Leaching is the process by which inorganic - , organic contaminants or radionuclides are released from the solid phase into the waterphase under the influence of mineral dissolution, desorption, complexation processes as affected by pH, redox, dissolved organic matter and (micro)biological activity. The process itself is universal, as any material exposed to contact with water will leach components from its surface or its interior depending on the porosity of the material considered.

Source: Surface and Aqueous Geochemistry Group, Stanford, USA