CCN activation of carbonaceous aerosols from different combustion emissions sources: A laboratory study

Abstract

A laboratory-based experiment has been carried out to understand the cloud condensation nuclei (CCN) activation of carbonaceous aerosols from various sources of emissions such as combustion of wood, cow dung cake, wood-coal burning and diesel generator (DG). The aerosol particles from DG exhaust found to activate completely to cloud condensation nuclei (CCN) at a higher supersaturation (SS) of 0.9% (100.9% RH). However, the CCN activation was faster in carbonaceous aerosol emission from combustion of cow dung cake, where complete CCN activation of particles was observed at 0.3% SS. Wood burning also showed a faster activation at 0.4% SS, whereas for wood-coal burning, the CCN activation has occurred at 0.7% SS. Organic carbon (OC) was found to be the dominant carbon component in all four emission sources compared to elemental carbon (EC) and black carbon (BC). Among all four combustion emissions, wood-burning had the highest OC/EC ratio (8.35) and the lowest was for DG emissions (2.03). BC mass concentration was higher in DG emissions compared to other emissions for the same number of aerosol particles. The non-refractory aerosol chemical composition analysis showed that organic species dominate inorganic species in all the emissions. The study indicates that the carbonaceous aerosols originating from direct emission sources have the potential to get activated as CCN at high supersaturations.