Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RADIOACTIVE FALLOUT”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,405 records · Page 78Linked to original sources
PubMed2005

238Pu and 239+240Pu inventory and distribution through the lower Rhone valley terrestrial environment (Southern France).

Because of atmospheric global fallout due to thermonuclear tests performed between 1945 and 1980 and to the American SNAP 9A satellite explosion in 1964, plutonium's long-lived alpha emitter isotopes ((238)Pu, (239)Pu and (240)Pu) can be found everywhere in the environment. In the soils of the lower Rhone valley, over a surface area of approximately 11,000 km(2), existing results allow estimation of the total inventory resulting from this origin of 551 GBq as regards these radionuclides. The Marcoule Nuclear Reprocessing Plant (NRP) has been releasing (238)Pu and (239+240)Pu into the environment for over 40 years in the region and is as such a second likely source for Pu input. This article gives a global review of plutonium distribution in this particular region. It is shown that releases from Marcoule, although accounting for less than 2% of the total Pu inputs into the terrestrial environment, are responsible for localised and measurable Pu enrichments close to the facility (+2.8 GBq), and in the Rhone delta where sediments from the river settled during the past floods (+0.1 GBq). Irrigating with water from the Rhone River also allowed the transfer of approximately 3.8 GBq of (238)Pu and (239+240)Pu to the soils for the whole 1960-1998 period. These inputs, distributed over wide irrigated surface areas, do not induce significant increases of soil Pu-activity levels. In a second section, this study confirms that most of the plutonium existing in the terrestrial environment is accumulated in the soil. Less than 0.1% of the activities exist currently in the plant compartments, and the flows exported by agricultural productions are very low, although we are interested here in a French region where agriculture prevails.

Air Pollutants, Radioactive↗
PubMed2006

Using total beta-activity measurements in milk to derive thyroid doses from Chernobyl fallout.

Following the Chernobyl accident, more than 200 childhood thyroid cancer cases have been observed in Brest Oblast of Belarus in territories slightly contaminated with 137Cs, but with suspected relatively high 131I fallout. The most helpful measurements available that can be used to estimate thyroid doses for the population of Brest Oblast are the total beta-activity measurements in cow's milk performed using DP-100 device within a few weeks after the accident. The 131I concentrations in milk were derived from the total beta-activity measurements on the basis of (1) a radioecological model used to estimate the variation with time of the radionuclide composition in milk and (2) the determination of the calibration factors of the DP-100 device for the most important radionuclides present in milk. As a result, 131I concentrations in milk were reconstructed for territories with different levels of 137Cs deposition. A non-linear dependence of the 131I concentration in milk on the 137Cs deposition density was obtained; it was used to estimate the thyroid doses from the consumption of 131I-contaminated cow's milk by the population of Brest Oblast. The average individual thyroid doses have been estimated to be 0.15, 0.18, 0.12, 0.06, 0.04 and 0.03 Gy for newborn, children aged 1, 5, 10 and 15 y and adults, respectively. The collective thyroid dose for the entire population of Brest Oblast is estimated to be 64,500 man Gy, the contribution from the adult population being about one half of the total. The methodology that is described could be applied in the framework of epidemiological studies of the relationship between radiation exposure to the thyroid gland and thyroid cancer in areas where numerous total beta-activity measurements in cow's milk were performed within a few weeks after the accident.

Adolescent↗
PubMed2003

Deposition and distribution of Chernobyl fallout fission products and actinides in a Russian soil profile.

