Purpose. The purpose of the study is to assess the geochemical characteristics (granulometric composition, content of organic and inorganic/carbonate carbon) and their impact on the features of spatial distribution of heavy metals in the surface layer of bottom sediments in the southern and central Sea of Azov.
Methods and Results. The data obtained during the expeditions at the R/V Professor Vodyanitsky in 2019–2020 were used. The sediments surface layer (0–5 cm) was sampled by the Peterson grab sampler (capture area is 0.1 m²). The analysis of a modern data set on the sediments granulometric composition of the bottom surface layer in the Azov Sea made it possible to assess the patterns in spatial distribution of the following fractions: gravel (10–1 mm), sand (1–0.1 mm), aleurite-pelitic (0.1–0.05 mm), and pelite-aleuritic (< 0.05 mm) ones. The presence and degree of anthropogenic pollution of sediments with heavy metals were assessed by calculating various pollution indices (CF, Igeo, PLI, and Cdeg) including the values of average characteristic concentration which leveled out the impact of the sediments type. The obtained results showed that the Azov Sea bottom sediments were formed predominantly by pelite-aleuritic silts (on average 77%) with fragmentary inclusions of sandy material (on average 5%), and at some stations, a predominant portion of shell detritus (on average 18%) was noted. The organic carbon content varied from 0.6–1.9% in the gravel-sand sediments to 2.6–3.1% in the aleurite-pelitic silt sediments with an average value 2.0% (n = 15). Among the trace elements determined in pore waters, the reduced forms of iron and manganese were predominant. It was noted that, on average, all the determined trace elements (except for Sr and Mn) had shown, on the one hand, a negative correlation with the gravel and sand fractions, and with the carbonate carbon content, and, on the other hand, a positive correlation with the portion of clay material, the pelitic fraction contribution, and the organic carbon content.
Conclusions. Application of modern in situ data on the geochemical characteristics of bottom sediments made it possible to confirm that the main factors in the sedimentation process in the Sea of Azov are the coastal abrasion, the biogenic sedimentation and the bottom topography features. The resulting assessments of content of trace elements in the bottom sediments characterize them as predominantly unpolluted and moderately polluted. Exceeding of the multiplicity of average characteristic concentration, as well as moderate pollution level (by Igeo index) were observed for Cr, Cu, and Zn.