雅鲁藏布江上游夏季水化学特征及来源解析

为探究雅鲁藏布江上游干支流的无机水化学特征，于2020年8月在雅鲁藏布江上游河源和河流段采集干支流水样，分析了水体主要离子的化学组成和空间变化规律，并对离子来源进行了解析.结果表明，雅鲁藏布江上游干支流水体中的阴离子以HCO₃^-、SO₄^2-为主，分别占阴离子总量的71.11%、23.16%；优势阳离子为Ca²⁺、Na⁺，分别占阳离子总量的47.90%、34.76%；总溶解性固体变化范围为43.5~187.3mg/L，平均值为116.4mg/L，水体矿化度较低.干支流的水化学类型整体上以HCO₃·SO₄-Ca·Na型为主，其中河源段杰玛央宗曲和库比曲水化学类型为HCO₃-Ca·Na型；从上游向下，干流HCO₃^-、SO₄^2-、Ca²⁺等主要离子浓度的沿程变化较为剧烈，主要受冰川融水和支流汇入的影响.雅鲁藏布江上游干支流水化学特征主要受岩石风化作用控制，主要离子来源于碳酸盐岩及硅酸盐岩风化，蒸发岩（硫酸盐）溶解也起到一定作用，而受人为因素的干扰较小.

Hydrochemical characteristics and sources of the upper Yarlung Zangbo River in summer

To explore inorganic hydrochemical characteristics of the upper Yarlung Zangbo River, water samples were collected from the main stream and different tributaries in this region in August 2020. The chemical compositions and spatial variations as well as the sources of the main ions were analyzed. Results showed that the main anions in the river were HCO₃^- and SO₄^2-, accounted for 71.1% and 23.2% of the total anions, respectively; the main cations were Ca²⁺ and Na⁺, accounted for 47.9% and 34.8% of the total cations, respectively; the total dissolved solids (TDS) ranged between 43.5~187.3mg/L, with an average of 116.4mg/L (this indicated a low salinity of water). The dominate pattern of hydrochemical type in the Yarlung Zangbo River Upstream Basin was HCO₃·SO₄-Ca·Na, while exhibited HCO₃-Ca·Na pattern in some headwater (i.e., Jiemayangzong river and Kubi river). Then, there existed drastically changes of HCO₃^-, SO₄^2-, and Ca²⁺ along the mainstream, which was mainly affected by glacier melt water and the inflow water from different tributaries. In general, in the upper Yarlung Zangbo River, the hydrochemical characteristics was controlled by rock weathering with the ions mainly originated form the carbonate rock and silicate, and the evaporite (sulfate) dissolution was also another source. In contrast, this area was less affected by human activities.