高放废物处置库甘肃北山野马泉预选区地下水化学特征及水-岩作用模拟

在高放废物处置库场地选择和性能评价中,地下水化学特征是最重要的因素之一。文中以野外水文地球化学调查资料为基础,应用水文地球综合分析方法和地下水地球化学模拟技术,探讨中国高放废物处置库甘肃北山野马泉预选区地下水化学特征、时空分布规律及水岩作用机理。主要结论是:野马泉地区地下水以咸水为主, 具有高矿化的特征,水化学类型以Cl·SO4 Na和SO4·Cl Na型为主,pH值大多在7~8 之间;地下水化学成分显示出明显的分带特征;地下水对石盐和石膏欠饱和,对黄铁矿以及铝硅酸盐过饱和;方解石、钠长石在补给区地下水中呈不饱和状态,在排泄区地下水中呈饱和状态。由水岩作用模拟可知,沿水流路径地下水溶解岩石中的钠长石、黑云母、石盐等矿物,溶解二氧化碳,沉淀析出方解石、伊利石和萤石等矿物;发生明显地下水蒸发作用、二氧化碳溶解作用和Ca2+/ Na+离子交换作用, 说明溶滤、沉淀、离子交换和蒸发浓缩作用是区内地下水化学行为的控制因素。

Chemical characteristics of groundwater and water-rock interaction: Modeling of the Yemaquan preselected area for China's high level radioactive waste repository

In the siting and site characterization studies for high-level radioactive waste repository, the chemical features of groundwater are one of the most important evaluation factors. Based on data from field hydrogeochemical investigations, and applying the synthetic hydrogeochemical analytical method and modeling technique, this paper discusses the chemical features of groundwater, temporal and spatial variations and water-rock interaction mechanisms in the Yemaquan preliminary selected area for China's high-level radioactive waste repository. The main conclusions are as follows: 1groundwater in the study area is mainly saline water with high dissolved solids, 7～8 pH value and Cl·SO_4-Na, SO_4·Cl-Na chemical species; 2the groundwater chemical compositions show a clear zonal distribution; 3gypsum and salt are undersaturated and tend to dissolve in the groundwater; (4)pyrite and aluminum-silicate minerals are oversaturated; (5)calcite and albite are undersaturated in recharge areas and oversaturated in discharge areas. Water-rock interaction modeling indicates that along the water flow path, albite, biotite and salt were dissolved and calcite, illite and fluorite were precipitated. The groundwater evaporation, CO_2 dissolution, and Ca~(2+)/Na~+ exchange are also present along the flow path. These indicate that the dissolution, precipitation, ion exchange and evaporation are the dominant factors in establishing the groundwater chemistry in the area.