Partitioning between Gas and Aerosol Phases

PAH vapor pressures vary over seven orders of magnitude (Table 14.19). As a result, at 25°C at equilibrium, naphthalene exists exclusively in the gas phase, while BaP, chrysene, and other PAHs with five and six rings exist predominantly in the aerosol phase. The 

FIGURE 14.19 Size distributions of benzo[a] anthracene (a) measured inside a tunnel and (b) in the ambient atmosphere of southern California. (Reprinted with permission from Venkataraman, C., and Friedlander, S. K. Size distributions of polycyclic hydrocarbons and elemental carbon. 1. Sampling, measurement methods and source characterization. Environ. Sci. Technol. 28. Copyright 1994 American Chemical Society.) 

TABLE 14.18 Reactivity Scale for Electrophilic Reactions of PAHs 

I Benzo[a]tetracene, dibenzo[a,/i]pyrene, pentacene, tetracene 

II Anthanthrene, anthracene, benzo[a]pyrene, cyclopen ta[c41pyrene, dibenzo[a,/]pyrene, 

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To find answers to these crucial questions and to establish if the occurrence of psychotropic substances in the atmospheric aerosols is just a curiosity or rather a potential problem for the community, a series of investigations have been carried out both in the laboratory and in the field. Dedicated procedures have been optimised, for instance, for cocaine and cannabinoids (see sections below), and the chemical stability of cocaine in airborne particulates and its partition between gas and aerosol phases were estimated, as well as its accumulation in fine rather than coarse particles. Furthermore, cocaine and cannabinoids concentrations have been measured in several cities over the world through field studies. After the first detection of cocaine in ambient air by Hannigan et al. [1] in Los Angeles, measurements were performed more extensively in Italy (for instance over 10 consecutive months in downtown Rome, or in 38 Italian localities) and Spain... 

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