Abstract
ABSTRACTThe light absorption properties of brown carbon aerosols generated in a lab scale experiment from wood (Magnifera indica) and dung cake were studied. Mie theory along with experimentally derived values for imaginary refractive index was used to estimate mass absorption coefficient for the samples. It was observed that for both wood and dung cake major portion of brown carbon were generated above 150°C. The light absorbing properties of brown carbon from wood depended on temperature of pyrolysis which was not the case for dung cake. The spectral dependence of absorption for brown carbon samples was estimated in terms of Absorption Angstrom Exponent and found to be greater than 2. The brown carbon aerosols from dung cake pyrolysis were having twice the light absorbing potential (in the wavelength range 280 nm to 750 nm) than brown carbon emitted from mango tree wood pyrolytic combustion.
Highlights
Since last few decades there is a growing concern on effects of aerosols on climate
Important properties in the context of light absorption by organic carbon (OC) aerosols generated in laboratory are discussed
Laboratory scale experiments were performed for sampling of OC aerosols generated during pyrolytic combustion of wood (Magnifera indica) and dung cake
Summary
Since last few decades there is a growing concern on effects of aerosols on climate. Intergovernmental Panel on Climate Change (IPCC, 2007) reviews climatic effects of aerosols and brings to focus its highly uncertain role. Aerosols can absorb sunlight causing direct warming of atmosphere and scatter light resulting in cooling effect. Carbonaceous aerosols form major fraction of atmospheric aerosols (IPCC, 2001). These aerosols can be grouped as visible light absorbing black carbon (BC) and scattering organic carbon (OC) aerosols. Experimental measurement suggests some part of organics in aerosols (OA) to be light absorbing in blue and ultraviolet region (Andreae and Gelencser, 2006; Mosmuller et al, 2011). This light absorbing OC is called as brown carbon (BrC). Filter paper collected OA generated from biomass burning and extracted with acetone show light absorption
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