In this article the distribution of fission products and actinides in a soil profile from Novo Bobovicky in Russia, which was contaminated due to the Chernobyl nuclear power plant accident, is described. The ground deposition of long-lived fission products determined by gamma-spectrometry was (recalculated to 26 April 1986) 1600 kBq (137)Cs/m(2), 900 kBq (134)Cs/m(2) and 60 kBq (125)Sb/m(2). Of these radionuclides (137)Cs shows the dominating activity at the present time. After 6.5 years 90% of the Cs and Sb activity was contained in the upper 4 cm. A (239,240)Pu ground deposition of 77.4+/-8.0 Bq/m(2) was determined by alpha-spectrometry. The (238)Pu/(239,240)Pu activity ratio of 0.30+/-0.03 and (241)Pu/(239,240)Pu activity ratio of 115+/-14 (in 1986) measured in the soil profile, indicates that the analysed Pu originates mainly from the Chernobyl accident. The average (234)U/(238)U activity ratio of 1.06+/-0.29 indicates that the uranium in this soil is dominated by naturally occurring uranium. The alpha- and beta-autoradiography revealed that the activity is mainly present in particulate form. It could further be observed that the spots containing alpha- or beta-activity originated from different particles. A comparison of alpha-autoradiography with the bulk Pu and Am activity showed that 92% of the alpha-activity was present as clearly detectable alpha-spots. The beta-active particles, located by beta-autoradiography were correlated with gamma-spectrometric measurements and contained only (137)Cs. These hot spots ranged from 0.02 to 0.15 Bq.It could be concluded that the vertical transport of (137)Cs and fuel fragments occurs mainly by movement of particles through the soil. It could also be concluded that the fuel fragments found, in this soil were depleted in respect to Cs, Sb and Eu. Comparison of the analysed (238)Pu/(239,240)Pu, (241)Pu/(239,240)Pu and (241)Am/(239,240)Pu ratios with the ratios calculated with ORIGEN-S code gave an estimate of the average burn-up of the fuel particles to be in the range of 11-12 GWd/tU. The results presented in this article are valid for this single soil profile and should not be generalised unless validated in a more rigorous study of a larger number of soil profiles.

Actinoid Series Elements↗
PubMed2005

Long-term stability of decontamination effect in recreational areas near the town Novozybkov, Bryansk Region, Russia.

In 1995 and 1997, experimental decontamination campaigns were carried out in two recreational areas, Novie Bobovichi and Guta-Muravinka, near the town of Novozybkov, Bryansk Region, Russia. These areas were strongly affected by the Chernobyl fallout in 1986. In order to examine the long-term stability of the clean-up procedures, a programme has been carried out to continuously monitor the radiological situation in and around the decontaminated areas. This follow-up program consists of regular (1-3 times per year) measurements of absorbed gamma-dose rate in air (DR) at reference indoor and outdoor locations, repeated DR measurements on a grid, and gamma-spectrometric analysis of soil and other environmental samples. Very similar dynamics of the Chernobyl-related DR, mostly attributed to radiocaesium decay, were found in all the locations. For the period under study (September 1995-May 2003), the half-lives (years) for the reduction in radiocaesium-dependent DR contribution due to contaminant migration (in the following termed 'DRM half-lives') were, respectively, 52+/-26, 57+/-23, 43+/-21, 46+/-15, and 80+/-56 for the following locations: untreated outdoors, treated outdoors, untreated indoors, treated indoors, and undisturbed forest-grassland plots outside the recreational areas. These relatively high values of the current DRM half-lives correspond very well with the results of soil core analyses, which showed no time-dependent changes in the mean mass depths of the (137)Cs distribution, neither at treated nor at undisturbed plots. The following signs of natural restoration of the disturbed forest-meadow ecosystems have been observed at treated areas: formation of a new litter layer, development of grassy spots, mushroom growths and new generations of pines and birches. The levels of the (137)Cs content in grass and mushrooms from treated plots were one or two orders of magnitude lower, than those registered in the samples from untreated areas. The follow-up study demonstrates the long-term stability and efficiency of the decontamination carried out. There are two main reasons for the sustainment of the effects: careful implementation of adequate clean-up procedures and natural strong fixation of radiocaesium in soil-associated matrices of the ecosystems.

Agaricales↗
PubMed1992

Mathematical modeling of radionuclide dispersion in the Pripyat-Dnieper aquatic system after the Chernobyl accident.

