Study On Hydrochemical Characteristics And Water Quality Evaluation Of River Water And Groundwater In Shaliu River Basin

River water and groundwater are the most widely distributed natural water bodies in the Qinghai lake basin,and they are also the essential water sources for the development of local agriculture and animal husbandry as well as ecological water.The hydrochemical characteristics of river water and groundwater can reflect the characteristics of the water environment and water quality in the basin.Shaliu river as an important tributary of Qinghai lake,studying the hydrochemical characteristics of river water and groundwater in the Shaliu river basin is of great importance to the assessment of water quality and environmental sustainability.Selected Shaliu river basin of the Qinghai lake as the study area,based on high-density samples of river water and groundwater and data of hydrochemistry ion content in January,from April to December 2020,this paper studied characteristics of anion and cation content in river water and groundwater,chemical types,ion source and irrigate suitability.The purpose of this study was to master the hydrochemical characteristics of the river water and groundwater in this basin,to evaluate the water quality of the river water and groundwater in this basin,and to provide basic data and theoretical support for the water quality monitoring and water environment management of the river water and groundwater in the Shaliu river basin.The results showed:(1)During the study period,the p H values of river water and groundwater in the Shaliu river basin of Qinghai lake were 7.58 and 7.33,respectively,and the electrical conductivity(EC)values were 383.69?s·cm^-1 and 541.16?s·cm^-1,respectively.The order from high to low of the average concentration of river water cations was Ca²⁺>Mg²⁺>Na⁺>K⁺>NH₄⁺>Li⁺;the order of the average concentration of anions from high to low was HCO₃^->SO₄^2->Cl^->NO₃^->NO₂^->F^-.The order from high to low of the average groundwater cation concentration was Ca²⁺>Mg²⁺>Na⁺>K⁺>NH₄⁺>Li⁺;the order from high to low of the average anion concentration was HCO₃^->SO₄^2->Cl^->NO₃^->NO₂^->F^-.The main cation of river water and groundwater was Ca²⁺,and the main anion was HCO₃^-;the Piper diagram showed that the chemical types of river water and groundwater were mainly HCO₃-Ca·Mg and HCO₃-Ca.(2)The water chemical ions Ca²⁺,Mg²⁺,Na⁺,K⁺,HCO₃^-,SO₄^2-and Cl^-in the river water and groundwater of the Shaliu river basin in different months were all sources of total dissolved solids(TDS).Affected by precipitation,the concentration of Ca²⁺and HCO₃^-ions in the river water from June to August in the basin was significantly lower than those in other months,with the lowest in June.The concentrations of Ca²⁺and HCO₃^-ions in the groundwater in January,from June to August were significantly lower than those in the other months,with the lowest in June.(3)The Gibbs diagram showed that rock weathering was the main factor affecting the chemical composition of river water and groundwater in the Shaliu river basin.Piper diagram of river water and groundwater,ion correlation analysis and(Ca²⁺+Mg²⁺)/(Na⁺+K⁺)and(Ca²⁺+Mg²⁺)/HCO₃^-equivalent ratio results showed that the chemical properties of river water and groundwater were mainly affected by carbonate rock weathering.The equivalent ratios of Mg²⁺/Ca²⁺,Na⁺/Ca²⁺and(Ca²⁺+Mg²⁺)/(HCO₃^-+SO₄^2-)in river water and groundwater indicated that the water-rock process was dominated by the dissolution of calcite minerals.(4)The Ca²⁺and Mg²⁺in the river water and groundwater of the Shaliu river basin mainly came from the dissolution of carbonate.Na⁺was affected by ion exchange,which was another important mechanism that affected the chemical composition of river water and groundwater in the Shaliu river basin.The Chlor-Alkali Index(CAI)indicated that positive cation exchange occurred mainly in the river water and groundwater of the Shaliu river basin.(5)Four water quality indices,including sodium adsorption ratio(SAR),percent sodium(Na+%),residual sodium carbonate(RSC)and permeability coefficient(PI),combined with USSL diagram and Wilcox diagram,indicated that the river water and groundwater of the Shaliu river basin had good irrigation suitability and excellent water quality.