资源环境科技发展态势分析平台

Air quality in China is tending to improve, especially in urban areas. Nevertheless, rural areas and underdeveloped cities in northern China are still suffering from severe air pollution in winter due to large usage of coal and unfavorable meteorological conditions. In this study, size-segregated aerosol samples were collected from a typical coal-combustion rural site in Linfen, China during an extreme air pollution episode in winter 2017. The polycyclic aromatic hydrocarbons (PAHs), n-alkanes, hopanes and steranes were identified to better understand the emission sources of the organic compounds and the health effects of the PAHs in the ambient air here. The PAHs showed a bimodal mode with the major peak in the Aitken mode (<0.4 μm) and the minor one in the size range of 0.7–2.1 μm. Daily PAHs level ranged from 0.5–1.6 μg m⁻³ (average: 1.1 ± 0.3 μg m⁻³) which was 1–2 orders of magnitude higher than other major cities in China. The plots of log (PAH/PM)-log(Dp) showed the slope near −1 for four-, five- and six-ring PAHs, indicating both the adsorption and absorption mechanisms controlled the size distribution. The deposition efficiency displayed a bimodal mode in alveolar region (AR), and the major peak was within the Aitken mode. The total deposition flux (DF) in AR region was 92.7 ng h⁻¹, and the DF based lifetime cancer risk (LCR) was about 2.7 × 10⁻⁴ for adults and 2.0 × 10⁻⁴ for children which were 2 orders of magnitude higher than the acceptable level of 10⁻⁶ proposed by United States Environmental Protection Agency (US EPA). In summary, the residential coal combustion was the most important source of PAHs, especially they emitted a large amount of PAHs in Aitken mode which led to the terrible air quality and high level of health risk. Therefore, the environmental protection measures should be tightened in such rural areas of north China.