Soil Pollution with Polycyclic Aromatic Hydrocarbons and Petroleum Hydrocarbons in the North of Western Siberia: Spatial Pattern and Ecological Risk Assessment

摘要

The assessment of soil pollution and soil toxicity in the area of oil and gas fields in tundra and northern taiga of Western Siberia was performed. The contents of petroleum hydrocarbons (HCs) and polycyclic aromatic hydrocarbons (PAHs) in soils were analyzed for four sites of sludge spills and along the winter road. Speciation of PAHs and its relationship with the HC content determined by the methods of infrared spectroscopy (HCIR) and fluorimetry (HCFL) were analyzed. The HCIR content was several times higher than the HCFL content. The high content of HCIR in soils of oil and gas production areas attested to their contamination with crude oil during well construction. An increase in the HCFL content was mainly related to the input of pyrogenic PAHs with emissions from heavy vehicles. The total PAHs content ranged from 95 to 22 114 mu g/kg. Low-molecular-weight compounds-naphthalene (12%), phenanthrene (23%), and fluoranthene (16%)-predominated among PAHs, which was explained by soil contamination with light oil as a result of well drilling. The vertical migration of pollutants in the soil profile was weak, and they mainly concentrated in the upper part of the peat horizon. The distance of lateral migration of pollutants from the spill did not exceed 50-150 m and depended on the landscape and geochemical conditions. The ecological risk of soil toxicity was assessed using the contamination danger index based on the benzo[a]pyrene (BaP) toxicity equivalent and the schedule proposed by the authors. According to calculations, 62% of the studied soil samples were uncontaminated, 37% were characterized by moderate and low levels of environmental pollution risk, and one sample (< 1%) corresponded to its high level.