[Pollution Characteristics and Sources of Carbonaceous Components in PM_2.5 in the Guanzhong Area]

In order to study the pollution characteristics and sources of fine particulate matter in the Guanzhong area of China, PM_2.5 samples were collected and observed by hand from September 4, 2017 to January 19, 2018 at five sites (XA, WN, TCH, BJ and XY). The carbonaceous component of these samples was analyzed by thermal-optical transmission, which showed that the average concentrations of OC and EC in the fine particulate matter were (14.48±7.86) μg·m^-3 and (2.27±0.95) μg·m^-3, respectively, Percentages of OC and EC were 18.04% and 2.99%, respectively. Compared with other cities, the measured levels of pollution in the Guanzhong areas were more severe. The spatial distribution of percentage of carbon component in PM_2.5 was XY > WN > XA > BJ > TCH, and the concentrations in winter were higher than in autumn. The correlation between OC and EC was significant (R²=0.79), which indicates a common source. The highest proportion of OC1 was 23.44%. The concentration of the carbonaceous component from high to low was OC1 > EC2 > EC3 > OC4 > EC1 > OC2 > OC3 > EC4 > EC6 > EC5. The results of PMF modeling show that the four main contributing sources of carbon components in pollution in this area are biomass combustion and coal-burning, gasoline vehicle exhaust emissions, diesel vehicle exhaust emissions, and road dust, contribution 48.63%, 23.07%, 18.82%, and 9.47%, respectively. Furthermore, there were clear differences in the pollution structure at each study site.