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1.
This paper examines the viability of using Canoparmelia texana lichen species as a bioindicator of air pollution by radionuclides and rare earth elements (REEs) in the vicinity of a tin and lead industry. The lichen and soil samples were analyzed for uranium, thorium and REEs by instrumental neutron activation analysis. The radionuclides 226Ra, 228Ra and 210Pb were determined either by Gamma-ray spectrometry (GRS) (soils) or by radiochemical separation followed by gross alpha and beta counting using a gas flow proportional counter (lichens). The lichens samples concentrate radionuclides (on the average 25-fold higher than the background for this species) and REEs (on the average 10-fold higher), therefore they can be used as a fingerprint of contamination by the operation of the tin industry.  相似文献   

2.
137Cs and 60Co, two of the radionuclides more representative of discharges from nuclear facilities, are of interest for radiological protections because of their great mobility in biosphere and affinity with biological systems. The aim of the present work is the investigation of the possible influence of the vertical distribution of 137Cs and 60Co in soil upon their uptake by lettuce as function of plant's growth. An experiment ad hoc has been carried out in field conditions. The results show that (i) the transfer of 137Cs and 60Co from soil to lettuce is independent by their distribution in soil, (ii) the soil–plant transfer factors of 137Cs and 60Co show a similar trend vs. growth stage, (iii) the 40K transfer factor trend is different from those of anthropogenic radionuclides, and (iv) 137Cs and 60Co specific activities are about 1 Bq/kg, in the mature vegetable with soil activity from 9 to 21 kBq/m2.  相似文献   

3.
Sediments can act as a sink for contaminants in effluents from industrial and nuclear installations or when released from dumped waste. However, contaminated sediments may also act as a potential source of radionuclides and trace metals to the water phase due to remobilisation of metals as dissolved species and resuspension of particles. The marine mussel Mytilus edulis is a filter-feeding organism that via the gills is subjected to contaminants in dissolved form and from contaminants associated to suspended particles via the digestive system. In this paper the bioavailability of sediment-associated and seawater diluted Cs, Co, Cd and Zn radioactive tracers to the filtering bivalve M. edulis has been examined. The mussels were exposed to tracers diluted in ultrafiltered (<10 kDa) seawater (Low Molecular Mass form) or to tracers associated with sediment particles from the Stepovogo Fjord at Novaya Zemlya in short-term uptake experiments, followed by 1-month depuration experiments in flow-through tanks. A toxicokinetic model was fitted to the uptake and depuration data, and the obtained parameters were used to simulate the significance of the two uptake pathways at different suspended sediment loads and sediment-seawater distribution coefficients. The results of the model simulations, assuming steady state conditions, suggest that resuspended particles from contaminated sediments can be a highly significant pathway for mussels in the order 109Cd ≌ 65Zn < 134Cs < 60Co. The significance increases with higher suspended sediment load and with higher Kd. Furthermore, the experimental depuration data suggest that Cs is retained longer and Co, Cd and Zn shorter by the mussels when associated with ingested sediments, than if the metals are taken up from the low molecular mass (LMM) phase.  相似文献   

4.
Vertical distributions of 60Co are determined in soil cores obtained from a 10-ha grassland, where anaerobically digested sludge was applied by surface spraying from 1986 to 1995 on the U.S. Department of Energy's Oak Ridge Reservation. These results, along with historical application records, are used to estimate vertical-migration rates and perform a mass balance. The presence of 60Co results solely from the sludge-application process. Soil, vegetation, and surface-water samples were collected. Eleven soil cores were sectioned into 3-cm increments and analyzed by gamma-ray spectrometry. No 60Co was detected in the vegetation or water samples. The downward migration rate of 60Co in the upper 15 cm of soil ranged from 0.50 to 0.73 cm/yr. About 98%, 0.020 ± 0.011 Bq/cm2, of 60Co remained in the upper 15 cm of soil, which compared favorably with the expected 60Co activity based on historical records of 0.019 ± 0.010 Bq/cm2.  相似文献   

