Potential Impact of Climate Change on Mineralization and Main Ions Ratio in Surface Fresh Waters (a Review)

The article deals with problem of the fresh waters salinization in view of its relevance for normal functioning of the aquatic ecosystems, development of different branches of industry and agriculture, and human health. Attention is focused on the fact that the fresh waters' salinization inevitably results in decrease of the ecosystem services scope. The main factors and anthropogenic sources of influence on total dissolved solids in the fresh waters and metamorphosis of their ion composition are considered. It is stated that climate changes potentially affect and will affect the surface waters mineralization in future owing to volume and frequency of the atmospheric precipitation, intensity of the rocks and minerals weathering, the ground feeding of the rivers, the marine water penetration into the estuaries along with reducing of the river water yield, etc. The possible impact of mineralization changes on migration of substances from bottom sediments into the water thickness, that is on the intensity of its secondary pollution, is discussed. This impact can be direct and indirect. First of all, it concerns the migration ability of metals in bottom sediments. Elevated content of Na+, Ca2+ and Mg2+ in water intensifies migration of metals of the exchangeable fraction of bottom sediments. The indirect effect of elevated mineralization is expressed in the oxygen regime of the water bodies, which usually deteriorates in the near-bottom water layers of deep lakes and reservoirs, mouth areas of the rivers and estuaries. The dissolved oxygen deficit becomes usual, anoxic conditions are formed, which favor release of Fe(III) and Mn(IV) from oxyhydroxides or the oxide fraction of the bottom sediments. A review also considers some aspects of potential impact of the fresh waters salinization on survival of the aquatic plants and animals and biodiversity.