Comprehensive assessment of the Kerch Strait marine and coastal bottom sediments pollution after an accidental fuel oil spill (December 2024)

The study investigates the spatial distribution of geochemical characteristics and accumulation of pollutants in the surface layer of coastal and marine sediments of the Kerch Strait and in its pre-strait zone after the tanker accident in December 2024. Coastal sediments consisted primarily of shell and gravel material with an organic matter content ranging from 0.6% to 3.0%; pollutant concentrations were low, corresponding to pollution level I (<500 mg/kg). The organic matter content in the marine sediments ranged from 0.8% to 8.5%, falling within the natural range of organic matter levels observed in Black Sea shelf water areas. Petroleum hydrocarbon concentrations in the marine sediments ranged from 15 to 145 mg/kg. Maximum values were recorded in the gravel-sand sediments, which indicates the presence of an additional man-made source of pollution. The content of chloroform-extractable substances in the marine sediments was 70–270 mg/kg, corresponding to pollution level I. The majority of elements, except Zn, Cr, Co and Sr, accumulated in silt sediments. Over a five-year period, the concentrations of Cu, Fe, Mn, Ti, V, Pb, Zn, and Cr in the southern part of the Kerch Strait increased (by 12–65%), while those of Sr, As, and Ni decreased (by 7–37%). Factor and cluster analyses confirmed the decisive influence of silty material on the accumulation of pollutants. Co-accumulation of Cr and petroleum hydrocarbons was observed in gravel sediments, indicating a possible additional input of pollutants linked to the fuel oil tanker accident in the Kerch Strait in December 2024.