This study deals with an assessment of radiation dose dynamics to fish and higher aquatic plants (helophytes) in Glyboke Lake (10-km exclusion zone) during the early phase of the Chernobyl accident. Models of radioactive contamination of water and sediment and models of radioactive contamination and radiation dose to fish and aquatic plants were developed. It was found that, in 1986, the total dose rate to fish reached 0.25 Gy d-1. Within 6 months after the accident, the dose rate due to 90Sr, 134Cs and 137Cs had increased. The absorbed dose to prey fish of Glyboke Lake for this period was estimated as being 27-81 Gy of which 4-40 Gy was formed by 131I exposure. The radiation dose rate due to 90Sr, 106Ru, 134+137Cs and 144Ce to aquatic plants reached its quasi-equilibrium values approximately 50 days after the accident and remained virtually unchanged until the end of the 1986 growing season. The highest levels of 89Sr, 91Y, 95Zr, 103Ru, 141Ce exposure were observed between 30 and 50 days with a decrease by 2-3 times at the end of the growing season. Radiation exposure of the short-lived 131I, 140Ba, 140La, 239Np reached its maximum within 5-15 days after the accident. The absorbed dose rate to aquatic plants reached 0.69 Gy d-1, while the contribution of cerium radionuclides to the total dose rate formed 50% in the initial period and reached 90% at the end of the growing season. The magnitude of the radiation dose rate to plant roots was 2.4 times higher than aboveground organs, and that of rhizomes was 1.6 times higher. During the growing season of 1986 the total dose of exposure of plants in Glyboke Lake was about 78 Gy. The results of this study emphasise the necessity to consider the history of exposure of past generation of living organisms as part of the assessment of current radiation effects.
Keywords: Absorbed dose; Chernobyl NPP accident; Fish; Glyboke Lake; Higher aquatic plants; Radioactive contamination.
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