2 . Accumulation of Radionuclides by Hydroblonts and Its Results . 

 (G. 6. Polikarpov) 



The accumulation of radionuclides, like other substances, by marine 

 organisms is one difference between the processes by which they reach 

 the environment and are removed from the environment. In the extreme 

 case, when removal can be ignored, for example in the building of 

 skeletons, the maximum capability of hydrobionts for accumulation of an 

 element and its radioactive isotopes from the marine environment is 

 revealed, that is, practically all of the element is accumulated. For 

 example, the skeleton of Acantharia consists of strontium sulfate; 

 therefore, their spicules contain 6 10^ times more strontium (and Sr^^) 

 than the environment. The shells of mollusks are constructed of calcium 

 carbonate in the process of biologic extraction of calcium from sea 

 water. In addition to the practically permanent store of Sr in the 

 spicules of the Acantharia or Ca in the shells of the mollusks, these 

 and other elements are metabolized in their bodies. The higher the rate 

 of excretion, the lower (in the case of the excreting store of the 

 element and its radioisotope) the level of accumulation of the substance 

 in question. When the rates of excretion are similar to the rates of 

 accumulation of an element (radionuclide) is prevented and the result is 

 identical to the result of processes which prevent penetration of the 

 element (radionuclide) through the tissue and membrane barriers. 



Of course, during a period of time which is short in comparison to 

 the life cycle of the organism the accumulation is not great, since it 

 involves only the quantity of the corresponding element (radionuclide) 

 and population of its carrier which are present. The maximum possible 

 accumulation in all of the stores, including those which have little or 

 no exchange with the environment, occurs when an element (or 

 radionuclide) is constantly present in the environment throughout the 

 entire life cycle of an organism. If the organism is exposed only to 

 rapidly exchanging supplies of a given element (radionuclide), 

 relatively brief contact of the organism with the element (radionuclide) 

 may be sufficient. This is also correct if the element (radionuclide) 

 is accumulated only by adsorption from solution (in the form of ions, 

 suspensions, on micelles, etc.). Therefore, the accumulation factors 

 must be subdivided into saturated and unsaturated factors. 



Values of concentration function . --The many reports which have been 

 published on the accumulation coefficients of the chemical elements 

 whose radionuclides are formed upon nuclear explosions or operation of 

 nuclear enterprises are summarized in Table 4. The range of these 

 coefficients is great: from insignificant (1) to tremendous (10 ). For 

 many elements, a similarity is observed between the values of 

 accumulation coefficients for all trophic levels, while for some a 

 decrease or, conversely, an increase is observed at the level of the 

 predators. 



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