The effect of H₂O adsorption on cloud drop activation of insoluble particles: a theoretical framework

Abstract. Cloud droplet activation of wettable insoluble compounds has been studied theoretically by assuming that droplet growth happens through multilayer adsorption. The idea is to include an adsorption isotherm in Köhler theory instead of the solute term. This makes it possible to describe the equilibrium growth of insoluble particles and to find out their critical saturation ratios. The critical saturation ratios calculated in this way are comparable to those of completely soluble particles at certain ranges of adsorption isotherm parameter values. The results indicate that adsorption could cause wettable insoluble compounds to activate in atmospheric conditions. However, more data on the adsorption parameters for wettable organic substances is needed to confirm this conclusion.