondary sulfate in the atmosphere remains controversial, and it is urgent to seek for a new method to quantify different sulfate formation pathways. Thus, SO2 and PM2.5 samples were collected from 4 to 22 Dec. 2019 in Nanjing. Sulfur and oxygen isotope compositions were synchronously measured to study the contribution of SO2 homogeneous and heterogeneous oxidation to sulfate. Meanwhile, the correlation of δ18O values between H2O and sulfate from SO2 oxidation by H2O2 and Fe3+/O2 were investigated in the lab. Based on isotope mass equilibrium equations, the ratios of different SO2 oxidation pathways were calculated. The results showed that secondary sulfate constituted higher than 80 % of total sulfate in PM2.5 during the sampling period. Laboratory simulation experiments indicated that δ18O of sulfate was linearly dependent on δ18O of water, and the slopes of linear curves for SO2 oxidation by H2O2 and Fe3+/O2 were 0.43 and 0.65, respectively. The secondary sulfate in PM2.5 was mainly ascribed to SO2 homogeneous oxidation by OH radicals and heterogeneous oxidation by H2O2 and Fe3+/O2. SO2 heterogeneous oxidation was generally dominant during sulfate formation, and the contribution of SO2 heterogeneous oxidation was about 52 %. Especially, SO2 oxidation by H2O2 predominated in SO2 heterogeneous oxidation reactions with an average ratio around 55 %. This study provided an insight into precisely evaluating sulfate formation pathways by combining stable sulfur and oxygen isotopes.

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Journal article(s) based on this preprint

21 Feb 2024
Quantifying SO2 oxidation pathways to atmospheric sulfate using stable sulfur and oxygen isotopes: laboratory simulation and field observation
Ziyan Guo, Keding Lu, Pengxiang Qiu, Mingyi Xu, and Zhaobing Guo
Atmos. Chem. Phys., 24, 2195–2205, https://doi.org/10.5194/acp-24-2195-2024,https://doi.org/10.5194/acp-24-2195-2024, 2024
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

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The formation of secondary sulfate in the atmosphere remains controversial, and it is urgent to...
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