Hydrochemical characteristics of surface water and genetic mecha-nism of high fluorine water in Qingshui River Basin in Ningxia

The most representative samples were collected three times at 30 points in the Qingshui River Basin in Ningxia in level period(May), wet period(July) and dry period (December) of 2022 in order to explore the hydrochemical control factors and the causes of high-fluorine water in the Qingshui River Basin. The spatial and temporal distribution characteristics of hydrochemical components and fluorine was analyzed, the formation and enrichment mechanisms of high fluorine water were analyzed, and the contribution of different factors to the hydrochemical components of surface water in the basin was calculated by APCS-MLR. The results show that the surface water in Qingshui River Basin is weakly alkaline, the anion concentration was SOT >C1~ >HCO,~, and the cation concentration was Na+ >Mgf+ >Ca2+ >K+ . The F~ concentration was dry period > wet period > level period, tributary > reservoir > trunk stream. The main hydrochemical type of surface water is SQ-Cl-Na type, followed by S04-Cl-Ca-Mg type. The formation of high fluorine water is controlled by evaporation and concentration, rock weathering, mineral dissolution and precipitation, cation exchange and adsorption, and the enrichment of high fluorine water is controlled by climate, terrain and hydrochemical composition. Natural factors are the key driving factors for the hydrochemistry of surface water in Qingshui River Basin, contributing 77.56% to the hydrochemical components of surface water in the study area, and human activities mainly contribute TP (59%), SOiT (10%) and Ca2+ (10%). The contribution of natural sources to the hydrochemical components of surface water in the study area is as follows: sulfate mineral weathering > Silicate mineral weathering > carbonate mineral weathering > rock salt weathering, and the main contribution source of F~ is sulfuric acid rock mineral weathering (56%). © 2024 Science Frontiers editorial department. All rights reserved.