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1.
137Cs speciation and distribution in the components of the biogeocenosis of the Yenisei River floodplain such as soils, rhizosphere, and plants were studied. The study was carried out near zones of influence by the Krasnoyarsk Mining and Chemical Combine (MCC). Variation in the specific activity of radionuclides with increasing distance from the pollution source and its ratio in the soil and rhizosphere and distribution in the plant body were studied. A variety of occurrence forms of 137Cs, including mobile ones, was revealed. The amount of 137Cs leached from plants during flooding was calculated from the results of laboratory experiments.  相似文献   

2.
Long-term data series of ice cover on lakes and river temperatures from the mountain areas of Norway are lacking. The present study analyses the last four decades of ice data from the subalpine lake, Øvre Heimdalsvatn, and water temperature data from its outlet river, Hinøgla. These data are compared to water temperature data from three neighbouring, quite different locations, the glacier-fed rivers Leirungsåi and Sjoa, and the alpine lake, Bessvatn. The study also examines the air temperature/river temperature relationships, and the air temperature/ice freeze-up and break-up dates. During the months of July, August and September, the water temperature in Hinøgla was well correlated to the air temperature, but the correlation was poor in the remaining months due to the ice cover and snow conditions. A significant temperature increase of 2–3°C has been observed in Hinøgla in the months August–October since 1984. There were only minor changes in the duration of the ice cover season during the last 40 years, but a delay of 9 days was found in the freeze-up date and a delay of 6 days in the break-up date, although the latter was not significant.  相似文献   

3.
Age-dependent accumulation of 137Cs in the muscles and bodies of the pike Esox lucius (aged two to seven years) inhabiting a section of the Yenisei River polluted with artificial radionuclides has been studied. The content of 137Cs in muscles varied from 0.5 to 7.0 Bq/kg of fresh weight. The maximum content of the radionuclide has been found in juveniles. The content of 137Cs in pike muscles and body decreased considerably with age. The high content of 137Cs in the muscles of juveniles is probably a consequence of their higher intensity of feeding as compared to older individuals, which is due to the intense growth of juveniles.  相似文献   

4.
The assessment doses due to ingestion of 137Cs and 90Sr for the population suffering from the Chernobyl accident was performed on the basis of the new mechanistic ecological model for assessment of radiological consequences of agricultural lands contamination (EMARC). The EMARC model allows estimation of internal doses based on ecological factors influencing the contamination of foodstuff, for the post-accidental years in the countries of the former Soviet Union. The EMARC model allows estimation of all quantities required in radiation hygiene practice. For example, the proposed analytical method may be used for both retrospective dose reconstruction and prospective estimates of annual dose and integrated “life-time” dose, for different age intervals. According to the EMARC model, estimated reference “life-time” doses for adults are between 7 and 269 μSv kBq−1 m2 for 137Cs, and between 25 and 235 μSv kBq−1 m2 for 90Sr. Maximal doses were estimated for persons who were 3, 9 and 11 years old, at the time of the accident and these doses exceed those for adults by a factors of 1, 5 for 90Sr, and 1.4 for 137Cs.  相似文献   

5.
There are few data reported on radionuclide contamination in Antarctica. The aim of this paper is to report 137Cs, 90Sr and 238,239+240Pu and 40K activity concentrations measured in biological samples collected from King George Island (Southern Shetlands, Antarctica), mostly during 2001–2002. The samples included: bones, eggshells and feathers of penguin Pygoscelis papua, bones and feathers of petrel Daption capense, bones and fur of seal Mirounga leonina, algae Himantothallus grandifolius, Desmarestia anceps and Cystosphaera jacquinotii, fish Notothenia corriceps, sea invertebrates Amphipoda, shells of limpet Nacella concina, lichen Usnea aurantiaco-atra, vascular plants Deschampsia antarctica and Colobanthus quitensis, fungi Omphalina pyxidata, moss Sanionia uncinata and soil. The results show a large variation in some activity concentrations. Samples from the marine environment had lower contamination levels than those from terrestrial ecosystems. The highest activity concentrations for all radionuclides were found in lichen and, to a lesser extent, in mosses, probably because lichens take up atmospheric pollutants and retain them. The only significant correlation (except for that expected between 238Pu and 239+240Pu) was noted for moss and lichen samples between plutonium and 90Sr. A tendency to a slow decrease with time seems to be occurring. Analyses of the activity ratios show varying fractionation between various radionuclides in different organisms. Algae were relatively more highly contaminated with plutonium and radiostrontium, and depleted with radiocesium. Feathers had the lowest plutonium concentrations. Radiostrontium and, to a lesser extent, Pu accumulated in bones. The present low intensity of fallout in Antarctic has a lower 238Pu/239+240Pu activity ratio than that expected for global fallout.  相似文献   