The Chernobyl accident heavily contaminated the largest aquatic system in the Ukraine, requiring the development of a model-based decision support system in the field of aquatic radioecology. The main objectives of the system were to simulate and predict radionuclide dispersion in the Pripyat-Dnieper River-reservoir system, assess the effectiveness of special hydraulic countermeasures designed to decrease the rate of radionuclide dispersion in the water bodies, and support the Dnieper reservoirs' management operations. A hierarchy of mathematical models was developed. A two-dimensional (2-D) vertical-longitudinal model, a 2-D lateral-longitudinal model, a one-dimensional (1-D) channel model and a box-type model are briefly presented. These models describe the main features of radionuclide dispersion, including the processes governing radionuclide-sediment interactions. Examples of the models' applications are presented to show the peculiarities of radionuclide dispersion in this aquatic system.

Accidents↗
PubMed2005

Ecological lessons from the Chernobyl accident.

The Chernobyl nuclear accident in 1986 not only caused serious ecological problems in both the Ukraine and Belarus, which continue to the present day, but also contaminated a large part of the higher latitudes of the northern hemisphere. In this paper an overview is given of the latter problems in upland UK, where ecological problems still remain some 17 years after initial contamination. Following deposition of radiocaesium and radioiodine in May 1986, measurements of radioactivity in grass and soil indicated a rapidly declining problem as the radioiodine decayed and the radiocaesium became immobilised by attachment to clay particles. However, these studies, as well as the advice received by the Ministry of Agriculture, Fisheries and Food, were based on lowland agricultural soils, with high clay and low organic matter contents. The behaviour of radiocaesium in upland UK turned out to be dominated by high and persistent levels of mobility and bioavailability. This resulted in the free passage of radiocaesium through the food chain and into sheep. Consequently the Ministry banned the sale and movement of sheep over large areas of upland Britain, with bans remaining on some farms to the present day. Present day predictions suggest that these bans will continue in some cases for some years to come. The causes of radiocaesium mobility in upland areas have subsequently been the subject of intense investigation centred around vegetation and, in particular, soil characteristics. Soil types were identified which were particularly vulnerable in this respect and, where these coincided with high levels of deposition, sheep bans tended to be imposed. While much of the earlier work suggested that a low clay content was the main reason for continuing mobility, a very high organic matter content is now also believed to play a major role, this being a characteristic of wet and acidic upland UK soils. The overall message from this affair is the importance of a fundamental understanding of biogeochemical pathways in different ecosystems when attempting to predict the impacts of large-scale contamination.

Animals↗
PubMed2005

Radiocaesium soil-to-wood transfer in commercial willow short rotation coppice on contaminated farm land.

The feasibility of willow short rotation coppice (SRC) for energy production as a revaluation tool for severely radiocaesium-contaminated land was studied. The effects of crop age, clone and soil type on the radiocaesium levels in the wood were assessed following sampling in 14 existing willow SRC fields, planted on radiocaesium-contaminated land in Sweden following Chernobyl deposition. There was only one plot where willow stands of different maturity (R6S2 and R5S4: R, root age and S, shoot age) and clone (Rapp and L78183 both of age category R5S4) were sampled and no significant differences were found. The soils differed among others in clay fraction (3-34%), radiocaesium interception potential (515-6884 meq kg(-1)), soil solution K (0.09-0.95 mM), exchangeable K (0.58-5.77 meq kg(-1)) and cation exchange capacity (31-250 meq kg(-1)). The soil-to-wood transfer factor (TF) of radiocaesium differed significantly between soil types. The TF recorded was generally small (0.00086-0.016 kg kg(-1)), except for willows established on sandy soil (0.19-0.46 kg kg(-1)). Apart from the weak yet significant exponential correlation between the Cs-TF and the solid/liquid distribution coefficient (R2 = 0.54) or the radiocaesium interception potential, RIP (R2 = 0.66), no single significant correlations between soil characteristics and TF were found. The wood-soil solution 137Cs concentration factor (CF) was significantly related to the potassium concentration in the soil solution. A different relation was, however, found between the sandy Trödje soils (CF = 1078.8 x m(K)(-1.83), R2 = 0.99) and the other soils (CF = 35.75 x m(K)(-0.61), R2 =0.61). Differences in the ageing rate of radiocaesium in the soil (hypothesised fraction of bioavailable caesium subjected to fast ageing for Trödje soils only 1% compared to other soils), exchangeable soil K (0.8-1.8 meq kg(-1) for Trödje soils and 1.5-5.8 meq kg(-1) for the other soils) and the ammonium concentration in the soil solution (0.09-0.31 mM NH4+ for the Trödje soils compared to 0.003-0.11 mM NH4+ for the other soils) are put forward as potential factors explaining the higher CF and TF observed for the Trödje soils. Though from the dataset available it was not possible to unequivocally predict the Cs-soil-to-wood-transfer, the generally low TFs observed point to the particular suitability for establishment of SRC on radiocaesium-contaminated land.

