成都西南郊区大气PM1中水溶性离子季节变化特征

为研究成都市西南郊区PM₁中水溶性离子的季节特征及其来源,于2019年1,4,7,10月采集PM₁样品并对其中的8种水溶性离子(NO₃-、SO₄2-、NH₄+、Ca2+、Cl-、K+、Na+和Mg2+)进行分析,开展PM₁和水溶性离子质量浓度及其相关关系的对比分析。结果表明:2019年,成都市西南郊区PM₁和水溶性离子年均总浓度分别为(30.1±12.5),(8.5±6.2)μg/m3,各离子浓度高低顺序为NO₃->SO₄2->NH₄+>K+>Ca2+>Cl->Na+>Mg2+;二次离子SNA(SO₄2-、NO₃-、NH₄+)占总水溶性离子比例达到90.0%以上,其在PM₁中占比的季节差异明显,冬季(35.0%)>春季(23.6%)>秋季(22.0%)>夏季(17.5%)。春、夏季NO₃-/SO₄2-分别为0.9和0.6,而秋、冬季NO₃-/SO₄2-分别为1.2和2.1,说明春夏季固定源对PM₁贡献更大,秋冬季移动源对PM₁的贡献更加显著。受来源和气象条件影响,SOR和NOR年均值分别为0.37和0.04,表明观测期间SO₂的二次生成率更为突出。主成分分析结果显示,成都市西南郊区PM₁中水溶性离子的主要来源有二次无机源、燃煤、生物质燃烧和扬尘。

SEASONAL CHARACTERISTIC OF WATER-SOLUBLE IONS OF PM1 IN SOUTHWEST SUBURB OF CHENGDU

To investigate the seasonal characteristics and sources of water-soluble ions in PM₁ in the southwest suburb of Chengdu, samples were collected during typical seasonal months(January, April, July and October)of 2019, and 8 main kinds of water-soluble ions, including NO₃-, SO₄2-, NH₄+, Ca2+, Cl-, K+, Na+, Mg2+ in the samples were detected, and finally the mass concentrations and correlation among PM₁ and its water-soluble ions components were analyzed in this research. The result showed that the annual average concentrations of PM₁ and total water-soluble ions were(30.1±12.5) μg/m3 and(8.5±6.2) μg/m3, respectively. Concentrations of ions were, from more to less, in an order of NO₃->SO₄2->NH₄+>K+>Ca2+>Cl->Na+>Mg2+. Secondary ions(SNA) contributed as high as 90.0% of the total water-soluble ions, and their contributions to PM₁ were different between seasons, which were 35.0%, 23.6%, 22.0% and 17.5% in winter, spring, autumn and summer, respectively. The ratios of NO₃-/SO₄2- were 0.9 and 0.6 in spring and summer, and 1.2 and 2.1 in autumn and winter, which revealed that the vehicle sources played an important role in the formation of PM₁ in autumn and winter. The mean values of sulfur oxidation rate(SOR) and nitrogen oxidation rate(NOR) were 0.37 and 0.04, due to the variations in sources and meteorological conditions, respectively, indicating that there was a higher secondary aerosol transformation rate of sulfur. The results of principle component analysis indicated that the secondary inorganic sources, coal combustion, biomass burning and dust were the main sources of the water-soluble ions during the sampling periods.