Small, soluble fractions are sufficient for fine mineral dust particles to serve as efficient CCN

Mineral dust particles include many different components, but are often treated by models as insoluble resulting in limited activation to cloud droplets. Experimental critical supersaturations of mineral dust particles 0.2 μm in diameter from different sources indicate that their composition is partially soluble. Using a Köhler model, the soluble fraction of each dust sample was calculated from the measured critical supersaturation and used to predict the fraction of fine (< 1 μm) particles that could activate using atmospherically relevant conditions (e.g. a supersaturation of 0.2%) and size distribution parameters representative of fine dust particles. Activated fractions ranged from 0.01-0.41 with the sensitivity of these results depending primarily on particle size. The results indicate that dust particles with as little as 3% soluble material can be up to ~80% as efficient at activating cloud droplets as pure ammonium sulfate particles with the same size distribution characteristics.