137Cs concentrations in the water and sediments of the Caspian Sea (1999-2003)

Samples of the sediments and water have been collected from Iranian coastal region of the Caspian Sea in 5 consecutive years. The samples were processed in the laboratory for determining of 137Cs concentrations which is radioecologically significant. Sampling locations are shown. The sediments were dried at constant temperature, the seawater samples were filtered through a membrane filter (Millipore HA, 0.45μm pore size). Dissolved 137Cs in seawater were extracted with two procedures including ammonium phosphomolybdate (AMP) and the sorbent Anfezh from 20-100 liters of seawater samples. 137Cs concentrations in sediments and prepared water samples were determined directly by using a shielded coaxial high pure germanium (HPGe) detector with an energy resolution of 2 keV. At energy of 1332 keV and relative efficiency of 20% coupled to an integrated signal processor and multichannel analyzer (MCA) and PC via an interface. Energy and efficiency calibration of the gamma spectrometer were performed using IAEA reference materials. The counting time for each samples as well as the background were fixed to 100,000 seconds. Mean 137Cs activity in the water and the sediments of the Caspian Sea for the depth of 0-20, 0-50 and 0-100 m are summarized. The determination of 137Cs in seawater samples showed a level between 3-9 Bq.m-3 and recent analyses on sediment showed concentrations between 12-60 Bq.kg-1 dry. Establishment radioactivity monitoring in the Iranian region of Caspian Sea, for measurements of the concentration levels of radionuclides in marine ecosystem is important in the environmental quality state and human health, mainly after nuclear accidents