Distribution Of 137Cs Research Articles

A study of Cs-137 spatial distribution in soil thin sections by digital autoradiography and microscopy

Digital autoradiography with imaging plates and microprobe analysis was used to study 137Cs micro-distribution in thin sections of the podzolic sandy soil typical for the Chernobyl remote impact zone 25years after the accident. The zone is notable for contamination of the so-called condensation type where the contribution of the “hot” fuel particles was comparatively low. The initial 137Cs contamination level of the study plot located on the Iput river terrace ca. 20km to the east of the town of Novozybkov, Bryansk region, was approx. 40Ci/km2. According to the modern soil core data the main portion of cesium radioisotopes is still concentrated in the 10–20cm thick surface layer. Thin sections were prepared from the top 0–10cm layer of the soil profile located on the shoulder of the relatively steep northern slope of the forested hill. Autoradiography of the thin sections has clearly shown both cluster and dispersed patterns of 137Cs distribution presumably reflecting initial radiocesium accumulation in the surficial organic layer with mineral admixture and subsequent lateral and vertical propagation due to water movement and filtration. The propagation was accompanied by fixation of 137Cs ions on surfaces of soil particles. High sensitivity (0.03Bq/cm2) and resolution (ca 40μm) of the applied technique enable us to reveal concentration and dispersion zones in soil thin sections on microscale level. Soil micro-morphology and microprobe analysis have shown to be helpful in deciphering soil chemical and mineral composition assumed to be responsible for 137Cs retention in the soil top layer.

Granulometric and mineralogic investigation for explanation of radionuclide accumulation in different size fractions of the Yenisey floodplain soils

A detailed study of soil fractions of different sizes and their mineralogy was performed to explain the distributions of 137Cs discharged by the Krasnoyarsk MCC in alluvial soils of the near and remote impact zones. Radionuclides were shown to concentrate in fine fractions enriched in hydromica and smectite. However, in natural conditions the dominant size fractions responsible for 137Cs accumulation appeared to belong to sizes from silt (0.010mm) to clay (0.001mm). Ultrasonic treatment helped to reveal that this occurs due to natural water-resistant aggregation of smaller particles. Aggregation of fine particles and a considerable contribution of coarse fractions to the total sample mass lead to a smoothing effect in the distribution of 137Cs inventory in different fraction masses constituting the soil layer. However, clay fractions <0.001mm, and aggregates sized 0.05(0.63)–0.010mm and 0.25–0.125mm appear to dominate in radiocesium storage in the studied layers supporting the contention that these fractions play a major role in the distribution and accumulation of technogenic contamination in the floodplain soils of the region.Mineralogical analysis of the samples proved that floodplain sediments are able to fixate cesium due to the presence of smectites, illite, feldspars and micas in fines and coarser fractions. Abundant feldspar transformed to sericite can also contribute to cesium sedimentation. The particle interval from <0.001 to 0.010mm would appear to be crucial for contamination levels of river sediments and floodplain soils as they are comparatively resistant in aqueous solution and prone to easy transport by the river. Therefore the alluvial soil fractions of these sizes are of prime importance in the studies of technogenic contamination of river systems.

137Cs in sediments of deep lakes

Sedimentation rate of suspensions (0.3–18.2 mm/yr) was determined on the basis of layer-by-layer distribution of 137Cs (global and Chernobyl) in the cores of bottom sediments (BS) from 16 lakes located in the high and moderate latitudes of the Northern Hemisphere. Profiles of 137Cs concentration in the BS cores were analyzed. Sedimentation rates in the limnic zones of deep-water lakes were calculated using 137Cs accumulated in the finely-dispersed component of mineral suspension.

137Cs vertical distribution at the deep basins of the North and Central Aegean Sea, Greece

Large volume seawater samples were collected for the determination of 137Cs concentration along with depth in the deep basins of North and Central Aegean Sea. The vertical 137Cs distribution showed maximum concentration at the bottom of the basins, while the minimum values corresponded to the intermediate layer, where Levantine water exists. The surface 137Cs activity is found to lie between the two limits and is originated from the Black Sea waters. The typical oceanographic advection–diffusion balance model is modified to a diffusion-settling-decay balance model to better understand the vertical distribution and variation of the 137Cs concentration in the deep basins. In addition, the diffusivity of each basin, as well as the settling speed of particulate 137Cs is also estimated. The results are compared with theoretical approach as well as with previous data.

