Department of Environmental Science & Engineering, Jiangwan Campus, Fudan University, No. 2205 Songhu Road, Shanghai 200438, China.
Department of Environmental Science & Engineering, Jiangwan Campus, Fudan University, No. 2205 Songhu Road, Shanghai 200438, China; Institute of Eco-Chongming, East China Normal University, No.3663 Northern Zhongshan Road, Shanghai 200062, China.
Sci Total Environ. 2021 Sep 1;785:147345. doi: 10.1016/j.scitotenv.2021.147345. Epub 2021 Apr 26.
Nitrate aerosol is ubiquitous in the atmosphere. Nitrate in the particulate and aqueous phase can affect various atmospheric chemical processes through its hygroscopicity and photolysis. The impacts of nitrate photolysis on the heterogeneous oxidation of SO have been attracting attention. However, the influence of nitrate on heterogeneous aqueous phase formation of atmospheric sulfate aerosol is still not very clear. In this study, the effects of nitrate on aqueous phase oxidation of bisulfite under different conditions were investigated. Results show that nitrate photolysis can promote the oxidation of bisulfite to sulfate, especially in the presence of O. It is found that pH plays a significant role in the reaction, and ammonium sulfate has significant impacts on the enhancement of aqueous phase sulfate production through regulating the pH of solution. An apparent synergism is found among halogen chemistry, nitrate and its photochemistry and S (IV) aqueous oxidation, especially the oxidation of halide ions by nitrate and its photolysis and by the intermediate products produced by the free radical chain oxidation of S (IV) in acidic solution, leading to the coupling of the redox cycle of halogen with the oxidation of bisulfite, which promotes the continuous aqueous oxidation of bisulfite and the formation of sulfate. In addition, the role of nitrate itself in the aqueous phase oxidation of bisulfite is revealed. These results provide a new insight into the heterogeneous aqueous phase oxidation pathways and mechanisms of SO in cloud and fog droplets and haze particles.
硝酸盐气溶胶在大气中普遍存在。颗粒相和水相中的硝酸盐通过吸湿性和光解作用可以影响各种大气化学过程。硝酸盐光解对 SO 异相氧化的影响已引起关注。然而，硝酸盐对大气硫酸盐气溶胶异相水相形成的影响仍不是很清楚。在这项研究中，研究了硝酸盐在不同条件下对亚硫酸氢盐水相氧化的影响。结果表明，硝酸盐光解可以促进亚硫酸氢盐向硫酸盐的氧化，特别是在存在 O 的情况下。研究发现，pH 值在反应中起着重要作用，铵盐通过调节溶液的 pH 值对水相硫酸盐生成的增强有显著影响。卤族化学、硝酸盐及其光化学与 S（IV）水相氧化之间存在明显的协同作用，特别是硝酸盐及其光解以及 S（IV）自由基链氧化产生的中间产物对卤化物离子的氧化作用，导致卤族元素的氧化还原循环与亚硫酸氢盐的氧化耦合，促进亚硫酸氢盐的连续水相氧化和硫酸盐的形成。此外，揭示了硝酸盐本身在亚硫酸氢盐水相氧化中的作用。这些结果为云、雾滴和霾粒子中 SO 的异相水相氧化途径和机制提供了新的认识。
