Cloud condensation nuclei (CCN) activity and water adsorption of model insoluble atmospheric aerosols: Application of Adsorption Activation Theory

Abstract:

The aerosol indirect climate effect remains the most uncertain factor that contributes to climate change. Cloud condensation nuclei (CCN) activity measurements and our theoretical understanding of cloud formation are important for quantifying the role of atmospheric aerosol on cloud formation and the resulting indirect climate effect. However, discrepancies exist in the literature between theoretical adsorption parameters measured from CCN activation and water adsorption of insoluble atmospheric aerosols, likely due to aerosol surface microstructure and fractality. The goal of the work presented is to demonstrate experimental closure between theoretical adsorption parameters measured from CCN activation and water adsorption measurements in the absence of surface microstructure, using polyhydroxylated nanospheres (PHS) as spherical model insoluble atmospheric aerosols. Adsorption model parameters were measured by applying Frenkel Halsey Hill Adsorption Activation Theory (FHH) to bulk water adsorption and direct CCN activation measurements of size-selected PHS spheres. Results suggest that, in the absence of surface microstructure, climate model parameters determined from CCN activity and bulk water adsorption measurements are in agreement, further supporting the hypothesis that the source of experimental discrepancies in the literature arise from aerosol surface microstructure and fractality.