6.
In many Swedish lakes, the fallout of 137Cs from the Chernobyl accident in April 1986 has largely accumulated in the sediments. The availability and transfer of deposited 137Cs to biota is influenced by factors such as resuspension. The frequency of resuspension and the 137Cs-content of different fish species was studied in three shallow lakes in Uppland, central Sweden, and in one deeper lake in northern Sweden. Resuspension was measured by the use of sediment traps. Sedimentation rates measured from the traps in the shallower lakes were 5–10 times higher than normal for this type of lake, indicating that resuspension was an important factor. The decrease of the 137Cs-content in muscle tissue of pike, perch and roach was slow in each of the shallow lakes. 137Cs decreased by about 30% over a period of 2 years in the shallowest lake (maximum depth 4 m), whereas 137Cs decreased by 50% in the deeper lakes (maximum depth 10 m). The slower rates of decline of 137Cs in biota from the shallow lakes, are probably a function of sediment dynamics (mainly influenced by lake morphometry, wind direction and strength). They may be influenced, also, by bioavailability of resuspended sediment material. In the deepest northern lake, much of the 137Cs-containing material collected in the sediment traps originated from the catchment area. Resuspension was minimal, and the high activity of 137Cs in the sediment had no effect on content or decline of 137Cs in lake fish.  相似文献   

7.
The Norwegian mountain lake, Øvre Heimdalsvatn, received major fallout from the Chernobyl accident in the spring of 1986. Activity concentrations of 137Cs have been monitored annually in the brown trout (Salmo trutta) population of the lake over a 22-year period since 1986. The activity concentrations of 137Cs in brown trout have declined over the period, although in recent years there has been little or no reduction in activity concentrations. Throughout the period, there has been considerable individual variation in 137Cs activity concentrations. Within a single year, fish weight was the most significant factor affecting activity concentrations of 137Cs in individual fish, although sex and age·weight were significant explanatory variables. The “size effect” was not significant during the initial period after fallout and in some recent years. During the first years after fallout, the ecological half-life of 137Cs in brown trout was 3–4 years, but during the last decade this has increased significantly and has approached the physical half-life of 30 years for 137Cs, suggesting a dynamic equilibrium between catchments inputs, possible remobilisation from lake sediments and lake outputs of 137Cs.  相似文献   

8.
Hidden Lake is a perched, brown-water lake located in the centre of Great Sandy Island (Fraser Is.), S.E. Queensland. It is highly acid (pH 4.0), oligotrophic and is thermally and chemically stratified for most of the year. The sediments revealed a 137Cs profile which departed from the temporal pattern of 137Cs fallout in Brisbane and was represented by an exponential increase of 137Cs towards the surface sediments from ca. 32 cm depth. The possible causes of the divergent profile are discussed, including physical and biological mixing, lag in the transport of catchment material to the sedimentary basin, diffusion, recycling and biological concentration. It is hypothesised that a combination of the last four processes, with diffusion facilitated by the highly acid conditions, are the major causes of the observed 137Cs profile. Possible recycling and bioconcentration of 137Cs raises questions as to the validity of this method of dating in similar environmental conditions, and as to the interpretation of other palaeochemical data. These hypotheses are to be tested against profiles obtained from 14C, 210Pb, 239/240Pu analyses of the sediment, and the measurement of 137Cs activity in the water and biota of the lake.  相似文献   

