Gaseous and particulate polycyclic aromatic hydrocarbons (PAH) from the marine atmosphere

Abstract

Despite their importance in environmental studies, there are very few data concerning the gaseous polycyclic aromatic hydrocarbons (PAH) in the marine atmosphere and their potential importance. We present here concentrations and distributions for gaseous and particulate PAH sampled in the atmosphere over the Tropical and Equatorial East Atlantic. After collection respecting ultra-clean conditions, PAH were isolated and analysed through capillary GC and GC/MS. Concentrations of gaseous PAH ranged from 7 to 18 ngm −3. They are an order of magnitude higher than those encountered for particulate PAH. This enhances the importance of gaseous PAH vs PAH associated with aerosols and strongly shows their mode in transport and ocean-atmosphere exchange processes. Gaseous PAH are composed almost entirely of extremely volatile compounds such as phenanthrene. On the other hand, aerosol PAH distributions exhibit a predominance of phenanthrene, but also contain substantial amounts of other PAH: fluoranthene, pyrene, chrysene, benzofluoranthenes and benzopyrenes. The comparison between the distributions of PAH and their alkylated homologues, both in the atmosphere and the sea surface mkrolayer collected in the same area, suggests a mixed origin for the gaseous PAH: non-combusted petroleum residues and pyrolytic-like compounds emitted from the ocean.