Zhao Xueyan, Wang Jing, Xu Bo, Zhao Ruojie, Zhao Guangjie, Wang Jian, Ma Yinhong, Liang Handong, Li Xianqing, Yang Wen
State Key Laboratory of Coal Resources and Safe Mining, College of Geoscience and Surveying Engineering, China University of Mining and Technology (Beijing), Beijing, 100083, China.
Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
Environ Sci Pollut Res Int. 2022 Apr;29(16):23994-24009. doi: 10.1007/s11356-021-17431-4. Epub 2021 Nov 24.
To develop effective mitigation policies, a comprehensive understanding of the evolution of the chemical composition, formation mechanisms, and the contribution of sources at different pollution levels is required. PM samples were collected for 1 year from August 2016 to August 2017 at an urban site in Zibo, then chemical compositions were analyzed. Secondary inorganic aerosols (SNA), anthropogenic minerals (MIN), and organic matter (OM) were the most abundant components of PM, but only the mass fraction of SNA increased as the pollution evolved, implying that PM pollution was caused by the formation of secondary aerosols, especially nitrate. A more intense secondary transformation was found in the heating season (from November 15, 2016, to March 14, 2017), and a faster secondary conversion of nitrate than sulfate was discovered as the pollution level increased. The formation of sulfate was dominated by heterogeneous reactions. High relative humidity (RH) in polluted periods accelerated the formation of sulfate, and high temperature in the non-heating season also promoted the formation of sulfate. Zibo city was under ammonium-rich conditions during polluted periods in both seasons; therefore, nitrate was mainly formed through homogeneous reactions. The liquid water content increased significantly as the pollution levels increased when the RH was above 80%, indicating that the hygroscopic growth of aerosol aggravated the PM pollution. Source apportionment showed that PM was mainly from secondary aerosol formation, road dust, coal combustion, and vehicle emissions, contributing 36.6%, 16.5%, 14.7%, and 13.1% of PM mass, respectively. The contribution of secondary aerosol formation increased remarkably with the deterioration of air quality, especially in the heating season.
为制定有效的减排政策，需要全面了解不同污染水平下化学成分的演变、形成机制以及源的贡献。于2016年8月至2017年8月在淄博市的一个城市站点采集了1年的PM样本，随后对化学成分进行了分析。二次无机气溶胶（SNA）、人为源矿物质（MIN）和有机物（OM）是PM中最主要的成分，但只有SNA的质量分数随着污染的演变而增加，这意味着PM污染是由二次气溶胶尤其是硝酸盐的形成所致。在供暖季（2016年11月15日至2017年3月14日）发现了更强烈的二次转化，并且随着污染水平的增加，硝酸盐的二次转化比硫酸盐更快。硫酸盐的形成主要由非均相反应主导。污染期间的高相对湿度（RH）加速了硫酸盐的形成，非供暖季的高温也促进了硫酸盐的形成。在两个季节的污染期间，淄博市都处于富铵条件下；因此，硝酸盐主要通过均相反应形成。当RH高于80%时，随着污染水平的增加，液态水含量显著增加，这表明气溶胶的吸湿增长加剧了PM污染。源解析表明，PM主要来自二次气溶胶形成、道路扬尘、煤炭燃烧和机动车排放，分别占PM质量的36.6%、16.5%、14.7%和13.1%。二次气溶胶形成的贡献随着空气质量的恶化而显著增加，尤其是在供暖季。
