A Model of Chemical Weathering of Silicate Minerals
The behavior of quartzose and olivinic sands subjected to water percolation is important in studying the weathering of a sediment. Sorption of H + ions from the water and desorption of metal ions from the sediment take place in a fashion similar to that caused by an ion exchange resin. This fact permits the construction of a mathematical model that gives the expected amount of H + sorption for a bed as a function of time and space. Sorption-desorption processes in sediments are responsible for weathering of silicate beds, water quality changes, and possibly play a role in porosity changes. These sorption-desorption reactions are pH dependent and also vary according to the O:Si ratio. It seems that all sorption phenomena at the sediment-water interface can be conceived as adjustments to produce a minimum of free energy difference between the crystal, the surface, and the external environment.