Radiation dose reconstruction for higher aquatic plants and fish in Glyboke Lake during the early phase of the Chernobyl accident.

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.

Accumulation and distribution of radionuclides in higher aquatic plants during the vegetation period.

The long-term observations of the dynamics of 90Sr and 137Cs concentration, as well as the physicochemical forms of these radionuclides in 10 species of higher aquatic plants during the vegetation period of Glyboke Lake in the Chornobyl Exclusion Zone were presented. The accumulation of radionuclides depends on the influence of environmental factors and species characteristics of the studied plants. It has been shown that the accumulation of 90Sr and 137Cs by plants mainly occurs in accordance with the physiological stages of their development. Under conditions of intensive growth and accumulation of biomass in the juvenile period, plants disproportionately uptake 137Cs from the environment; during the seed ripening period at the stage of aging, plants mainly accumulate 90Sr, as evidenced by the non-correlation of this radionuclide concentration in water and plants in the considered periods. The specific features of the accumulation of radionuclides by plants were studied by the method of analysis of physicochemical forms, which consists in the sequential extraction of radionuclides from plant preparations and makes it possible to quantitatively investigate potentially exchange and fixed forms. The analysis of physicochemical forms confirmed the patterns of seasonal distribution of radionuclides, as well as their accumulation in cells, tissues and in the whole plant obtained from long-term observations.

Disorders of the initial ontogenesis of seed progeny of the common reed (Phragmites australis) from water bodies within the Chernobyl Exclusion Zone.

The peculiarity of seeds germination of the common reed Phragmites australis, which is a cosmopolitan plant and widespread at littoral zone of the Chernobyl Exclusion Zone water bodies, was studied. The complex of vitality, physiological and morphological indices of seedling as seed germination, germination energy, seedling survivability and seed vitality, length of initial leaf and root and abnormalities of seedlings were investigated. The current average absorbed dose rate on the reed vegetative plants ranged from 0.05 to 34 µGy h-1. Data demonstrated correlation between dose rate and seed progeny vitality. All investigated indices of the common reed's progeny from impacted water bodies significantly differed from reference ones - viability indices were decreased, seedling growth was slower and number of seedling abnormalities were increased. Logistic regressions were found for growth of seedlings initial root and leaf from impacted sites and mostly exponential and linear for reference ones. An essential abnormalities percentage up to 75% was registered for reed seedlings from the impacted sites. Significance of dormancy for improvement of reed seeds germination from the Chernobyl Exclusion Zone was discussed.

EFFECT OF ADDITIONAL ACUTE IRRADIATION ON CYTOMORPHOLOGICAL ABNORMALITIES OF ERYTHROCYTES OF THE PRUSSIAN CARP (CARASSIUS GIBELIO BLOCH) FROM WATER BODY CONTAMINATED WITH RADIONUCLIDES. / VPLYV DODATKOVOGO GOSTROGO OPROMINENNIa NA TsYTOMORFOLOGIChNI PORUShENNIa ERYTROTsYTIV KARASIa SRIBLIaSTOGO (CARASSIUS GIBELIO BLOCH) IZ ZABRUDNENOÏ RADIONUKLIDAMY VODOY̆MY.

OBJECTIVE: Assessment of the effect of additional acute irradiation (AAI) in sub-lethal range on the peculiarities of formation of qualitative composition of red blood and adaptive possibilities of the hematopoietic system of fish in reservoirs within the Chernobyl Exclusion Zone (CEZ), contaminated with radionuclides. MATERIALS AND METHODS: We studied the Prussian carp Carassius gibelio Bloch (2-3 years old) from Vershyna Lake (impacted reservoir in the CEZ) and Dibrova Lake (reference reservoir), where the average absorbed dose rate (ADR) was, respectively, 110.80 and 0.07 µGy/h. The fish were exposed by a single X-ray dose at the unit RUM-17 (ADR - 0.89 Gy/min) at dose of 2.5, 5.0 and 10.0 Gy. Morphological and cytogenetic studies of red blood cells were per- formed dynamically for the 1st, 7th and 30th day after irradiation. The blood was taken from the tail vein and stained by Pappenheim's method. Cytomorphological abnormalities of erythrocytes were analyzed for 3000 cells (‰). RESULTS: In blood of fish from the impacted reservoir (Vershyna Lake) on the 1st day after AAI, the average number of all types of deformations of erythrocytes cells increased in 2.1 times, and in fish of the reference reservoir (Dibrova Lake) - in 5.2 times. General spectrum of erythrocyte disturbances in fish of Vershyna Lake has increased from 4 to 6 types (in 1.5 times), and Dibrova Lake - from 2 to 5 types (in 2.5 times). However, further observations of the dynamics of morphological disorders of fish's blood cells from Vershyna Lake on the 7th and the 30th day after AAI showed a significant increase in pathological processes in comparison with the reference reservoir, namely - an increase in the number of gross damage of DNA molecules - amitosis (on average in 14.8 times), erythrocytes with septum in the nucleus (in 1.9 times), as well as structural disorders in the cells - protuberances (in 10.5 times), cells with vacuolate cytoplasm (in 8.6 times). CONCLUSIONS: The red blood cells of the fish of the impacted reservoir show a greater vulnerability to AAI, which manifests itself in an increase in the number of erythrocytes with pathology of mitosis and may indicate a violation of the genetic structures of cells due to long-term radiation exposure.

