MP3 Heterogeneous Chemistry of Atmospheric Particles and Trace Gases
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(ROT-1117-815885) Sorption of a diverse set of organic vapors to diesel soot, road tunnel aerosols and urban aerosols.

Roth, C.^{1, 2, 3}, Goss, K.-U.^{2, 3}, Schwarzenbach, R.^{2, 3}, ¹ Harvard University, Boston, MA, USA² Swiss Federal Institute for Environmental Science and Technology (EAWAG), Duebendorf, Switzerland³ Swiss Federal Institute of Technology (ETHZ), Zurich, Switzerland

ABSTRACT- Sorption to aerosols is a key process in determining the transport and fate of organic pollutants in the atmosphere. The sorption properties of four aerosol samples representing different exhaust sources and different atmospheric lifetimes have been determined. For a large set of diverse organic vapors sorption has been measured by inverse gas chromatography. The dominant sorption process could be identified for the 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. For pure diesel soot we could identify adsorption to EC as the dominant sorption process. We used our experimental equilibrium adsorption coefficients in order to derive a predictive model for adsorption on soot in line with adsorption models for other surfaces published earlier. On road tunnel aerosols, both adsorption to EC and absorption in OM governed the observed sorption and the data could not be further evaluated in terms of a specific sorption mechanism. On two urban aerosols sorption was dominated by absorption into OM and 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 glassy polymers.

Key words: inverse gas chromatography, aerosol/air partitioning, sorption models, aerosol properties