Characterization and sources of fine carbonaceous aerosol in winter over a megacity on Indo-Gangetic plain

The characteristics and sources of carbonaceous aerosol (CA) was studied during winter in the lower atmosphere Kolkata, a megacity situated Indo-Gangetic plain region. city air laden with typically high EC (15.4 ± 9.4 μg/m3) OC (32.2 17.8 winter. NASA's MERRA-2 reanalysis products underestimated PM2.5, EC, mean bias 41.0 56.8 μg/m3, 10.1 9.3 10.8 18.2 respectively. EC/BC ratio for Kolkata estimated to be 1.03 0.50. Levoglucosan PM2.5 as biomass burning tracer (266.9 189.5 ng/m3). Source apportionment CA using method indicated 43% (19% total PM2.5) secondary origin. 49% (21% from fossil fuel combustion, consisting 23% 26% OC. Biomass contributed 8% 3% PM2.5. diel trend equivalent primary emission throughout day except being significantly morning time rush hours traffic increased residential combustion. Despite dispersion, formation much higher sunlight, indicating extensive organic formation.