摘要：Severe air pollution with visibility deterioration has long been a focus in the North China Plain (NCP). In this study, concentration and light extinction analysis of PM2.5 chemical components were carried out from 2014 to 2017 to study the pollution characteristics in Baoding, a case city of the NCP. The annual average concentration of total PM2.5 components showed a declining trend, decreasing by 11 μg m−3 (water-soluble inorganic ions), 23 μg m−3 (carbonaceous aerosols), and 1796 ng m−3 (inorganic elements). Contributing 82.9% to the concentration of total ions, the dominant components, NH4 , NO3 −, and SO4 2− became the main pollutants in PM2.5 pollution. Based on the IMPROVE algorithm, the average reconstructed PM2.5 mass concentration was 93 ± 69 μg m−3 during the observation period. Meanwhile, the light extinction coefficients were 373.8 ± 233.6 M m−1, 405.3 ± 300.1 M m−1, 554.3 ± 378.2 M m−1 and 1005.2 ± 750.3 M m−1, in spring, summer, autumn, and winter, respectively. Ammonium sulfate, ammonium nitrate, and organic matter were the largest contributors to light extinction, accounting for a total of 55%–77% in the four seasons. The bsca (light scattering by particles and gases) reconstructed from PM2.5 components (Rbsca) and the bsca converted from visibility (Vbsca) were compared to evaluate the performance of the IMPROVE algorithm, revealing a high correlation coefficient of 0.84. The high values of Vbsca were underestimated while the low values were overestimated, as determined through comparison with the one-to-ne line. Especially, when Rbsca > 1123 M m−1 (corresponding to < 2.0 km, approximately), Vbsca was underestimated by 17.6%. PM2.5 mass concentration and relative humidity also had an impact on the estimation.
关键词：PM2.5 Chemical component Visibility IMPROVE algorithm Light extinction
