“Air Pollution from Biomass Burning in India”

Air pollution is the most difficult challenge India is facing today, and anthropogenic biomass burning (ABB) is one of the major and least understood sources, leading to serious health and climate implications by affecting air quality, visibility, atmospheric chemistry, the Earth’s radiation budget and biogeochemical cycling. Scientific understanding of the composition, chemistry and regional dynamics of biomass burning (BB) emissions is still limited, thus constraining the implementation of appropriate research and policy interventions. The broad categories, associated complex emissions and spatio-temporal variations of ABB in India are discussed here. Major types of ABB that are prevalent year-round all over India include BB for cooking, heating purposes and open waste burning. Moreover, crop residue burning (CRB) in the Indo-Gangetic plain (IGP) during pre- (April–May) and post-monsoon (October–November) seasons, CRB in South India during January–February, forest fires in Central India and slash-and-burn agriculture in Northeast India during March–May are the other dominant sources that are active during specific months and in specific regions. Over the IGP, CRB along with other episodic ABB events and stagnant meteorology result in severe air quality and poor visibility (<∼300 m) with reported daily mean PM _2.5 concentrations shooting up to 15 times higher than Central Pollution Control Board standards. When compared with wheat residue burning, higher fire counts and emissions are reported during paddy residue burning events. During winters, BB’s contribution to 37% of the aerosol oxidative potential in Delhi indicates its health implications. Meta-analysis of data obtained from representative source apportionment studies on PM _10 shows >24% BB contribution in Assam, Ahmedabad, Kanpur and Visakhapatnam, 20%–24% in Patiala and Kolkata, and 10%–14% in Delhi. With regard to PM _2.5 , BB contributions of >24% in Ahmedabad and Agra, and 15%–19% in Delhi, Mumbai and Kolkata are reported, while with regard to PM _1 , BB contributed 19%–24% in Kanpur, Patiala and Assam and <10% in Delhi. Observed spatio-temporal variations in ABB sources and composition over India call for region-specific solutions through airshed-based management.