Component and Source Analyses of PM_2.5 in Typical Agricultural Regions of North China

Air pollution resulting from regional development is having a significant impact on agroecological regions of North China. To understand the seasonal distribution characteristics of atmospheric PM_2.5 (fine particulate matter) pollution in agricultural areas of North China, seasonal PM_2.5 analysis was conducted at the Yucheng Comprehensive Experimental Station of the Chinese Academy of Sciences in Yucheng, Shandong Province in July, September, December 2017, and April 2018. Samples were collected and 30 chemical components were determined for each sample. The results showed that the overall concentration of carbonaceous aerosols was 13.11±8.37 μg m⁻³. The OC (organic carbon) concentration was high in winter and spring. The EC (elemental carbon) concentration was high in autumn and winter. Simultaneously, the OC/EC ratio was significantly low in autumn, indicating that the contribution of secondary carbonaceous aerosols to PM_2.5 was small in autumn. The overall concentration of water-soluble ions is highest in winter and lowest in spring. The \rmNO^-_3 /\rmNO^2-_4 ratio, representing the contribution of traffic and fixed point sources (such as factories) to atmospheric pollution, is significantly low in summer at 0.69, indicating that the contribution of fixed point sources to air pollution is relatively high in the summer. The trace metals in atmospheric particles are mainly crust elements such as Na, Mg, Al, Ca, K, and Fe. The annual average concentration levels of trace metals such as Co, Cr, Ni, Pb, and As are 0.32±0.24 ng m⁻³, 5.40±5.42 ng m⁻³, 10.23±7.46 ng m⁻³, 42.23±27.75 ng m⁻³, and 5.66±3.79 ng m⁻³. The calculated results of the PMF (Positive Matrix Factorization) receptor model show that the main sources of PM_2.5 are secondary pollution sources, biomass combustion sources, coal-fired fuel sources, diesel vehicle exhaust, and soil sources with contribution rates of 37.1%, 18.2%, 14.2%, 9.4%, and 7.9%. Pollution from fine particles is affected by the multiple effects of industry and agriculture in the North China agricultural region.