Applications and limitations of chernobyl radiocaesium measurements in a carpathian erosion investigation,Poland

The bomb-test fallout radionuclide caesium-137, has found increasing application in geomorphological investigations of soil erosion. Comparatively little work has investigated the potential for using ¹³⁴Cs and ¹³⁷Cs derived from the 1986 Chernobyl accident. Results are reported from an agricultural foothill environment in the Beskidy Mountains of southern Poland. The high degree of spatial variability associated with Chernobyl fallout deposition poses considerable limitations on the potential for using radiocaesium measurements to elucidate detailed patterns of soil loss. Despite this problem, the redistribution of radiocaesium from field plots to terrace edges suggests a means for estimating the overall budgets for sediment transfer on cultivated slopes.     

Application of Chernobyl-derived Cs for the assessment of soil redistribution within a cultivated field

Vast areas of Europe were contaminated by the Chernobyl-derived ¹³⁷Cs in April–May 1986. This paper reports a detailed study of the post-fallout ¹³⁷Cs redistribution within a 1 ha field located in the Chasovenkov Verh catchment in the northern part of the Middle-Russian upland. Particular attention was paid to the study of reference inventories. It is shown that the random spatial variability of ¹³⁷Cs is similar within undisturbed and cultivated parts of a flat interfluve. Systematic spatial variability is not essential for a relatively short (200 m) topographical unit with simple relief. The analysis of a soil redistribution pattern within the study field using the Chernobyl ¹³⁷Cs technique demonstrates that it is possible to identify areas of soil loss/gain. This pattern does not reflect soil redistribution for the whole field, because these have been only 12 years since the Chernobyl accident. Net erosion rates based on ¹³⁷Cs method were comparable to soil losses directly measured at the study field.     

Assessment of the trend of degradation of arable soils on the basis of data on the rate of stratozem development obtained with the use of <Superscript>137</Superscript>Cs as a сhronomarker

A new approach for determining the trend of changes in the rate of degradation of arable soils is suggested. It is based on the assessment of volumes of soil material eroded from arable fields and accumulated on the bottoms of first-order valleys during two time intervals: 1954(1963)?1986 and 1986?2015. For dating of this material, ¹³⁷Cs of global fallout and Chernobyl fallout are used. This approach in combination with a detailed morphometric characterization of the valley bottoms, the pathways of sediment transport from the fields, and the morphology and composition of the sediments accumulated on the bottoms makes it possible to give reliable estimates of the volumes of soil loss from tilled slopes. The benchmarks of 1963 and 1986 are related to maximum ¹³⁷Cs fallout during nuclear bomb testing and immediately after the Chernobyl accident. As an example, the rates of formation of stratozems (stratified aggraded soils formed due to accumulation of eroded sediments) within the first-order catchment of the Veduga River basin (Voronezh oblast, Russia) are analyzed. The results of the study indicate that the mean annual rate of soil loss from arable fields of the catchment in 1986–2015 was at least two times lower than that in the preceding period from 1954 (the beginning of the global fallout) to 1986 (the Chernobyl accident).     

Examining the Relationships Between the Activities of 3H in Precipitation and 137Cs in Ground-Level Air in Belgrade City Area

Specific activity of tritium (³H) in precipitation and specific activity of ¹³⁷Cs in ground-level air were monitored at three locations in Belgrade (Meteorological Station of Belgrade at Zeleno Brdo (ZB), Meteorological Station Usek (USEK), and Vin?a Institute of Nuclear Sciences (VINS)). Data presented cover the period 1985?C1997 for ¹³⁷Cs for all locations and 1985?C2009 (ZB), 1988?C1997 (USEK), and 1988?C2009 (VINS) for ³H. Concentrations of ³H in precipitation have been determined using electrolytic enrichment and liquid scintillation spectrometer LKB-Wallac 1219 RackBeta. The activity of ¹³⁷Cs in air was determined on an HPGe detector (Canberra, relative efficiency 23?%). ³H concentrations in precipitation ranged from 0.40?±?0.08 to 74.6?±?5.2?Bq?l^?1 decreasing with distance from the nuclear facilities. Significantly higher tritium levels were measured in samples in VINS compared with those from an off-site location. The observed seasonal variations of tritium concentration indicate the stratospheric source of tritium. Increases in activity concentration of ¹³⁷Cs in the atmosphere were observed after the nuclear plant accident at Chernobyl in April 1986. The concentrations obtained for ¹³⁷Cs in 1986 were compared with the integrated air concentrations of ¹³⁷Cs in the region. The increases of ¹³⁷Cs air concentrations in 1987 and 1988 were attributed to local resuspensions from the ground. Since 1989, the activity level before the accident has been obtained. The average monthly concentrations of ¹³⁷Cs in ground-level air were shown spread maximum in spring?Csummer period and pronounced maximum during winter. The obtained results were statistically analyzed, i.e., the following parameters were determined: tritium deposition, monthly activities of ³H and ¹³⁷Cs, seasonal indices, radionuclide loading indices, and linear correlation coefficients.     

