Dynamics of crystallization and dissolution of calcium orthophosphates at the near-molecular level

Although extensive investigations of biogenic and geological calcium phosphate crystallization/dissolution and their phase transformations have been performed, the mechanisms of crystallization and dissolution of sparingly soluble calcium phosphates in geological settings have not been completely determined at the near-molecular level. In particular, an understanding of the physical-chemical processes at the earliest nucleation stage and the subsequent crystal surface dynamics in soil solutions is lacking. This review focuses on the earliest events in homo/heterogeneous nucleation from an initial supersaturated solution phase, the subsequent growth of calcium phosphate phases, and the relevant influences of the presence of additional inorganic and organic molecules in both geological and biological settings. These studies have implications for the understanding of the complex processes of calcium phosphate transformations in soils, and provide possible physical-chemical mechanisms for the biogeochemical behavior of phosphorus at the near-molecular level.