PECULIARITIES OF RADIONUCLIDE ACCUMULATION BY SILVER CARP IN THE ZAPORIZKE RESERVOIR

  • T. V. Ananieva Oles Honchar Dnipro National University
  • O. V. Fedonenko Oles Honchar Dnipro National University
  • O. Yu. Klymenko Oles Honchar Dnipro National University
Keywords: radionuclides, specific activity, coefficient of accumulation, silver carp, the Zaporizke Reservoir

Abstract

The purpose of the work was to determine the content levels and the features of accumulation of the main dose-forming radionuclides in the tissues of the silver carp (Hypophthalmichthys molitrix Val.) in the Zaporizke Reservoir. The fish were selected at the lower part of the Zaporizke Reservoir (near the village of Viyskove) during spring and autumn period of 2016-2017. The fish was catch with shuttered nets with cells of 50 – 150 mm. Preparation of samples for radiospectrometric measurements consisted of separating tissues, chopping and drying at a temperature of 105°C in a dry-fryer box. Specific activity of radionuclides in prepared samples was determined using the scintillation spectrometer of gamma radiation energy SEG-001 «ACP-C» and the beta-spectrometer SEB-01-150. Specific radioactivity of radionuclides is given in Bequerels per kilogram (Bq/kg) of wet, natural weight. The muscle tissue, bone, scales, liver and gills of fish were selected for the assay. Statistical analysis of the research results was carried out by generally accepted methods of variation statistics for a small sample using the Excel 2007 software package. According to our research, the average contents of 137Cs and 90Sr in the silver carp tissues were significantly lower than the hygienic concentrations in Ukraine and were follows: 137Cs – from 10 to 11,5 Bq/kg, 90Sr – from 2,5 to 6 Bq/kg. The muscle and bone tissue had the greatest accumulation capacity for 137Cs and 90Sr, and scales and liver of fish had the smallest one. The gill apparatus and the external surfaces of the fish body had low permeability to 137Cs. By the ability to 90Sr accumulation, the silver carp occupies an intermediate position between the benthophages and the ichthyophages. Relatively high levels of radioactive isotopes of 137Cs and 90Sr in fish meal and gills indicate an effective self-cleaning mechanism from incorporated radiation. Since the contents of radionuclides were low in water, the fish absorbed them mainly from the feed, but they were isolated by the covering tissues. In the spring, the indices of the artificial radionuclide contents in the silver carp significantly exceeded the autumn values. The distribution of 137Cs in the body of the silver carp occurs as follows: at spring – liver > gills > bones > scales > muscles; at autumn – bones > muscles > gills > scales > liver. For 90Sr, the following data series were observed: at spring – gills > bones > scales > liver > muscles; at autumn – bones > muscles > gills > scales> liver. The results of studies on the natural radionuclide contents of 232Th, 226Ra and 40K in silver carp tissues showed that 232Th was most often found in bones and muscles of fish above 59 Bq/kg, the content of 226Ra was the highest in bone tissue – from 50 to 70 Bq/kg. The content of 40K was found at a level of 60–98 Bq/kg. The smallest average content of 40K was recorded in the muscle tissue of fish, the largest in the bone tissue. The natural isotope of potassium is fairly common, especially in the Dnipro region, which has a high radioactive background, and therefore its content in the fish of the Zaporizke Reservoir reaches high values. Specific radioactivity of natural potassium-40 was quite high, and its content in any living cells is always very significant, since it belongs to macroelements. Spring values of 232Th in muscle tissue of fish were higher than at the autumn. In bone tissue, the content of 232Th increased at autumn. The content of 40K decreased by the fall, and the content of 226Ra remained at a constant level. At the spring, the arrival of radionuclides occurs due to surface runoff from adjacent areas and the outflow of radioactive substances from the upper reservoirs of the Dnipro cascade. Climatic conditions of the reservoir affect the withdrawal of radionuclides. Decrease of water temperature in the autumn period to 5°C inhibits the process of radionuclides removal and increases the half-life by 2–3 times. By the calculated coefficients of radionuclide accumulation relatively to water 137Cs was accumulated 3 times more intensively than 90Sr in muscle tissue of the silver carp. Radionuclides of 137Cs are the main factors of the internal dose of irradiation with artificial radionuclides for the silver carp of the Zaporizke Reservoir. The accumulation rate in the muscle tissue of the silver carp could accommodate the radioisotopes under study in the following sequence: 137Cs > 226Ra > 232Th > 90Sr > 40K. Radionuclides of 40K were found in fish at high concentrations, but accumulate from water much less than 137Cs, which is a chemical analogue of potassium. The results of the study of the radionuclide contents and their distribution in the tissues of the silver carp indicated that the largest amounts of radioactive substances were contained in both muscle and bone tissues, that can be explained by a slower exchange and rate of recovery of these tissues compared with liver parenchyma and gill epithelium. The revealed patterns of accumulation of natural and artificial radionuclides in the tissues of the silver carp of the Zaporizke Reservoir provide the basis for prediction and modeling of migration processes and radioactive contamination of the water ecosystem for further monitoring observations

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Published
2018-07-03
How to Cite
Ananieva, T. V., Fedonenko, O. V., & Klymenko, O. Y. (2018). PECULIARITIES OF RADIONUCLIDE ACCUMULATION BY SILVER CARP IN THE ZAPORIZKE RESERVOIR. Visnyk of ZNU: Biological Sciences, (1), 23-29. https://doi.org/10.26661/2410-0943-2018-1-03
Section
ZOOLOGY AND ANIMAL ECOLOGY