Radiation-induced cytogenetic and hematologic effects on aquatic biota within the Chernobyl exclusion zone.

During 1998-2014 the rate of chromosomal aberrations in embryo tissues of the pond snail (Lymnaea stagnalis) and root meristems of higher aquatic plants, and also hematologic indexes of mantle liquid of the adult snails and peripheral blood of fishes in water bodies within the Chernobyl exclusion zone (EZ) was studied. The absorbed dose rate for hydrobionts from water bodies of the EZ registered in a range from 0.25 to 420 µGy h(-1) and in the reference ones - up to 0.09 µGy h(-1). The level of chromosomal aberrations in the molluscs from the most contaminated water bodies of the EZ was registered within range of 18-27% and for the molluscs from the reference lakes this index was on the average 1.5% with the maximal values 2.3%. The rate of chromosomal aberrations in root meristematic cells of higher aquatic plants from the contaminated lakes of the EZ was in range of 7-17% and in the plants from reference water bodies was not exceed 2.1%. The positive correlation between chromosomal aberration rate and absorbed dose rate in the pond snail's embryos and root meristems of higher aquatic plants in water bodies of the EZ was registered. Analysis of hemolymph structure of snails from the most contaminated water bodies showed a high rate of dead and phagocytic cells as well as decrease of the young amoebocytes quantity. Hematologic research of fish allows to determine on the one hand an insignificant changes of leukogram structure, and from the other hand a high level of red cells with different abnormalities in the peripheral blood of fishes from the water bodies with high levels of radioactive contamination. It is suppose that qualitative indexes of red cells in peripheral blood of fish are more sensitive to long-term radiation impact in comparison with elements of white blood, which can be used for conducting of the hematologic monitoring of radioactive contaminated water bodies.

[Radioecological problems of aquatic ecosystems of the Chernobyl exclusion zone].

The results of radioactive contamination dynamics in the main components of aquatic ecosystems and the absorbed dose rate for hydrobionts within the Chernobyl accident exclusion zone was analysed. Some cytogenetical and haematological effects of long-term irradiation on aquatic organisms as well as damage of higher aquatic plants by parasitic fungi and gall-producing arthropods were considered.

[Decreasing of 137Cs specific activities in hydrobionts inhabiting water-bodies of different type].

The rate of decrease of 137Cs content in hydrobionts from water-bodies of Ukraine that contaminated as result of Chernobyl accident has been calculated. The retrospective analysis of 137Cs content in fish of water-bodies has been transmitted.

[Radioecological studies of freshwater mollusks in the Chernobyl accident exclusion zone].

Species-specificity and dynamics of 90Sr, 137Cs and some transuranic elements accumulation in bivalve and gastropod freshwater molluscs of the Chernobyl exclusion zone during 1997-2008 was analyzed. The results of radiation dose and chromosome aberration rate estimation and the analysis of hemolymph composition of freshwater snail (Lymnaea stagnalis L.) was produced. The absorbed dose rate was registered in the range of 0.3-85.0 microGy/h. In closed water bodies the heightened chromosome aberration rate (up to 27%) in embryo tissues, and also the change of haematological indexes for the adult individuals of snails was registered.

[The main radionuclides and dose formation in fish of the Chernobyl NPP exclusion zone].

