Analysis of Hydrochemical and Environmental Conditions of the Right-bank Tributaries of the Mezen River

The results of a comprehensive study of the Kyma and Sula, the northern right-bank tributaries of the Mezen River are presented for the first time. The paper provides the characteristics of hydrological and hydrochemical parameters based on the results of observations in September 2021. Changes in pH, mineralization, dissolved oxygen, biogenic elements, as well as petroleum hydrocarbons in water and bottom sediments are shown. The compliance of the obtained parameters with the regulatory requirements for the quality of river water was assessed. According to the chemical composition, the water of the Kyma and Sula rivers belongs to the hydrocarbonate class with low mineralization (39.8–76.1 mg/L) and neutral type (pH = 7.14–7.43). The results allow concluding the absence of noticeable anthropogenic impacts on the analyzed watercourses: the concentration of oil hydrocarbons varied from 0.010 to 0.025 mg/L in river water and from 2.05 to 4.60 mg/kg in bottom sediments, which did not exceed the maximum permissible concentrations (MPC). In both rivers, the distribution of oil hydrocarbons in the water along the longitudinal profile had a similar pattern, in which their concentrations increased from the upper reaches to the mouth of the river. The maximum content of hydrocarbons in the soil of the Kyma River was recorded in the lower reaches, where bottom sediments are represented by coarse-grained sand. The maximum concentration of hydrocarbons in the Sula River was registered in the middle reaches at the right-bank station, where the soil is represented by clay. In addition, the paper establishes relationships between various environmental parameters.