Temporal variations of PM concentrations, and its association with AOD and meteorology observed in Nanjing during the autumn and winter seasons of 2014–2017

Abstract The present study aims to investigate temporal evolutions of particulate matter (PM) concentrations and its association with the meteorology and aerosol optical depth (AOD) during autumn and winter of 2014–2017 at an urban city, Nanjing in the Yangtze River Delta, East China. The seasonal mean PM2.5 (PM10) was found maximum and minimum with 81.2 ± 41.5 μg m−3 (135.6 ± 57.1 μg m−3) and 33.7 ± 19.1 μg m−3 (65.8 ± 34.5 μg m−3) during winter and autumn seasons, respectively. Furthermore, the mean ratio of PM2.5/PM10 was around ~0.57 for the entire study period, with a lower contribution (0.53) in autumn and higher (0.60) in winter. However, the seasonal mean AOD440, precipitable water vapor content, Angstrom exponent (AE440-870) was found maximum with 0.97 ± 0.31, 1.58 ± 0.80 cm, and 1.14 ± 0.23 during autumn, and a minimum of 0.62 ± 0.34, 0.60 ± 0.27 cm, and 1.29 ± 0.19 in winter, respectively. The potential source contribution function (PSCF) and concentration weighted trajectory (CWT) models revealed considerable long-distance transport of PM2.5 from north and northwest China. Besides, the concentration bivariate probability function (CBPF) revealed a significant contribution of PM2.5 occurred when the winds blown from southerly and northwesterly directions. The relationship between PM2.5 and meteorology found that PM2.5 concentration had a positive relationship with AQI, while negative correlations with the major meteorological parameters. A notable spatial heterogeneities and trends were observed in AOD and AE, with negative correlations (−0.5 to 0) in winter over East China.