Afshin Shaham - Assistant professor of the Islamic Azad University–the south Tehran Branch
Hilda Dadfar - Ph. D. Candidate of the Environmental Sciences–Amsterdam University

The bottom sediments collected in different parts of the Caspian Sea are analyzed for some natural and man-made radionuclides. The vertical profiles of radionuclides vary significantly for samples collected in different parts of the Caspian Sea. The 210Pb age-dating was performed for several sediment core samples together with determination of Plutonium isotope ratios that gave the indication of the origin of the radionuclides. Bottom sediments are scavengers for some Uranium and Thorium chain radionuclides, man-made radionuclides and other pollutants. Historical deposition records could be build up using the radionuclide activities in the bottom sediments. The current knowledge of natural and artificial radionuclides in the vertical profiles of bottom sediments collected in different parts of the Caspian Sea is presented in this review. The atmospheric nuclear tests in 50-60ss and accident at the Chernobyl NPP (1986) are the main sources of man-made radionuclide contamination of the Caspian Sea. The possibility of some impact by the contemporary nuclear activities of European Countries is possible as well. The sediment cores were collected in the Anzali region. The 210Pb age-dating and 238Pu/ 239, 240Pu, 241Pu/ 239, 240Pu ratios were used to determine the sedimentation rates and origin of the man-made radionuclides.