深圳大气PM2.5中水溶性有机物的来源特征

对2017年9月~2018年8月深圳市北部大气PM_2.5中水溶性有机物（WSOM）的质量浓度、质谱及来源结构进行测量和分析.结果表明：PM_2.5的质量浓度为（32.3±18.4）μg/m³，WSOM的质量浓度为（9.4±5.7）μg/m³，占颗粒物总有机物的（77.6%±14.0%）.质谱分析显示，WSOM的氧碳比（O/C）平均值达到（0.57±0.09），属于二次有机物的O/C值范围，且生物质燃烧排放的离子碎片C₂H₄O₂⁺的丰度显著，说明WSOM的来源中有显著的生物质燃烧排放的有机气溶胶.为了明确WSOM的来源结构，利用正矩阵因子分解法（PMF）模型进行来源解析，发现3个合理因子：高氧化态有机气溶胶（MO-OOA），低氧化态有机气溶胶（LO-OOA）和生物质燃烧（BBOA），贡献比例分别为51.7%，31.8%和16.5%.MO-OOA和BBOA贡献浓度均呈现秋冬高、春夏低的季节变化特征，反向轨迹分析显示其与内陆污染传输关系密切.LO-OOA的变化相对稳定，本地源的贡献较大.结合¹⁴C同位素示踪法对秋冬季WSOM样品分析，发现机动车等化石源二次有机物是WSOM的主要来源，贡献比例达到53.9%，需继续加强对化石燃料控制来降低WSOM污染.

Source apportionment of water-soluble organic matter in PM2.5 in Shenzhen

This study systematically analyzed the Water-Soluble Organic matter (WSOM) in PM_2.5 collected during September 2017 to August 2018 in the northernzone in Shenzhen. The mass concentration, mass spectraand sources of WSOM were obtained. The average mass concentration of PM_2.5 was (32.3±18.4)μg/m³. WSOM was determined to be 77.6%±14.0% of the organic matter (OM), with anaverage mass concentration of (9.4±5.7)μg/m³. As shown in the mass spectrometry, the average O/C ratio of WSOM was 0.57±0.99, which was within thetypical range ofthe O/C valuesof SOA. Meanwhile, the abundant C₂H₄O₂⁺ proved that biomass burning organic aerosol (BBOA) contributed significantly to the WSOM. Furthermore, positive matrix factorization (PMF) model was applied to perform source apportionment of WSOM and three reasonable factors were identified, including BBOA, more oxidized oxygenated OA (MO-OOA) and less oxidized oxygenated OA (LO-OOA), accounting for 16.5%, 51.7% and 31.8%, respectively. Compared to spring and summer, BBOA and MO-OOAcontributed more in autumn and winter,which was more closely related to inland pollution transport based on backward trajectory analysis. Thelittle variation of LO-OOA in different air masses possibly impliedits local sources. ¹⁴C measurement was conducted to help separate fossil and non-fossil emissions of WSOM, and the fossil fuel-derived secondary organic matterwas found to dominate the WSOM mass (53.9%). Therefore, it's necessary to strengthen the control of fossil fuel sources in order to reduce WSOM pollution.