Long-lived unstable nuclei as microindicators for some processes of nature

137Cs and 90Sr are the long-lived radioactive isotopes generated from nuclear tests/accidents. These isotopes take part in various processes of nature. Radioactivities due to these isotopes in environmental samples relate closely not only to date, site, characteristics, etc. of nuclear tests/accidents, but also to mechanism of processes in which the isotopes are presented. Determination and analysis of 137Cs and 90Sr radioactivity of environmental samples would disclose interesting information of some natural processes and other relating issues. In this paper the following topics will be discussed: - 1. The radial distribution of 137Cs and 90Sr in annual tree rings. - 2. The relation with accumulative deposition of radioactive fallout. - 3. What would be the mechanism of internal transfer processes during tree aging