Biodegradation, Environmental↗
PubMed2005

The EXPURT model for calculating external gamma doses from deposited material in inhabited areas.

EXPURT, NRPB's model for calculating external gamma doses in inhabited areas, was originally developed in the mid-1980s. Deposition on surfaces in the area, the subsequent transfer of material between different surfaces or its removal from the system, and dose rates in various locations from material on the different surfaces are modelled. The model has been updated to take account of more recent experimental data on the transfer rates between surfaces and to make it more flexible for use in assessing dose rates following an accidental release. EXPURT is a compartmental model and models the transfer of material between the surfaces using a set of first order differential equations. It enables the impact of the decontamination of surfaces on doses and dose rates to be explored. The paper describes the EXPURT model and presents some preliminary results obtained using it.

Air Pollutants, Radioactive↗
PubMed2005

Transfer of 137Cs to rice plants from various paddy soils contaminated under flooded conditions at different growth stages.

Soil blocks from 18 paddy fields around three Korean nuclear power plant sites were put into lysimeters. Greenhouse experiments were carried out to investigate the (137)Cs transfer from these paddy soils to rice plants for its deposition at different growth stages. A solution of (137)Cs was applied to the flooded lysimeters at 2-3 different stages. The applied (137)Cs was mixed with the topsoil only at the pre-transplanting application. The transfer was quantified with a transfer factor based on the unit-area deposition (TF(a), m(2)kg(-1)-dry). The TF(a) in the pre-transplanting application showed a remarkable variation with the soils. However, the differences in the mean values among the study sites were not statistically significant. The straw TF(a) was 2-3 times higher than the corresponding seed value. The early-tillering stage and booting stage applications resulted in a higher transfer than the pre-transplanting application by factors of, on an average, 2 and 16 for the straws, and 3 and 25 for the hulled seeds, respectively. The (137)Cs transfer was found to correlate negatively with the soil pH and positively with the organic matter content. Based on the present results, the representative (137)Cs TF(a) values for the rice are proposed for use in the whole of Korea for the deposition at three different growth stages.

Cesium Radioisotopes↗
PubMed2002

Survey of natural and anthropogenic radioactivity in environmental samples from Yugoslavia.

The radioactivity of 238U, 226Ra, 232Th, 40K and 137Cs in sediments, soil, turf and honey from Serbia and Kosovo (Yugoslavia) was measured using gamma and alpha spectrometry in order to estimate the radiation hazard from natural and man-made sources, as well as to compile a database for radioactivity levels in those regions. One sample, collected in the vicinity of a "depleted uranium" (DU) shell of the recent Balkan war, revealed a high 238U activity and a non-natural 235U/238U activity ratio, confirming therefore its anthropogenic origin. However, some other soil samples coming from characteristic DU craters did not show any characteristic level of radioactivity. The other sediment and turf samples taken all around the country show low radioactivity levels for all the isotopes here considered. With the aim of obtaining some indication about radioactivity migration in the food chain, several honey samples have been examined too. All samples show very low radioactivity content, often indistinguishable from natural background.

Environmental Monitoring↗
PubMed2003

An inventory of long-lived radionuclides residual from underground nuclear testing at the Nevada test site, 1951-1992.