Laboratory experiments to investigate the influence of microbial activity on the migration of cesium in a forest soil

Factors affecting the velocity of downward migration of Cs in the soil were studied in the laboratory. Undisturbed soil cores were irrigated under various conditions. The displacement of ¹³⁷Cs and ¹³⁴Cs which was deposited at the soil surface during the atmospheric nuclear weapon testing in the sixties and after' the reactor accident at Chernobyl in 1986 was measured. The mobilization of Cs was found to be independent of the chemical composition of the irrigation water and the soil type. A significant displacement of Cs was observed only by heating the soil cores to 30 and 40 °C, respectively. This mobilization may be due to an increased turnover of soil organic material, as indicated by a raised CO₂ production in the cores and an increased DOC concentration in the seepage water.     

Vertical distribution and bioavailability of 137Cs in organic and mineral soils

The vertical distribution and bioavailability of ¹³⁷Cs in Histosols and mineral soils with different physicochemical properties from the southeast of Bavaria (Germany) more than ten years after the Chernobyl accident were the focus of this study. The vertical distribution of ¹³⁷Cs was low in the investigated soils. About 85–98 % of the total ¹³⁷Cs was located in the upper 10 cm of the mineral soils. Slightly higher ¹³⁷Cs percentages were observed in deeper soil layers of the peat soils. Although the organic matter is assumed to enhance ¹³⁷Cs mobility in soils, ¹³⁷Cs was also located in the upper 10 cm of the peat soils (73–85 %). The highest ¹³⁷Cs‐activities were found in the humus layers of forest soils, where 45–93 % of the total ¹³⁷Cs soil inventories were observed. To determine the bioavailability of radiocesium, the soil‐to‐plant transfer of ¹³⁷Cs and additionally added ¹³⁴Cs was investigated under controlled conditions. The results revealed that the ^134+137Cs soil‐to‐plant transfer factors as well as the percentages of NH₄‐exchangeable ^134+137Cs were much higher for the peat soils and humus layers than for the mineral soils. Nevertheless, the migration of ¹³⁷Cs from the humus layers to the underlying soils was low. Considering the high bioavailability and low migration of radiocesium in the humus layers, it is suggested that radiocesium is involved in a shortcut element cycle in the system humus layer‐plant uptake‐litter. Furthermore, the organic matter has to be taken into account for radiocesium immobilization.     

Forms and rates of release of 137Cs in two peat soils

Cation exchange resin saturated with H⁺ and Ca²⁺ was used to extract ¹³⁷Cs from peat soil at two sites in Britain affected by ^l37Cs deposition following the Chernobyl accident. The technique identified three classes of ¹³⁷Cs, similar to those observed for K⁺ in soils: ‘Fast’, ‘Intermediate’ and ‘Slow’. These classes are probably related to the selectivity for ¹³⁷Cs of the cation exchange sites on the organic matter and the clay minerals, and to the structure of the soil. With one exception, most ¹³⁷Cs was in the ‘Slow’ form and was only very slowly released to the resins, if at all. However, there was enough ^l37Cs in the ‘Fast’ and ‘Intermediate’ forms to contaminate pasture and thus grazing animals for some years. Based on the resin technique, it is estimated that contamination will persist for several decades in uplands contaminated at these activity concentrations.     

137Cs dating of lacustrine sediments and human impacts on Dalian Lake,Qinghai Province,China

¹³⁷Cs and grain-size analyses indicate the total amounts of ¹³⁷Cs deposited by wind and water in the Dalian Lake of Gonghe Basin, Qinghai Province. The vertical profile of ¹³⁷Cs in the lacustrine sediments shows three ¹³⁷Cs activity peaks and one trough: the main peak corresponds to the global ¹³⁷Cs fallout in 1963; the two secondary peaks correspond to the leakage of the Chernobyl reactor in 1986 and complete desiccation of the lake in 1994. The trough corresponds to aeolian deposition caused by extensive reclamation of farmland in late 1980s and early 1990s. The ¹³⁷Cs dating was used to evaluate sedimentation rates in Dalian Lake since 1963. They are divided into three periods: two with slow deposition (1963–1986 and 1994–1998), and one with rapid deposition (1986–1994). ¹³⁷Cs seems to have the same potential for indicating environmental changes and human interference in the arid and semiarid regions as in humid regions.     

