Projected climate change is strongly influenced by clouds. The oxidative processing of pollutants in clouds affects droplet size and reflectivity, important climatic effects. Clouds contain naturally occurring lipids forming films on the droplet. Oxidation and removal of this film can prevent precipitation and cause cloud evaporation. Oxidation is by aqueous sulphate radical, produced in the oxidation of sulfur, i.e. acid rain. We will study the kinetics of sulphate radicals with a proxy film DSPC. Specifically, (a) demonstrate a common aqueous cloud oxidant, sulphate radical, can penetrate and remove the organic film, (b) calculate the effect of reaction on the hygroscopic properties of a cloud, demonstrates organic film removal may cause cloud evaporation, (c) measure the rate constants for film oxidation and assess atmospheric relevance (d) Support a STFC/NERC CASE award PhD student