Geochemical processes at mineral surfaces / Геохимические процессы на поверхности минералов

The phase discontinuity that occurs at the mineral-water interface greatly influences the geochemical cycles of many elements. The composition of natural waters and the flux of material through the hydrosphere are largely controlled by the weathering of minerals and the precipitation of new phases -- processes in which the mineral-water interface plays a fundamental role. In addition, mineral surfaces may act as catalysts for chemical or biological transformations that occur within the hydrosphere. Reactions at the mineral-water interface are of interest in the study of ore genesis, geochemical exploration, mineral separation processes such as flotation and sedimentation, transport of adsorbed nutrients or pollutants in rivers and lakes, scavenging of trace elements in the oceans, and the transport of nuclear or other hazardous waste materials in groundwaters.
Because these processes are so complex, we rely to a great extent on models to understand our observations of the geochemical behavior of solutes in water. The models typically contain several components; for example, solute transport models may be composed of a hydrologic model coupled with a chemical or biological submodel. The chemical submodel can be as simple as a distribution coefficient to represent the partitioning of an element between solid and aqueous phases, or if the aqueous chemical composition is expected to be controlled by the dissolution of a mineral, a solubility product or rate constant for dissolution would be included in the model. Ideally, the chemical model would describe geochemical behavior in terms of a series or combination of elementary processes, e.g. adsorption, ion exchange, precipitation, dissolution, or electron transfer reactions. In reality, the behavior of geochemical systems is often so complex that the actual mechanisms of the processes observed are not wel1 understood. <...>