5.
Knowledge about propagation of radionuclides from nuclear power plants (NPPs) along the course of a river is of great interest in radioecological assessments. By use of a model previously applied in the cases of the Rhine and Weser Rivers, the distribution of various radionuclides released into the Moselle from the NPP Cattenom at normal operation is described with 58Co, 60Co and 110mAg as tracers. A comparison of field measurements with calculated values revealed that the radionuclide concentrations in suspended matter and nuclide loads calculated from emission rates agreed with the measured data by a factor of less than two on average.Radionuclide concentrations and loads along the river course decrease mainly due to deposition of particulate radioactive matter in high-sedimentation areas and due to dilution with uncontaminated material from tributaries and other sources. The rate constants of both processes were evaluated, and the mean range of suspended radioactive particles in the Moselle was estimated. Moreover, this study showed anew that suspended matter has to be considered as the main carrier by which the radionuclides from NPPs may be transported over long distances.  相似文献   

6.
Accumulation and clearance of 134Cs and 60Co by the Baltic bivalve Macoma baltica were experimentally investigated in a laboratory microcosmos. The nuclides were added to the water and the activities in bivalve flesh, shell, feces and sediment were determined at regular intervals. The uptake was quite rapid, 40% (Cs) and 55% (Co) of the final steady state values being attained after 24 h. The subsequent releases were also rapid, 50% (Cs) and 40% (Co), of the accumulated activity being lost within 6 days. The experiments demonstrated that the major intake route following short-term releases of activity will be from the water column and that the close relationship between activity in water and organism can thus be used for predictive purposes without the complication of radionuclide uptake from contaminated sediments. However, for longer periods, the subsequent intake of sediments will generate a significant exposure pathway for this deposit-feeding bivalve.  相似文献   

7.
The effect of the spatial variability of Kd on calculations of contaminant travel time in the vadose zone was determined. Depth discrete measurements of Kd were made for a suite of radionuclides (109Cd, 57Co, 60Co, 85Sr, 137Cs, and 88Y) utilizing a sediment core from the E-Area at the Savannah River Site. The Kd’s were ordered as 85Sr2+ < 137Cs+ < 109Cd2+ < 57Co2+ = 60Co2+ << 88Y3+ and the values generally fell below or near the lowest quartile of values reported in the literature. Correlations were generally weak between soil properties and Kd values. Most importantly, all of the Kd distributions could be reasonably approximated as log-normal. Deterministic and stochastic calculations of contaminant travel time to the water table were made. The deterministic calculations were based on each of three conceptual models of the vadose zone: complete stratification (17 strata, each with a different Kd), two strata (two sections of the vadose zone, each characterized by a single, average Kd), and unstratified (a single zone with an average Kd). Stochastic calculations were based on log-normal fits to the Kd data. The two strata model generally yielded travel times 2× greater than those in the completely stratified model. The unstratified model yielded travel times that were between 3 and 5 times greater than the completely stratified model. The stochastic mean travel times were comparable to those of the two strata model.  相似文献   

8.
The dry deposition of various radionuclides emanating from the plume from the Chernobyl reactor accident was measured at two locations in southern Sweden at the beginning of May, 1986. Samples of Fucus, taken at or near these locations, were also analysed. No precipitation had fallen during the time between the accident and the time of sampling. The ratios between activity concentrations in Fucus and dry depositions on the water surface have been calculated. For any specific radionuclide, this ratio was found to be the same at the two locations, after differences in salinity and in uptake between F. vesiculosus and F. serratus had been taken into account.  相似文献   

9.
Plutonium and americium have been measured in surface waters of the Greenland and Barents Seas and in the northern North Sea from 1980 through 1984. Measurements in water and biota, Fucus, Mytilus and Patella, were carried out in North-English and Scottish waters in 1982 and Fucus samples were collected from the Irish coast in 1983. Fallout is found to dominate as a source of 239+240Pu north of latitude 65°N, while for 238Pu a substantial fraction originates from European nuclear fuel reprocessing facilities. The 238Pu/239+240Pu isotope ratio provides clear evidence of the transport of effluent plutonium from the latter to Spitsbergen waters. Fallout plutonium in Arctic waters has a residence time of the order of several years, while for Pu from Sellafield we estimate mean residence times of 11–15 months in Scottish waters and, tentatively, 1·5-3 y during transport from the North Channel (north of the Irish Sea) to Spitsbergen. 241Am found in Arctic waters probably originates from the decay of fallout 241Pu and, like Pu, tentatively has a residence time of the order of several years. Americium from Sellafield has an estimated mean residence time of 4–6 months in Scottish waters.  相似文献   

