摘要
岩溶水的pH值主要取决于水中碳酸体系的平衡移动。由于岩溶水文地球化学系统内部的CO_2含量通常远高于大气中的CO_2含量,水一旦离开原系统而与大气接触,原碳酸体系的平衡就遭到破坏,使得水的pH值迅速增高,直至与大气达到新的平衡为止。因此,根据室内测定的pH值计算的饱和指数明显高于该水样在野外测定的pH值计算的饱和指数,从而可能出现据野外pH值计算的水样是不饱和的、而根据室内pH值计算却是饱和或过饱和的相反结论。笔者通过热力学的理论分析及实例计算阐述了这些现象,并进而指出:在岩溶水文地球化学的研究中,必须在野外现场直接测定水的pH值。
The pH value of kars groundwater depends mainly on the shifting of equilibrium of carbonic acid svstem in the water However, because the CO2 conten in the inner part of karst hydrogeochemical system is much higher than that in the atmosphere, the equilibrium of the system will be destroyed once groundwater flows out of the system and contacts the atmosphere, resulting in rapid escape of CO2 from water and the increase of pH value of water until reequilibrium with the atmosphere. Therefore, the saturation index calculated according to the pH value measured in the lab is obviously higher than that according to the pH value measured in situ, leading probably to the inverse conclusion that the water sample is saturated or oversaturated to calcite according to pH in the lab, whereas unsaturated according to pH in situ.
The author explains all these phenomena based on theoretical thermodynamic analysis and practical cases for calculation, and considers that in karst hydrogeochemistry research, the pH value of groundwater should be measured in situ.
出处
《中国岩溶》
CAS
CSCD
北大核心
1990年第4期310-317,共8页
Carsologica Sinica
基金
国家自然科学基金资助项目
