The effect of moisture on volatile organic chemical gas-to-particle partitioning with atmospheric aerosols-competitive adsorption theory predictions

Junge's (Junge C.E., 1977, in Fate of Pollutants in the Air and Water Environments, pp7-25, John Wiley, New York) aerosol/vapor adsorption algorithm for organic air pollutants is extended to account for the water vapor content in air. A model, based on classical competitive adsorption theory and supported by ancillary data, is proposed to quantify the role of relative humidity (r.h.) on the equilibrium distribution of semivolatile organic chemicals (SOCs) between the aerosol (solid) and vapor phases. In general the model shows that aerosols contain significantly less SOCs for r.h. in the range of 10-90%. Quantitative predictions are made and one calculation shows that as air r.h. increases to 60% the aerosol associated SOC fraction is reduced by 80%. The model also suggest that dry aerosols and those with complete water films have the highest SOC content.