Climate Change as an Important Factor of the Formation of the Chemical Composition of Surface Waters at the Present Time (a Review)

Abstract

Results of the study of climate change impact on the chemical composition of surface waters given in literature have been generalized in the paper. It has been shown that climate change influences mainly hydrologic, chemical, and biological processes occurring in water bodies and watercourses. Climate change can result in change in river runoff and in water level in lakes, reservoirs, and limans. The increase in water temperature can result in time displacement and in the increase in the duration of temperature stratification in lake systems. Shallow lakes are most vulnerable to climate change. Temperature stratification in lakes and reservoirs is accompanied by oxygen stratification. As a consequence, the water of hypolimnion is characterized by prolonged dissolved oxygen deficiency, and also by the formation of anaerobic zones. Under such conditions, the intensity of nutrients and organic matter migration from bottom sediments into water column will increase. This process will be accompanied by the increase in the degree of eutrophication of water bodies, in particular by the increase in the intensity of phytoplankton development. Climate change influences salt composition of surface waters and relationship between its main components. It will result in the increase in the concentration of allochthonous organic matter (in particular of humic acids) as a result of its influx from the bottom sediments of swamps with increasing the amount of precipitation, and also in the increase in the concentration of autochthonous organic matter as a result of the increase in bioproductivity of water bodies. Prolonged solar radiation in summertime will favor the increase in the intensity of photochemical reactions in water bodies, which will manifest itself in transformation of high molecular organic matter into the compounds with lower molecular mass. Other aspects of climate change impact on the chemical composition of surface waters are also discussed in the paper.