10.
Tests using reconstituted samples have been performed to assess the diffusive transport of 137Cs and 60Co through natural regolith materials from a region in South Australia being considered for a radioactive waste repository. A double diffusion cell apparatus made of polycarbonate resin was developed to estimate the effective diffusion (De) and sorption coefficients (Kd) that allowed large withdrawals from the source and collector cells and has enabled tests with low concentrations of radioactivity. An alternative to porous stainless steel filter plates has also been used to reduce uncertainty in test interpretation. Analysis of the transient data used a staged method of the Laplace transform to take into consideration the volume of the samples withdrawn from the apparatus during testing. At test completion samples were cut into slices and analysed for radionuclide concentration. Data obtained from the sliced samples confirmed that both numerical and experimental data produced acceptable mass balance. The De values obtained in this study were of the order of 10−6 cm2 s−1 for both species, higher than previously published data. The Kd values from the diffusion and batch sorption tests were in reasonable agreement for 137Cs, but an order of magnitude different for 60Co. The sorption of the latter radionuclide was strongly pH dependent, and this dependency during diffusion tests would benefit from further investigation.  相似文献   

11.
During the JCO-accident in Tokai-mura in 1999, the surrounding village was irradiated by an uncontrolled neutron flux. At some locations in that village, the thermal neutron flux was determined retrospectively by measurement of the very low activity of 51Cr and 60Co in stainless-steel spoons using γ-ray spectrometry in underground laboratories. Activities determined in the HADES underground facility are presented here, together with calibrations performed using a well-defined thermal neutron flux to directly estimate the fluence of thermal neutrons independent of most assumptions. The results show measurable 51Cr in three samples and 60Co in four samples taken from locations at distances of up to 430 m from the accident location despite the elapse of 4 half-lives of 51Cr before measurement. Effects of air transport of the samples were considered and shown to be negligible.  相似文献   

12.
Radium isotopes have been used extensively to trace the movement of groundwater as well as oceanic water masses, but these radionuclides (and their daughters) are also useful chronometers for the determination of the time scales of other Earth and environmental processes. The purpose of this overview is to present the application of Ra and Ra daughters in the dating of carbonates. We show that the choice of dating method (decay of excess radionuclide or ingrowth of daughter) depends strongly on the parent/daughter activity ratios in the water in which the carbonate was precipitated. Thus freshly precipitated carbonates uniformly show excesses of 226Ra relative to its parent 230Th, and 226Ra decay can provide ages of carbonates over Holocene time scales. In contrast, carbonates are precipitated in waters of greatly varying 210Pb/226Ra. Corals, deep-sea hydrothermal vent clams and the shelled cephalopod Nautilus live in waters with significant dissolved 210Pb and all show excesses of 210Pb in their carbonate. Bivalve molluscs from nearshore and coastal waters, and carbonates deposited from groundwater environments (e.g. travertines) in which 210Pb is efficiently scavenged from solution, show deficiencies of 210Pb relative to 226Ra. In contrast, fish otoliths strongly discriminate against 210Pb regardless of the environment in which the fish lives. Deficiencies of 228Th relative to 228Ra are common in all carbonates. Useful time ranges for the 210Pb/226Ra and 228Th/228Ra chronometers are ∼100 y and ∼10 y, respectively.  相似文献   

