Long-term monitoring of oil contamination of profile-differentiated soils on the site of influence of oil-and-gas wells in the central part of the Boryslav-Pokuttya oil-and-gas bearing area

Abstract

The dynamics of oil contamination of profile-differentiated soils of the Precarpathian region in the area of influence of deep wells of the Vilhivska oil exploration area of the Boryslav-Pokuttya oiland-gas bearing area is investigated. The research was conducted during 2007-2016. Soils were tested in the intervals of the distribution of humus-eluviated (H (e) gl), eluvial-humous (Eh (gl)), iluvial (Ih (gl)) horizons, iluviated parent rock (Pigl), and unchanged parent rock (Quaternary sediments) to the depth up to 2.0 m. The concentrations of oil products in pollution sources are analyzed. The zoning of the research territory according to the distribution of elementary geochemical landscapes is carried out. Within the various elementary geochemical landscapes, regularities in the horizontal and radial distribution of oil products have been revealed. The highest pollutants concentration is established in the silts of elementary transsuperaqual landscapes in the number up to 1750 mg/kg. In deeper horizons, the concentration of pollutants decreases nonlinearly, and the dynamics of this process is different in various elementary geochemical landscapes. The dynamics of the change in the oil concentration over time during the 9-year period of field observations were established. In particular, 1.5 years after the drilling operations cessation, the average concentration of oil products in the interval of the humus-eluviated horizon decreased 2.7 times and more than 4 times after 2.5 years. In the interval of the eluvial-humus horizon, the dynamics of the pollutant concentration change was less intensive, as the processes of desalination and decomposition of oil products were accompanied by the introduction of new pollutant amounts from the upper horizons. Obtained results are unique considering the natural conditions and long duration of the study (9 years). It can be useful in predicting changes in the concentration of oil products in soils, in designing environmental protection measures and civil protection measures. Highlighted in the article, the results of research support and develop the theory of geochemistry of technogenesis, the theory of geochemical landscapes, creating a reliable experimental basis for improving the scientific methods of ecological and crisis monitoring.