| Title: | Effects of NO(2) and RH on secondary organic aerosol formation and light absorption from OH oxidation of omicron-xylene |
| Author(s): | Liu S; Wang Y; Xu X; Wang G; |
| Address: | "Key Lab of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai, 210062, China; Institute of Eco-Chongming, 3663 North Zhongshan Road, Shanghai, 200062, China. Key Lab of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai, 210062, China. Key Lab of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai, 210062, China; Institute of Eco-Chongming, 3663 North Zhongshan Road, Shanghai, 200062, China. Electronic address: ghwang@geo.ecnu.edu.cn" |
| DOI: | 10.1016/j.chemosphere.2022.136541 |
| ISSN/ISBN: | 1879-1298 (Electronic) 0045-6535 (Linking) |
| Abstract: | "Omicron-xylene is an important aromatic volatile organic compound (VOC) in the atmosphere over urban areas. In this work, the effect of nitrogen dioxide (NO(2)) concentration and relative humidity (RH) on the mass concentration of secondary organic aerosols (SOA) formed from omicron-xylene OH oxidization was investigated in a photooxidation chamber. The omicron-xylene SOA mass concentration increased from 54.2 mug m(-3) to 127.2 mug m(-3) during dry conditions, but decreased from 177.7 mug m(-3) to 146.5 mug m(-3) during high RH conditions when the initial NO(2) concentration increased form 0 ppbv to about 900 ppbv. An increase in the ratio of [NO(3)(-)]/[Org] and a decrease in the oxidation state of carbon (OS(C)) of SOA suggested that acid-catalyzed heterogeneous reaction was responsible for enhancing SOA formation with increasing NO(2) concentrations in dry conditions. In contrast, in humid conditions, the high molecular diffusion capacity of SOA could promote the reactivity of OH towards the interior of SOA, and the enhancement of nitrous acid (HONO) formation under high NO(2) conditions could promote the SOA aging processes and be responsible for the decreasing trend of SOA formation with NO(2). Light absorption by SOA was also measured, and both NO(2) and RH enhanced the mass absorption coefficient (MAC(lambda = 365 nm)) value for the optical properties of omicron-xylene SOA. The highest MAC(lambda = 365 nm) value of omicron-xylene SOA was 0.89 m(2) g(-1), observed during humid conditions with an initial NO(2) concentration of 862 ppbv, which was 3.9 times higher than in the experiment conducted in the absence of NO(2) under dry conditions. The formation of nitrogen-containing organic compounds (NOCs) and humic-like substances (HULIS) were responsible for the increased MAC(lambda = 365 nm) values of omicron-xylene derived SOA. This study provides new insight into the effect of NO(2) on SOA formation through the change in omicron-xylene photooxidation under different RH conditions, and the complex effect of multiple environmental factors on SOA formation was also important and should not be ignored" |
| Keywords: | Aerosols *Air Pollutants/analysis Carbon Nitrogen Nitrogen Dioxide Nitrous Acid Oxidation-Reduction *Volatile Organic Compounds Xylenes Aerosol mass spectrometry Mass absorption coefficient Secondary organic aerosol omicron-xylene; |
| Notes: | "MedlineLiu, Shijie Wang, Yiqian Xu, Xinbei Wang, Gehui eng England 2022/09/24 Chemosphere. 2022 Dec; 308(Pt 3):136541. doi: 10.1016/j.chemosphere.2022.136541. Epub 2022 Sep 20" |