13.
Various sources contribute to the radioactive contamination of the Moselle River, among which the French NPP Cattenom with four units of 1300 M We represents the most important. Appropriate operational precautions were taken in order to monitor the nuclide transfer on different pathways under normal and accidental conditions and the effectiveness of these measures has been tested using natural (214Pb/214Bi, 7Be, 40K) and artificial radionuclides. (3H, 58Co, 60Co, 131I, 137Cs) as tracers. Measurements of suspended matter have revealed that the inputs of natural nuclides exceed the discharges of the NPP Cattenom. In 1992 the annual loads of 7Be and 40K in suspended matter at Palzem amounted to 21 and 130 GBq year−1, whereas the emission rates of 60Co and 137Cs were about 2.6 and 1.0 GBq year−1. The total nuclide load of 137Cs at Palzem reached 6.2 GBq year−1, which is about six times the quantity emitted by the NPP Cattenom in the same year. This excess is due to the accident at Chernobyl and to a lesser extent to prior atmospheric weapons tests.  相似文献   

14.
The transfer of the radionuclide 60Co from feed to milk, meat and the organs of a cow and its incorporation into vitamin B12 were studied in order to determine the transfer coefficient of 60Co into vitamin B12 in cattle. Upper limits of transfer coefficients for 60Co organically complexed into vitamin B12 were determined to be 6·0 × 10−5 days/litre in milk and 3·9 × 10−5 days/kg in meat, based on values measured after 140 days in bovine liver.  相似文献   

15.
Freshwater mussels, Velesunio angasi, along Magela Creek in Australia’s Northern Territory were examined to study radionuclide activities in mussel flesh and to investigate whether the Ranger Uranium mine is contributing to the radium loads in mussels downstream of the mine. Radium loads in mussels of the same age were highest in Bowerbird Billabong, located 20 km upstream of the mine site. Variations in the ratio of [Ra]:[Ca] in filtered water at the sampling sites accounted for the variations found in mussel radium loads with natural increases in calcium (Ca) in surface waters in a downstream gradient along the Magela Creek catchment gradually reducing radium uptake in mussels. At Mudginberri Billabong, 12 km downstream of the mine, concentration factors for radium have not significantly changed over the past 25 years since the mine commenced operations and this, coupled with a gradual decrease of the 228Ra/226Ra activity ratios observed along the catchment, indicates that the 226Ra accumulated in mussels is of natural rather than mine origin. The 228Th/228Ra ratio has been used to model radium uptake and a radium biological half-life in mussels of approximately 13 years has been determined. The long biological half-life and the low Ca concentrations in the water account for the high radium concentration factor of 30,000-60,000 measured in mussels from the Magela Creek catchment.  相似文献   

16.
The evaluation and assessment of monitoring data generated over a period of 1983-2007 (25 years) of a nuclear facility is presented. Time trends of particulate radioactivity, correlation between 137Cs in discharge canal seawater and station discharged activity and correlation of 137Cs, 60Co, and 131I in marine species such as sponge and Nerita (gastropod) and corresponding discharged activity are discussed. The concentration of 137Cs and 131I in seawater versus biota are discussed. A good correlation between 137Cs in seawater and 137Cs in liquid waste discharged was observed (R2 = 0.8, p < 0.001). Similarly, correlation was good for Nerita and discharged concentration of 137Cs, 131I and 60Co (R2 = 0.55-0.73 and p < 0.001). The measurements over the years indicated that there is no accumulation of radionuclides in either the terrestrial or aquatic environments. The mean 137Cs decreased from the pre-operational levels: 7.0-3.6 Bq kg−1 in soil, 0.91-0.016 Bq L−1 in milk and 0.28-0.036 Bq kg−1 in vegetation. Similarly, the mean 90Sr in these matrixes decreased from 3.9 to 0.26 Bq kg−1; 0.37-0.011 Bq L−1 and 0.34-0.022 Bq kg−1 respectively. Cesium-137 of about 700 μBq m−3 was measured in the air filter disks during 1986 and there was a decrease of three orders of magnitude in concentration over the 25 years. The evaluation of environmental data indicated that the radionuclide concentrations and potential impacts, in terms of effective dose to the members of public, have significantly reduced since 1969.  相似文献   

