Biomass Combustion a Dominant Source of Carbonaceous Aerosols in the Ambient Environment of Western Himalayas

Use of biomass combustion as primary energy source emit substantial amounts of carbonaceous aerosols (CA) in the Himalayan environment. Any understanding regarding the impact of CA on human health and climate requires a reliable estimation of compositional variability of CA associated carbon forms: Elemental carbon (EC), Organic carbon (OC), and Light absorbing organic carbon (LAOC). This investigation spanning over 14 months was undertaken in the rural part of the Western Himalayas to estimate temporal variability in the ambient aerosol load (PM10, PM2.5), CA associated carbon forms. All CA associated carbon forms were part of PM2.5 size fraction, their significantly high concentrations in winter corresponded with the high biomass combustion. Source apportionment of CA done on the basis of Char-EC/Soot-EC estimates showed that > 90% of the EC was Char-EC contributed by biomass and coal combustion in winter. Estimates of K+ (tracer for biomass combustion) showed a strong association with CA associated carbon forms. The estimated values of CA associated carbon forms during winter matched with the reported values of emission factors for biomass burning. Both the mass and composition of ambient aerosol were predominantly contributed by biomass combustion in the region.