长江水系水文地球化学特征及主要离子的化学成因

Hydro-geochemistry and genesis of major ions in the Yangtze River,China

在分析长江流域76个位点的水化学数据的基础上,运用吉布斯(Gibbs)图、三角图、主成分分析方法研究岩性对长江水系河水中离子化学特征的影响和流域的主要风化过程。结果表明,长江水系的主要离子化学特征受岩石风化作用的影响,其中碳酸盐和蒸发岩矿物对干流水系溶质的贡献率分别为43.6%和37.9%,而对支流水系溶质的贡献率分别为33.1%和39.1%。干流流域内主要的风化反应以白云石和方解石的溶解为主,而支流流域内Cl-/(Na++K+)接近1:1,体现出蒸发岩风化的显著特性。Si/K比值较低,表明长江流域内的风化反应是在表生环境中进行的,且产物是富含阳离子的次生矿物。

Based on the data of 76 water samples of the Yangtze River （36 of them located in the main stream and 40 of them in major tributaries and anabranches）, the effect of lithology and main weathering process of the river water have been studied by means of statistical approaches such as Gibbs figure, Triangle plot and principal component analysis （PCA）. The results show that the geochemistry of major ions in the Yangtze River are mainly controlled by rock weathering. Among them, carbonates and evaporates account for 43.6% and 37.9% of total ion equivalent concentration for the main stream, while the contribution for tributaries are 33.1% and 39.1%, respectively. The primary weathering process in the main stream of the Yangtze River is the solution of dolonmite and calcite. The ratio of Cl^-/（Na^＋K^＋） in the main stream is close to 1：1, reflecting the significance of evaporite weathering. The lower Si/K ratio indicates that the weathering reactions took place in superficial environment and its products are cation-rich secondary minerals.