17.
The amounts of cobalt-60 and caesium-137 bound in the sediment in a bay off the Studsvik research station were determined. Of the cumulative released activity during 22 years, 19% of 60Co and 1.8% of 137Cs were found in the sediments within an area of 23 km2. The rate of input through sedimentation and the loss rate through physical decay were of the same order in 1981 and were close to steady state for 60Co while for 137Cs they had only reached 30% of that level. The sedimentation coefficients calculated for the bay were 6·5 year−1 for 60Co and 0·49 year−1 for 137Cs, higher values than many published previously. Cobalt-60 seemed to precipitate close to the outlet and to migrate near the bottom as bed-load.  相似文献   

18.
Around 130 publications reporting studies on radionuclide transfer to freshwater biota species conducted in the former USSR were reviewed to provide the concentration ratio values. None of these studies were available up to now in the English language reviews or publications. The values derived have been compared with the CR values used for freshwater systems in the International reviews. For some radionuclides reviewed in this paper, the data are in good agreement with the mean CR values presented earlier, however for some of them, in particular, for 241Am (bivalve molluscs, gastropods and pelagic fish), 60Co (gastropods, benthic fish and insect larvae), 90Sr and 137Cs (benthic fish and zooplankton), the mean values given here are substantially different from those presented earlier. The data reported in this paper for thirty five radionuclides and eleven groups of freshwater species markedly improve the extent of available data for evaluation of radiation impact on freshwater species.  相似文献   

19.
Modified tannins are used as deflocculant additives in the formulation of water-based drilling fluids (WBDF) for drilling operations in any scenario. Due to their high heavy metals content, these additives are toxic and hazardous for any environmental scenario. Deflocculant efficiency of unmodified tannins (UDT) extracted from fruit pods of “dividivi” (Caesalpinia coriaria) as an additive for WBDF was assessed. Raw materials for UDT elaboration come from the rural and sustainable exploitation of natural occurring dividivi trees, growing in dry tropical forests in Anzoátegui state (Orinoco Oil Belt, eastern Venezuela). The tannins extract, in the form of dividivi fruit powder, contains 47.0 % of total tannins (hydrolyzable tannins plus condensed tannins), of which 67.4 % corresponds to hydrolyzable tannins. Dividivi tannins in WBDF showed nine (9) times deflocculant efficiency than heavy metals commercial modified tannins. Moreover, commercial modified tannins do not improve their deflocculant efficiency with increased tannin content. Ecotoxicological studies were carried out for WBDF formulations with UDT, using freshwater microalgae Scenedesmus dimorphus as chronic toxicity bioindicator. Toxicity bioassays performed with these microalgae did not show significant effects on its population growth. The EC50 values resulted in over 100,000 mg L?1, and these formulations were therefore considered non-toxic. Values of LC50 obtained this time with Poecilia reticulata, as acute toxicity bioindicator are around 100,000 mg L?1, with no significant effects on population mortality. Thus, WBDF formulated with UDT can be considered non-toxic formulations for populations of this freshwater fish. From the social perspective, the use of UDT in WBDF fosters organized communities economical activities based on the maintenance of a sustainable supply chain for processing fruits in a quantity enough to obtain three thousand seven hundred fifty kilograms (3750 Kg). The UDT so obtained was used as deflocculant in four (4) oil wells producing excellent performance and relevant savings compared with commercial modified tannin.  相似文献   

20.
Accumulation and clearance of 134Cs and 60Co by the Baltic bivalve Macoma baltica were experimentally investigated in a laboratory microcosmos. The nuclides were added to the water and the activities in bivalve flesh, shell, feces and sediment were determined at regular intervals. The uptake was quite rapid, 40% (Cs) and 55% (Co) of the final steady state values being attained after 24 h. The subsequent releases were also rapid, 50% (Cs) and 40% (Co), of the accumulated activity being lost within 6 days. The experiments demonstrated that the major intake route following short-term releases of activity will be from the water column and that the close relationship between activity in water and organism can thus be used for predictive purposes without the complication of radionuclide uptake from contaminated sediments. However, for longer periods, the subsequent intake of sediments will generate a significant exposure pathway for this deposit-feeding bivalve.  相似文献   

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