Polycyclic Aromatic Hydrocarbons

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds that have two or more fused aromatic rings. They have relatively low solubility in water and are highly lipophilic. The term polycyclic organic matter (POM) defines a broad class of compounds that generally includes all organic structures that have two or more fused aromatic rings. Polycyclic organic matter has been identified with as many as seven fused rings and, theoretically, millions of POM compounds could exist; however, only about 100 species have been identified and studied, and typically only a small fraction of them are regularly tested for as part of emissions measurement programs. Any effort to quantify emissions of POM relies on the group of compounds or analytes targeted by the test method employed. The EPA has defined these eight major categories of compounds in the class known as POM. polycyclic aromatic hydrocarbons (PAHs); aromatic hydrocarbons that contain nitrogen in a heterocyclic ring; aromatic hydrocarbons that contain a carbon–nitrogen double bond (CNH); aromatic hydrocarbons that contain a one‐ring carbonyl divalent group (CO), also known as quinones; contain two‐ring carbonyl divalent groups; carbonyl arenes that contain hydroxy groups and possibly alkoxy or acyloxy groups; oxa arenes are aromatic hydrocarbons that contain an oxygen atom in a heterocyclic ring; thia arenes are aromatic hydrocarbons that contain a sulfur atom in a heterocyclic ring; and some polyhalo compounds, such as polychlorinated dibenzo‐ p ‐dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), may be considered POM although they do not have two or more fused aromatic rings.