Hydrochemistry and Heavy Metal Pollution in the Qingshui River around a Historical Thallium Mining Area
Water samples were collected at 20 sites in the Qingshui River basin in Guizhou Province,China,during the flood,normal and dry season.Taking advantage of mathematical statistics,Piper three-line diagram,ion ratio and Nemero pollution index,the hydrogeochemistry of the water bodies in the Qingshui River basin were analyzed.Furthermore,the spatial evolution of water chemistry in the basin was explored and the spatial and temporal variability of heavy metals such as Tl and their pollution status were clarified.The results showed that water in the Qingshui River basin is weakly alkaline,with Ca2+and Mg2+as the major cations,HCO3-and SO42-as the dominant anions,belonging to Ca·Mg-HCO3·SO4(SO4·HCO3)type water.The seasonal and spatial differences of main ion concentrations were insignificant,and the hydrochemical composition is mainly controlled by carbonate weathering and evaporite disso-lution.The Qingshui River is heavily polluted with by Tl,whose concentration fluctuated remarkably in different seasons.The Tl con-centration was relatively stable during the flooding and normal periods but was significantly affected by underground springs and histori-cal waste residues,fluctuating up to 4.036 µg/L.The assessment results of the Nemerow pollution index indicated that the Qingshui River was heavily polluted with Tl and other heavy metals.Although the water quality of the Qingshui River has been improved after the ecological restoration,the pollution of heavy metals such as Tl has not been eradicated.Thus,there is an urgent need to comprehen-sively reveal the groundwater quality within the basin and scientifically remediate the historical mining residues in the river.
heavy metalshydrochemistryspatio-temporal variationion sourcemine rehabilitation
NETL
NSTL
万方数据
