School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
Faculty of Frontier Engineering, Institute of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
Environ Sci Technol. 2020 Aug 18;54(16):9862-9871. doi: 10.1021/acs.est.0c01540. Epub 2020 Jul 29.
Photolysis of iron chlorides is a well-known photolytic source of Cl in environmental waters. However, the role of particulate chlorine radicals (Cl and Cl) in their multiphase oxidative potential has been much less explored. Herein, we examine the effect of Cl/Cl produced from photolysis of particulate iron chlorides on atmospheric multiphase oxidation. As a model system, experiments on multiphase oxidation of SO by Cl/Cl were performed. Fast sulfate production from SO oxidation was observed with reactive uptake coefficients of ∼10, comparable to the values necessary for explaining the observations in the haze events in China. The experimental and modeling results found a good positive correlation between the uptake coefficient, γ, and the Cl production rate, d[Cl]/dt, as γ = 5.3 × 10 × log(d[Cl]/dt) + 4.9 × 10. When commonly found particulate dicarboxylic acids (oxalic acid or malonic acid) were added, sulfate production was delayed due to the competition of Fe between chloride and the dicarboxylic acid for its complexation at the initial stage. After the delay, comparable sulfate production was observed. The present study highlights the importance of photochemistry of particulate iron chlorides in multiphase oxidation processes in the atmosphere.
铁氯化物的光解是环境水中氯的一种众所周知的光解源。然而，颗粒态氯自由基（Cl 和 Cl）在其多相氧化潜力中的作用还远未得到充分探索。在此，我们研究了由颗粒态铁氯化物光解产生的 Cl/Cl 对大气多相氧化的影响。作为一个模型体系，我们进行了 Cl/Cl 氧化 SO 的多相氧化实验。观察到 SO 氧化产生快速硫酸盐，其反应吸收系数约为 10，与解释中国雾霾事件观测结果所需的值相当。实验和建模结果发现，吸收系数γ与 Cl 生成速率 d[Cl]/dt 之间存在良好的正相关关系，即 γ=5.3×10×log(d[Cl]/dt)+4.9×10。当添加常见的颗粒态二羧酸（草酸或丙二酸）时，由于在初始阶段，Cl 与二羧酸竞争与 Fe 形成配合物，硫酸盐的生成会因 Fe 的竞争而延迟。延迟后，观察到可比的硫酸盐生成。本研究强调了颗粒态铁氯化物光化学在大气多相氧化过程中的重要性。
