A. Bolsunovsky

Evidence of the radioactive fallout in the center of Asia (Russia) following the Fukushima Nuclear Accident.

It was recently reported that radioactive fallout due to the Fukushima Nuclear Accident was detected in environmental samples collected in the USA and Greece, which are very far away from Japan. In April-May 2011, fallout radionuclides ((134)Cs, (137)Cs, (131)I) released in the Fukushima Nuclear Accident were detected in environmental samples at the city of Krasnoyarsk (Russia), situated in the center of Asia. Similar maximum levels of (131)I and (137)Cs/(134)Cs and (131)I/(137)Cs ratios in water samples collected in Russia and Greece suggest the high-velocity movement of the radioactive contamination from the Fukushima Nuclear Accident and the global effects of this accident, similar to those caused by the Chernobyl accident.

Effect of low-level α-radiation on bioluminescent assay systems of various complexity

This study addresses the effects of low-level α-radiation on bioluminescent assay systems of different levels of organization: in vivo and in vitro. Three bioluminescent assay systems are used: intact bacteria, lyophilized bacteria, and bioluminescent system of coupled enzyme reactions. Solutions of 241Am(NO3)3 are used as a source of α-radiation. It has been shown that activation processes predominate in all the three bioluminescent assay systems subjected to short-term exposure (20–55 h) and inhibition processes in the systems subjected to longer-term exposure to radiation. It has been found that these effects are caused by the radiation component of 241Am3+ impact. The intensity of the 241Am3+ effect on the bioluminescent assay systems has been shown to depend on the 241Am3+ concentration, level of organization and integrity of the bioluminescent assay system. The bioluminescent assay systems in vivo have been found to be highly sensitive to 241Am3+ (up to 10−17 M).

Artificial radionuclides in sediment of the Yenisei River

Releases from the nuclear facility Mining-and-Chemical Combine (MCC) located at Zheleznogorsk have contributed to the radionuclide contamination of the Yenisei River since operations commenced in 1958. The aim of this study was to assess the activity concentrations of artificial radionuclides and the strength of their binding in Yenisei River sediments. Investigation of Yenisei River sediment samples revealed the presence of artificial radionuclides typical of the MCC radioactive discharge: namely, isotopes of europium, caesium, 60Co and transuranium elements. The concentrations of artificial radionuclides in the sediment layers remain relatively high as far as 200 km downstream of the MCC. In sediment cores collected upstream of the MCC, γ-spectrometric measurements registered only one artificial radionuclide, 137Cs, with a maximal activity of 8 Bq·kg−1. Sequential extraction performed on samples of the upper layers of the sediment core showed different degrees of potential environmental availability for artificial radionuclides: the highest was recorded for 241Am and 152Eu (up to 85% of initial activity), followed by 60Co (up to 32%), and finally, 137Cs (up to 15%). In a few samples, 241Am was present in the unextractable form, which may be accounted for by the presence of reactor fuel microparticles.

Low doses of gamma-radiation induce SOS response and increase mutation frequency in Escherichia coli and Salmonella typhimurium cells.

This study addresses use of two bacterial test systems (the Ames test and the SOS chromotest) to estimate the effects of low doses of γ-radiation. The most substantial increases in induction of SOS response and mutation frequencies were observed in the first 24h of exposure to γ-radiation as compared to the cells in the exposure-free control. Gamma-radiation also impaired growth and survival of S. typhimurium cells in the first 24h. The effects were attenuated at lower exposure doses and at longer exposure times. In the experiments conducted in this study, at 96h of exposure, the values of some of the γ-radiation effects were lower than the MID (minimum inducing dose) detection limits and, thus, were neglected. Long-term exposure to γ-radiation could also result in combined effects of γ-radiation and the death of cells in the culture.

Use of the aquatic plant Elodea canadensis to assess toxicity and genotoxicity of Yenisei River sediments

The toxicity, cytotoxicity, and genotoxicity of bulk sediments from the Yenisei River (Siberia, Russia) were estimated in laboratory bioassays based on several endpoints in the aquatic plant Elodea canadensis. The bottom sediment samples were collected in the Yenisei River upstream and downstream of the sources of chemical and radioactive contamination. The testing revealed different sensitivities of Elodea endpoints to the quality of the bottom sediment: weight of shoots < length of shoots < mitotic index < length of roots < percentage of abnormal cells. The response of the genotoxicity endpoint (percentage of cells with chromosome abnormalities in roots of Elodea) was the highest in sediments with chemical pollution, whereas the highest inhibition of toxicity endpoints (shoot and root length) occurred in sediments with the highest level of radioactive pollution. The extreme response of Elodea endpoints to the quality of certain sediment samples may be regarded as related to the possible presence of unknown toxicants. The results show that E. canadensis can be used as an indicator species in laboratory contact testing of bottom sediment. The responses of shoot and root length growth endpoints of Elodea can be recommended as basic sensitivity indicators of bottom sediment toxicity. Analysis of cells carrying abnormal chromosomes in the apical root meristem of Elodea can be performed optionally in the same test to assess the genotoxicity of sediments.