The results of the researches of spices-specificity, accumulation dynamics and distribution of 90Sr, of 137Cs and of transuranic elements in fish of the Chernobyl NPP exclusion zone are analysed. The data of estimations of absorbed doze rate from incorporated radionuclides for pray fish and predatory species are given. For the fish from the lake of the left-bank floodplain of the Pripyat River the increase of 90Sr specific activity is registered which is presumably connected with the dynamics of the physical-chemical forms of the radionuclide in soils and their wash out in water bodies from the catchment basin. Now about 90% of internal dose rate of fish from closed aquatic ecosystems within the Chernobyl NPP exclusion zone is caused by 90Sr incorporation.

Hydrotechnical facilities within the Chernobyl nuclear power plant exclusion zone: impacts on hydrologic regime and plant growth patterns of floodplain water bodies of the Pripyat River.

As result of the Chernobyl nuclear power plant accident the territory of the left-bank flood-lands of the Pripyat River have undergone intensive radionuclide contamination. With the purpose of preventing the washing away of radioactive substances, a complex of flood protection dams was constructed. This construction changed the hydrological regime of these territories and caused overgrowth by higher aquatic plants. Absence of a flowing mode of reservoirs, the stagnant phenomena during spring and seasonal high waters on the embank site have caused amplification of eutrophication processes, swamping and, connected with it, increase of water-marsh floristic complex in the structure of the vegetative cover.

[90Sr, 137Cs, 238Pu, 239+240Pu, and 241Am radionuclides in macrophytes within the Krasnensky flood plain: species specificity of concentration and distribution in phytocenosis components]. / Radionuklidy 90Sr, 137Cs, 238Pu, 239+240Pu i 241Am v makrofitakh Krasnenskoi poimy: vidospetsifichnost' kontsentrirovaniia i raspredelenie v komponentakh fitotsenoza.

The analysis of the content of radionuclides 90Sr, 137Cs, 238Pu, 239 + 240Pu and 241Am in water vegetation of flood plain reservoirs has allowed studing features of radionuclide accumulation by various species of macrophytes and revealing bioindicators of radionuclide contamination. Thus species-specificity of radionuclide accumulation can essentially change the contribution of different species to a percentage ratio of the radionuclide content in phytomass of reservoirs in comparison with fund of higher aquatic plants.

[Functional-ecological and age-specific regularities in radionuclide concentration in freshwater molluscs from the Chernobyl Atomic Energy Station exclusion zone]. / Funktsional'no-ékologicheskie i vozrastnye zakonomernosti kontsentrirovaniia radionuklidov presnovodnymi molliuskami zony otchuzhdeniia Chernobyl'skoi AES.

The results of the studies on 90Sr and 137Cs content in the tissues of bivalve and gastropod mollusks of water basins in the exclusion zone of the Chernobyl NPP have been analyzed. The dependence of radionuclide accumulation factors on the peculiarities of morphological structure, functional ecology and nutrition type was found. The age dynamics of 137Cs content in some species of Gastropoda was studied.

[90Sr and 137Cs in higher aquatic plants of the Chernobyl nuclear plant exlusion zone]]. / 90Sr and 137Cs v vysshykh vodnykh rasteniiakh zony otchuzhdeniia Chernobyl'skoi AES.

The content of radionuclides 90Sr and 137Cs in higher aquatic plants of water objects within Chernobyl NPP exclusion zone has been analysed. Biodiversity of phytocenose was studied and species-indicators of radioactive contamination were revealed. The seasonal dynamics of radionuclide content in macrophytes was studied and the role of main aquatic plant clumps in processes of 137Cs and 90Sr distribution in abiotic component of biohydrocenose was demonstrated.

[Dynamics of tritium content in flood-lands reservoirs of the Pripyat river and cooling pond of the Chernobyl nuclear plant]. / Dinamika soderzhaniia tritiia v poimennykh vodoemakh r.Pripiat' i prude-okhladitele Chernobyl'skoi AES.

Tritium content in water from natural and artificial reservoirs within 30-km exclusion zone of the Chernobyl NPP has been determined. The increase of Tritium activity in the involved water reserwous has been registered in May 1994 and April 1995. As supposed the source of the increase, nuclear power plants, equipped with WWER reactors and located in catchment area of Pripyat river.