Book excerpt: Provides an introduction to the chemistry of the solid-water interface, progressing from the simple to more complex and applied. Discusses the important interfaces in natural systems, especially geochemistry, in natural waters, soils and sediments. The processes occurring at mineral-water, particle-water and organism-water interfaces play critical roles in regulating the composition and ecology of oceans and fresh waters, the development of soils and plant nutrient's supply, preserving the integrity of water repositories and in such applications as water technology and corrosion science.