Reconciling Modeled and Observed Δ 17 O(NO 3 − ) in Beijing Winter Haze With Heterogeneous Chlorine Chemistry

作者：Zhongyi Zhang, Zhuang Jiang, Tao Zhou, Lei Geng · 发表于：Journal of Geophysical Research Atmospheres · 年份：2024 · DOI：10.1029/2023jd039740 · 被引用次数：6 · 研究领域：Atmospheric chemistry and aerosols、Atmospheric Ozone and Climate、Air Quality Monitoring and Forecasting

Abstract The fine particulate matter (PM 2.5 ) in Chinese megacities has declined significantly after the implementation of strict mitigation strategies since 2013. However, the concentration of wintertime nitrate in PM 2.5 (p‐NO 3 ‐ ) has only changed slightly and became the dominant inorganic component despite considerable precursor emission reductions. Discerning chemical mechanisms leading to nitrate growth during haze events is critical to implementing effective pollution mitigation policies. The oxygen isotope anomaly of nitrate (Δ 17 O(NO 3 − )) is a powerful means to distinguish nitrate formation mechanisms. Nevertheless, the observed high Δ 17 O(NO 3 − ) values were significantly underestimated by chemical transport models during extreme haze events (PM 2.5 > 225 μg m −3 ) in Beijing, indicating an incomplete understanding of nitrate chemistry. To reconcile this model‐observation discrepancy, we compiled reported Δ 17 O(NO 3 − ) data in Beijing haze along with relevant observational parameters (e.g., hydroxyl (OH) reactivity, peroxyl radical concentrations), then tested assumptions on Δ 17 O of key precursors (e.g., OH and nitrogen dioxide (NO 2 )), recalculated Δ 17 O(NO 3 − ) and compared them with observations. Our results indicate that considering heterogeneous dinitrogen pentoxide reactions on chlorine‐containing aerosols (N 2 O 5 + Cl − chemistry) with a nitryl chloride (ClNO 2 ) yield of ∼0.75 can explain the observed high Δ 17 O(NO 3 − ) during extreme haz...