[en] This sheet summarizes the behavior of the chemical element in the main compartments of terrestrial and aquatic ecosystems, under the following two assumptions. Isotopic discrimination is negligible, which is the case for most of the elements discussed. When the element has stable isotopes, the analogy in behavior between its stable and radioactive isotopes is implicitly accepted, bearing in mind, however, that for naturally occurring elements, the chemical form and emission medium of anthropogenic discharges are likely to involve transfer pathways and processes other than those identified for the naturally stable element. The radioactive isotope(s) designated in the heading of the data sheet correspond to radionuclides of major radioecological importance, in terms of quantities and persistence in the environment. Other isotopes, whether radioactive or stable, may also be cited. The information, which is deliberately simplified, is intended to reflect the state of knowledge on the subject at the time of updating, and to propose values for the main radioecological parameters used to estimate transfers in the environment, and more particularly within the food chain