15 - Polycyclic Aromatic Hydrocarbons (PAHs)

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are sometimes referred to as polynuclear aromatic hydrocarbons (PNAs), condensed ring aromatics, or fused ring aromatics. They are a class of organic compounds consisting of two or more fused aromatic rings. Polycyclic aromatic hydrocarbons most commonly encountered in the environment contain two (naphthalene) to seven (coronene) fused benzene rings, though PAHs with greater number of rings are also found. Natural sources of petrogenic PAHs arise from oil seepages and erosion of petroliferous shales, while natural sources of PAHs from combustion or pyrolysis include PAHs from incomplete combustion of wood and biomass via forest and grass fires. Anthropogenic (pollution) related PAHs inputs can result in similar, but not identical, PAH compounds and assemblages of PAHs to those of natural origin. Anthropogenic inputs of PAH arise from the release into the environment of petrogenic PAHs through accidental acute petroleum spillages and through chronic non-point source and point-source inputs such as urban (storm water) runoff and municipal waste treatment plane discharges. The most common and ubiquitous sources of anthropogenic PAHs, however, are those associated with pyrogenic inputs.