北京市大气细颗粒物污染与来源解析研究

Pollution and source apportionment of atmospheric fine particles in Beijing

采集北京市2014年冬、春、夏、秋4个季节代表月1、4、7、10月的大气细颗粒物PM_(2.5)样品,分析研究了PM_(2.5)质量浓度、化学特征、季节变化和污染成因.同时,采用正交矩阵因子分析法(PMF)对PM_(2.5)进行了来源解析.结果表明,北京市2014年PM_(2.5)年均浓度为87.74μg/m3,是国家环境空气质量标准年均浓度限值的2.5倍.轻、重污染期间,PM_(2.5)浓度较常日分别增加了1.5和3.9倍,其季节变化表现为冬季>夏季>秋季>春季.地壳元素Mg、Al、Fe、Ca、Ti在轻度污染和重度污染期间较常日略有升高,分别是常日浓度的1.1~1.2倍和1.2~1.5倍.污染元素S、Pb、Zn、Cu浓度变化显著,轻度污染和重度污染期间分别是常日浓度的1.3~2.7倍和1.9~5.9倍.S元素是PM_(2.5)中受人为活动影响较为严重的组分,其相应的SO_4^(2-)年均浓度为13.43μg/m^3,在轻度污染和重度污染期间分别是常日浓度的2.7和5.9倍.硫酸盐的形成主要受O_3浓度、温度、相对湿度等气象要素的协同影响,较高的O_3浓度、较高温度和相对湿度有利于硫酸盐的生成.PM_(2.5)主要来源于机动车排放、燃煤、地面扬尘和工业排放,其贡献率分别为37.6%、30.7%、16.6%和15.1%.

Aerosol samples of PM2.5 were collected in Beijing during January, April, July and October 2014, which stoodfor winter, spring, summer and autumn respectively, to investigate the physical and chemical characteristics, seasonalvariation and formation factors of PM2.5. At the same time, source apportionment was carried out by using the positivematrix factorization analysis method. The results showed that the annual average concentration of PM2.5 reached87.74μg/m3 in Beijing in 2014, 2.5 times as high as the national air quality standard. The PM2.5 concentrations during lightand heavy pollution periods increased more than 1.5 and 3.9 times compared with normal days, respectively, and itsseasonal variation was significant, with the order of winter>summer>autumn>spring. The concentrations of crustalelements, such as Mg, Al, Fe, Ca, Ti, during light and heavy pollution days were 1.1~1.2 and 1.2~1.5 times as high asthose in normal days, respectively, and the concentrations of pollution elements, such as S, Pb, Zn and Cu, showedsignificant changes during light and heavy pollution days, with 1.3~2.7 and 1.9~5.9 times as high as those in normal days,respectively. S was the most important anthropogenic pollution element in PM2.5, and its SO42- annual averageconcentration was 13.43μg/m3. The concentrations of SO42- in light and heavy pollution days were 2.7 and 5.9 timeshigher than that in normal days, respectively. The formation of sulfate was mainly influenced by the concentration of O3,air temperature and relative humidity etc.. Higher O3 concentration, temperature and relative humility were in favor of theformation of sulfate. PM2.5 was mainly from mobile emission, coal combustion, re-suspended dust and industrial emission,which contributed to PM2.5 about 37.6%, 30.7%, 16.6% and 15.1%, respectively.