Hydrochemical Characteristics And Material Sources Of Lakes And Wetlands In Qinghai-Tibet Plateau

Due to the limitation of factors,such as the complex geographical environment,bad climate conditions,extremely backward traffic and other factors in Qinghai-Tibet plateau,it is particularly difficult to carry out a comprehensive and systematic study in Qinghai-Tibet plateau,where monitoring stations are sparse and monitoring data are lacking in completeness and systematicness.Many areas in science is still in the blank state,the basic situation of many lakes and their respond to climate change is still not known,and need to be studied continuously.In order to investigate the hydrochemical characteristics of surface water on Qinghai-Tibet plateau and enrich the basic data of scientific research in the region,from September to October 2016,we conducted field surveys and collected 32 water samples from 21 tectonic lakes along G315 in the northeast,S301,S302 and S206 in the central region,and G219 and G318 in the south of Qinghai-Tibet plateau,as well as 4 glacial lakes and 7 wetland in the north slope of the middle Himalayas in the yuru zangbo basin.The physicochemical characteristics,hydrochemical composition and types of the water bodies of the tectonic lakes,glacial lakes and wetlands on the Qinghai-tibet plateau were analyzed by piper three diagram and Gibbs model,and the water-rock chemical processes and material sources were discussed.At the same time,based on the temperature and precipitation data of surface meteorological stations near the sampling points and the regional atmospheric driven data set in China,the hydrochemical characteristics of tectonic lakes in the Qinghai-Tibet Plateau in recent40 years and its responses to regional climate change are further analyzed.In addition,as the contradiction between the ecological protection of the wetland and the improvement of local residents'life is increasingly prominent in dingjie county,the present situation of water quality was evaluated by single factor water quality evaluation method and Nemero pollution index.The main research results are as follows:Firstly,The concentration of TDS?total dissolved solid?is high in the tectonic lake of Qinghai-Tibet Plateau,and the content of calcium and magnesium in most of the tectonic lake is high.The physicochemical characteristics of the glacial lake in the yuru zangbo basin are strongly similar to those of the wetland water.The TDS concentration of the water body is generally low,but the concentration of the physicochemical parameters of the wetland water is slightly higher than that of the glacial lake.Second,According to the chemical composition classification,the tectonic lakes are mainly chloride salt lakes,16 lakes in 21 tectonic lakes are of Na?K?-Cl,including a Ca?Mg?-SO₄ lake,three Ca-HCO₃ lake and a Na-HCO₃ lake.The four glacial lakes are all Ca?Mg?-SO₄ lakes.In seven wetland sampling sites,five wetland are Ca?Mg?-SO₄,and two are Ca-HCO₃.Third,In the past 40 years,the concentration of TDS and main ions in most tectonic lakes decreased,and the water showed a trend of desalination to varying degrees,which was mainly affected by the multiple effects of increased precipitation,decreased evaporation,and increased glacial melt water in the basin,reflecting that the highest temperature on the Qinghai-Tibet plateau was on the rise year by year.Fourth,The wetland water in the yuru zangbo basin is all polluted to varying degrees.The sampling points W1,W2,W3 and W7 were seriously polluted by Cr and Ni.Fifth,The ion concentration in most tectonic lakes in Qinghai-Tibet Plateau is mainly controlled by evaporation and concentration,and the glacier lake and wetland is mainly affected by the weathering of rocks in the basin.The ions in the tectonic lake are mainly derived from the dissolution of?Na?K?Cl?,calcite?CaCO₃?and magnesium sulfate?MgSO₄·2H₂O?.The content of the ions in the glacier lake is mainly from the dissolution of calcite?CaCO₃?,dolomite?CaMg?CO₃?₂?and magnesium sulfate?MgSO₄·2H₂O?.The source of the ions in the wetland water sample is widely,mainly from calcite?CaCO₃?,magnesium sulfate?MgSO₄·2H₂O?and the silicate minerals such as mica(K?Mg,Fe,Al?₃Al₂O₁₀?OH?₂),albite?Na₂O·Al₂O₃·6SiO₂?and orthoclase?K?Al₂O₈??.