Dating young Holocene coastal sediments in tropical regions: Use of fallout 239,240Pu as alternative chronostratigraphic marker

We present a study on the use of 239,240Pu as a chronostratigraphic marker to constrain 210Pb ages in young Holocene sediments from four coastal locations of Cuba (Caribbean Sea). The selected sites typify a variety of deposition environments such as a bay, a gulf, a coastal lagoon and a river estuary. The vertical distributions of 210Pb (and 226Ra), 239,240Pu and 137Cs in the sediment cores were determined in order to quantify the sedimentation processes. Mean activity ratios of 0.04 ± 0.01 for 238Pu/239,240Pu and 0.3 ± 0.2 for 241Am/239,240Pu indicated that atmospheric nuclear weapon tests (NWT) fallout was the main source of the anthropogenic radionuclides. Marine sites (Havana Bay and Gulf of Batabano) were characterized by low or negligible signals of 137Cs, which impeded its use as a chronostratigraphic marker. In the Sagua River Estuary and the Guanaroca Lagoon, where mixing of fresh and saline waters take place, depth profiles of 137Cs and 239,240Pu were in good agreement. A simple model that assumes a well-mixed reservoir in surface ocean waters and constant sediment accumulation was used to interpret the 239,240Pu profiles. The model corroborated the 210Pb ages, except in the case of the highly mixed sediment cores from the Gulf of Batabano. The apparent mean residence time of 239,240Pu in the well-mixed reservoir ranges from 5 to 50 years, with longer timescales for marine sites. 239,240Pu showed to be a useful time tracer in coastal sediments where the 137Cs signal is very low.

Seasonal variation of the concentrations of 137Cs in sediment, sea water, and some organisms collected from Izmir Bay and Didim

137Cs in the marine environment mainly originates from fallout of atmospheric nuclear weapon tests, accidental releases from nuclear facilities, and from the Chernobyl accident. After the latter accident, many studies have been carried out in Turkey. The objective of this study is to assess the spatial distribution of 137Cs in the coastal marine environment of the Aegean Sea.The concentrations of 137Cs in sediment, sea water, mussel (Mytilus galloprovincialis), and fish samples collected from the coast of the Aegean Sea at Izmir Bay and near Didim (Akbük) have been monitored for seasonal variability by the means of gamma spectroscopy: they vary between 0.10 ± 0.01 and 1.5 ± 0.3 Bq kg−1, 1.3 ± 0.1 and 4.3 ± 0.4 Bq m−3, <0.2 and 1.3 ± 0.3 Bq kg−1, and 0.20 ± 0.03 and 1.8 ± 0.3 Bq kg−1, respectively.

Measurement of distributions of cesium and rubidium in rice grains using micro-PIXE for detailed examinations of contaminated food

We used micro-PIXE to investigate the distribution of Cs and Rb in rice grains. We succeeded, for the first time, in measuring the elemental distributions in entire rice grains (with dimensions of 6.25 mm [Formula: see text] 6.25 mm) at micrometer spatial resolution. We found that Cs and Rb accumulated in the bran and germ of the rice. The distributions of P, K, Rb and Cs were similar within the rice grain. The concentrations of Cs and Rb in the rice were proportional to those in the soil, as well as to the exposure time. The uptake of Rb was significantly larger than that of Cs. Furthermore, the behavior of Rb was similar to that of Cs in the micrometer-scale regions in plants. It follows that the distribution of Rb can be used to investigate the behavior of radioactive Cs in plants.