An inventory of long-lived radionuclides produced by 828 underground nuclear tests conducted at the Nevada test site (NTS) from 1951 to 1992 includes residual tritium, fission products, actinides, and activation products. Recently, the US Department of Energy approved the declassification of the NTS radionuclide inventory by principal geographic test centers. This permits unclassified publication of radionuclide totals for the Yucca Flat, Pahute Mesa-Area 19, Pahute Mesa-Area 20, Frenchman Flat, and Rainier Mesa/Shoshone Mountain testing locations. Activities are reported as of September 23, 1992, the date of the last underground nuclear test conducted at the NTS, and September 23, 2492, after 500 years of radioactive decay. The availability of these data affords an opportunity for the analysis of the radiologic source term within the boundaries of local hydrogeologic units and provides insight to where radionuclides are sited relative to potential exposure pathways.

Forecasting↗
PubMed2003

Use of (137)Cs technique for soil erosion study in the agricultural region of Casablanca in Morocco.

Accelerated erosion and soil degradation currently cause serious problems to the Oued El Maleh basin (Morocco). Furthermore, there is still only limited information on rates of soil loss for optimising strategies for soil conservation. In the present study we have used the (137)Cs technique to assess the soil erosion rates on an agricultural land in Oued el Maleh basin near Casablanca (Morocco). A small representative agricultural field was selected to investigate the soil degradation required by soil managers in this region. The transect approach was applied for sampling to identify the spatial redistribution of (137)Cs. The spatial variability of (137)Cs inventory has provided evidence of the importance of tillage process and the human effects on the redistribution of (137)Cs. The mean (137)Cs inventory was found about 842 Bq m(-2), this value corresponds to an erosion rate of 82 tha(-1) yr(-1) by applying simplified mass balance model in a preliminary estimation. When data on site characteristics were available, the refined mass balance model was applied to highlight the contribution of tillage effect in soil redistribution. The erosion rate was estimated about 50 tha(-1) yr(-1). The aspects related to the sampling procedures and the models for calculation of erosion rates are discussed.

Agriculture↗
PubMed2003

137Cs in marine samples from the Brazilian southeastern coastal region.

The present work presents the results of (137)Cs concentration in seawater, fish and sediments samples collect in 11 sampling points, crossing the Brazilian Southeastern coastal region, from Vitória (ES) to Santos (SP), on a routine basis from 1997 to 2002. This monitoring program was carried out by the Instituto de Radioproteção e Dosimetria (IRD/CNEN/MCT), in cooperation with the Instituto de Estudos do Mar Almirante Paulo Moreira (IEAPM/Brazilian Navy), aiming at determining artificial radionuclides in marine samples. Additionally to the (137)Cs results, (90)Sr concentrations in fish samples from 1998 to 2002 are also reported. The (137)Cs in seawater follows a lognormal distribution, with a geometric mean of 1.8 Bq m(-3) and a geometric standard deviation of 1.4 (n=54), decay corrected to June/2002. For (137)Cs levels in fish samples a geometric mean of 0.19 Bq kg(-1) and a geometric standard deviation of 2.9 (n=39), decay corrected to June/2002, with a range of 0.03 to 1.7 Bq kg(-1), were obtained. Based on the (137)Cs mean concentration in fish as well as in seawater, a transfer factor of 1 x 10(2) was calculated, which is quite in agreement with the recommended value found in the Safety Report Serie 19.

Animals↗
PubMed1988

The environmental behavior of 131I in northwestern Greece following the nuclear reactor accident at Chernobyl.

A three compartment (air-grass-milk) milk contamination model for 131I has been applied to atmospheric, grass and milk data, following the April 1986 nuclear accident at Chernobyl. Samples of ovine and bovine milk collected daily by a large dairy company in Ioannina (northwestern Greece), throughout the month of May 1986 have been employed. The contamination impulse in the area, which provides the input to the model, has been approximated by a first order gamma-variate curve. Transfer rates and decay constants have been extracted by fitting predictions of the model independently to each set of data (air, grass and milk). All model parameters obtained from more than one set of data show remarkable consistency. These parameters are used to calculate the transfer coefficients fm for the transport of radioiodine at equilibrium for sheep and cows. The results are also employed for the extraction of radiation dose estimates sustained through ingestion and inhalation by the population in the area.

Accidents↗