Abstract

Thermodynamic prediction of weathering products from primary aquifer minerals around underground disposal sites was investigated. The distribution of solubility quotients for kaolinite-smectite reactions showed the trend of reaching at equilibrium with Ca-, Mg-, and Na-smectite for deep groundwaters in granitic aquifers. The values of 10^-14.56, 10^-15.73, and 10^-7.76 were proposed as equilibrium constants between kaolinite and Ca-, Mg-, and Na-smectite end members, respectively. On stability diagrams, most of deep groundwaters were located at equilibrium boundaries between stability fields of kaolinite and smectites or on stability fields of smectites and illite. Shallow groundwaters in basic rock aquifer were plotted at the same stability areas of deep granitic groundwaters on stability diagrams. The results indicated that the primiary mineralogical composition may be important to predict weathering products in deep aquifers.

Keywords underground disposal sites, groundwater, weathering products, thermodynamic phase stability, kaolinite, smectite