Immobilization of metal hexacyanoferrates in chitin beads for cesium sorption: synthesis and characterization

Five metal-potassium hexacyanoferrate/chitin composites (based on Cu, Ni, Zn, Co or Fe co-metal) have been prepared and characterized, using SEM-EDX, TEM, X-ray diffraction and FT-IR, before being compared for Cs(I) and 137Cs(I) sorption. The Zn-ion exchanger was characterized by a much larger crystal size of about 250 nm compared with a few tens of nm for other ion-exchangers. The ion-exchangers are well distributed in the whole mass of the composite and they are fully accessible to Cs(I), as evidenced by Cs(I) distribution after metal sorption. Uptake kinetics can be modeled using both the pseudo-second order rate equation and the Crank equation (resistance to intraparticle diffusion coefficient). Sorption isotherms showed substantial differences in the sorbents that can be ranked as Cu > Ni > Zn > Co > Fe. However, based on 137Cs Kd values, the sorbents can be ranked as Co ≫ Fe ≫ Cu ≫ Ni > Zn. Taking into account the cost and toxicity of metals (both in terms of manufacturing and potential metal release) a Prussian Blue based sorbent (i.e., iron-potassium hexacyanoferrate/chitin composite) sounds to be a good composite for Cs(I) recovery from radionuclide-containing effluents.

Depth and Areal Distribution of Cs-137 in the Soil of a Small Water Catchment in the Sopron Mountains

Abstract - The study presents the depth and areal distribution of Cs-137 activity concentration in the forest soils of Farkas Trench, a small water catchment in the Sopron Mountains, in 2001 and 2010, moreover the possible reason of the alteration in activity concentration. The Cs-137 activity values were measured in 30 plots in 2001, and in 5 in 2010. In 2001, the depth distribution of Cs-137 activity concentration in the measurement plots was shaped in accordance with a decreasing exponential function. It appeared in the 2010 data that the highest Cs-137 activity concentration had shifted lower from the top layers, and the depth distribution changed along an increasing or a stagnating function until a depth of 4 to 6 cm (in function of slope inclination), then along a decreasing function. In 2001, activity concentration in the surface soil layers (0 - 2 cm) altered between 15 and 609 Bq/kg, whereas in 2010 between 26 and 72 Bq/kg. A correlation was found between activity concentration in the surface soil layer and slope inclination. It was concluded that one of the main reasons for differences in distribution of Cs-137 activity concentration was the differing extent of soil movement.

Radiocaesium distribution in the bottom sediments of the Kara Sea

The article presents the results of radiogeochemical studies carried out by the Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, RAS (IGEM RAS), in the Kara Sea and the estuaries of the Ob and Yenisei rivers in 1995–2003. The studies were carried out onboard the Akademik Boris Petrov research vessel, belonging to the Institute of Geochemistry, RAS. Based on studies of circa 1500 samples of bottom sediments, taken from 172 marine and river stations, a map of 137Cs distribution in the surface sediments has been compiled. Four zones of radiocesium overactivity (>15 Bk/kg) have been identified: Novaya Zemlya Zone, Vaigach Zone, Ob Zone, and Yenisei Zone. The zones have different radiocesium concentration levels, as well as different input sources, but all of them have formed under the influence of complex geochemical barriers. Data from 47 sectioned cores of bottom sediments, sampled in Ob and Yenisei overactivity zones, demonstrate distinct differences in the vertical radiocesium distribution. These differences have been shown to be due to many-year oscillations of suspended silt discharge, which are main transfer agents of solvable and poorly solvable radiocesium forms and to be independent of sedimentation conditions and the geochemical characteristics of the deposition environment.

Measurements and modelling of 137Cs distribution on ground due to the Chernobyl accident: a 27-y follow-up study in Northern Greece

Following the Chernobyl accident, an area of ∼1000 m(2) in the University farm of the Aristotle University of Thessaloniki was considered as a test ground for radioecological measurements. The radiocesium deposition in this area, due to the Chernobyl accident, was 20 kBq m(-2). The profile of (137)Cs in the soil of this area was measured systematically from 1987 to 2012. The form of the profile has changed over the years. During the 1987-2000 period the (137)Cs distribution was reproducible by a sum of two exponentials. However, at least since 2005 the (137)Cs distribution can be successfully fitted by a single exponential function. The long-time (∼27 y) evolution study of the (137)Cs distribution in soil permit one to extract with the use of a simple compartment model, the mean vertical migration velocity of (137)Cs. Vertical migration of (137)Cs in soil is a very slow process. The mean vertical migration velocity is estimated to be 0.14 cm y(-1).The relative good comparison between the time dependence of the (137)Cs distribution in soil and the model predictions indicate that the simple model used is realistic.

