Artificial and natural radioisotopes as environmental tracers and chronometers

Radioisotopes in the environment, artificial or natural, can pose serious hazards to living organisms and are therefore monitored with highly sensitive equipment. Investigations of environmental pathways are in many cases focused on the radiation dose in the endpoint organism, which is then compared to recommended or imposed limits. Such experimental and modelling studies are necessary for the assessment of effects caused by accidental or routine releases of radioisotopes into the environment, and also for the prediction of effects caused by planned installations like future nuclear waste repositories. On the other hand, current radiometric methods are able to detect many radioisotopes, and in most environmental media, in concentrations orders of magnitude below a hazardous level. This opens up the possibility to follow these isotopes through many compartments of the ecosphere. This way radioisotopes can become valuable environmental tracers, independent of their radiological relevance, like natural ⁷Be in the atmosphere or medical ¹³¹I in rivers. Furthermore, application of the radioactive decay law offers the possibility for radiometric dating for a variety of isotopes beyond the well-known ¹⁴C, e.g. the established ²¹⁰Pb/¹³⁷Cs and the experimental ³²Si for sediments. Examples will show environmental tracer and chronology applications of radioisotopes. The results can be of high relevance for non-radiological disciplines, e.g. climatology.