Abstract
In Central Asia, Uzbekistan experiences water scarcity and stress, being highly dependent on external flow from the upstream water-rich neighboring countries. Chirchik and Akhangaran are the main rivers in the Tashkent province, taking their sources from the Middle Tien Shan Mountains, flowing through floodplains, and becoming major tributaries of Syrdarya river, providing water to the Aral Sea. In this study, the major and trace element chemistry were obtained on surface- and groundwater collected in October 2023 from the Chirchik and Akhangaran river, with the aim to investigate the geogenic and anthropogenic contributions to the dissolved load. The results indicate that the geochemistry of water from the upstream catchments reflect silicate and carbonate weathering, mostly belonging to the Ca-HCO3 hydrofacies. The downstream increase in Na+, K+, SO42−, Cl−, and NO3− indicates loadings from fertilizers used in croplands, mostly in the Chirchik river. Water quality parameters (SAR and Na%) indicate that waters are generally suitable for irrigation purposes, even if the TDS increasing downstream suggests possible salinity hazard. The concentration of trace elements is lower than the thresholds set for water quality by different regulations. However, an exceedingly high concentration of Zn, Mo, Sb, Pb, Ni, U, As, and B compared with the averaged river water worldwide is observed. The B content increases with nitrate in Chirchik, indicating anthropogenic inputs. Water in a coal fly-ash pond related to the Angren coal-fired power plants distinguishes for the highest As, Al, B, Mo, and Sb concentration, due to leaching from the coal fly-ash.