Background Content of Polycyclic Aromatic Hydrocarbons during Monitoring of Natural and Anthropogenically Transformed Landscapes in the Coastal Area Soils

The large-scale studies of the Lower Don and the Taganrog Bay coastal zone were carried out to determine the background concentrations of polycyclic aromatic hydrocarbons (PAHs) in soils. The content of 15 priority PAHs was determined by saponification method with HPLC detection and varied widely from 77 & mu;g kg(-1) to 16,017 & mu;g kg(-1) with mean and median values of 1040 & mu;g kg(-1) and 406 & mu;g kg(-1), respectively. PAHs' highest concentration level was observed in the soils of the Don River delta and industrial areas of Taganrog city affected by pyrogenic contamination sources. Background monitoring sites were mostly represented with hydromorphic (Fluvisols Salic and Tidalic Fluvisols) and automorphic (Rendzic Leptosols, Mollic Leptosols) soil types in the study area. The PAHs content in the soils of the background plots did not exceed 600 & mu;g kg(-1), with a share of low-molecular-weight PAHs: about 50%. Benzo(a)pyrene content did not exceed the maximum permissible concentration (20 & mu;g kg(-1)), and low-molecular-weight compounds did not exceed the threshold level for the impact of polyarenes. In automorphic soils, naphthalene and phenanthrene (35-54%) dominated in the composition of the low-molecular-weight PAHs compounds, and only phenanthrene (59-70%) dominated in hydromorphic soils.