青海尕斯库勒盐湖水体的化学组分存在形式及饱和指数研究

Study on existence forms of chemical compositions and saturation indexes of waters from Gasikule Salt Lake, Qinghai Province

以青海西部尕斯库勒盐湖不同水体为研究对象,通过PHREEQC软件计算了水体的化学组分存在形式及饱和指数,探讨了该盐湖水文地质补给顺序,建立了水文地质概念模型。研究表明,水体中所有元素Na、K、Ca、Mg、C(4)、Cl和S(6)主要以自由离子Na^+、K^+、Ca^(2+)、Mg^(2+)、HCO_3^-、Cl^-和SO_4^(2-)形式存在,只有少量Mg、C(4)和S(6)与其他离子形成络合物。该盐湖水文地质概念模型为:大气降水和冰雪融水形成的河流水大部分补给至含砂泥岩层形成承压水;大部分承压水补给至潜水,最终汇入湖内形成湖水;在冷干条件下,湖水经过强烈蒸发和浓缩作用形成湖表卤水和晶间卤水;氯化钙型深部水通过湖表卤水区东部隐伏断裂持续补给至湖表卤水,而氯化钙型盐溶水通过盐溶通道长期补给晶间卤水;湖表卤水与晶间卤水间存在水体交换。该研究为青藏高原盐湖水文地质演化过程提供一些基础资料。

In order to explore the hydrogeological supply order and conceptual hydrogeological model of the Gasikule Salt Lake, PHREEQC software is used to calculate the existence forms of chemical compositions and saturation indexes of various waters from Gasikule salt lake located in the western margin of Qinghai province. The results reveal that Na, K, Ca, Mg, C（4）, Cl and S（6） are mainly in the forms of free ions Na^＋, K^＋, Ca^2＋, Mg^2＋, HCO3^-, Cl^- and SO4^2-, while only small amounts of Mg, C（4） and S（6） form complexes with other ions. The conceptual hydrogeological model is shown as follows. Firstly, most of the stream water formed by precipitation and snow melt supplies the mudstone layer and forms the confined water. Secondly, most of the confined water supplies pore water and eventually enters lake water. Thirdly, the lake water is transfered to surface brine and intercrystalline brine after strong evaporation and concentration effect due to cold and dry climate. Fourthly, the deep CaCl2 type brine continuously supplies the surface brine area and intercrystalline brine area by the buried faults existing at the east surface brine area and the Karst channel existing at the salina, respectively. Fifthly, the surface brine and intercrystalline brine exchange deeply. This study may provide some basic information for the hydrogeological evolution of the salt lake in the Qinghai-Tibet Plateau.