摘要:

Secondary organic aerosol (SOA) is a major component of aerosols in the atmosphere, which plays a crucial role in climate change, regional pollution and human health. Laboratory simulations are usually used to mimic SOA formation. The most commonly used simulation facilities are environmental chambers and potential aerosol mass (PAM) reactors. Here in this work, we review the studies about influencing factors and mechanisms of SOA formation, as well as the evolution of SOA aging. We summarize the influencing factors on SOA yields, i.e. OH exposure, NOx level, and the loading and chemical composition of seed particles. The effects of NOx level (i.e. VOCs/NOx) and OH exposure are nonmonotonic. The NOx level influences the fate of RO2 radicals, so SOA yields will increase and then decrease with the addition of NOx. Similarly, the increase of OH exposure affects the major oxidation mechanism from functionalization to fragmentation, leading to the up and down trend of SOA yields. The higher seed particle loading provides more surface area for condensable products and then increases the SOA yields. The particle acidity favors the uptake process for gas-phase products and promote the SOA formation via further reactions in the condense phase. Trace components e.g. transition metals and minerals can be involved in the SOA formation and aging by catalysis or affecting the uptake of oxidants and their products. Chambers and PAM reactors are usually used to explore SOA formation potential of different sources. SOA formation potential from vehicles will be influenced by engine types, engine loading and composition of fuel. The highest SOA enhancement ratio (SOA/POA) from gasoline engines is about 4~14, when the equivalent photochemical days are 2~3 d. The SOA production mass from gasoline vehicles is from about 10~40 to 400~500 mg/kg fuel. The SOA formation potential is about 400~500 mg/kg fuel. The largest SOA enhancement ratio for biomass burning is 1.4~7.6, which occurs at 3~4 photochemical days. The SOA enhancement ratio from ambient air differs from region to region. However, the highest ratios all occur at the photochemical age of about 2~4 d. We summarize the SOA characteristics evolution with aging. Oxidation state of particles will increase with OH exposure. Changes of H/C and O/C with increasing OH exposure can be plotted in the Van Krevelen diagrams. The slopes of fitted curve range from -1 to 0, indicating OA evolution chemistry involving addition of carboxylic acids or addition of alcohols/peroxides. In addition, the volatility and hygroscopicity of oxidized OA will be higher than primary organic aerosols. In the future, more studies should be focused on developing new technologies to measuring the oxidized intermediate products at a molecular level. Also the researches on the mechanism of SOA formation from complex precursors are also crucial to understand the SOA formation at real atmosphere. © 2020 Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.

附注:

Export Date: 20 August 2020通讯地址: Guo, S.; State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking UniversityChina; 电子邮件: songguo@pku.edu.cn基金资助详情: State Key Laboratory of Multi-phase Complex Systems基金资助详情: 2016YFC0202000基金资助详情: National Natural Science Foundation of China, NSFC, 91844301, 41977179, 21677002, 51636003基金资助文本 1: * E-mail: songguo@pku.edu.cn Received February 16, 2020; published May 25, 2020. Project supported by the National Key R&D Program of China (No. 2016YFC0202000), the National Natural Science Foundation of China (Nos. 51636003, 41977179, 21677002, 91844301) and the Open Research Fund of State Key Laboratory of Multi-phase Complex Systems (No. MPCS-2019-D-09). 项目受国家重点研发计划(No. 2016YFC0202000)、国家自然科学基金(Nos. 51636003, 41977179, 21677002, 91844301)和多相复杂系统国家重点实验室 开放课题(No. MPCS-2019-D-09)资助.