Polycyclic Aromatic Hydrocarbons in Peat Mounds of the Permafrost Zone

Abstract

The accumulation of polycyclic aromatic hydrocarbons (PAHs) in the profiles of permafrost-affected peat mounds is related to certain groups of plant residues produced in the Atlantic climatic optimum of the Holocene. Both “heavy” (benzo[ghi]perylene, dibenz[a,h]anthracene, and benzo[b]fluoranthene) and “light” (pyrene and naphthalene) PAHs predominate in them. The polyarenes preserved in the permafrost horizons are not subjected to transformation in contrast to the polyarenes in the active layer. Dynamic freeze–thaw processes at the boundary between seasonally thawed and permanently frozen layers result in considerable transformation of plant remains, humic substances, and nonspecific organic compounds with the accumulation of 5–6-nuclear PAH structures. The composition of PAHs in peatlands and a significant increase in the weight fraction of PAHs at the boundary between seasonally thawed and permafrost layers may serve as indicators of permafrost response to climate changes in high latitudes.