Purpose. The study aims to identify the characteristic features of the content of dissolved macrocompounds and nutrients in estuarine areas of rivers in Bolshoi Sochi (Sochi, Matsesta, Khosta, Kudepsta and Mzymta).

Methods and Results. Surface water samples were collected from the estuaries of the Sochi, Matsesta, Khosta, Kudepsta and Mzymta rivers in early November during the autumn-winter flood season. Nutrient concentrations were determined using spectrophotometric methods, while macrocompound concentrations were measured via capillary electrophoresis. The distribution of hydrochemical characteristics follows the classical pattern typical of river-sea system. The chemical composition of river water is predominantly of the hydrocarbonate-calcium type, except for the Matsesta River, which exhibits a mixed composition. The highest concentrations of nitrogen compounds were observed in the Matsesta and Kudepsta rivers, while elevated phosphate levels were found in the Sochi River. The Kudepsta River water is characterized by exceptionally high total alkalinity. For domestic water use, measurements of nutrient concentrations showed no excess of maximum permissible levels.

Conclusions. The chemical composition of water in the river mouths under study is influenced by both natural and anthropogenic factors. In the Matsesta River, the primary natural factor is the discharge of mineral groundwater, while the main anthropogenic factor is wastewater discharge. The combination of these factors and the mouth overlap resulted in the development of eutrophication processes. In the Kudepsta River, the high background alkalinity is of natural origin, whereas elevated nutrient concentrations (nitrogen and phosphorus) are linked to intensive construction activities in the mouth area.