青藏高原湖泊小流域水体离子组成特征及来源分析

对青藏高原咸水湖蓬错、昂仁金错、打加错,淡水湖打加芒错、达格架温泉及各湖入湖支流阴、阳离子组成进行了分析.咸水湖阴离子以HCO-3、SO2-4为主,阳离子以Na+为主,属HCO3-SO4-Na和HCO3-Na型水;各湖支流及淡水湖阴离子以HCO-3或SO2-4为主,阳离子以Ca2+或Mg2+为主,属HCO3-Ca、HCO3-Ca-Mg、HCO3-Mg-Ca、HCO3-SO4-Ca、SO4-HCO3-Ca型水;达格架温泉阴离子以HCO-3为主,阳离子以Na+为主,属HCO3-Na型水.咸水湖主要受蒸发-结晶作用控制,各湖支流及淡水湖主要受碳酸盐岩风化控制,达格架温泉主要受热水-花岗岩作用控制.碳酸盐矿物沉淀时Ca2+优先Mg2+被移除,导致咸水湖具有较高的Mg2+/Ca2+比值.在阳离子组成端元贡献中,碳酸盐岩贡献最大(54%~79%),硅酸盐岩(13%~29%)和蒸发盐岩(4%~23%)次之,大气输入(3%~7%)最小.

Composition Characteristics and Source Analysis of Major Ions in Four Small Lake-watersheds on the Tibetan Plateau, China

To investigate the ionic compositions of small lake-watersheds on the Tibetan Plateau, water samples from the brackish lakes (Pung Co (lake), Angrenjin Co and Dajia Co), the freshwater lake (Daggyaima Co), their inflowing rivers and the hot spring (Dagejia Geothermal Field), were collected during July-August 2013. The results showed that the major anions and cations of the brackish lakes were HCO₃^-, SO₄^2- and Na⁺, respectively, and the hydrochemical types were HCO₃-SO₄-Na and HCO₃-Na. The major anions and cations of the inflowing rivers and the freshwater lake were HCO₃^-, SO₄^2- and Ca²⁺, Mg²⁺, respectively, and the hydrochemical types were HCO₃-Ca, HCO₃-Ca-Mg, HCO₃-Mg-Ca, HCO₃-SO₄-Ca and SO₄-HCO₃-Ca. The major anions and cations of the hot spring were HCO₃^- and Na⁺, respectively, and the hydrochemical type was HCO₃-Na. Water chemistry in the brackish lakes was primarily dominated by evaporation-crystallization processes, while the inflowing rivers and the freshwater lake were mainly influenced by carbonate weathering, and the hot spring was mainly controlled by hot water-granite interaction. Ca²⁺was preferentially removed over Mg²⁺ from the water when carbonate minerals precipitation occured, which resulted in the high Mg²⁺/Ca²⁺ molar ratios of the brackish lakes. In the contribution of cation compositions, the largest contribution was carbonate weathering (54%-79%), followed by silicate weathering (13%-29%) and evaperite dissolution (4%-23%), and the smallest was atmospheric input (3%-7%).