Accumulation of natural and artificial radionuclides in water and hydrobionts of fishing ponds of Dnipropetrovsk region

Abstract

The paper presents the results of radioecological studies conducted in fish farms of the Dnipropetrovsk region. The distribution of radionuclides of natural and artificial origin is an urgent problem for various types of ecosystems, given the different routes of entry of these substances. The level of accumulation of radionuclides in the waters of the Zelenodolsk, Krynychansk and Kryvorizk fish farms was determined in a course of the presented study prior to the 2022 russian invasion of Ukraine. Content indicator of radium-226 in water ranged from 3.8 to 7.4 Bq/kg, thorium-232 - from 2.95 to 44.4 Bq/kg, potassium-40 - from 74.2 to 82.4 Bq/kg. Obtained in the present study results evidence that bottom sediments significantly accumulate the radionuclides. The registered content of radium-226 in them was from 30.1 to 14.8 Bq/kg, thorium-232 - from 9.6 to 41.5 Bq/kg, potassium-40 from 134.8 to 182.2 Bq/kg. The coefficients of accumulation of natural radionuclides in water and bottom sediments was registered as ranging from 1.4 to 5 for radium-226, from 0.82 to 3.3 for thorium-232, from 1.72 to 2.26 for potassium-40. The content of artificial radionuclides in water and bottom sediments determined in the study corresponded with their biochemical properties. In water, their value ranged from 0.13 to 1.8 Bq/kg for cesium-137 and from 0.05 to 0.08 Bq/kg for strontium-90. Taking into account the fact that bottom sediments accumulate a significant proportion of pollutants from water, the determined indicators were significantly higher than those in water, namely, from 5.6 to 10.4 Bq/kg for cesium-137 and from 1.5 to 2, 4 Bq/kg for strontium-90. The coefficients of accumulation of radionuclides of artificial origin in water and bottom sediments ranged from 3.3 to 80 for the content of cesium-137 and from 18.7 to 48 for the content of strontium-90. The levels of accumulation of natural radionuclides in the body of silver carp and carp were studied. The level of potassium-40 in the body of silver carp is lower than that of radium-226 and thorium-232 and ranges from 20.2 to 34.4 Bq/kg in all three fish farms. The same amount of radium-226 and thorium-232 was noted in the silver carp of the Krynychan fish farm which was on the level of 47 Bq/kg. In carp, the levels of natural radionuclides were significantly higher in all three fish farms. The content of cesium-137 was registered as approximately the same in silver carp and carp, with the exception of the Kryvyi Rih fish farm, where its level was significantly lower in the body of carp. Strontium-90 content was found in similar amounts in both types of fish. The concentration of radionuclides did not exceed the permissible levels.