Quantification of the Effect of Humidity on the Gas/Mineral Oxide and Gas/Salt Adsorption of Organic Compounds

The transport of organic pollutants in the atmosphere is strongly affected by their tendency to sorb to aerosol particles or to terrestrial surfaces. Adsorption to the surfaces of mineral oxides or salts is one of the relevant processes. In a previous paper, a conceptual model for the quantification of gas/surface adsorption equilibria was presented. Here we report surface parameters that are required by this model for a number of natural inorganic surfaces as a function of relative humidity. With these values it becomes possible to include the estimation of the adsorption equilibrium of organic vapors to inorganic surfaces into fate models for the exchange between the atmosphere and soil surfaces where so far only absorption into soil organic matter has been considered. The reported surface parameters can also be used for a comparison of the sorption capacity of inorganic aerosol particles with the sorption capacity that has been measured for urban aerosol particles. The results show that the sorption capacity of urban particles is much too high to be explained by the prevalence of inorganic particles.