Dynamics of Chernobyl <Superscript>137</Superscript>Cs contamination fields at long distances

Structural changes in the ¹³⁷Cs contamination fields in natural and agroecosystems of the northern forest steppe (the remote zone of the Chernobyl accident) were studied. It was shown that the lateral and vertical distribution of ¹³⁷Cs in soils of different biogeocenoses depends on the features of functioning biogeocenoses and the spatial variation of the initial fallout. The effect of biogeocenosis on the spatial variation of the contaminant distribution increases with time. At present, the variation of primary distribution in soils of agrocenoses is changing. The soils of forest biogeocenoses have retained the features of primary distribution, particularly in the upper 0-to 5-cm sublitter layer. The ¹³⁷Cs penetration depth is greatest in the soils of layland and functioning agrocenosis and least in the soils of forest biogeocenoses.     

Historical and Geographical Trends in Sediment Chronology from Lakes and Marine Sites Along the Norwegian Coast

Sediment cores collected from 12 lakes and eight marine sites along the Norwegian and Svalbard coast as part of a project investigating polycyclic aromatic hydrocarbons (PAH) in sediments were dated radiometrically using ²¹⁰Pb, ¹³⁷Cs and ²⁴¹Am fallout radionuclides. In all lake cores, except on Svalbard, the ¹³⁷Cs activity versus depth profile appears to have been significantly modified by post-depositional migration within the sediment column. The relatively low ¹³⁷Cs inventories suggest that these sites were not significantly impacted by fallout from the 1986 Chernobyl accident. All the marine cores have ¹³⁷Cs inventories that are substantially lower than in lake sediments almost certainly due to leaching of ¹³⁷Cs from the marine sediments due to higher solubility in the seawater. In the marine surface sediments, the unsupported ²¹⁰Pb concentrations are up to an order of magnitude lower than in the corresponding lake sediments reflecting the higher (dry mass) sedimentation rate at the marine sites. Five of the cores including marine sites and lakes have unusual high ²¹⁰Pb flux most likely due to sediment focusing. Most of the irregularities in the ²¹⁰Pb records seem to be due to slump events but some patterns are also due to possibly increased accumulation rates. Three of the marine cores show systematic increase in their sedimentation rate from c.1960 towards the present while only one lake shows the same systematic increase.     

Influence of rehabilitation measures on <Superscript>137</Superscript>Cs uptake by crops from soils contaminated during the Chernobyl NPP accident

The dynamics of ¹³⁷Cs uptake by crops and the influence of rehabilitation measures on the accumulation of this radionuclide in agricultural products have been estimated by the example of southwestern regions of Bryansk oblast. In 20 yr after the Chernobyl NPP accident, three stages of a decrease in the concentration of ¹³⁷Cs in the crops can be distinguished. At present (in 15–20 yr after the accident), the rate of the decrease in the concentration of ¹³⁷Cs in some crops corresponds to the half-decay period of this radionuclide.     

Radionuclide Behaviour and Transport in a Coniferous Woodland Ecosystem: The Distribution of Radionuclides in Soil and Leaf Litter

A coniferous woodland in the vicinity of theBritish Nuclear Fuels reprocessing plant atSellafield, Cumbria, was used to examine the spatial,temporal and depth distribution of ¹³⁴Cs,¹³⁷Cs, ²³⁸Pu, ^239+240Pu and ²⁴¹Amin soil and leaf litter. All the radionuclides, withthe exception of ¹³⁴Cs, showed a consistent fallin accumulated soil and litter deposits withincreasing distance from the woodland edge nearest toSellafield. ¹³⁷Cs levels in soil declined from 53to 28 kBq m^-2, ^239+240Pu from 5.5 to 3.6 kBqm^-2 and ²⁴¹Am from 2.9 to 1.1 kBq m^-2within 100 m of the forest edge. This decline isattributed to greater deposition occurring at theleading edge of the woodland. The uniform depositionpattern of ¹³⁴Cs in soil is consistent with thehypothesis that, at the time of sampling, thesedeposits derived largely from wet deposition duringpassage of the Chernobyl plume over Cumbria in May1986. Results for the leaf litter indicate a similarspatial distribution to that observed in soil.Radionuclide concentrations were also similar but thisis not attributable to adventitious soil contaminationbecause significant differences between isotopicratios of ¹³⁴Cs:¹³⁷Cs and ²³⁸Pu:^239+240Pu imply that the contamination on leaflitter is of more recent origin than that in soils.     

