基于水化学和同位素的典型岩溶水系统溶质演化过程—以西昌市仙人洞为例

仙人洞岩溶水系统是西昌市南部典型的地下水系统,亦是该区饮用水和灌溉用水的唯一水源,对其水源成因和溶质组分演化过程的研究具有重要的科学价值和现实意义。本文以仙人洞岩溶水系统为研究对象,通过分析岩溶水、基岩裂隙水和地表水水化学组分、氢氧同位素和氚同位素特征,探讨了这三类水的成因和溶质演化过程。结果显示：仙人洞三类水阳离子以Ca₂₊为主,阴离子以HCO_3-为主,水化学类型主要为Ca-HCO_3-型水；水化学指标和同位素信息揭示三类水均以大气降水补给为主,但岩溶水属于具有快速通道的深循环、长径流途径的水循环模式,而基岩裂隙水则属于浅表层循环模式。系列水化学图示和离子比值系数表明岩石风化作用、碳酸盐岩溶解和离子交换过程是影响这三类水组分演化的主要化学过程。

Application of Hydrochemical and Isotopic Analysis to Research a Typical Karst Groundwater System: A Case Study at Xinrendong, Xichang city

The karst groundwater system of Xianrendong, as a unique water resource for drinking and irrigation purposes, is a typical groundwater system in southern Xichang city. Therefore, understanding the genesis of recharge source and evolution process of groundwater system is of scientific value and practical significance. In this paper, chemical compositions, oxygen and hydrogen and tritium isotopes of karst water, fissure water and surface water in the Xianrendong karst groundwater system are combined to discuss the genesis, and evolution processes of three water types. The results demonstrate that three water types are dominant of Ca₂₊ and HCO_3-, and are of Ca-HCO_3-type. The analyses of chemical components, oxygen and hydrogen and tritium isotopes indicate that three water types are of meteoric origin. However, karst groundwater belongs to the deep circulation with fast passage and long runoff path, while fissure water is of shallow surface circulation. Furthermore, those graphic hydrochemical methods and ionic ratio coefficients illustrate that rock weathering, the dissolution of carbonate, and ion exchange are major factors affecting hydrochemical processes.