1. Соловьева О. В. (Soloveva O. V.)
2. Тихонова Е. А. (Tikhonova E. A.)
3. Алемов С. В. (Alyomov S. V.)
4. Stepanyan O. V.
   
   Federal Research Centre the Southern Scientific Centre, Russian Academy of Sciences, Rostov-on-Don, Russian Federation (ru)

Methods and Results. Water and bottom sediment samples were collected in the summer of 2024 along the coast, including areas with high anthropogenic impacts as well as nature conservation zones. Concentrations of hydrocarbons and n-alkanes were determined by gas chromatography and diagnostic indices were calculated to identify possible sources of hydrocarbons. Hydrocarbon concentrations varied: 0.048–0.172 mg/L (mean 0.084 ± 0.030 mg/L) in water, 0.01–0/19 mg/L (mean 0.09 ± 0.05 mg/L) in suspended matter, 1.00–3.80 mg/kg (mean 2.48 ± 0.96 mg/kg) in bottom sediments. Hydrocarbon concentrations in water at all stations, except one, exceeded the maximum permissible concentration for fishery water bodies (0.05 mg/L). The distribution of n-alkanes in the studied components suggests predominantly natural sources of hydrocarbons: in water and suspended matter, these sources are primarily macrophytes and the bacterial communities, while in coastal sediments, they are organic compounds originating from terrestrial sources. The CPI₂ (> 1) indices and the pristane/phytane ratio (< 1) in most samples, along with the absence of unresolved complex mixtures in the chromatograms, indicate a primarily biogenic rather than petroleum origin for the hydrocarbons.

Conclusions. The observed exceedance of the maximum permissible concentration for total hydrocarbon content in water is attributed to natural processes. The predominantly biogenic origin of hydrocarbons is explained by the influx of organic matter from terrestrial vegetation, as well as the activity of macrophytes and bacterial communities under conditions of summer water warming. Hydrocarbon accumulation in sandy bottom sediments is minimal. Thus, no evidence of oil pollution was detected in the studied water area, and the observed hydrocarbon concentrations are mainly due to natural biogeochemical processes characteristic of the Sea of Azov.