洞穴滴水水文地球化学的季节变化及其环境指示意义:以贵州大消洞为例

Seasonal changes in hydrogeochemistry of cave drip water and its environmental indicator significance:A case study of Daxiao cave in Guizhou

为探明洞穴滴水水化学的季节变化规律并揭示其环境指示意义,对黔西南大消洞的3处滴水开展了1个水文年的动态监测和采样,分析了滴水点附近的CO_(2)浓度以及各处滴水的pH、电导率(EC)和Ca2+、Mg^(2+)、Ba^(2+)、Sr^(2+)等离子变化,结果表明,洞穴滴水的滴率和EC在响应大气降雨时存在一定的滞后,滴水pH和HCO3-在雨季受稀释效应的影响明显,雨季时滴水以溶蚀作用为主,旱季则以沉积作用为主,滴水pH与洞穴空气CO_(2)浓度之间无显著关联。3个滴水点的常、微量离子浓度呈现“雨季低、旱季高”的季节变化规律,在雨季均受到不同程度降雨稀释作用的影响。除此之外,离子浓度变化还受到活塞效应和PCP作用等水文地球化学过程的影响。Mg/Ca、Sr/Ca、Mg/Sr均表现出旱季高、雨季低的特点,其中,Mg/Ca与Sr/Ca之间存在良好的正相关关系,滴水Mg/Ca和Sr/Ca可以综合反映外界气候的季节干湿变化,3个滴水点中仅有DX-3的Mg/Sr与当地气温之间存在很好的反相关。

In order to investigate the seasonal changes in water chemistry of cave dripping water and to reveal its environmental significance,dynamic monitoring and sampling were carried out for one hydrological year at three dripping water sites in the Daxiao Cave in southwest Qianjiang.The pH of dripping water and HCO3-are affected by the dilution effect in the rainy season.The dripping water is mainly dissolved in the rainy season,while the dry season is mainly deposited.The concentrations of constant and trace ions at the three drip sites showed a seasonal variation of“low in the rainy season and high in the dry season”,and were influenced by the dilution effect of rainfall to varying degrees in the rainy season.In addition,the ion concentration variation is also influenced by hydrogeochemical processes such as piston effect and PCP effect.Mg/Ca,Sr/Ca and Mg/Sr all show the characteristics of high in the dry season and low in the rainy season,among which,there is a good positive correlation between Mg/Ca and Sr/Ca,and drip Mg/Ca and Sr/Ca can comprehensively reflect the seasonal dry and wet changes of the external climate.