PNNL

Abstract

India faces significant air quality challenges, with one of the highest air pollution levels of any country in the world. Here, we examine two decades (2001-2019) of both particulate matter (PM2.5) concentration and aerosol optical depth (AOD) over the country. Increases are seen between these two decades; 2001-2010 and 2010-2019, particularly in the Indo-Gangetic Plain (IGP). IGP region, including Bihar, West Bengal, Jharkhand, and Uttar Pradesh, shows the highest increases in AOD (+0.03, 13%) and PM2.5 (+8 µg/m³). Seasonal AOD patterns fluctuate, with the IGP experiencing the highest wintertime increase, especially in Bihar (+0.07). Summer increases occur in the southern and eastern coastal regions, while monsoons slightly raise AOD except in Rajasthan. Post-monsoon, the IGP sees a significant AOD rise (+0.057, 25%), potentially driven by biomass burning in Bihar (+0.11) and Uttar Pradesh (+0.075). Separating our study area into urban and peri-urban clusters (n=2791), AOD is found to be similar, possibly due to advective mixing. However, urban-rural differences are more pronounced, increasing in the second decade. Correlations between AOD and PM2.5 vary, highest in Kanpur (R² = 0.61) and lower in Delhi (R² = 0.42), highlighting the need for more ground monitoring but suggesting that satellite-derived AOD can generally be used to examine trends in PM2.5 over longer time frames.