呼和浩特市两区大气PM2.5及其中多环芳烃的分布特征
Distribution characteristics of atmospheric PM2.5 and its polycyclic aromatic hydrocarbons in two districts of Hohhot
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摘要:
目的 监测呼和浩特市大气颗粒物PM2.5质量浓度（下称浓度），并分析样品中多环芳烃（PAHs）的污染特征，为呼和浩特市大气污染相关研究提供科学数据。
方法 于2015年1-12月在呼和浩特市回民、赛罕两区采集PM2.5样品，分析样品中16种优先控制PAHs的浓度特征与污染状况，并采用特征分子比值法对PAHs的来源进行定性分析。
结果 呼和浩特市回民、赛罕两区PM2.5浓度范围分别为10.0~290.0 μg/m3和10.0~170.0 μg/m3，全年平均浓度分别为90 μg/m（3 95%CI：70.0~100.0）和60.0 μg/m（3 95%CI：50.0~70.0），回民区PM2.5浓度总体高于赛罕区，差异有统计学意义（P < 0.05）。两区PM2.5浓度有季节变化趋势，即冬季＞秋季＞春季＞夏季。对两个监测地区PM2.5中PAHs进行测定，发现回民、赛罕两区PM2.5中PAHs浓度范围分别是0.36~217.0 ng/m3和0.36~131.4 ng/m3，全年平均浓度分别为43.42 ng/m（3 95%CI：30.0~56.8）和23.40 ng/m（3 95%CI：13.6~29.8）；两区PAHs中浓度排在前三位的成分一致，依次为萘、苯并b荧蒽和二苯并a，h蒽，苯并a芘浓度分别为2.32 ng/m3和1.46 ng/m3。特征分子比值分析表明，回民区4种特征分子比值荧蒽（/荧蒽+芘）、蒽（/蒽+屈）、苯并a芘/苯并g，h，i苝、蒽（/蒽+菲）分别为0.04、0.49、2.32和0.38，赛罕区分别为0.14、0.36、24.3和0.34。
结论 呼和浩特市大气PM2.5中PAHs浓度较高，呈现混合污染特点，燃煤和机动车排放是PAHs的主要来源。
Abstract:Objective To monitor the concentrations of atmospheric fine particulate matters (PM2.5) in Hohhot City, and analyze the distribution characteristics of polycyclic aromatic hydrocarbons (PAHs) in the samples collected, so as to provide scientific evidence for the research on the air pollution of Hohhot.
Methods PM2.5 samples were collected from Huimin District and Saihan District of Hohhot from January to December 2015. The concentrations and pollution characteristics of 16 pollution-control-prioritized PAHs were analyzed. A qualitative analysis of PAHs sources was performed using characteristic molecular ratio.
Results The PM2.5 concentrations ranged 10.0-290.0 μg/m3 in Huimin District and 10.0-170.0 μg/m3 in Saihan District, the annual average concentrations of PM2.5 were 90 μg/m3 (95%CI:70.0-100.0) and 60.0 μg/m3 (95%CI:50.0-70.0), respectively, and the average concentration of PM2.5 in Huimin District was higher than that in Saihan District (P < 0.05). PM2.5 concentrations showed a seasonal variation in both districts:winter > autumn > spring > summer. The PAHs concentrations ranged 0.36-217.0 ng/m3 with an average of 43.42 ng/m3 (95%CI:30.0-56.8) in Huimin District, and the concentrations ranged 0.36-131.4 ng/m3 with an average of 23.40 ng/m3 (95%CI:13.6-29.8) in Saihan District. The leading three components of PAHs in PM2.5 were naphthalene, benzobfluoranthene, and dibenza, hanthracene for the two districts; in particular, the benzo a pyrene concentrations were 2.32 ng/m3 for Huimin District and 1.46ng/m3 for Saihan District. According to the results of characteristic molecular ratio analysis, the characteristic molecular ratios of fluoranthene/(fluoranthene+pyrene), anthracene/(anthracene+chrysene), benzo(a)pyrene/benzo(g, h, i)pyrene, and anthracene/(anthracene+phenanthrene) were 0.04, 0.49, 2.32, and 0.38, respectively, for Huimin District, and 0.14, 0.36, 24.3, and 0.34, respectively, for Saihan District.
Conclusion The concentration of PAHs in PM2.5 is high in Hohhot City, displaying a mixed pollution pattern. Coal combustion and motor vehicle emissions are the main sources of PAHs.
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