The Characteristics and Sources of PAHs on PM_2.5 during Summer and Winter in the Urban Area of Taiyuan

Objectives  To investigate the characteristics of PAHs on PM_2.5 in different areas of Taiyuan in summer and winter, and to identify the sources of ambient PAHs on PM_2.5.

Methods  The level of PM_2.5 and PAHs at three sampling sites in Taiyuan were detected from June 2017 to January 2018. Samples were collected both in summer and winter. The concentration of PM_2.5 and PAHs in different season and sites were compared. A characteristic ratio method was used to identify the source of PAHs.

Results  The concentration of PM_2.5 and PAHs in summer was 69.2 μg/m³ and 4.33 ng/m³; and that in winter was 111.9 μg/m³ and 39.71 ng/m³, respectively. The concentration of PM_2.5 and PAHs in winter was significantly higher than that in summer (P < 0.05). There was no significant difference of PAHs concentration between the sampling site in the polluted area and two sampling sites in the downtown during summer, but the concentration of PAHs in the polluted area was significantly higher than that in downtown area during the first sampling period of winter. The result of characteristic ratio showed that the source of ambient PAHs in Taiyuan City mainly came from coal combustion. In winter, the source of PAHs mainly came from coal combustion, while in the summer mainly came from a mixed source of motor vehicle exhausting and coal combustion.

Conclusions  The level of PM_2.5 and PAHs in Taiyuan city was different in summer and winter. The concentration of PAHs was different in different areas. Coal combustion and motor vehicle exhausting were important contributors to ambient PAHs in Taiyuan.