Impact of drilling waste pollution on land cover in a high subarctic forest-tundra zone

Global climate changes can lead to the destruction of the permafrost zone and contribute to the active transfer of pollutants to natural waters.This can be especially pronounced in the areas of oil and gas production in the Arctic.This study aimed to define the landscape components(i.e.,groundwater,soil water,soil,and indicator plant species)of chemical pollution with metals,oil hydrocarbons,and polycyclic aromatic hydrocarbons,from the discharge of drill cuttings.Studies at two sites in the forest-tundra zone of Western Siberia(Russia)were carried out within two years of pollution.Pollutant migration was found in peaty-gley heavy loamy soils and iron-illuvial clayey podburs,but lateral migration of different pollutants did not exceed 200 m.Additionally,radial migration was practically absent owing to the high buffering capacity of the soil organic horizon and the upward flow of matter in the seasonal melt layer.The main indicators of drilling waste pollution were high concentrations of Sr,Ba,petroleum hydrocarbons,and Cl^(-)ions.At the waste disposal sites,the concentration of Ba and Sr in the soil water were 1150 and 1410μg L^(-1),respectively;in groundwater,they reached 721 and 2360μg L^(-1),respectively.In the soil,Ba and Sr accumulated in the peaty horizon(798 and 706 mg kg^(-1),respectively).The concentration of Cl^(-)ions in the soil water at the site of waste discharge was 1912 mg L^(-1),and at a distance of 200 m,it decreased to 77.4 mg L^(-1).The Cl^(-)concentration in the groundwater was lower,and at a distance of 200 m,it was 38.9 mg L^(-1).The highest concentration of petroleum hydrocarbons in the surface layer was found in the peaty-gley soils(up to 2400 mg kg^(-1)).In glandular-illuvial podburs,it was 420 mg kg^(-1).In horizons BH and BC,it was close to the background values(27 and 33 mg kg^(-1),respectively).Alkalinization of soils and water under the influence of drill cuttings led to the death of oligotrophic and acidophilic vegetation at a distance of up to 50 m,and to the restructuring of the species and spatial structure of plant communities up to 100 m.