137Cs vertical migration in a deciduous forest soil following the Fukushima Dai-ichi Nuclear Power Plant accident

The large amount of 137Cs deposited on the forest floor because of the Fukushima Dai-ichi Nuclear Power Plant accident represents a major potential long-term source for mobile 137Cs. To investigate 137Cs mobility in forest soils, we investigated the vertical migration of 137Cs through seepage water, using a lysimetric method. The study was conducted in a deciduous forest soil over a period spanning 2 month to 2 y after the Fukushima nuclear accident. Our observations demonstrated that the major part of 137Cs in the litter layer moved into the mineral soil within one year after the accident. On the other hand, the topsoil prevented migration of 137Cs, and only 2% of 137Cs in the leachate from litter and humus layer penetrated below a 10 cm depth. The annual migration below a 10 cm depth accounted for 0.1% of the total 137Cs inventory. Therefore, the migration of 137Cs by seepage water comprised only a very small part of the total 137Cs inventory in the mineral soil, which was undetectable from the vertical distribution of 137Cs in the soil profile. In the present and immediate future, most of the 137Cs deposited on the forest floor will probably remain in the topsoil successively, although a small but certain amount of bioavailable 137Cs exists in forest surface soil.

Reconstruction of the historical deposition environment from 210Pb and 137Cs records at two tidal flats in China

To examine the historical depositional environment with the evolution of vegetation at tidal flats, sediment samples were collected and grain-size distribution, 137Cs and 210Pb characteristics, heavy metals content, stratigraphy and the vegetation information were measured at Linhong and Chongming Dongtan tidal flat in China. Sediment grain size parameters exhibited transitional lines of the unvegetated flat to the vegetated flat. The vertical profiles of the 137Cs and 210Pbex reflected different depositional environment at the tidal flats. The linear/slumps profiles of 210Pbex indicated complex hydrodynamics or rapid changes in sediment supply. The maximum peaks of 137Cs activity were observed in some cores. The sedimentation rates from the 137Cs maximum deposition peaks in 1963–1964 were comparable with the results from the 210Pbex-CRS (Constant Rate of Supply) method. Positive relationships between the average activities of 137Cs, 210Pbex, inventory of 210Pbex and the mean clay composition, suggested that grain size control effect was an important factor to influence the characteristics of 137Cs and 210Pb distribution at the tidal flats. For heavy metals, only Hg, Cd and Cr were moderately polluted at the Linhong tidal flat and the Chongming Dongtan, respectively. Integrating the results above and the stratigraphy, the vegetation introduction historical information, the clearer sedimentation evolution processes of the tidal flats were reconstructed, which is necessary for the coastal zone management and the pollution evaluation.

Description of spatial patterns of radionuclide deposition by lognormal distribution and hot spots

Spatial distributions of activity density (kBq/m2) and activity concentration (Bq/kg) are studied on sites with non-cultivated soils. Fitting datasets with lognormal, Weibull and normal distributions with sampling size n ≥ 60 showed that radionuclide deposition (90Sr, 137Cs, 238Pu, 239+240Pu, 241Am) due to Chernobyl fallout no more than in 10% of cases are described by Weibull distribution, and in the rest of the cases – by lognormal distribution. However asymptotics of “righthand tail” of empirical (sample) distribution quite often differs from the right-hand tail asymptotics of lognormal distribution. Thereby lognormal distribution is only an approximate statistical model of radionuclides' spatial pattern.Estimates of site surface area with “hot spots” are considered. Also distributions of 137Cs and 134Cs activity concentration on the territory contaminated by Fukushima fallout are reviewed. Characteristics of activity concentration for Fukushima and Chernobyl fallouts are collated. The results obtained make it possible to suggest that in both cases spatial contaminations of soil are described by approximately the same statistical models.

