Airborne Polycyclic Aromatic Hydrocarbons (PAH) in Bangkok Urban Air I. Characterization and Quantification

The behavior of airborne PAH is related to their physical and chemical properties. Thus, in a tropical urban environment, they are expected to have phase distributions and reactivities which are quite different from those established for temperate areas. Nevertheless, such studies are still scarce in the tropics. In this study, the characteristics of PAH in Bangkok urban air were investigated with respect to gas-particle partitioning and dependency on particle size. A sampling system which consisted of an 8 stage size fractionating cascade impactor (Andersen “low volume” Sampler) and a downstream XAD-2 adsorbent tube was used for sample collection. Nine PAH, classified as carcinogenic and co-carcinogenic compounds—Pyrene (PYR), Benz(a)Anthracene (BaA), Benzo(e)Pyrene (BeP), Dibenz(a,c)Anthracene (DBacA), Benzo(k)Fluoranthene (BkF), Benzo(a)Pyrene (BaP), Dibenz(a,h)Anthracene (DBahA), Benzo(ghi)Perylene (BghiP) and Trimethylcholanthrene (3MC)—were quantified by ultrasonic extraction and HPLC with fluorescence detection. The quantitative and qualitative compositions of these nine PAH samples are described. It was concluded that the sampling system designed in this study is suitable for the investigation of airborne PAH (with molecular weights of 202 and above) in the tropical climate since even at sampling temperatures of ∼35°C, none of the listed PAH was traceable in the second layer of the XAD-2 adsorbent tube.