Radiological methods in the study of environmental processes

This article gives an overview on the use of natural radionuclides in aquatic and atmospheric sciences to study environmental processes. Of primary importance is the matching of the time scale of the investigated biogeochemical process with nuclide's half live. The useful radionuclides derive from the dacay of natural radioactive series (238U and 232Th) and from cosmogenic sources (7Be, 14C, etc.). The advantage of radionuclides is their known input function given by: 1) disequilibrium of parent/daughter nuclides of the U and Th decay chains; 2) the cosmic ray flux producing radioactive isotopes by interactions with atmospheric gases. Another advantage of radionuclides is that time time decay is independent both of the chemical and physical state, and temperature and pressure. The age dating, evaluation of residence time and exchange rates (e.g. the rates of gas exchange, water mixing, or rates of sorption reactions to particles, of particle settling, particle resuspension, sediment mixing and accumulation, etc.) are the usual applications of natural radionuclides to environmental studies