2016~2020年上海市PM2.5化学组成特征和来源解析

2016~2020年在上海市区和郊区的6个点位开展了颗粒物系统性观测研究,分析了PM_2.5的质量浓度以及水溶性离子、有机碳/元素碳、无机元素等化学组分,并利用正矩阵因子分解模型对PM_2.5的来源进行了解析。结果表明,上海PM_2.5浓度水平呈现下降趋势,年均质量浓度依次为46,43,37,40,39μg/m³,表现为冬高夏低,西高东低的时空分布特征。有机物在PM_2.5中占比最高(30%~32%),不同年份和季节间的差异较小。二次无机离子(硫酸盐、硝酸盐和铵盐)的区域性特征明显,其中硝酸盐的占比在5a间升高最多,且在冬季污染过程中起到了关键作用。解析得到PM_2.5的来源有9类,分别为二次硝酸盐(30.6%)、二次硫酸盐(20.7%)、机动车(12.6%)、工业(8.0%)、生物质燃烧(7.7%)、扬尘(6.5%)、燃煤(5.8%)、海盐(4.8%)和船舶(3.2%)。机动车和船舶等移动源、秸秆焚烧和烟花爆竹燃放等生物质燃烧源的贡献浓度在研究期间呈现下降趋势,体现了相关治理措施的管控效果。

Chemical characterization and source apportionment of fine particulate matter in Shanghai during 2016~2020

A systematic observation of particulate matter was carried out from 2016 to 2020 at six urban and suburban sites in Shanghai. Chemical species including water-soluble ions, organic carbon/elemental carbon, and inorganic elements of fine particulate matter (PM_2.5) were analyzed. Source apportionment of PM_2.5 was conducted using the Positive Matrix Factorization model. Results show that the annual PM_2.5 mass concentrations of Shanghai from 2016 to 2020 were 46, 43, 37, 40, and 39μg/m^-3 successively, exhibiting a decreasing annual trend and spatiotemporal features of higher in the west and in winter while lower in the east and in summer. Organic aerosol was the most abundant species in PM_2.5 (30%~32%), with small annual and seasonal variations. Secondary inorganic ions including sulfate, nitrate and ammonium showed an evidently regional characterization. Among all the inorganic species, nitrate played an important role in pollution episode in winter, and its proportion increased the most from 2016 to 2020. Nine PM_2.5 sources were identified, including secondary nitrate (30.6%), secondary sulfate (20.7%), vehicle emission (12.6%), industry (8.0%), biomass burning (7.7%), dust (6.5%), coal combustion (5.8%), sea salt (4.8%) and ship emission (3.2%). Owing to the atmospheric emission control strategies, the contributions of mobile sources including vehicle and ship emissions as well as biomass burning sources including straw burning and fireworks emission showed a decreasing trend during the focused period.