Polycyclic aromatic hydrocarbons (PAHs) are generally emitted to the atmosphere as a mixture which presents a substantial toxic hazard. Levels in the atmosphere are almost everywhere dominated by combustion sources. Gas-particle partitioning (GPP) of PAHs is a key process of atmospheric cycling and to assess the long-range transport potential and persistence, but still incompletely understood. Field data of PAH GPP and its temperature dependency support the hypothesis of both adsorptive and absorptive mechanisms contributing, i.e. dual models seem to best explain observations [1] and long-range transport trends [2]. The whole range of various models emphasizing different processes on the molecular level to determine the overall process had hardly ever been tested, because of lack of input data, such as OM and BC mass fractions and aerosol specific surface concentration, S.  Current knowledge is reviewed and field data from measurement campaigns, 2007-12, at urban, rural, and high mountain [3] central European sites, and at urban, rural [4], and marine Mediterranean sites (including so far unpublished data) are used to conclude on the process and trends across aerosol types. A number of GPP models are tested, including a poly-parameter linear free energy relationship model. GPP is for the first time expressed in size fraction-specific terms. Knowledge gaps are identified.  References: [1] Lohmann, Lammel (2004): Adsorptive and absorptive contributions to the GPP of PAHs (�), Environ. Sci. Technol. 38, 3793-3803. [2] Lammel, Sehili, Bond, Feichter, Grassl (2009): GPP and global distribution of PAHs (�), Chemosphere 76, 98-106.  [3] Lammel, Kl�nov�, Kohoutek, Proke�, Ries, Stohl (2009): Observation and origin of OCPs, PCBs and PAHs in the free troposphere over central Europe, Environ. Pollut. 157, 3264-3271.  [4] Lammel, Kl�nov�, Ilic, Kohoutek, Gasic, Kovacic, �krdl�kov� (2010): PAHs on small spatial and temporal scales (�), Atmos. Environ. 44, 5022-5027.

Gas-particle partitioning of polycyclic aromatic hydrocarbons: State of knowledge

246th National Meeting (2013)

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