成都春季复合污染下PM2:5 的化学消光贡献

为探讨复合污染条件下气溶胶的消光特性, 选取成都市 O3 与 PM2:5 同步污染的春季开展气溶胶组分与消光 特性观测, 并结合美国 IMPROVE 化学消光算法研究了组成与消光特征的关系。结果表明, 2018 年春季成都 PM2:5 平 均浓度与散射系数 bsp 分别为 (50.3±22.4) µg·m?3 和 (237.5±140.2) Mm?1, 且二者均呈现“单峰单谷”的日变化趋势; 大 气气溶胶的消光系数为 (268.4±153.7) Mm?1, 对其贡献最大的组分是 NH4NO3 (26.0%) 和有机物 (OM) (24.4%)。分析 表明在 PM2:5 与 O3 复合污染情况下, 二次污染组分 SNA (SO42?、 NO3?、 NH4+ 三者之和)、二次有机碳 (SOC) 的含量 显著增加, 与清洁天相比分别升高了 1.0 和 1.3 倍; OM 成为最大消光贡献者 (32.2%), 其次是 NH4NO3 和 (NH4)2SO4, 分别贡献 22.8% 和 20.5%。因此, 进一步减少气态前体物如 SO2、 NOx、 NH3 和 VOCs 的排放可以有效改善成都地区 空气质量和能见度。

Contribution of PM2.5 to chemical extinction under combined pollution during spring in Chengdu

To explore the aerosol chemical extinction during complex air pollution, a field campaign was carried out to investigate the composition and extinction characteristics of PM2:5 in spring when O3 and PM2:5 combined pollution occurred in Chengdu, China, and the relationship between chemical composition and extinction characteristics was studied using the chemical extinction algorithm proposed by IMPROVE in the United States. The results showed that the average concentration of PM2:5 and scattering coefficient bsp in the spring of 2018 in Chengdu were (50.3±22.4) µg·m?3 and (237.5±140.2) Mm?1, respectively, and both of them showed the similar diurnal variation trend with “single peak and single valley”. The extinction coefficient of spring PM2:5 in Chengdu was (268.4±153.7) Mm?1, and the chemical components that contributed the most to it were NH4NO3 (26.0%) and organic matter (OM) (24.4%). In the case of PM2:5 and O3 combined pollution, the mass of secondary pollution components (SNA, the sum of SO42?, NO3?, NH4+) and secondary organic carbon (SOC) increased significantly, which increased by 1.0 and 1.3 times respectively compared with the clean day, and OM became the largest extinction contributor (32.2%), followed by NH4NO3 and (NH4)2SO4, contributing 22.8% and 20.5% respectively. Therefore, it is shown that further reducing the emission of precursor gases such as SO2, NOx, NH3 and VOCs may be efficient to improve the air quality and visibility in Chengdu district.