Purpose. The purpose of the study is to present the geochemical characteristics of the Beysug Estuary (the Sea of Azov) based on the data obtained during field studies of the chemical composition of water and bottom sediments in spring, summer and autumn of 2018.
Methods and Results. Water and bottom sediments were sampled in the western part of the estuary under calm weather conditions. The chemical composition of water was assessed using the following parameters: major ions (chlorides, sulfates, bicarbonates, magnesium, calcium, sodium, and potassium), nutrients (total nitrogen and its mineral forms, total phosphorus and phosphate phosphorus), petroleum products, organic matter, metal compounds (iron, copper, zinc, lead, cadmium, nickel, arsenic, chromium, mercury), phenols, benzo(a)pyrene, and synthetic surfactants. The grain-size composition of bottom sediments, as well as the mass fractions of sulfate ions, phosphate ions, petroleum products and phenols in the sediments, was determined. The obtained results indicate that, during the field research period, the ionic composition of the water in the studied area of the estuary (salinity ranged from 16.0 to 18.1) was stable. The concentrations of the studied forms of nitrogen and phosphorus exhibited pronounced seasonal variability (except for nitrite nitrogen). A similar trend was characteristic of petroleum products and organic matter. Slight exceedances of the maximum permissible concentrations were noted for readily oxidizable organic matter (BOD5) (by 1.5–1.6 times), iron compounds (by 1.3–5.2 times), petroleum products (by 1.5–1.8 times) and ammonium ions (by 1.6 times). In most cases, trace element concentrations in water were below the detection limits of the applied analytical methods. The grain-size composition of bottom sediments showed a predominance (>60%) of the aleurite-pelitic fraction (0.01–0.05 mm). The concentrations of petroleum products and phenols in the bottom sediments exhibited variability, while those of sulfate ions and phosphate ions remained relatively stable.
Conclusions. The geochemical parameters of water and bottom sediments in the Beysug Estuary are mainly determined by the prevailing hydrometeorological conditions, which govern the patterns of pollutant migration and accumulation.