The impact of the Russian oil industry on surface water quality (a case study of the Agan River catchment, West Siberia)

Water quality in the Agan River catchment (West Siberia, Russia) was assessed based on data obtained between 1993 and 2017 at 25 monitoring stations. The purpose of the research was to assess the impact of oil field development on the quality of surface waters. Monitoring stations were located in the oil fields characterized by various levels of impact, from "moderate" (number of wells < 0.5 per 1 km(2)) to "extreme" (number of wells > 1 per 1 km(2)). Comparisons with the thresholds indicated that metal (Ni, Hg Pb, Zn, Cu, Mn and Fe) concentrations exceeded the standard limits for fisheries in 10.8%, 14.5%, 22.3%, 24.7%, 54.7%, 88.6% and 99.2% of samples, respectively. The high contents of Mn, Fe and Cu can be generally regarded as the natural results of intensive leaching of elements from acid soils. The total petroleum hydrocarbons (TPH) value exceeds the threshold in 34.6% of samples. The water quality was estimated using the Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI). The water quality of the Agan River catchment was classified as "poor" and "marginal". The TPH values displayed a significant positive correlation with the density of wells and with the percentage of oil-contaminated lands. Positive correlations were found between Cl(-)and the density of wells, the frequency of accidents and the area of contaminated lands. Trends of pollution are sensitive to changes of accident rate. The decrease in accident rate for the last decade resulted in declines in TPH and Cl concentrations.