Technogenic Radionuclides Research Articles

Peculiarities of spatial structure of137Cs contamination field in landscape toposequence: Regularities in geo-field structure

A study of spatial structure of 137 Cs contamination field was performed 1,8 km north to set. St. Vyshkov, Bryansk oblast in pine forest on the Iput river terrace with sandy podzolic soils and pronounced relief. 137 Cs was used as a tracer of atmospheric pollutant migration to test the hypothesis of a regular character of the secondary 137 Cs redistribution in natural landscapes and its dependence on landscape structure. In 2005–2007 95% to 98% of the total 137 Cs activity was still preserved in the upper 15–20-cm soil layer. Field gamma–spectrometry performed in nested grids (5 m for the whole area; 1 m for 5 × 5 m plot; 0,2 m for 1 × 1 m plot) revealed a system of 137 Cs polycentric anomalies at different scales. Detailed cross-sections along and cross the slopes with the step of 0,5 m and 1 m showed specific wave-like variation of surface activity often inversely related to micro-relief that is believed to result from 137 Cs involvement in water and snow-melting mass migration after the aerial fallout. In mosses 137 Cs also showed regular spatial distribution related to that in topsoil. The study proved that technogenic radionuclides formed a definite spatial polycentric structure in natural landscapes that should be accounted of in sampling strategy and in estimates of spatial variation.

Sedimentation rates in the sea of Azov inferred from 137Cs and 241Am specific activity

The sedimentation rate is an important factor influencing the quantitative distribution and composition of sedimentary material, the thickness of bottom sediments, and the dynamics of their transformation at the early diagenesis stage [1]. In [2‐4], the average sedimentation rates were largely determined for the entire Sea of Azov using calculation methods (balance method and comparison between bathymetric charts). At the same time, subsequent natural and anthropogenic changes that occurred in the Don and Kuban river basins resulted in reorganization of the structure and dynamics of water masses, salinity, and sedimentary matter fluxes. In this connection, additional study of the spatial distribution and dynamics of sedimentation rates by advanced methods is needed. During several expeditions conducted in 2006 and 2007, bottom sediments were taken by a gravity corer (designed by the State Oceanographic Institute) and sampled in the layer-by-layer manner at ten stations located in the Russian segment of the Sea of Azov and mouth areas of the Don and Kuban rivers. The maximal length of cores is 100 cm [5]. In total, the activity of 137 Cs and 241 Am radionuclides was measured in over 60 samples. Technogenic radionuclides presently contained in

On radiocarbon and plutonium leakage to groundwater in the vicinity of a shallow-land radioactive waste repository

A shallow-land radioactive waste repository operated in boggy forest environment from 1963 to 1989. During the operation period, a considerable amount of technogenic radionuclides, in solidified state, was disposed into the vault established in the geological structure at the depth of up to 3 m. Environmental monitoring activities started after the closure of the repository in 1989. Recent investigations revealed transfer of radiocarbon and plutonium to the groundwater in the prevailing flow direction. Activity concentration of 239,240Pu in non-filtered fraction of the groundwater from observation well no. 4 determined by alpha-spectrometry was 6.4 × 10 −5 Bq l −1 in 2005, and 3.2 × 10 −4 Bq l −1 in 2006. Further analysis of colloid-facilitated transport of plutonium is planned. Variation of 14C activity concentration in the same well was monitored in 2006. It varied from 0.2 ± 0.1 Bq l −1 in October to 2.8 ± 0.6 Bq l −1 in June and July. Results imply further research into radiocarbon transfer to atmosphere and selected plant species.

