Unmasking Emissions: Tracing organic aerosols around a coal-fired power plant in India

Coal-fired thermal power plants (TPP) are projected to be a major energy source in India for the foreseeable future. Their continued operation and planned expansion will increase emissions, further degrading the air quality in the Indo-Gangetic Plains and undermining long-term sustainability. In this study, we collected for one-year particulate matter (PM_2.5) at an upwind and downwind site from a super-category TPP and analyzed polycyclic aromatic hydrocarbons (PAH), n-alkanes, and levoglucosan. The annual mean of PM_2.5 level was about 2.5 times the Indian National Ambient Air Quality Standards (NAAQS) (40 μg/m³) and 40 times the WHO standard (5 μg/m³). The annual mean of benzo[a]pyrene concentration was over five times the NAAQS level (1 ng/m³) and 40 times the European Environment Agency reference level (0.12 ng/m³, assuming an acceptable risk of additional lifetime cancer risk of 1 in 100,000). Diagnostic PAH ratios and n-alkane indices indicated the primary emission sources. n-Alkanes were mainly derived from petrogenic sources, while pyrogenic sources were the main contributor to PAHs. Levoglucosan indicated more biomass burning during winter and post-monsoon, with higher emissions at the downwind rural site compared to the upwind suburban site. We also used backward trajectory modeling, including clustering and concentration-weighted trajectories, to identify emission hotspots. They revealed elevated benzo[a]anthracene, benzo[b]fluoranthene, and dibenz[a,h]anthracene levels due to TPP emissions.