Study On Hydrochemical Characteristics And Genesis Of Xinjiang River Basin

Water environment and water ecology are important contents of ecological civilization construction in Poyang Lake.The study on the chemical characteristics and causes of surface water and groundwater in Xinjiang River Basin can not only provide a theoretical basis for the protection of water ecological environment,but also lay a foundation for the utilization and management of water resources in China.Therefore,this study takes the Xinjiang River Basin in Jiangxi Province as the research object,using field investigation（field sampling in three different hydrological periods）,indoor analysis（hydrochemical analysis）,isotope technology（hydrogen and oxygen isotope analysis）,mathematical statistics（descriptive statistical analysis）and model calculation（Gibbs model,rock weathering end-member model）.The chemical characteristics,hydrochemical types,hydrochemical genesis and the effects of human activities on hydrochemistry of surface water and groundwater in Xinjiang basin were studied.The main research results are as follows:（1）The surface water in different hydrological periods is weakly alkaline and is in an oxidizing environment,and the TDS is less than 1 g·L^-1,which belongs to fresh water.The cations and anions are mainly Ca²⁺and HCO₃^-.In the spatial distribution characteristics of ions,the higher value areas are mainly in the middle and upper reaches,and the hydrochemical type is mainly 8-A type water,that is,HCO₃·SO₄-Ca type water with TDS less than 1.5 g·L^-1.The groundwater in different periods is in an oxidizing environment,TDS is less than 1 g·L^-1,which belongs to fresh water,and the acidity is different,in which the average water is weakly alkaline,the high water season and the low water period are weak acidic,the p H value of some groundwater samples in the three periods exceeds the standard limit of groundwater class III water in China,the cations and anions are mainly Ca²⁺and HCO₃^-,and the main hydrochemical types are 1mura and 8-A water.That is,HCO₃-Ca and HCO₃·SO₄-Ca type water with TDS less than 1.5 g·L^-1.（2）The variation ranges ofδD andδ¹⁸O of surface water and groundwater in Xinjiang basin are within the range ofδD andδ¹⁸O in global atmospheric precipitation and atmospheric precipitation in China,and are recharged by atmospheric precipitation,and the d-excess of surface water and groundwater are negatively correlated withδ¹⁸O,which reveals that the marine air mass is the control air mass of precipitation in Xinjiang basin,and the low mountains and hills on both sides of Xinjiang River are the recharge area of groundwater in this area.（3）Based on the analysis of the chemical genesis of surface water and groundwater in Xinjiang River basin,the components of surface water and groundwater are mainly affected by rock weathering,in which carbonate and silicate minerals are dissolved,followed by human activities.The sources of Na⁺（K⁺）in surface water and groundwater are complex.In addition to the dissolution of salt rocks,it may also come from silicate rocks,the dissolution of other sodium salts or the input of human activities.Ca²⁺,Mg²⁺,HCO₃^-and SO₄^2-mainly come from the dissolution of minerals such as calcite,dolomite and gypsum.（4）The NO_-3of surface water in different periods accords with the quality standard of surface water in China.Combined with the relationship between NO_-3/Cl^-and Cl^-of surface water,the NO_-3of surface water in high water period mainly comes from atmospheric precipitation,while the NO_-3of surface water in flat and low water periods comes partly from atmospheric precipitation and partly from the input of human activities such as industrial sewage,domestic sewage and agricultural chemical fertilizer,and human activities have little influence on surface water.About 50%of the groundwater NO_-3concentration in each period exceeded the standard.Combined with the relationship between groundwater NO₃^-/Cl^-and Cl^-,NO₃^-mainly came from the leachate of agricultural chemical fertilizer and the input of human activities such as industrial and domestic sewage,and the groundwater was seriously affected by human activities.