1999 Volume 38 Issue 3 Pages 145-152
Geochemistry of groundwater originated from rainwater can be interpreted in terms of model calculations based on chemical equilibrium between aqueous species and minerals, dissolution kinetics of silicates and carbonates and groundwater flow. The model calculations predict increases in pH and Si, Ca, Na and K concentrations in groundwater interacting with feldspar. This theoretical prediction is consistent with natural groundwater chemistry in general. Weathering trend in granitic rocks from the surface to deeper part (gibbsite → kaolinite → montmorillonite) can be reasonably explained by the model calculations. The geochemical evolution of groundwater and weathering trend depend on initial composition of rainwater, minerals interacting with groundwater, minerals precipitating from groundwater, kinetic factors, physical properties of rocks (permeability, porosity etc.), and whether the system is open to atmosphere or closed.
