Overview
- CREA used NASA’s MERRA-2 reanalysis for 2024 to estimate that secondary ammonium sulfate contributes 17% to 42% of PM2.5 across Indian states.
- In Delhi, secondary ammonium sulfate constitutes about one-third of annual PM2.5 and rises to 49% in the post-monsoon and 41% in winter, compared with about 21% in summer and monsoon.
- Coal-dominated states show the highest shares, led by Chhattisgarh at 42% and Odisha at 41%, with Jharkhand and Telangana at 40%.
- India emits about 11.2 million tonnes of SO2 annually, with coal-fired power plants identified as the main source driving sulfate formation alongside ammonia.
- CREA reports roughly 78% of coal plants are exempt from flue-gas desulfurisation and recommends reinstating mandatory FGD, precursor controls, and composition monitoring in the NCAP revision.