9.
To date, there is scant information on in vivo induction of chromosomal damage by heavy ions found in space (i.e. 56Fe ions). For radiation-induced response to be useful for risk assessment, it must be established in in vivo systems especially in cells that are known to be at risk for health problems associated with radiation exposure (such as hematopoietic cells, the known target tissue for radiation-induced leukemia). In this study, the whole genome multicolor fluorescence in situ hybridization (mFISH) technique was used to examine the in vivo induction of chromosomal damage in hematopoietic tissues, i.e. bone marrow cells. These cells were collected from CBA/CaJ mice at day 7 following whole-body exposure to different doses of 1 GeV/amu 56Fe ions (0, 0.1, 0.5 and 1.0 Gy) or 137Cs γ rays as the reference radiation (0, 0.5, 1.0 and 3.0 Gy, at the dose rate of 0.72 Gy/min using a GammaCell40). These radiation doses were the average total-body doses. For each radiation type, there were four mice per dose. Several types of aberrations in bone marrow cells collected from mice exposed to either type of radiation were found. These were exchanges and breaks (both chromatid- and chromosome-types). Chromosomal exchanges included translocations (Robertsonian or centric fusion, reciprocal and incomplete types), and dicentrics. No evidence of a non-random involvement of specific chromosomes in any type of aberrations observed in mice exposed to 56Fe ions or 137Cs γ rays was found. At the radiation dose range used in our in vivo study, the majority of exchanges were simple. Complex exchanges were detected in bone marrow cells collected from mice exposed to 1 Gy of 56Fe ions or 3 Gy of 137Cs γ rays only, but their frequencies were low. Overall, our in vivo data indicate that the frequency of complex chromosome exchanges was not significantly different between bone marrow cells collected from mice exposed to 56Fe ions or 137Cs γ rays. Each type of radiation induced significant dose-dependent increases (ANOVA, P < 0.01) in the frequencies of chromosomal damage, including the numbers of abnormal cells. Based upon the linear-terms of dose-response curves, 56Fe ions were 1.6 (all types of exchanges), 4.3 (abnormal cells) and 4.2 (breaks, both chromatid- and chromosome-types) times more effective than 137Cs γ rays in inducing chromosomal damage.  相似文献   

10.
The studies of 137Cs and 90Sr accumulation characteristics by birch wood (Betula pendula Roth.) growing in different edaphic conditions. Were conducted was stated that the increase in soil fertility from trophotops A to D results in 5-fold 137Cs transfer factor decrease and 2-fold decrease of 90Sr. Soil humidity increase for each grade of trophic net results happens the increase of 137Cs transfer factors to wood and decrease for 90Sr. Total activity of 37Cs and 90Sr in birch wood plantation depends on plantation productivity and on radionuclide transfer factors depending on different plantation conditions. In the most prevailing edaphotops (B2, B3, C2 and C3) birch wood accumulates 0.6-1.2% of 137Cs and 13-19% of 90Sr from total activity of radionuclides in biogeocenosis.  相似文献   

11.
Radiometric dating for recent lake sediments on the Tibetan Plateau   总被引:1,自引:0,他引:1  
We present radiometric data from nine lakes across the Tibetan Plateau, and compare their reliability in relation to recent research. Unsupported 210Pb profiles show, except for one particular lake, non-exponential decline of 210Pb activity with sediment depth. Stratigraphic dates based on global atmospheric nuclear weapons maximum fallout of 137Cs (1963) support the use of the constant rate of 210Pb supply (CRS) model in four of the dated cores. The discrepancy in the others is likely due to recent increased input of catchment-derived 210Pb. 210Pb dates in this study suggest that post depositional diffusion of 137Cs activity has been significant. The practice of assigning early 1950s dates (start of global atmospheric thermonuclear testing) to lake sediment sequences on the Tibetan Plateau should be used with caution. 137Cs profiles from Tibetan lake sediment cores and their geographical distribution suggest that 137Cs derived from the 1986 Chernobyl accident or atmospheric testing in China was not sufficient to form a significant peak effective for dating.  相似文献   

12.
Partitioning of 14C-labelled photosynthates to various parts of un-pruned tea clones TV1 and TV25 was assessed in vivo by exposing maintenance leaves to 14CO2 at monthly intervals throughout the year. The plants from shoot apex to root tip were divided into twelve components to assess the allocation and retention of 14C-photosynthates by the maintenance foliage. Out of the total photosynthates produced by the maintenance leaves, only 11.08 % was allocated to the commercially useful harvestable two and a bud shoots which is accepted as the harvest index of tea. The photosynthetically active maintenance leaves retained 19.05 % while 24.56 % was distributed to the branches. The bottom and the top parts of the trunk utilized 7.44 and 7.21 %, respectively. The thick roots at the base of the trunk, medium sized roots, pencil size roots, and feeder roots imported 7.28, 7.72, 7.65, and 8.01 % of 14C assimilates, respectively. Except retention by leaves, all the plant parts of vigorous clone TV25 required higher percentage of assimilates than TV1. The mean quantities of net photosynthates utilized by the stem and the roots were 69.37 and 30.63 %, respectively.  相似文献   