Design, development and utilisation of a tomography station for γ-ray emission and transmission analyses of light water reactor spent fuel rods

A tomographic measurement station has been designed and developed for the investigation of light water reactor spent fuel rod segments. A unique feature of the station is that it allows both γ-ray transmission and emission computerised tomography to be performed on individual fresh or burnt fuel rods. The basics of the tomographic station design, construction and operation are presented together with the results of four burnt UO2 fuel rod segments investigated, with rod average burnups of 54, 71, 91 and 121 MWd kg−1.The combination of transmission and emission tomography techniques performed on an individual object provides a synergetic experimental approach. By performing transmission tomography, not only the average material density but also detailed spatial distributions of the density and of the γ-ray linear attenuation coefficient have been determined for each sample. By performing emission tomography, the determination of within-rod internal radial distributions of 134Cs, 137Cs and 154Eu has also been achieved for each individual pin. The results have indicated large central depressions in the caesium distributions because of isotope migration, with varying magnitude from sample to sample.Finally and in addition to the tomographic reconstructions, the possibility to use single isotope activities, and/or isotopic concentration ratios from 134Cs, 137Cs, and 154Eu, as burnup indicators at very high and ultra-high burnups, has also been investigated. This paper presents in a comprehensive manner the large panel of analysis performed for this interesting set of spent fuel samples which represents a valuable experimental insight in the physics of ultra-high burnups.

Depth Distribution of 137Cs in Anthrosol from the Experimental Field “Radmilovac” Near Belgrade, Serbia

This is a preliminary study of the depth distribution of (137)Cs radionuclides in cultivated anthrosol soil of a 15-year old peach tree plantation at the experimental field "Radmilovac" near Belgrade. Before planting, the soil was ploughed at the depth of 1 m. The soil had not been annually ploughed, irrigated and treated with mineral fertilizers for three years before sampling. Activity concentration for (137)Cs ranged from 1.8 Bq kg(-1) to 35 Bq kg(-1). Along the soil depth it varied highly, reaching as high a total variation coefficient as 83 %. Radiocaesium distribution patterns depended on the extent of soil mixing in the plough layer, as it was mechanically transferred from the surface to the lower soil layers during cultivation. (137)Cs was associated with humus content and fixation to clay fractions in the soil. Our results single out soil's hygroscopic water as a valuable parameter for (137)Cs behaviour that could be used commonly if the measurement is standardised.

Influence of calcium ion concentration on the selective sorption of 137Cs with illite

The 137Cs sorption and desorption equilibrium between illite and a solution containing 0.5 mM K+ and 1 to 100 mM Ca2+, determined using a kinetic method with direct measurement of the radioactivity in the sorbent solid phase, was attained within 20–25 days. The kinetic curves of the 137Cs sorption onto/desorption from illite, normalized on the maximal sorbed radioactivity, almost coincided at different Ca2+ concentrations. An increase in the 137Cs distribution coefficient (Kd) with a decrease in the Ca2+ concentration did not exceed 60% and was due exclusively to the influence of the solution ionic strength. With an increase in the Ca2+ concentration from 1 to 100 mM, the fraction of 137Cs extracted with 1 M CH3COONH4 (αEx) decreased from 24.1 to 14.8%.

Particle size distribution of radioactive aerosols after the Fukushima and the Chernobyl accidents

Following the Fukushima accident, a series of aerosol samples were taken between 24th March and 13th April 2011 by cascade impactors in the Czech Republic to obtain the size distribution of 131I, 134Cs, 137Cs, and 7Be aerosols. All distributions could be considered monomodal. The arithmetic means of the activity median aerodynamic diameters (AMADs) for artificial radionuclides and for 7Be were 0.43 and 0.41 μm with GDSs 3.6 and 3.0, respectively. The time course of the AMADs of 134Cs, 137Cs and 7Be in the sampled period showed a slight decrease at a significance level of 0.05, whereas the AMAD pertaining to 131I increased at a significance level of 0.1. Results obtained after the Fukushima accident were compared with results obtained after the Chernobyl accident. The radionuclides released during the Chernobyl accident for which we determined the AMAD fell into two categories: refractory radionuclides (140Ba, 140La 141Ce, 144Ce, 95Zr and 95Nb) and volatile radionuclides (134Cs, 137Cs, 103Ru, 106Ru, 131I, and 132Te). The AMAD of the refractory radionuclides was approximately 3 times higher than the AMAD of the volatile radionuclides; nevertheless, the size distributions for volatile radionuclides having a mean AMAD value of 0.51 μm were very close to the distributions after the Fukushima accident.

