2016—2017年武汉市城区大气PM_(2.5)污染特征及来源解析

Characteristics and Source Apportionment of PM_(2.5) in Urban Areas of Wuhan During 2016-2017

利用2016年1月至2017年9月湖北省环境监测中心站大气复合污染自动监测站的在线监测数据,对武汉市城区PM_(2.5)的污染特征及主要来源进行解析。结果表明,武汉市城区PM_(2.5)质量浓度呈现出明显的季节差异,季节变化规律为冬季>春季>秋季>夏季。水溶性离子的主要成分SO■、NO^-_3和NH^+_4占总离子质量浓度的82.0%。PM_(2.5)中阴离子相对阳离子较为亏损,颗粒整体呈碱性。夏季气态污染物的氧化程度较高且SO_2较NO_2氧化程度高。后向轨迹分析结果表明,区域传输是武汉市PM_(2.5)的一个重要来源,在4个典型重污染阶段,武汉市分别受到局地、东北、西北及西南方向气团传输的影响。PMF模型解析出武汉市PM_(2.5)五大主要来源及平均贡献率:扬尘22.0%、机动车排放27.7%、二次气溶胶21.6%、重油燃烧14.9%和生物质燃烧13.8%。

Online monitoring data collected by Hubei Provincial Environmental Monitoring Centre from January 2016 to September 2017 were utilized and analyzed using multiple methods to better understand the characteristics and sources of fine particles(PM2.5) in urban area of Wuhan. The results showed that PM2.5 concentrations had an obvious seasonal variation with the highest concentration occurring in winter followed by spring, autumn and summer. Sulfate, nitrate and ammonium were found to be the main components of PM2.5, accounting for 82% of the total concentration of water soluble ions. Water soluble anions levels in PM2.5 were less abundant than the corresponding cations, indicating the alkaline characteristic of ambient aerosol in Wuhan. It is worth noting that gaseous pollutants exhibited high degree of oxidation in summer. Among them, higher degree of oxidation was observed in SO2 than that of NO2. Besides, backward trajectory analysis demonstrated that regional transported air masses could be a crucial contributor to PM2.5 pollution in Wuhan. During four typical heavy pollution episodes, the concentrations of PM2.5 in Wuhan were significantly affected by air masses originated from local, northeast, northwest as well as southwest, respectively. The positive matrix factorization(PMF) model identified five sources of PM2.5, i.e., fugitive dust, vehicle emissions, secondary aerosol, heavy oil combustion, and biomass burning, and the percentage contribution of above sources to PM2.5 mass was 22.0%, 27.7%, 21.6%, 14.9% and 13.8%, respectively.