Polycyclic aromatic hydrocarbons in materials of burned peatlands

Polycyclic aromatic hydrocarbons are common in small amounts in the environment as a natural con-stituent of organic-rich rocks. They are mostly formed under oxygen-depleted conditions during burning of materials containing organic carbon. The samples, collected from peatlands which had been partially burned were analyzed for 17 unsubstituted PAHs. The profiles sampled encompassed: peat layer, burned peat layer and surficial newly formed turf-root layer. The average contents of determined PAHs in the burned peat layer is 0.114±0.048 ppm, and is similar to that in the underlying peats (0.101±0.039 ppm). The newly formed surficial root layer reveals concentrations nearly three times higher, i.e. 0.313±0.144 ppm. The PAH spectrum of both peat types practically includes only acenaphthene, fluorene, phenanthrene and fluoranthene. The presence of hydrocarbons with higher molecular weight, i.e. pyrene and chrysene, was noted only in some samples of burned peats; perylene was recorded only in moss peats. The PAH spectrum of newly-formed turf–root layer is different, and is characterized by the presence of all determined 4-ring and partly 5-ring [benzo(b)fluoranthene and benzo(e)pyrene] hydrocarbons. The relatively poor spectrum of PAHs in the burned peat layer, and the presence of larger amounts and greater diversity of these com-pounds in the newly-formed surficial layer, may indicate that most of these hydrocarbons must have origi-nated from airborne PAH deposition.