太原城区PM2.5中多环芳烃、硝基多环芳烃的污染特征、来源解析和健康风险评价

以2013—2014年期间太原城区大气细颗粒物(PM_(2.5))为研究对象,定量分析了其中多环芳烃和硝基多环芳烃的浓度.结果显示,太原城区PM_(2.5)中16种多环芳烃和12种硝基多环芳烃的浓度分别为13.8~547和0.70~4.33 ng·m~(-3),硝基多环芳烃浓度低于多环芳烃浓度1~2个数量级.太原城区PM_(2.5)中多环芳烃最高值出现在冬季,最低值出现在夏季,冬季污染物浓度平均值高于夏季20倍,主要是由于北方采暖期间取暖用煤量的增加使得多环芳烃排放量大幅提高;与之不同的是,硝基多环芳烃浓度季节变化并不显著,冬季浓度均值与夏季差异小于5倍(除9-硝基蒽),反映出硝基多环芳烃生成主要与机动车尾气排放有关,其排放不受季节控制,这与实际情况是吻合的.此外,基于因子分析和化合物比值结果发现,太原城区大气PM_(2.5)中9-硝基蒽有来自周边地区木材燃烧的贡献.健康风险评价结果表明,必须对多环芳烃排放进行有效控制来降低人群在冬季大气中的暴露风险;对于硝基多环芳烃,其健康风险更要引起足够的重视.

Concentration,source identification,and exposure risk assessment of PM2.5-bound PAHs and nitro-PAHs in the atmosphere of Taiyuan

Sixteen PAHs (16 PAHs) and twelve nitro-PAHs were measured in PM_2.5 samples collected over one year (2013-2014) in Taiyuan. During the sampling period,concentrations of the total nitro-PAHs (0.70~4.33 ng·m^-3) were one or two orders of magnitude lower than the total 16 PAHs (13.8~547 ng·m^-3). 16 PAH concentrations exhibited their highest concentrations in winter and lowest concentrations in summer. The concentrations in winter were approximately 20-fold higher than those in summer,due to local PAH emissions related to intensive industrial activity and domestic coal combustion for heating. On the contrary,the difference of mean atmospheric concentrations of nitro-PAHs in winter and summer is less than 5-fold,with the exception of 9-nitroanthracene (9n-Ant),suggesting that they may came from secondary formation rather than direct combustion emission. Emission of nitro-PAHs did not exhibit seasonal variations,which is consistent with reality. Principal component analysis and isomer ratio results indicate that 9n-Ant partly originated from adjacent biomass burning. The results of exposure risk assessment suggest that it is necessary to control PAH emission in order to reduce the health risk from PAHs in Taiyuan,especially during the wintertime,while more attentions should be paid to prevent nitro-PAH pollution.