First evidence for concentrations of transuranium curium in the Yenisei floodplain ecosystem

The long-term activity of the Mining‐Chemical Plant (MCP) of the Federal Agency for the Atomic Energy of the Russian Federation (Rosatom) in Zheleznogorsk, Krasnoyarsk region resulted in pollution of the Yenisei River [1‐4]. The radiochemical study of bottom sediments of the Yenisei River revealed in its channel segments concentrations of transuranium elements ( 238 Pu, 239,240 Pu, 241 Am) tens of times higher than the previously published data [1] and 100 times higher than the global background value. The previously performed determinations of concentrations of transuranium elements (particularly, 241 Pu and 237 Np) in bottom sediments have shown that their activity remains high over a distance as long as 200 km downstream from the MCP [3]. Occurrence of bottom sediment layers with anomalously high activity of transuranium elements ( 239,240 Pu up to 280 Bq/kg and 241 Pu up to 1430 Bq/kg) testifies to both a high migration ability of actinoids in the river ecosystem and ongoing discharge of technogenic radionuclides from the MCP [3]. The results of radiochemical analyses for transuranium elements have been obtained previously only for bottom sediments, floodplain soil, and hydrophytes of the Yenisei River [1‐4]. No data are available for land plants in the Yenisei floodplain. By analogy with the published data on concentrations of Cm isotopes ( 243,244 Cm) in the soil polluted as a result of the Chernobyl disaster [5‐7] and taking into account the production of Cm in plutonium reactors [8], it may be expected that this element is contained in samples near the MCP. However, the data on pollution of the Yenisei floodplain with 243,244 Cm isotopes have not been available to date. Curium, a transuranium element with the highest atomic number 96 accessible in gram quantities, is formed by the successive capture of neutrons beginning from 239 Pu or heavier isotopes ( 242 Pu and 243 Am). 243 Cm and 244 Cm are rather longlived isotopes with half-lives equal to 28.5 and 18.1 yr, respectively.

Radiation Conditions in Obninsk

Monitoring data are used as a basis to examine the radiation conditions in Obninsk, including an analysis of the radioactive emissions from the Physics and Power-Engineering Institute and the Scientific-Research and Physicochemical Institute, the content of technogenic radionuclides in atmospheric air, soil, surface waters, and the components of agricultural natural ecosystems, and an estimate of the dose and radiation risk to the public. The monitoring results show relatively low levels of technogenic radionuclides in the environment, much lower than the admissable values. It is recommended that regular radiation monitoring of the content of tritium in surface and underground waters and also iodine isotopes in air near the ground at Obninsk be continued.

Comparative analysis of heavy metal and radionuclide contaminants in Black Sea green and red macroalgae

A comparative analysis about the accumulation of heavy metal, natural and technogenic radionuclides from the Black Sea environment in different Bulgarian coastline regions is made. The possibilities to use Chlorophyta and Rhodophyta algae phylums as bioindicators in marine environment are investigated. Environmental contamination in the Black Sea alga species (green and red) was studied from 1992 to 2003. Sampling sites were selected to cover the whole coastal region. Low level gamma spectrometry was used to determine the natural and technogenic nuclide concentrations. The heavy metal concentrations were measured by Atomic Absorption Spectrometry (AAS). The obtained data show that radionuclide and metal concentrations depend on the macrophyte type. Tendencies in the concentration of pollutant variations during the studied period are examined and all data give information about different macrophytic species' ability to accumulate certain elements from one and the same sampling location. All obtained results show that use of macroalgae in marine environmental monitoring reduces the need for complex studies on chemical speciation of aquatic contaminants and makes algae valuable indicators for seawater quality assessment. All data show the lack of serious pollution along the Bulgarian Black Sea coast.

Radionuclide accumulation in green and brown macroalgae at the Bulgarian Black Sea coast

The concentration of technogenic and natural radionuclides were measured in brown and green macroalgae from the Bulgarian Black Sea coast for the period 1996 and 2003 using low-level gamma spectroscopy. Mean values and concentration range for the studied species enables the comparison of the nuclide content in macroalgae showing that brown algae accumulate the studied radionuclides to a higher extent.

Migration Peculiarities of Technogenic Radionuclides in the Ecosystem of Lake Drūkšiai Under Anthropogenic Conditions in 1988–1998

Activity concentrations of 137Cs, 60Co and 54Mn were determined in bottom sediments as well as in different species of hydrophytes and fish sampled at observation stations in Lake Drūkšiai and the Ignalina Nuclear Power Plant (INPP) wastewater canals. The radiogeochemical cartography of the distribution of radionuclide activity concentrations in hydrophytes growing in the littoral zone of the lake was produced. Sources of radionuclide inputs to the lake were identified. The impact of the Ignalina NPP wastewaters on bioaccumulation processes and migration of technogenic radionuclides in lake ecosystems was evaluated. It was established that in 1988–1998 the radioecological situation of Lake Drūkšiai was not stable. In hydrophytes, fish and bottom sediments of Lake Drūkšiai the lowest activity concentration values of radionuclides were observed in 1996–1998. Hydrophytes act as a primary barrier to radionuclide movement and reflect the one-season radioecological situation in a hydroecosystem most efficiently. However, bottom sediments, as a more conservative system, better reflect the long-lasting pollution with radionuclides.

