Water-to-fish transfer of stable elements in near-coastal seas around a nuclear site of Korea

In radiation dose assessment models for wildlife, the transfer of radionuclides to plant and animal species is usually quantified with concentration ratios (CRs) between them and environmental media. The IAEA recently produced a handbook of CR values covering various radionuclides and many kinds of plant and animal species. However, CR values can vary considerably with wildlife species and environmental conditions. Therefore, it is desirable to use as many site-specific CR data as possible. In the present study, the CR values of various stable elements as surrogates for radionuclides were investigated for several marine fish species inhabiting near-coastal seas around a nuclear power plant site of Korea. In May to June, 2012, fish and seawater samples were collected from six points in the sea within 10 km from Wolsung NPP site. For seawater samples, temperature, pH and salinity were measured immediately after collected. Fish samples were put in an icebox and carried to the laboratory, where they were freeze-dried and homogenized for the whole bodies using a grinder. Aliquots of the homogenized samples were changed into liquid samples as a result of chemical treatments. Sea water samples were filtered using a membrane filter (0.2 μm in pore size). Elemental concentrations were measured with the prepared liquid samples using the ICP-MS and ICP-AES. The CR value (L/kg-fresh) was expressed as the ratio of the fish concentration (Bq/kg-fresh) to the seawater concentration (Bq/L). The numbers of the elements and fish species investigated were 21 and 14, respectively. The CR values of Na and Mg were lower than 1 for all the fish species, whereas those of the remaining elements were always higher than 1 except for Li and U. Zn, Mn, Al and Fe formed a group of the highest CR values in general and their CR values mostly ranged from hundreds to thousands. In the case of Zn, CR values even higher than ten thousands were observed for seven species including greenling, sea bass and jack mackerel. The CR values of Cr and Cu were comparatively high with most of them being in the range of tens to thousands. Sr and Cs values were mostly lower than 10 and 100, respectively. Variations of the CR values with the fish species were comparatively high for Al, Cr, Zn and Th, whereas the opposite was true for K, Ca, Na, Mg, Sr and Cs. Particularly for Al, the minimum and maximum values differed by a factor of about 500.The present results are going to be used for establishing a database of CR values for Korean wildlife species and further studies are planned for a wide variety of plant and animal species. Document available in abstract form only. (authors)