乌鲁木齐市重污染期间PM2.5污染特征与来源解析

目前有关我国城市大气重污染期间PM_2.5污染特征及其来源的研究较少,为深入了解典型城市大气重污染期间PM_2.5的污染特征与来源构成,于2013年1月19—30日在乌鲁木齐市采集PM_2.5样品,并依据相关划分标准,确定1月19—28日为重污染天气. 分析了重污染天气下ρ(PM_2.5)及主要化学组成(包括水溶性离子、无机元素和碳组分),运用统计学方法研究了重污染期间PM_2.5的污染特征,并且采用富集因子法和CMB受体模型解析了PM_2.5的来源构成.结果表明:大气重污染期间ρ(PM_2.5)严重超标,其中米东区环境保护局采样点的ρ(PM_2.5)最高,其次是铁路局、市监测站；PM_2.5化学组分以SO₄2-、TC、Si和NO₃-为主,其中二次离子占ρ(PM_2.5)的43.1%；城市扬尘、煤烟尘和二次粒子是环境空气中PM_2.5的主要污染源类,三者在乌鲁木齐市以及米东区的分担率分别为24.7%、15.6%、38.0%和20.8%、28.0%、36.2%,其中二次硫酸盐的分担率在两地更分别达到28.6%和27.0%. 

Pollution Characteristics and Source Apportionment of PM2.5 during Heavy Pollution Process in Urumchi City

Recently heavy air pollution episodes have frequently happened in many cities of China, which attracts much social public attention. Limited researches on characteristics of PM_2.5 and source apportionments during the heavy pollution process in China have been reported in publications. This study aimed to deeply understand characteristics of PM_2.5 and source contributions during the heavy pollution process in typical cities of China. The ambient PM_2.5 samples were collected in Urumchi City from 19th-30th, January, 2013. Based on the Technical Regulation on Ambient Air Quality Index (on trial), heavy pollution episodes were identified based on data of mass concentrations from 19th-28th, January. The PM_2.5 and main chemicals (e.g., water solvent ions, inorganic elements and carbon species) were analyzed and presented by correlation analysis to identify the characteristics of PM_2.5. The enrichment factor was used to assess contributions of crustal and anthropogenic sources. The source apportionment of PM_2.5 was conducted via the CMB model. The results showed that the average mass concentration of PM_2.5 was over than the National Air Quality Standard. The PM_2.5 concentration was the highest at the site of Midong Environmental Protect Agency, followed by sites of Tielu Agency and Monitoring Station. SO₄2-, TC, Si and NO₃- were the main chemical compositions and secondary ions accounted for 43.1% in PM_2.5. Resuspended dust, coal combustion dust and secondary particles were the main contents of the ambient PM_2.5, with contributions of 24.7%, 15.6% and 38.0% in the urban area of Urumchi City and 20.8%, 28.0% and 36.2% in Midong District, respectively, while the corresponding contributions of secondary sulfate were 28.6% and 27.0%.