Partitioning of semivolatile organic compounds in the presence of a secondary organic aerosol in a controlled atmosphere

The gas-particle partitioning of select semivolatile organic compounds (SOCs) was studied by injecting the SOCs into a 190 m(3) Teflon film chamber containing a secondary organic aerosol (SOA) generated by volatilizing liquid alpha-pinene into an ozone-concentrated atmosphere. The concentration of total suspended particulates (TSP) and gas and particle-phase SOCs was measured over the course of three experiments spanning a temperature range of 268-297 K and a relative humidity range of 55-100%. An equilibrium partition coefficient, K-p, was calculated for each sampling event. Empirical relationships were then developed to predict the partitioning of the SOCs on the SOA particle source as a function of temperature. Partitioning in this SOA system was compared to that of a SOA generated by the photochemical reaction of NOx with m-xylene. The results indicate that partitioning is similar between the two SOA systems. The effects of multiple particle sources on partitioning was also examined, revealing that a weighted average of predicted K-p values for individual sources can be used to predict partitioning in aerosol mixtures.