Krasnoyarsk scientists have estimated the disappearance rate of artificial radioactive isotopes from the vegetation of the Yenisei River. Over the past 15 years, the content of most of the technogenic radionuclides has decreased, and they are not found in aquatic plants of the Yenisei. However, the cesium isotope is still present in the biomass of water moss and pondweed. The research results are published in the Journal of Environmental Radioactivity.
"Pollution of natural reservoirs with artificial radioactive elements is a serious environmental problem. For example, in the Yenisei there are radionuclides that got there due to discharges of plutonium production enterprises at the Mining and Chemical Combine (MCC). The last nuclear reactor at the MCC was shut down in spring 2010, but according to the official publicly available reports of the Federal Service for Hydrometeorology and Environmental Monitoring, radioactive discharges into the Yenisei in the amounts allowed by the standards continue," said the representatives of the Institute of Biophysics of the Siberian Branch of the Russian Academy of Sciences.
Scientists of the Federal Research Center "Krasnoyarsk Science Center of the Siberian Branch of the Russian Academy of Sciences", using two species of aquatic plants, experimentally confirmed a decrease in the content of most technogenic radionuclides in aquatic plants of the Yenisei after the shutdown of the nuclear reactor at the MCC. Almost all previously detected radioactive isotopes, except for the cesium-137 isotope, have disappeared or significantly decreased their concentrations in the biomass of river plants.
Biologists examined long-term changes in the pollution of the Yenisei with radioactive substances from 2003 to 2018 during the direct operation of nuclear reactors and after their shutdown. To do this, they used two types of algae: shining pondweed (Potamogeton lucens) and water moss (Fontinalis antipyretica), which grow in abundance in the Yenisei. Scientists measured the content of radionuclides in the biomass of algae collected in different years and estimated the rate of its decline. Aquatic plants are widely used as bioindicators that reflect the pollution of water and bottom sediments with various metals and radionuclides.
“Aquatic plants absorb radionuclides well from water, therefore they are traditionally used for radioecological monitoring. At present, short-lived radionuclides formed in the core of a nuclear reactor are no longer registered in plants and fish inhabiting the Yenisei. Out of the gamma emitters, only radiocaesium is detected, which still enters the Yenisei in amounts permitted by the standards. The content of radiocaesium in fish is significantly lower than the standards established in Russia. In this work, we showed that plants reliably reflect the intake of technogenic radionuclides into the Yenisei. Therefore, they can be used for routine radioecological monitoring of the Yenisei, the relevance of which is not decreasing, which is due to the development of nuclear industry enterprises," said Tatyana Zotina, one of the authors of the article, Candidate of Biological Sciences, senior researcher at the Institute of Biophysics SB RAS.
According to the scientists, this work was supported by the grants from the Russian Foundation for Basic Research and the Krasnoyarsk Regional Science Foundation (No. 18-44-240003).