Cesium‐137‐based erosion‐rate determination of a steep mountainous region

Data on quantification of erosion rates in alpine grasslands remain scarce but are urgently needed to estimate soil degradation. We determined soil‐erosion rates based on ¹³⁷Cs in situ measurements. The method integrates soil erosion over the last 22 y (time after the Chernobyl accident). Measured erosion rates were compared with erosion rates modeled with the Universal Soil Loss Equation (USLE). The comparison was done in order to find out if the USLE is a useful tool for erosion prediction in steep mountainous grassland systems. Three different land‐use types were investigated: hayfields, pasture with dwarf shrubs, and pasture without dwarf shrubs. Our test plots are situated in the Urseren Valley (Central Switzerland) with a mean slope steepness of 37°. Mean annual soil‐erosion rates determined with ¹³⁷Cs of the investigated sites ranged between the minimum of 4.7 t ha^–1 y^–1 for pastures with dwarf shrubs to >30 t ha^–1 y^–1 at hayfields and pastures without dwarf shrubs. The determined erosion rates are 10 to 20 times higher compared to previous measurements in alpine regions. Our measurements integrated over the last 22 y, including extreme rainfall events as well as winter processes, whereas previous studies mostly reported erosion rates based on summer time and short‐term rainfall simulation experiments. These results lead to the assumption that heavy‐rainfall events as well as erosion processes during winter time and early spring do have a considerable influence on the high erosion amounts that were measured. The latter can be confirmed by photographs of damaged plots after snowmelt. Erosion rates based on the USLE are in the same order of magnitude compared to ¹³⁷Cs‐based results for the land‐use type “pasture with dwarf shrubs”. However, erosion amounts on hayfields and pasture without dwarf shrubs are underestimated by the USLE compared to ¹³⁷Cs‐based erosion rates. We assume that the underestimation is due to winter processes that cause soil erosion on sites without dwarf shrubs that is not considered by the USLE. Dwarf shrubs may possibly prevent from damage of soil erosion through winter processes. The USLE is not able to perform well on the affected sites. Thus, a first attempt was done to create an alpine factor for the USLE based on the measured data.     

Potassium bentonites reduce radiocaesium availability to plants

After the Chernobyl accident in 1986 the fate of radiocaesium from the fallout became of pressing concern. Specific soil amendments, as K fertilizer and specific clay minerals, promised to mitigate the worst effects. We therefore investigated the influence of bentonite and the K status of the soil on the radiocaesium equilibria in soil and on its availability to ryegrass. A sample of a sandy soil was contaminated with ¹³⁴Cs and amended with K and Ca salts (0–0.97 mmol kg^?1) and K bentonite (0–2%). After 4 weeks' incubation of the soil mixtures, ryegrass was grown for 18 weeks in a pot trial and harvested on seven occasions. No significant treatment effects on ¹³⁴Cs activity concentrations were found at the first and second harvest. From the third harvest onwards, however, ¹³⁴Cs activity concentrations in the grass were reduced up to twofold (P < 0.05) by increasing rates of K bentonite. Adsorption studies with ¹³⁷Cs revealed that the radiocaesium interception potential (RIP) of the soil–bentonite mixtures (> 1% bentonite) increased about 10‐fold during plant growth. The RIP of the K bentonite after plant growth was up to 10 times larger than that of pure illite. The formation of specific Cs sorption sites is ascribed to the in situ illitization of the K bentonite. The increase in RIP during plant growth is reflected in a decrease in exchangeable K⁺ at 2% K bentonite of about 18%. Radiocaesium concentrations in grass could be reliably predicted from the Cs⁺ and K⁺ concentrations in the soil solution. Adding K bentonite to a soil contaminated with radiocaesium is effective in fixing Cs in the soil.     

Migration of Cesium-137 in typical soils of North Germany ten years after the Chernobyl accident

Ten years after the Chernobyl disaster the Cs-137 migration of typical soils of North Germany (Folic Histosol, Haplic Podzol, Dystric Gleysol, Eutric Fluvisol) has been investigated and compared to their Cs distribution in 1986. In 1986 nearly 90% of the Cs-137 occurred in the upper 1–5 cm soil sections, whereas it was 50–70% in 1996. The more regular distribution ten years after the accident shows that migration processes have taken place. The Podzol presented a high migration with marked Cs-137 losses in the top soil. The Gleysol showed the lowest migration down to 10 cm depth. A nearly similar pattern at the top was found within the Histosol, however, a ratio of 10% Cs-137 in the 10–15 cm section indicated a deeper migration. Despite the large clay content, the Fluvisol showed a regular Cs distribution within its profile, probably resulting from cattle steps and/or peloturbation.     