Chromosomal abnormalities in roots of aquatic plant Elodea canadensis as a tool for testing genotoxicity of bottom sediments

Submersed freshwater macrophytes are considered as relevant indicators for use in bulk bottom sediment contact tests. The purpose of this study was to estimate the validity of endpoints of aquatic plant Elodea canadensis for laboratory genotoxicity testing of natural bottom sediments. The inherent level of chromosome abnormalities (on artificial sediments) in roots of E. canadensis under laboratory conditions was lower than the percentage of abnormal cells in bulk sediments from the Yenisei River. The percentage of abnormal cells in roots of E. canadensis was more sensitive to the presence of genotoxic agents in laboratory contact tests than in the natural population of the plant. The spectra of chromosomal abnormalities that occur in roots of E. canadensis under natural conditions in the Yenisei River and in laboratory contact tests on the bulk bottom sediments from the Yenisei River were similar. Hence, chromosome abnormalities in roots of E. canadensis can be used as a relevant and sensitive genotoxicity endpoint in bottom sediment-contact tests.

Bioaccumulation, inter-organ distribution, and retention of waterborne and dietary 241Am in silver crucian carp

The bioaccumulation of actinide 241Am from food and water in bodies of freshwater fish (Carassius auratus gibelio, silver crucian carp) has been investigated in laboratory experiments. Homogenized biomass of submerged macrophytes labeled with 241Am was injected into the fish gullet. Internal organs and tissues of crucian carp could be ranked according to activity concentration of dietary 241Am after depuration of the digestive tract as follows: liver > gonads > bones > muscles. Accumulation of waterborne 241Am in internal organs and tissues of crucian carp mainly occurred via the digestive tract. While the concentration of 241Am in liver of crucian carps decreased during depuration time, its concentration in bones increased indicating slower transfer of 241Am to skeleton compared to muscles and liver. The retention of dietary 241Am in the bodies of crucian carp reached 35%–46% of ingested 241Am: 20%–31% was retained in liver, 0.6%–0.8% in skeleton, and 1.4%–2.0% in muscles. The concentration factor of 241Am from water was 0.4 for the whole body, 0.3 for liver, 0.01 for muscles, and 0.01 for skeleton. Trace amounts of 241Am were recorded in viscera and muscles of a wild population of silver crucian carp inhabiting a radioactively contaminated part of the Yenisei River.

Hot Particles in the Floodplain of the Yenisei River

The purpose of this study was to investigate radionuclide composition of the hot particles found in the floodplain of the Yenisei River and to discuss their possible sources. Since 1995, researchers of the Institute of Biophysics have found a considerable number of hot particles that contain up to 29,000 kBq/particle of 137Cs in the Yenisei River floodplain. Investigations of the particles in Krasnoyarsk, Moscow, and Novosibirsk have confirmed their reactor origin and made it possible to roughly estimate their age. Based on comparative analysis of 137Cs/134Cs ratios, all the particles can be divided into two or three major groups, suggesting that over the 50-year period of the MCC operation, there have been two or three emergency situations at the MCC reactors, with nuclear fuel microparticles released into the Yenisei. Microparticles containing up to 36 Bq/particle of 241Am were detected in soil and sediment samples collected at the Yenisei River. In some of these particles the 137Cs/241Am ratio is high but in the others — low. It remains unknown how these particles have been formed. However, these microparticles occur in floodplain soils and sediments very frequently and, thus, can be considered to be the main form in which radionuclides are present in the Yenisei River floodplain. The presence of a large number of hot particles of different origin in the floodplain of the Yenisei River from the MCC production area down to the town of Yeniseisk (and, probably, farther downstream) is a source of potential health hazard to people.

