Sorption of a Diverse Set of Organic Vapors To Urban Aerosols

Sorption to urban aerosols is a key process in determining the transport and fate of organic pollutants in the atmosphere. The sorption properties of two urban aerosol samples have been determined using aerosol/air partition coefficients measured for a large set of diverse organic vapors. The dominant sorption process could be identified for both samples with two complementary methods: (a) by applying poly-parameter linear free energy relationships (LFERs) to the data sets, and (b) by evaluating the specific surface area, the elemental carbon (EC) content, and the organic matter (OM) content of the aerosols in combination with various sorbent-air partition coefficients from the literature. This revealed that sorption to the two urban aerosols was dominated by absorption into OM and that the diverse data set could be evaluated with an absorption model. The data further revealed that neither EC nor OM was fully available for sorption. The latter leads to the hypothesis that aerosol OM in urban samples has characteristics comparable to those of glassy polymers.