Some indices of biological cycle of <Superscript>137</Superscript>Cs and <Superscript>39</Superscript>K in forest ecosystems of Bryansk woodland in the remote period after chernobyl fallouts

The features of the biological cycle of ¹³⁷Cs and ³⁹K in the remote period after Chernobyl fallouts are considered on the example of forest ecosystems of Bryansk woodland. It is demonstrated that the maximum amount of ¹³⁷Cs in the total phytomass is concentrated in wood, the minimum amount of ¹³⁷Cs, in the external bark layers; for the annual production, in assimilating organs and the external bark layers, respectively. The distribution of ³⁹K in the total phytomass and the annual production is almost identical to that of ¹³⁷Cs. The arrival of ¹³⁷Cs to the soil with litter in pine and birch forests has recently been equal approximately to 50% of the capacity of the biological cycle. It mostly arrives with the assimilating organs (needles and leaves). In pine forests the return of ³⁹K into the soil with litter is closest to that observed for ¹³⁷Cs.     

Transport processes for chernobyl-labelled sediments: Preliminary evidence from upland mid-wales

The nuclear accident at Chernobyl in April 1986 resulted in a significant increase in the inventory of radiocaesium retained in the soil in many regions of the United Kingdom. The deposition of ¹³⁴Cs provides a convenient tool for the examination of erosional processes in upland systems. Detailed soil sampling has been undertaken within the Plynlimon experimental catchments to establish the pattern of deposition of Chernobyl-derived radionuclides. The preliminary results of a combined radiometric and mineral magnetic approach to the study of the transport of Chernobyl-labelled sediments and their source areas on these upland catchments in mid-Wales are described.     

Die horizontale Verteilung von Radiocäsium im Waldboden unter Fichte und Buche

Horizontal distribution of radiocesium in forest soils under spruce (Picea abies (L.) Karst.) and beech (Fagus sylvatica L.) The horizontal distribution of radiocesium in the soil under the canopy of several beeches and spruces was examined. At the base of spruces mean ¹³⁷Cs activities are about twice, and under beeches 5 to 15 times as high as under more distant parts of the canopy. Between 80 and 95% of the ¹³⁷Cs activity can be attributed to the Chernobyl fallout, the rest to the global fallout from weapons testing in the 1950s and 1960s. While the ¹³⁷Cs accumulation at the base of spruces can be explained by litter fall and remains of bark, the up to 30 times increased values at the base of beeches are explained by stemflow. Mean activity of radiocesium in the bark of spruce (0,62 Bq/g dry weight) is about twice as high as in the bark of a beech. This can be explained by considering that in contrast to beeches the ¹³⁷Cs activity in the soil under spruces is corresponding to some extend with the main rooting zone. Thus, we expect an increased uptake by the roots of this species and a subsequent transfer to the bark.     

Cesium-137 Monitoring Using Mosses from Macedonia,N. Greece

137Cs activities in mosses collected from four sites in Macedonia, N. Greece were measured for regular periods of time during the last decade following the reactor accident in Chernobyl. Samples taken in 1985 allow to determine the 137Cs contamination before the accident. A clear increase of the cesium interception was observed for about two years after the accident. Later a gradual decrease was detected which depended on various factors such as moss species, location, growth rate and substrate. Higher 137Cs amounts were observed in epilithic (Grimmia) in comparison to epiphytic or epigeic ones ( Encalypta, Tortula). From the studied biotopes Mt. Vermion presented the highest 137Cs activities. The high 137Cs values found 10 yr after Chernobyl suggest that mosses are effective and inexpensive biological detectors of the distribution and burden of fallout radionuclides.     

Radioecological aspects of recent soil pollution in small catchments of Kursk oblast

A small catchment with an area of 1.98 km² was chosen for detailed studies. The soils of the catchment area are dominated by leached and weakly leached chernozems on loess deposits. The ¹³⁷Cs activity in the soils on a relatively flat area was about 26.7 ± 1.2 Bq/kg. In 20 years after the Chernobyl accident, a contrasting pattern of the ¹³⁷Cs pollution density characterized the small catchment Gracheva Loshchina.