Polycyclic aromatic hydrocarbons (PAHs) are important organic pollutants in atmospheric PM2.5, and they are widely concerned due to their carcinogenic and mutagenic characters. Some of the PAHs with molecular weight of >300 (HMW-PAHs) had been found to be highly toxic, but study on the HMW-PAHs is very limited. To get better understanding of the concentration, composition and toxicity of HMW-PAHs in the fine atmospheric particles in Shanghai, PM2.5 samples were collected in Shanghai from April 2013 to April 2014 with high-volume sampler in this study. The concentrations and seasonal variations of 19 individual HMW-PAHs with molecular weight of 302 (∑302PAHs) were analyzed with GC-MS. Results showed that the concentrations of∑302PAHs in PM2.5 in Shanghai had obvious seasonal variation, and the average mass concentration in spring, summer, autumn and winter were 2.2, 1.4, 2.1 and 9.7 ng?m-3. While the composition of 302-PAH isomers in different seasons were very similar. The percentage of ∑302PAHs in the total PAHs in summer (19%) was higher than that in autumn (12%) and winter (11%), due to the fact that 302-PAHs are non-volatile while the gas-particle partitioning of the PAHs with lower molecular weight vary with the ambient temperature. The average mass concentrations of the 5 carcinogenic dibenzopyrene isomers in PM2.5 in Shanghai, DalBP, N23eP, DBaeP, DBaiP and DBahP, were 44, 1.6×102, 3.4×102, 43 and 5.2 pg?m-3. The carcinogenic potency to benzo[a]pyrene (BaPeq) of these 302-PAHs accounted for 23%, 47%, 21% and 21% of the BaPeq values of the total PAHs in PM2.5 in Shanghai in spring, summer, autumn and winter respectively. Brief estimation showed that the average atmospheric dry deposition flux and the yearly accumulated amount of dry deposition of 302-PAHs in Shanghai were 133 ng?m-2?d-1 and 304 kg. It is thus necessary to include 302-PAHs in the future risk assessment of the atmospheric PAHs. The results of this study provided fundamental data for the environmental assessment of atmospheric fine particles.%多环芳烃(PAHs)是大气颗粒物中重要的有机污染物,由于其致癌、致突变特性而广受关注.部分分子量大于300的高分子量多环芳烃(HMW-PAHs)已被发现具有很强的毒性,但目前对于HMW-PAHs的研究仍非常有限.为了解上海大气细颗粒物中HMW-PAHs的浓度、组成和毒性,使用大流量采样器于2013年4月—2014年4月期间采集了上海大气PM2.5样品,利用GC-MS分析了其中19种分子量为302的高分子量多环芳烃(∑302PAHs)的质量浓度、组成及其季节变化.结果表明,上海PM2.5中∑302PAHs的质量浓度具有显著的季节变化,春、夏、秋、冬季的平均质量浓度分别为2.2、1.4、2.1和9.7 ng?m-3,但302-PAHs的同分异构体组成没有明显的季节变化.HMW-PAHs不具挥发性,而低分子量PAHs在大气中的赋存状态受气-粒分配的影响,因此上海PM2.5中∑302PAHs质量浓度占全部PAHs的比例呈现明显的季节变化,夏季(19%)显著高于秋季(12%)和冬季(11%).5种具有明显致癌毒性的二苯并芘异构体DalBP、N23eP、DBaeP、DBaiP和DBahP在整个采样期间的平均质量浓度分别为44、1.6×102、3.4×102、43和5.2 pg?m-3;上述5种302-PAHs的苯并[a]芘毒性当量浓度(BaPeq)占全部PAHs的BaPeq的比例在春、夏、秋、冬四季分别为23%、47%、21%和21%.初步估算表明,2013—2014年采样期间上海∑302PAHs的平均大气干沉降通量为133 ng?m-2?d-1,年累计干沉降量约304 kg.因此,在进行大气多环芳烃风险评估时有必要将具有明显毒性的5种302-PAHs纳入.研究结果可为大气细颗粒物环境影响评价提供一定的基础数据.
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