The Study Of Hydrochemical Characteristics And Ion Sources Of Precipitation And River Water In Mountainous Areas In The Upper Reaches Of The Shiyang River

Water is an indispensable resource for human survival and development.It cannot be separated from industry,agriculture,production and living and water resources.With the global warming,glaciers retreating,ecological environment changes,etc.The problem of water resources has become increasingly prominent.Especially in the Hexi Corridor,the long-term and unreasonable use of water resources by humans has led to insufficient water supply in the region,and the quality of water resources has become increasingly prominent.Precipitation and river are important components of the water cycle of inland river basins.Through the study of surface water chemistry,water resources can be combined with earth element chemistry,so as to understand comprehensively its hydrochemical characteristics and influencing factors.Mastering the water cycle process and water quality in the region can provide a theoretical basis for regional environmental evolution,ecological environmental protection and sustainable development strategy.The Xiying River is the largest primary tributary in the Shiyang River Basin.As the main source of water resources in the middle and lower reaches of the river,it restricts regional economic development.This paper selected the Xiying River Basin as the study area,and collected 389 samples of precipitation and river from October 2016to October 2017,as well as relevant meteorological and hydrological data.Using enrichment factor method,backward trajectory method,Piper three-line diagram,Gibbs diagram,the mass balance method and the forward model,etc.The hydrochemical characteristics and ion sources of precipitation and river water were analyzed.The following are the main conclusions.(1)The precipitation and river water in the Xiying River Basin are alkaline throughout the year,and the average is 7.5 and 8.0.The Salinity,total dissolved solids,and electrical conductance of river water are significantly higher than precipitation.The composition of anion and cation is different from the ion concentration of standard crustal minerals and standard seawater.The proportion of NH₄⁺in precipitation is obviously higher,the water chemistry type is Ca Mg-HCO3 type,which is affected significantly by the weathering of rocks.(2)There are obvious seasonal differences in precipitation and river water in the Xiying River Basin.The precipitation from April to September accounts for about 81%of the whole year,and the runoff accounts for about 85%.Therefore,there are obvious temporal and spatial differences in hydrochemical characteristics and ion concentration.In terms of seasonal changes,they are affected significantly by precipitation and runoff,showing the characteristics of lower in summer and autumn but higher in spring and winter.In terms of spatial changes,they are quite different for precipitation,runoff,topography,soil,lithology,surface vegetation coverage and human activities.(3)The main source of ions in precipitation in the Xiying River Basin is terrestrial input.The proportions of terrestrial input of Na⁺,Mg²⁺,K⁺and Ca²⁺are 78%,90%,98%,and 99%,respectively.The ions input by the sea source are Na⁺(22%)and Cl^-(98%).The material from terrestrial input mainly comes from surface particulate matter in Europe and Central Asia brought by the westerly circulation,while the water vapor input from sea source mainly comes from the westerly circulation and monsoon circulation.The source of HCO₃^-are mainly derived from rock weathering,the source of SO₄^2-is mainly the dissolution of minerals and the contribution of human activities,and the source of NH₄⁺and NO₃^-are mainly input from human activities.(4)The source of ions in the river water of the Xiying River Basin is mainly controlled by the weathering of rocks,and the order of the contribution rates of different sources is:Silicate(41%)>Carbonatite(39%)>Evaporite(13%)>Atmospheric precipitation input(1%).The contribution rate of carbonate weathering from July to August was higher significantly than that in other months.Although the human activities in the Xiying River Basin have a certain impact on the precipitation and the river water,but overall,the impact on hydrochemical is minimal.