Types of cytogenetic abnormalities in apical root meristem of Elodea сanadensis from Yenisei River areas with different types of anthropogenic pollution

Background. The spectrum of cytogenetic abnormalities in the apical root meristem of Elodea сanadensis Michx. (elodea) from the Yenisei River was studied depending on the type of anthropogenic pollution. We compared elodea samples from areas with radiation-contaminated sediments (area affected by Rosatom Mining and Chemical Combine, MCC, Zheleznogorsk) and areas with chemical pollution (Krasnoyarsk). Materials and methods. The apical root meristem of elodea was fixed in acetic alcohol (96 % ethanol and glacial acetic acid, 3 : 1) and stained with 1 % aceto-orcein. The cytogenetic analysis of metaphase and ana-telophase elodea cells was carried out with temporal squashed preparations using an Olympus CX31 microscope. Results. At metaphase stage, the predominant types of abnormalities in elodea cells were disoriented chromosomes (up to 9 % of total metaphase cells) and chromosome agglutination (6 %). In the area affected by the MCC an increased content of ring chromosomes in elodea cells was detected, but in terms of frequency of their occurrence no significant differences were revealed between samples from areas with different types of pollution. Among abnormalities at ana-telophase stage, bridges (to 20% of dividing cells) and disoriented chromosomes (up to 8%) dominated. The following abnormalities were also detected: multipolar and asymmetrical mitoses, agglutination and cells with multiple chromosome abnormalities. It was shown that in areas with the highest content of 137Cs in bottom sediments the frequency of cells with bridges and multiple chromosome abnormalities significantly increased as compared to samples from other areas. Conclusion. In the radioactive contamination area of the Yenisei River the spectrum of abnormalities was dominated by chromosome aberrations (bridges, agglutination, chromosome fragmentation) and multiple abnormalities in one and the same cell. In areas with non-radioactive (chemical) contamination of sediments, mitotic spindle irregularities prevailed.

New Data on the Content of Tritium in a Tributary of the Yenisei River

The Zheleznogorsk Mining-and-Chemical Combine (MCC), Ministry of Nuclear Energy of Russian Federation, is situated in the town of Zheleznogorsk, Krasnoyarsk krai. Nuclear reactors and radiochemical technologies used at MCC gave rise to radioactive pollution of the Yenisei River basin [1–3]. Although two flow-type nuclear reactors were shut down in 1992, the third reactor is still in use. This reactor is planned to be out of use approximately by 2007. Considerable amounts of radioactive wastes have been accumulated during many years of MCC activity. Some wastes are stored in storage facilities and open reservoirs at the industrial sites of MCC, whereas the major fraction of radioactive wastes is discharged in the water-bearing horizons of the Severnyi testing site. According to the reports issued by MCC [4, 5], the Severnyi testing site is located at the watershed between the Yenisei River and the Bol’shaya Tel’ River, 12 km to the north of the MCC radiochemical plant (figure). Water-bearing horizons I and II are used for disposal of liquid radioactive wastes. These horizons are at depths of 370–465 and 180–280 m, respectively. According to the MCC reports, horizon II empties into the Bol’shaya Tel’ River basin, whereas horizon I is thought to flow partially into the Kan River basin (12–14 km to the north of the testing site) and partially into the Bol’shaya Tel’ River basin (by slow spillover to horizon II) [4, 5]. The Severnyi testing site came into operation in 1967. About 5 million cubic meters of liquid radioactive wastes with a total radioactivity of 1 × 10 19 Bq have been disposed in the two water-bearing horizons by the present time [6]. In addition to long-lived radionuclides (including transuranic elements), tritium ( 3 H) is also disposed into the underground horizons. The half-life of tritium is T 1/2 = 12.33 yr. According to the results reported in [4], specific radioactivity of tritium in some wells of the Severnyi testing site was as high as 330 000 Bq/l. However, according to the reports issued by MCC, an enhanced tritium content was observed neither outside the testing site boundaries nor in the monitoring wells. Water samples for estimating the tritium content were collected in the Yenisei River basin during a multipurpose radioecological expedition in August 1998 with the participation of MCC researchers. The results of the survey showed that the concentration of tritium in the MCC dumping site in the Yenisei River, the Bol’shaya Tel’ River mouth, and the Kan River mouth did not exceed 4.3 ± 0.2 Bq/l [5], which corresponded to the background level of the tritium content in surface inland waters of Russia [7]. Only in one tributary of the Kan River, the concentration of tritium was 1.3 times higher than the background level (5.3 ± 0.2 Bq/l [5]). Based on these findings, it was suggested [5] that there was a hydrological connection between surface waters and underground horizons of the Severnyi testing site. However, these were individual observations obtained during the period of a low flow rate of water current.