13.
Empirical data on the behavior of radionuclides in the biosphere are needed for validating radioecological models. In this study, data collected from two lakes in Northern Finland were used to investigate the transfer of 137Cs from lake water into fish during a 20-year period after the Chernobyl nuclear power plant accident. The results indicated that transfer of 137Cs in the food chains investigated is nonlinear: the water-to-fish concentration ratios (CRs) decreased with increasing 137Cs concentration in water. Major deviation from linearity (constant CR) commonly assumed in radioecological modeling was observed only at low 137Cs concentrations in water. Other findings of potential importance for radioecological models were that 137Cs concentrations were threefold higher in piscivores than in non-piscivores and that no differences in 137Cs uptake were found between the two piscivorous species (pike and perch) studied or between three non-piscivorous species (vendace, white fish, and roach) representing different feeding habits (planktivore, benthivore, and mixed diet).  相似文献   

14.
Caesium-137 and lead-210 dating of recent sediments from Mondsee (Austria)   总被引:1,自引:1,他引:0  
Mean annual sedimentation rates over the last 20–30 years were determined in the pre-alpine Mondsee (Upper Austria) using Cs-137 and Pb(Po)-210 profiles for sediment core dating and two natural sediment markers. Lower sedimentation rates of about 2–3 mm yr–1 were observed in the central part of the lake near the shore at 18–20 m and in the southern part at 30 m depth. Higher sedimentation rates of 4–7 mm yr–1 were found in the central part of the lake at 47 and 65 m and in the northern bay at 18 and 41 m depth. At both these sites the Pb-210 profiles were strongly disturbed in the upper zone of the sediment cores, whereas the Cs-137 pattern remained intact. The higher annual sediment accumulation rates can be explained only partly by deposition of allochthonous material discharged by the streams, enhanced eutrophication in these parts of the lake, erosion and sediment focusing by turbidity currents being also probable.  相似文献   

15.
The deposition of radiocaesium from nuclear weapons testing and the Chernobyl accident upon the Llyn Llygad Rheidol catchment in mid-Wales is described. Inventories of soil cores from the catchment support estimates of total atmospheric fallout. The mean inventory of weapons testing 137Cs in lake sediment cores is broadly similar to that in soil cores. The inventory of Chernobyl fallout in sediment cores is significantly lower and raises questions concerning the residence time of 137Cs in the catchment soils and lake waters. 137Cs and 241Am activities in a sediment core record the 1963 peak of fallout from nuclear weapons testing. The association of the peak activities of 137Cs and 241Am in the sediments with the falloot maximum is confirmed by 210Pb dating. The 210Pb dates also reveal a significant increase in sediment accumulation rates over the past 20 years.  相似文献   

16.
Spring wheat plants were grown in a 137Cs labelled nutrient solution, either in the presence or absence of NH4 as a secondary N source. Between 11 and 64 days after sowing (DAS), plants were harvested on nine occasions. The plants supplied with NH4 and NO3 had lower root 137Cs Activity Concentrations (AC) than those supplied with NO3 only. Shoot AC were equal in both nutrition treatments. Shoot and root 137Cs AC (dry weight basis) showed the same trends with plant age in both nutrition treatments. Shoot AC almost doubled between 11 and 28 DAS after which they gradually decreased concomitant with a similar decrease in K concentrations. Root AC were always higher than shoot AC and increased to a maximum at 35 DAS after which they fluctuated. Expressed on a tissue water basis, the 137Cs AC varied less during plant age than did dry weight based AC. Furthermore, root and shoot AC expressed on a tissue water basis were almost equal. It is shown that the initial increase in 137Cs AC in both root and shoot can largely be explained by the initial dilution of absorbed 137Cs in the unlabelled seedling tissues. No correlation was found between K and 137Cs distribution among ears, leaves, stems and roots in 64 old wheat plants. NH4 as a secondary N source in a nitrate nutrient solution marginally affected 137Cs distribution.Abbreviations AC activity concentrations - DAS days after sowing FAX no corresponding author: +3216321997  相似文献   

17.
Identifying resuspended particles using isotope ratios   总被引:5,自引:2,他引:3  
Three simple methods were developed to estimate the proportion of particles in lake water derived from resuspended material. These techniques use the different distributions of long and short-lived radioisotopes sorbed onto particles and were tested in the three basins of Lake Erie using 7Be, 137Cs and 210Po/210Pb.While the concentration of 210Po on particles did not vary significantly in the lake, resuspended particles were characterized by high concentrations of 137Cs and low concentrations of 7Be. The distribution of these radioisotopes is consistent with a simple mixing model in which the fraction of particles in the lake water derived from resuspension ranged from 8% to about 100%. Higher concentrations of resuspended particles were found in deeper samples from the nepheloid layer and in the shallow western basin where thermal stratification was very weak.  相似文献   