Short-term dispersal of Fukushima-derived radionuclides off Japan: modeling efforts and model-data intercomparison

Abstract. The Great East Japan Earthquake and tsunami that caused a loss of power at the Fukushima nuclear power plants (FNPP) resulted in emission of radioactive isotopes into the atmosphere and the ocean. In June of 2011, an international survey measuring a variety of radionuclide isotopes, including 137Cs, was conducted in surface and subsurface waters off Japan. This paper presents the results of numerical simulations specifically aimed at interpreting these observations and investigating the spread of Fukushima-derived radionuclides off the coast of Japan and into the greater Pacific Ocean. Together, the simulations and observations allow us to study the dominant mechanisms governing this process, and to estimate the total amount of radionuclides in discharged coolant waters and atmospheric airborne radionuclide fallout. The numerical simulations are based on two different ocean circulation models, one inferred from AVISO altimetry and NCEP/NCAR reanalysis wind stress, and the second generated numerically by the NCOM model. Our simulations determine that &gt; 95% of 137Cs remaining in the water within ~600 km of Fukushima, Japan in mid-June 2011 was due to the direct oceanic discharge. The estimated strength of the oceanic source is 16.2 ± 1.6 PBq, based on minimizing the model-data mismatch. We cannot make an accurate estimate for the atmospheric source strength since most of the fallout cesium had left the survey area by mid-June. The model explained several key features of the observed 137Cs distribution. First, the absence of 137Cs at the southernmost stations is attributed to the Kuroshio Current acting as a transport barrier against the southward progression of 137Cs. Second, the largest 137Cs concentrations were associated with a semi-permanent eddy that entrained 137Cs-rich waters, collecting and stirring them around the eddy perimeter. Finally, the intermediate 137Cs concentrations at the westernmost stations are attributed to younger, and therefore less Cs-rich, coolant waters that continued to leak from the reactor in June of that year.

Accumulation and distribution of 137Cs and 90Sr in the body of the wild boar (Sus scrofa) found on the territory with radioactive contamination

We studied the concentration and distribution of 137Cs and 90Sr in the bodies of 188 wild boar (Sus scrofa Linnaeus, 1758) taken near the Chernobyl site. Of these, 111 animals were taken in the Alienation Zone, 41 animals were taken in the Permanent Control Zone and 36 animals were taken in the Periodic Control Zone. The samples included muscle and bone (rib) tissues and samples of heart, liver, lungs, kidneys, spleen, genitals and skin. The weight of the samples was 0.5 kg fresh weigh. The average concentration of 137Cs in the muscles of the wild boar found in the Alienation Zone was 46 ± 10 kBq/kg, in the Permanent Control Zone – 13 ± 3.0 kBq/kg and in the Periodic Control Zone – 0.6 ± 0.1 kBq/kg. The largest concentration of 137Cs was detected in the muscle tissue and kidneys taken animals. In some samples of muscle tissue it reached more than 660 kBq/kg. The 137Cs concentrations were also high in heart and spleen up 64.3 kBq/kg and 67.5 kBq/kg – animals from the Alienation Zone and 10.3–10.6 kBq/kg – animals from the Permanent Control zone. The lowest concentration of 137Cs was found in the lungs and skin of animals. The analyses of 90Sr concentration in the organs and tissues of the wild boar showed that 90Sr was concentrated mainly in the bone tissue. The average level of 90Sr concentration in bone was 17.6 kBq/kg fresh weight animals from the Alienation Zone and 13.47 kBg/kg – animals from the Permanent Control zone. In muscle tissues and organs contained 90Sr – 30.0–110.0 Bq/kg in the Alienation Zone and 11.0–30.0 Bq/kg in the Permanent Control zone.