About the Mechanisms of Formation of the Chemical Composition of the High-Mountain Rivers of Central Asia: The Shakhdara River and its Contribution to the Hydrochemistry of the Transboundary Panj River

Agriculture still predominates in the use of water resources in Central Asia. About 90% of the water resources generated in the region are used for irrigation. The quality of irrigation water is an important element in obtaining ecological and safe varieties of crops because, according to the data of IAEA, the transfer of radionuclides to the human body is carried out along a water–soil–plant–human body chain. Although such a chain explains the movement of radionuclides, it will also probably be implemented when pollutants enter the human body. The aim of this work is to determine the origin of the chemical composition of the Shakhdara River and its contribution to the enrichment of the main river Panj with chemical elements. Water sampling from the rivers Shakhdara and Panj is carried out in accordance with the guidelines of Sanitary Regulation “Sanitary and Epidemiological Requirements for Water Sources, Water Abstraction Points for Economic and Potable Purposes, Economic and Potable Water Supply, Places of Recreational Water Uses and Safety of Waterbodies,” The elemental analysis is performed in the United States at the Laboratory of Ambient Environment and Geology of the Department of Geological Sciences of the University of Colorado (Boulder) as well as at the Laboratory of Moisture Chemistry of the Institute of Arctic and Alpine Studies. It is found upon comparing the results of chemical analyses with the criteria of various types of weathering (carbonate, silicate, evaporation of evaporites) that the formation of the chemical composition of the Shakhdara River occurs as a result of weathering of silicate rocks with the active participation of H 2 CO 3 and H 2 SO 4 . It is established that the Shakhdara River makes a significant contribution to the enrichment of the Panj River with 3 d (Fe, Co, Ni) elements as well as arsenic, vanadium, and scandium in addition to the alkaline (K, Na) and alkaline earth (Mg, Sr) elements.