Distribution of technogenic radionuclides in alluvial sediments and among fractions of the soil in the near zone of the krasnoyarsk mining and chemical combine

Distribution of technogenic radionuclides in the landscape of the Berezovyi Isl. (Yenisei River) is studied. The observed variations in the density of radioactive contamination are associated with nonuniform lithologic composition of soil-forming rocks and also with different duration of the flooding periods. Radionuclide distribution in alluvial sediments and among fractions of the soil in the region of the Balchug settlement is analyzed, making emphasis on the contribution of the clay fraction to accumulation of radionuclides.

Comparative Assessment of the Effect of Chemical and Radiation Factors on Workers and the General Public Resulting from the Salvaging of Nuclear-Powered Submarines

The results of observations performed over many years are used to make an assessment of the degree to which the concentration of chemical and radioactive substances escaping into the environment during salvaging of nuclear-powered submarines exceeds the admissable norms for workers at the main ship-repair facilities in Russia and for the general public in the surrounding territories. It is shown that the chemical substances are a determining factor in environmental contamination. Their content in the atmosphere and sea water exceeds the admissable norms near sources, on the territory of the enterprises, and (for individual indicators) at populated points. Under these conditions, the concentration of technogenic radionuclides does not exceed the admissable norms and its damaging effect on man is hundreds and thousands of times less than that of chemicals.

Dose Loads on Hydrobionts and the Population Living in the Operational Regions of Nuclear-Powered Ships

Data accumulated over many years of observations of radioecological conditions are used to analyze the accumulation coefficients for technogenic radionuclides in hydrobionts in interior bukhtas and zalivs in the north-western part of the Sea of Japan. Attention is focused on estimating the contribution of technogenic radionuclides to the dose according to their accumulation coefficients in marine biota and to determine more accurately the contribution of natural 40K to the total dose in the operational regions of nuclear-powered ships. On individual local sections of bukhtas and zalivs, the dose due to external irradiation from technogenic radionuclides in bottom deposits exceeds the natural level (regions of radiation accident in bukhta Chazhma, near the nuclear-powered submarine with the damaged nuclear power system in bukhta Pavlovskogo). However, the total dose due to technogenic irradiation of hydrobionts as a whole remains low and falls outside the dose range at which negative effects of radiation for marine organisms are observed.

Dynamics of Air, Soil, and Water Contamination by Technogenic Radionuclides on the Territory of the USSR and Russia in 1954–2000

The dynamics of radioactive contamination of air, soil, and water, caused by atmospheric nuclear weapons tests and the Chernobyl accident, over the entire time of regular observations of the radioactive contamination of the environment on the territory of the USSR and, after 1991, in Russia is examined. The reasons for the change in the radioactive contamination of these objects in nature are analyzed.

Study of Interaction between Technogenic Radionuclides and Floodplain Soils by Partitioning via Sequential Chemical Extraction

Several fractions of technogenic radionuclides were separated from floodplain soil by sequential extraction, among them radiocolloids of 60Co and Eu nuclides associated with components of polymeric organomineral films [Fe(III) and Al(III) oxides and hydroxides] and organomineral complexes of 60Co, 137Cs, and Eu nuclides with humic compounds. Changing the oxidizing agent, H2O2, for chromic acid in the sequential extraction procedure allowed a considerable increase in the yield of the radionuclides to the solution: from 6.5 to 46% for 60Co, from 1.4 to 36% for 137Cs, and from 5.2-8.5 to 23-32% for the Eu isotopes.

