Formation of the Composition of Polycyclic Aromatic Hydrocarbons in Hummocky Bogs in the Forest-Tundra–Northern Tundra Zonal Sequence.

The accumulation of polycyclic aromatic hydrocarbons (PAHs) in plants and peat of three natural subzones—forest-tundra, southern tundra, and northern tundra—is discussed. The content of polyarenes is estimated with high performance liquid chromatography. The absence of statistically significant differences in the PAH accumulation by the plants of the same species in the studied ecotones allows for extrapolation of the data on PAH composition of the studied plants to other background hummocky bogs. The PAH composition of dominant plants influences the PAH composition of the upper peat layers, as is demonstrated by high correlation coefficients. A gradual decomposition of the herbs and trees residues, enriched with lignin, leads to neoformation of heavy polyarene structures (absent in plants) in peat. The coefficients of correlation between peat and plant PAH compositions decrease with depth and the degree of peat decomposition. All studied peatlands display an inverse correlation between the accumulation of naphthalene and benzo[ghi]perylene and the decrease in PAH content in the upper layers of permafrost. The content of polyarenes in the permafrost horizons is determined by the specific historical features in peatland formation. The peak values of five–six ring PAH structures, mainly benzo[ghi]perylene, are observed in the peat layers formed during the Holocene climatic optimum under excessive moistening. As for the raised and transitional bogs having originated during the Subboreal, any increased benzo[ghi]perylene concentrations are unobservable. A decrease in the soil temperatures from south to north is a likely reason for the observed decrease in the PAH content in peatlands from the forest-tundra and southern tundra to northern tundra. [ABSTRACT FROM AUTHOR]