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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