西藏扎囊县水化学组成及演化特征

Hydrochemical Composition and Evolution Characteristics of the River Basin in Zhanang County of Tibet

为研究西藏扎囊县流域水化学特征以及演化,文章先后采集河水25组、井水15组,综合运用数理统计、Piper三线图、Gibbs模型等方法,分析了该区水文地球化学特征,并探讨了流域内的水化学演化规律。结果表明流域内以HCO_(3)-Ca型水和HCO_(3)-Ca·Na型水为主;区内地下水与地表水pH值一般在7.5~8之间,为中性水;TDS均<300 mg/L,地下水与地表水的TDS变化不大,均为低矿化度淡水;水化学样品均分布在Gibbs模型左中部,说明该流域水化学离子组成受岩石风化作用控制。

In order to study the hydrochemical characteristics and evolution of the waters in the river basin of Zhanang County,Tibet,40 water samples were collected from streams(25)and wells(15),and concentrations of the major ion in the water samples were measured.Furthermore,descriptive statistics,Piper triangular diagrams and Gibbs image model were used to investigate the hydrochemical characteristics,influencing factors,and hydrochemical evolution of the waters.The results showed that the major cations in the water were HCO_(3)-Ca and HCO_(3)-Ca·Na;both of the groundwater and surface water were neutral with pH values generally between 7.5~8.TDS(total dissolved solid)was lower than 300 mg/L;and the TDS of groundwater and surface water belonged to low salinity fresh water.Additionally,it was showed that the chemical composition of the water samples was located on the left of the Gibbs image model,indicating that the chemical composition of the river basin was controlled by the process of rock chemical weathering.