Wintertime source apportionment of PM2.5 pollution in million plus population cities of India using WRF-Chem simulation

Several major Indian cities experience elevated PM2.5 concentrations, particularly during the winter season. Effective air quality management in these densely populated urban areas necessitates a comprehensive understanding of the diverse emission sources contributing to air pollution. This study investigates PM2.5 pollution in 53 million-plus population cities (MPPC's) across India during the winter of 2015-2016 utilizing the Weather Research and Forecasting model coupled with chemistry (WRF-Chem). Multiple model simulations were employed to study the impact of various source sectors on local PM2.5 pollution and their emissions in these cities. The findings indicate significant contributions to local PM2.5 pollution from major emission source sectors in MPPCs. The influence of PM2.5 pollution plumes originating from these cities on regional PM2.5 pollution in India is evident across all sectors. In MPPCs situated in the east, north, and central regions of India, the primary contributors to local PM2.5 pollution include residential and transportation sectors, alongside energy sectors in specific cities marked by elevated emissions from power plants. In the MPPCs of western India, the industrial and energy sectors are identified as the primary contributors to local PM2.5 pollution. Meanwhile, in the MPPCs of south India, the major contributors are identified as industrial and residential sectors. In a comprehensive overview encompassing 53 MPPCs, the primary contributors to local PM2.5 pollution are identified as follows: the energy sector in 7 cities, the industrial sector in 8 cities, the residential sector in 29 cities, and the transportation sector in 9 cities. The correlation between PM2.5 pollution loadings and meteorological parameters reveals that PM2.5 pollution levels in MPPCs are influenced by both local emissions and meteorological factors. Specifically, wind speed and boundary layer height play critical roles in regulating the dispersion of pollution. Consequently, regulating emissions from these cities effectively requires consideration of both the primary emission source sectors and the prevailing meteorological conditions specific to each city's geographical location.