Keywords: water salinity, main ions, nutrients, organic matter, metals, water bodies, urbanized area

Features of the hydrochemical regime of water bodies located within the urbanized area are considered in the article. It has been established that in winter and spring, water salinity and the content of main ions undergo the greatest changes in water bodies that receive stormwater with chemical deicing chemicals. This leads to an increase in the water salinity in general and the concentration of chlorides, sulfates, sodium and magnesium ions in particular. An increase in the concentration of inorganic nitrogen, phosphorus, organic matter and metals compounds is observed in areas of localized water pollution. Water bodies subject to significant anthropogenic impact are dominated by the inorganic form of nitrogen and phosphorus, which reaches more than 50% of their total content. Anthropogenically altered water bodies are characterized by an increase in the concentration of dissolved organic matter due to an increase in the share of carbohydrates and other unidentified groups of organic compounds, while the share of humic substances decreases. A noticeable increase in the share of carbohydrates usually occurs in summer and autumn, when the water is blooming and phytoplankton and higher aquatic plants are dying off. Anthropogenic pollution of water bodies causes an increase in the share of the labile fraction of metals, which is potentially bioavailable and toxic to aquatic life. This fraction exceeds 50% of their concentration in the dissolved state. An increase in water salinity, the content of biogenic and organic substances, and the labile fraction of metals is also observed in the bottom horizon of water bodies during direct and reverse temperature stratification due to their inflow from bottom sediments. This is primarily due to dissolved oxygen deficiency, a decrease in Eh-potential values, and an increase in water temperature. Secondary water pollution by nutrients should be considered as an important internal source of increased eutrophication of water bodies. As a result, the aquatic environment becomes unsuitable for the life of many oxyphilic aquatic organisms. As the climate warms, these processes will intensify. Therefore, it is important to develop a number of measures to prevent or minimize both external and internal nutrient flows to surface water bodies.

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