Roles of Sulfur Oxidation Pathways in the Variability in Stable Sulfur Isotopic Composition of Sulfate Aerosols at an Urban Site in Beijing, China,Environmental Science & Technology Letters

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Roles of Sulfur Oxidation Pathways in the Variability in Stable Sulfur Isotopic Composition of Sulfate Aerosols at an Urban Site in Beijing, China
Environmental Science & Technology Letters ( IF 8.9 ) Pub Date : 2020-10-19 , DOI: 10.1021/acs.estlett.0c00623
Mei-Yi Fan _{1,

2,

3} , Yan-Lin Zhang _{1,

2,

3} , Yu-Chi Lin _{1,

2,

3} , Jianghanyang Li ₄ , Hongguang Cheng ₅ , Ning An ₅ , Yele Sun _{6,

7,

8} , Yanmei Qiu _{6,

7} , Fang Cao _{1,

2,

3} , Pingqing Fu ₉

Affiliation

Yale-NUIST Center on Atmospheric Environment, International Joint Laboratory on Climate and Environment Change, Nanjing University of Information Science and Technology, Nanjing 210044, China
Key Laboratory Meteorological Disaster, Ministry of Education & Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disaster, Nanjing University of Information Science and Technology, Nanjing 210044, China
Jiangsu Provincial Key Laboratory of Agricultural Meteorology, College of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China
Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, United States
Institute of Geochemistry, State Key Laboratory of Environmental Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China

Sulfate (SO₄^2–) is an important chemical species in atmospheric aerosols, which strongly impacts atmospheric chemistry processes and climate change. Stable sulfur isotopes (δ³⁴S) of sulfate aerosols in PM_2.5 were measured in Beijing from November 13 to December 2, 2018, to investigate the pathways of formation of sulfate aerosols. The results showed that SO₄^2– constituted a major fraction (18%) of water-soluble ions and significant enhancement of sulfate was observed during the haze period. The δ³⁴S-SO₄^2– values averaged at 4.4 ± 1.4‰ during the full period, exhibiting a downward trend with an increase in sulfate concentration. The change in sulfur isotope values could not be explained by the changes in emission sources. Significant correlations were found between observed δ³⁴S-SO₄^2– values and SO₂ oxidation ratios (R = −0.88; p < 0.01), indicating the changes in sulfur isotopes were attributed to the SO₂ oxidation processes. On the basis of Rayleigh distillation, the average fractionation factor between SO₂ and SO₄^2– was 4.0 ± 1.2‰. Combining sulfur isotopes and the Bayesian model, we quantified the contributions of primary sulfate, OH, H₂O₂/O₃, NO₂, and O₂ [catalyzed by transition metal ions (TMIs)] oxidation pathways to sulfate formation were 7%, 20%, 16%, 27%, and 30%, respectively. The contributions of TMI and NO₂ pathways increased from 24% and 20% during the clean period to 38% and 29% during the haze period, respectively. Our results highlighted that sulfur dioxide oxidized by TMI-catalyzed O₂ and NO₂ were the dominant pathways of sulfate formation in Beijing under haze pollution during the heating seasons.

更新日期：2020-12-08

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