忻州市大气PM2.5的化学组成质量平衡特征及来源解析

于2013年9月（非采暖季）、2014年2-3月（采暖季）、2014年5月（风沙季）采集忻州市3个监测点（新城区、开发区和旧城区）的PM2.5样品，分析其中的39种元素、9种水溶性离子及2种碳组分，并对PM2.5的质量浓度进行重构。结果表明，重构后的化学组分分为5类：矿物尘、微量元素、有机物、元素碳和二次粒子，其中矿物尘、二次粒子及有机物是忻州PM2.5的主要组成，分别占到ρ（PM2.5）的24.0%~36.2%、19.2%~32.6%和12.9%~25.7%；化学组成质量分数具有较明显的季节变化特征，风沙季矿物尘质量分数高于采暖季和非采暖季，采暖季有机物质量分数高于其他两季，非采暖季二次粒子质量分数略高于其他两季；化学组分的空间变化显示会展中心站点的二次粒子和矿物尘质量分数明显高于其他2个站点。应用化学质量平衡（CMB）模型进行来源解析，结果显示忻州市PM2.5的主要来源是扬尘（21%~35%）、二次粒子（25%~26%）和机动车尾气（21%~26%）。

Characterization of chemical composition mass balance and source appointment of ambient PM2.5 in Xinzhou city

PM2.5 samples were collected at three sites in an urban area of Xin Zhou (Shanxi Province, PRC) during a non-heating period (September, 2013), a heating period (February to March, 2014), and a windy period (May, 2014). Chemical species were analyzed for elements (e.g., Si, Al, Ca, Mg, Fe, Ti, K), water-soluble ions (i.e., Cl-, NO3-, SO42-, Na+, K+, NH4+, Ca2+, Mg2+), and carbonaceous compounds (OC, EC). PM2.5 mass was reconstructed from mineral matter (MIN), trace elements (TE), organic matter (OM), elemental carbon (EC), and secondary inorganic aerosol (SIA). The results showed that the major components of PM2.5 were MIN, followed by SIA and OM, accounting for 24.0% to 36.2%, 19.2% to 32.6%, and 12.9% to 25.7% of ρ(PM2.5), respectively. Significant temporal and spatial variation of chemical components was observed. The percentage of MIN in the windy period was higher than during the non-heating and heating periods. OM content in the heating period was higher than during the other two periods. SIA composition in the non-heating period was slightly higher than that in the other two periods. Spatial variation of chemical composition indicated significantly higher levels of SIA and MIN at the Huizhan site in an newer urban area. Source apportionment was calculated using the chemical mass balance (CMB) model. The result shows that dust, secondary inorganic aerosol, and traffic were the major sources of PM2.5, with contributions in the ranges 21% to 35%, 25% to 26%, and 21% to 26%, respectively.