CLOUD CONDENSATION NUCLEUS ACTIVITY OF THE ORGANIC-COMPONENT OF BIOMASS SMOKE PARTICLES

Natural and anthropogenic water-soluble inorganic aerosol species are efficient cloud condensation nuclei (CCN). Biomass smoke particles, al though composed mostly of organic material, are also known to be effic ient CCN. However because smoke particles consist of mixtures of organ ic and inorganic species, it has not been established whether the orga nic component is intrinsically CCN active or is intrinsically inactive and rendered CCN active only through association with water-soluble i norganic species. Here we report results of laboratory experiments on smoke particles produced by combustion of eucalyptus, redwood, and cel lulose which show that their water-soluble organic fraction is princip ally derived from smoldering combustion of the cellulosic fuel content . Because cellulose smoke particles are entirely organic, water solubl e, and CCN active (at 0.5% and 0.3% supersaturation), we conclude that the water-soluble organic species in smoke particles from smoldering biomass combustion are responsible for their intrinsic CCN activity.