Source apportionment of black carbon over Delhi: A case study of extreme biomass burning events and Diwali festival

Present study investigates the temporal and diurnal variations of Black Carbon (BC) and quantifies the contribution of fossil fuel (BCff) combustion and biomass burning (BCbb) to the BC concentrations in Delhi using the Aethalometer model. The average BC mass concentration and Absorption Angstrom Exponent were 12.6 +/- 8.2 mu g/m(3) (range: 1.73-37.0 mu g/m(3)) and 1.30 +/- 0.16 (range: 1.06-1.82), respectively. The average BCff and BCbb mass concentrations were 7.90 +/- 4.98 mu g/m(3) (range: 1.13-19.98 mu g/m(3)) and 4.73 +/- 5.23 mu g/m(3) (range: 0.21-26.85 mu g/m(3)), respectively. The contribution of BCbb was 31.15% and BCff was 68.85% to the overall BC concentration in the study period. The highest BCbb contribution, amounting to 52.04%, was found in the month of November (stubble burning season). The effect of Diwali firecrackers on BC concentrations was also investigated which was transient, lasted for few hours only. The probable major source regions of BC to the receptor site were Rajasthan, Gujarat, Punjab, Indo-Gangetic Plain and parts of Pakistan during monsoon season while Punjab, Haryana, and parts of Uttar Pradesh during post-monsoon season. The results revealed that the biomass burning activities in Punjab and Haryana contribute significantly to the Delhi's post-monsoon air pollution suggesting urgency to implement the carbonaceous aerosols emission abatement strategies over northern India.