Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Institute of Atmospheric Sciences, Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, China.
Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Institute of Atmospheric Sciences, Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, China; Shanghai Institute of Eco-Chongming (SIEC), No. 3663 Northern Zhongshan Road, Shanghai 200062, China.
Sci Total Environ. 2019 Feb 1;649:1393-1402. doi: 10.1016/j.scitotenv.2018.08.295. Epub 2018 Aug 23.
Adsorbed nitrate is ubiquitous in the atmosphere, and it can undergo photolysis to produce oxidizing active radicals. Nitrate photolysis may be coupled with the oxidation conversions of atmospheric gaseous pollutants. However, the processes involved remain poorly understood. In this study, the impact of adsorbed nitrate on the heterogeneous oxidation of SO on α-FeO was investigated in the absence and presence of simulated solar irradiation by using in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The results indicate that for α-FeO particles with no adsorbed nitrate, the formation of adsorbed sulfate on humid particles is stronger than that on dry particles. Meanwhile, light can also promote the heterogeneous conversion of SO and the formation of sulfate on dry particles because α-FeO is a typical photocatalyst. However, the heterogeneous conversion of SO on humid α-FeO particles is somewhat suppressed under light, suggesting the occurrence of photoinduced reductive dissolution. For the heterogeneous conversion of SO on α-FeO particles with adsorbed nitrate, the formation of sulfate on humid particles is still higher than that on dry particles. For the dry α-FeO particles with adsorbed nitrate, light promotes the formation of adsorbed sulfate. For the humid α-FeO particles with adsorbed nitrate, the heterogeneous conversion of SO under light is stronger than that under no light, indicating that the photolysis of adsorbed nitrate is coupled with the oxidation of SO and the formation of sulfate. The consumption of adsorbed nitrate and the formation of adsorbed NO are observed during the introduction of SO. A possible mechanism for the impact of adsorbed nitrate on the heterogeneous conversion of SO on α-FeO particles is proposed, and atmospheric implications based on these results are discussed.
吸附态硝酸盐在大气中普遍存在，它可以通过光解作用产生氧化性活性自由基。硝酸盐光解可能与大气气态污染物的氧化转化相耦合。然而，其中涉及的过程仍不清楚。在这项研究中，通过使用原位漫反射红外傅里叶变换光谱（DRIFTS），在没有和存在模拟太阳光照射的情况下，研究了吸附态硝酸盐对α-FeO 上 SO 异相氧化的影响。结果表明，对于没有吸附态硝酸盐的α-FeO 颗粒，在潮湿颗粒上形成的吸附态硫酸盐比在干燥颗粒上更强。同时，光也可以促进 SO 在干燥颗粒上的异相转化和硫酸盐的形成，因为α-FeO 是一种典型的光催化剂。然而，光下 SO 在干燥α-FeO 颗粒上的异相转化有些受到抑制，表明发生了光诱导的还原溶解。对于吸附态硝酸盐存在的α-FeO 颗粒上 SO 的异相转化，在潮湿颗粒上形成的硫酸盐仍然高于在干燥颗粒上。对于吸附态硝酸盐存在的干燥α-FeO 颗粒，光促进了吸附态硫酸盐的形成。对于吸附态硝酸盐存在的潮湿α-FeO 颗粒，光下 SO 的异相转化比无光下更强，表明吸附态硝酸盐的光解与 SO 的氧化和硫酸盐的形成相耦合。在引入 SO 时，观察到吸附态硝酸盐的消耗和吸附态 NO 的形成。提出了吸附态硝酸盐对α-FeO 颗粒上 SO 异相转化影响的可能机制，并根据这些结果讨论了大气影响。
