Behavior of Diesel Fuel Hydrocarbons in Soils of the Far North after Accidental Contamination

The accidental diesel fuel (DF) spill near the city of Norilsk in 2020 served as the basis for studying the behavior of hydrocarbons in soils of the Far North, which are characterized by a low rate of natural self-purification. The objective of this study is to determine the direction of transformation in the composition of DF hydrocarbons in various soil types, which is important for optimizing remediation measures for petroleum pollution in the Arctic zone of Russia. Using gas chromatography–mass spectrometry, the distribution of DF components—including normal and isoprenoid alkanes, alkylcyclohexanes, bicyclic naphthenes, alkyl-substituted benzene derivatives of normal and isoprenoid structures, naphthalenes, and phenanthrenes—are analyzed in Arctic soils differentiated by distance from the spill site and time elapsed since the accident. Differences in hydrocarbon composition in the vertical soil profile are identified, reflecting the pathways of contamination and the specific soil types. In sandy and waterlogged alluvial–gley soils near the spill site, the downward percolation of DF leads to an increased proportion of high-molecular-weight and branched hydrocarbons, attributed to exclusion chromatography effects during filtration through the soil. The transport of DF along the watercourse results in the loss of low-molecular-weight members across all homologous hydrocarbon series due to leaching and evaporation during aquatic migration. The deposition of residual diesel components in floodplain sod–alluvial–gley soils is accompanied by mixing in the upper soil layers, while the lower profile shows the accumulation of isoprenoid alkanes, alkylbenzenes, bicyclic naphthenes, naphthalenes, and phenanthrenes with a higher content of low-molecular-weight fractions. One year after the DF entered the watercourse, the redistribution of contaminants was observed in the floodplain sod–alluvial–gley soil profile under the influence of seasonal hydrodynamic processes, including the influx of a new portion of pollutants during spring floods. Traces of the initial contamination persisted only in the deeper soil layers.