Abstract: Objective To understand the main sources of polycyclic aromatic hydrocarbons（PAHs） in atmospheric fine particulate matter（PM_2.5） and the health risks to the population during the heating period in two urban areas of Xining City. Methods PM_2.5 samples were collected on the 10th-16th of each month from November 2020 to March 2021,and PAHs concentrations were detected by high performance liquid chromatography（HPLC）. The source analysis was performed using the characteristic ratio method and principal component analysis,and finally the population health risk was assessed by a lifetime excess cancer risk model. Results The median concentrations[M（P₂₅,P₇₅）] of PAHs during the heating period in Chengbei District and Chengdong District of Xining City were 74.92（35.31,171.09） and 45.13（26.54,68.92） ng/m³ respectively,and the difference was statistically significant（P<0.05）. The results of the characteristic ratio method as well as the principal component analysis method showed that the sources of PAHs pollution in the Chengbei District were mainly motor vehicle exhaust emissions（48.66%）,coal combustion（16.05%）,petroleum combustion（11.54%）,and gasoline combustion（9.53%）,while the sources of PAHs pollution in the Chengdong District were mainly a mixture of coal combustion and motor vehicle exhaust emissions（58.44%）,and petroleum combustion（17.07%）. The attainment rates of benzo[a]pyrene in the two urban areas were 26.19% and 40.48% respectively,and the difference was not statistically significant（P>0.05）. The total carcinogenic equivalent concentrations were 12.71 and 6.28 ng/m³ respectively. The carcinogenic risk range of PAHs was 4.28×10^-6-3.27×10^-5,and the expected life loss range was 26.60-203.33 min. Conclusion The PAHs pollution in atmospheric PM_2.5 during the heating period in Xining city has potential health risks for local residents.

Key words: PM_2.5, Polycyclic aromatic hydrocarbons, Source resolution, Health risks