18.
In the present work the distribution of ions in aboveground plant parts was studied in order to establish the suitability of using radiocaesium as a tracer for the plant absorption of nutrients, such as potassium (K+) and ammonium (NH4+). We present the results for the distributions of 137Cs, 40K and NH4+ from four tropical plant species: lemon (Citrus aurantifolia), orange (Citrus sinensis), guava (Psidium guajava) and chili pepper (Capsicum frutescens). Activity concentrations of 137Cs and 40K were measured by gamma spectrometry and concentrations of free NH4+ ions by a colorimetric method. Similarly to potassium and ammonium, caesium showed a high mobility within the plants, exhibiting the highest values of concentration in the growing parts of the tree (fruits, new leaves, twigs, and barks). A significant correlation between activity concentrations of 137Cs and 40K was observed in these tropical plants. The K/Cs discrimination ratios were approximately equal to unity in different compartments of each individual plant, suggesting that caesium could be a good tracer for 40K in tropical woody fruit species. Despite the similarity observed for the behaviour of caesium and ammonium in the newly grown plant compartments, 137Cs was not well correlated with NH4+. Significant temporal changes in the NH4+ concentrations were observed during the development of fruits, while the 137Cs activity concentration alterations were not of great importance, indicating, therefore, that Cs+ and free NH4+ ions could have distinct concentration ratios for each particular plant organ.  相似文献   

19.
Radionuclide dating of the recent sediments of Blelham Tarn   总被引:9,自引:0,他引:9  
Lake sediments of the last 1000 years provide a unique record of environmental changes. Methods of dating this record are reviewed and discussed. Sediments of the last 20 years, which are of particular biological significance because of their record of man-made changes in lakes (including enrichment and pollution) have been dated successfully by the distribution within them of the fallout product 137Cs, present in the atmosphere since 1954 and reaching a peak of supply in 1963. The structured pattern shown by the curve for 137Cs concentration in most sediments investigated indicates that faunal mixing of the surface muds does not destroy the vertical stratification of the sediment profile. Sediments up to 120 years old have been dated by a lead isotope technique, and the results of this proved consistent with both 137Cs dating and with palaeomagnetic dating where this was possible. Theoretical considerations of the application of radiocarbon dating to organic material of 18th and 19th century date are reviewed. Results of application of these radionuclide techniques to the sediments of a small lake, Blelham Tarn, near Windermere, are presented. Evidence from 137Cs and 210Pb dating of profiles from several different positions within the lake shows that the depth of the annual increment to the sediments varies by a factor of × 2 from place to place. The concentration within the sediment of chemical and biological variables shows no significant variation from one position to another; therefore calculated values for amounts of each variable included within unit area of the annual increment depend primarily on the thickness of this at the site chosen, and so cannot be directly related to the rates of supply of, for example, pollen grains or total organic matter, and so to rates of productivity. Results from nine 14C dates on material 400–1000 years old, when correlated with analyses for pollen and sediment composition, demonstrate the profound effects of agricultural practices in the catchment (assumed to be deforestation and ploughing) in disturbing the orderly transfer to lake sediments of material eroded from the catchment.  相似文献   

20.
241Am dating of lake sediments   总被引:2,自引:0,他引:2  
241Am derived from decay of fallout 241Pu is now frequently detected in analyses of lake sediments by low-background gamma assay, and offers an alternative to weapons test 137Cs in dating recent sediments at those sites where the 137Cs record has been degraded by post-depositional mobility or obliterated by Chernobyl fallout. Calculations of the in-growth of 241Am from 241Pu indicate a nominal distribution broadly similar to that of 137Cs, with the maximum 241Am activity occuring in fallout dating from 1963. Results from a number of sites suggest that 241Am is significantly less mobile in lake sediments than 137Cs, and that its distribution in cores reflects more closely the fallout record. Since further decay of existing weapons debris will increase 241Am concentrations by about 24% over the next 40 years, 241Am is likely to play an increasingly important role in assessing the validity of 210Pb dates at sites with varying sediment accumulation rates.  相似文献   

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