Chemical composition of different types of natural waters in Ukraine

Abstract

The results of studies of the chemical composition in various types of natural waters of the territory of Ukraine – atmospheric precipitation, surface (river and lake), groundwaters and sea waters are comprehensively summarized and presented for the territory of Ukraine in this paper. The chemical composition of Ukraine's natural waters (rivers, lakes, underground aquifers, seas) is the result of the interaction of a combination of natural factors, as well as their location, mainly in the temperate climatic zone. The average long–term mineralization of atmospheric precipitation is usually in the range of 20–40 mg/l, its chemical composition is predominantly sulfate magnesium–calcium. For the chemical composition of water in the small and medium rivers of Ukraine, hydrochemical zoning is observed in the direction from the northwest to the south-east of the country. Mineralization of river waters also increases in this direction (from 200–300 mg/l to 1,500–3,000 mg/l and more). The composition of the water varies from bicarbonate calcium in the north and west to sodium chloridein the south and southeast. The value of mineralization of lake water varies within very wide limits. There are lakes with very fresh water and low salinity (30 mg/l – small lakes of glacial origin in the Ukrainian Carpathians), and lakes whose water has a mineralization of more than 100 g/l (salt lakes of the Crimea). In the chemical composition of groundwater, the territory of Ukraine mainly exhibits vertical hydrochemical zoning, which manifests itself in the separation of zones of intensive or difficult water exchange. Hydrocarbonate or sulfate waters with a small mineralization (up to 1.0 g/l) are characteristic for the zone of active water exchange. Highly mineralized (50–300 g/l and more) chloride, sodium and chloride-sodiumcalcium waters are common in a zone of hindered water exchange. The ionic composition of the Black Sea water has all the characteristic features of ocean waters but differs from them in relative poverty with ions of chlorine and sodium, the average salinity of the Black Sea waters is 18–19 ‰. In the narrow coastal zone near the mouths of large rivers (the Danube, the Dniester, the Southern Bug, the Dnieper) a decrease in the salinity of the Black Sea waters (up to 5–10 ‰) is observed. The main factors that determine the salinity regime in the Azov Sea (10–13 ‰) are the inflow of saline Black Sea and fresh river (the Don and the Kuban rivers) waters that are mixed in the Azov Sea, as well as the arrival of atmospheric precipitation.