Wintertime study on bulk composition and stable carbon isotope analysis of ambient aerosols from North India

Ambient aerosols (PM2.5; particulate matter with aerodynamic diameter <= 2.5 mu m) collected during wintertime from Kanpur (26.30 degrees N, 80.14 degrees E; in Indo-Gangetic Plain: IGP) in December 2014 were studied for their chemical composition [organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), major ions] and stable carbon isotope composition (delta C-13) of total carbon (TC). Several source samples have also been strategically collected and characterized with delta C-13 value. Air-mass back trajectories arriving at the receptor site during the study period exhibited predominant influence of north-westerly winds. PM2.5 mass in ambient samples averaged at 240 +/- 72 mu g m(-3) and total carbonaceous aerosols (TCA) concentration averaged at 91 +/- 25 mu g m(-3) in these samples. The OC and EC concentrations contributed nearly 22% and 2%, respectively to the ambient PM2.5- mass. A significant variability in OC/EC ratio (8.7-14.8; Avg. +/- SD: 12 +/- 2) and WSOC/OC ratio (0.35-0.51; 0.43 +/- 0.05) has been recorded during the winter season in IGP. The ambient concentrations of secondary inorganic aerosol species (SIA) viz. SO42-, NO3 and NH4+ were 23.5 +/- 8.7, 10.5 +/- 6.0 and 12.8 +/- 4.9 mu g m(-3), respectively. The delta C-13 of TC in ambient aerosols varied from - 24.5 to - 26.2%o. Large scatter between delta C-13 and TC content in aerosols indicated signature from multiple sources of carbonaceous aerosols due to mixing of air-masses. Future studies with large PC data population in conjunction with bulk composition would be required to better characterize the carbonaceous aerosols over the Indian region.