Application of Fibrous Carbon Ferrocyanide Sorbents for Removing Cesium and Cobalt from Large Volumes of Sea Water

The results of comparative tests of the FN sorbent based on iron diferrocyanide with a matrix base form of fibrous carbon with known commercial and laboratory analogs are presented. The possibility of using this sorbent for selective removal of 137Cs and 60Co for large volumes of sea water and producing fast methods of analysis is examined. Information is presented on the content of technogenic radionuclides in sea water in regions of disposal of radioactive wastes in the Sea of Japan and in the region of the accident on a nuclear powered submarine. It is shown that the disposal of radioactive wastes in the Sea of Japan did not change the background radioecological conditions. The radioactivity of sea water at the epicenter of the accident in Bukhta Chazhma is a consequence of the accident and is due to 60Co; the presence of 137Cs and 90Sr is due to global fallout. The concentration of technogenic radionucldes in water and hydrobionts does not exceed admissable norms. Consumption of up to 100 kg/yr of marine products does not increase dose loads above the limit of the yearly individual lifetime risk established for the public and corresponds to a low radiation danger.

Radioecological modelling and the computer codes for calculations of doses to marine biota and man in the Arctic

Methodology and computer code DOSBIO are described for assessment of radiation doses to Arctic marine biota, and model parameters are evaluated. The algorithm and computer code DOSMAN are described for assessment of dose to man from consumption of arctic seafood products (fish, crustaceans and molluscs). The computer codes DOSBIO and DOSMAN are user-friendly tools for assessing the radioecological situation in the marine environment and analyzing the impact of technogenic radionuclides to both man and biota. The calculated values of dose conversion factors for 15 key species of arctic marine biota from exposure to 35 radionuclides are presented; dose conversion factors are given for internal and external exposure of arctic marine biota. The doses to Arctic marine biota and man were calculated from model runs, using actual environmental activity levels.

Characteristics of the Formation of the Radiation Situation on Territory of Primorskii Krai

The generalized data from 30 years of observations of the radioecological conditions on the territory of Primorskii Krai, which are determined by the natural sources of ionizing radiation, global fallout, the operation and utilization of nuclear-powered submarines in the Pacific Ocean fleet of Russia, are analyzed. Information is presented about the content and basic characteristics of the behavior of technogenic and natural radionuclides in various environmental objects. It is shown that the decommissioning and utilization of nuclear-powered submarines of the Pacific Ocean fleet do not have an inadmissable radiation effect on the public, the environment in Primorskii Krai, and the Far-East region, including also the accident involving the nuclear power system in the boat in Bukhta Chazhma in 1985.

Estimate of the reference concentration of radionuclides in seawater taking account of hygienic and radioecological criteria

The current limits on emissions of radioactive materials into the sea are analyzed. The admissable contents of technogenic radionuclides, which ensure the safety of the population and marine biota, in the marine waters of the Russian Federation are estimated, 3 tables, 23 references.

Natural radionuclides and cesium-137 content in Arabian Gulf bottom sediments

The activity concentration of natural radionuclides and137Cs in the bottom sediment samples from the coastal area of Kuwait on the Arabian Gulf have been determined by γ-ray spectrometry with REGe detector. The data for the samples are very similar to those obtained for surface soil samples in Kuwait.1 Two parent-progeny ratios for:23$Th−226Ra and228Ac−208Tl to evaluate the geochemical behavior of the radionuclides have been estimated. The existence of a serious disequilibrium between234Th and226Ra for samples taken from the vicinity of Kuwait islands and the Ras Al-Zoor area was found. The strait between the coast of Kuwait and Bubiyan island is proposed for the future sedimentation rate determinations on the basis of210Pb measurements. No serious contamination by technogenic radionuclides for this region of Arabian Gulf was observed.

Measurement of radioactive nuclides in the environment

The sources of environmental pollution by natural and technogenic radionuclides (3H, 14C, 85Kr, 129I, 90Sr, 134Cs, 137Cs, 144Ce and the transuranium elements) have been considered. Data on the content of transuranium elements in environmental samples and the distribution of plutonium in surface ecosystems are presented. In addition, data concerning the radiation dose received by the human body due to natural and technogenic sources are given. Various radiochemical and radiometric methods for the determination of radionuclides in soils, sediments, natural waters and biological materials are discussed.