137Cs Measurements Research Articles

Distribution and origin of organic matter in the Baltic Sea sediments dated with 210Pb and 137Cs

Organic carbon deposited in marine sediments is an important part of the global carbon cycle. The knowledge concerning the role of shelf seas (including the Baltic Sea) in the carbon cycle has increased substantially, however organic carbon accumulation rates in the Baltic sediments still require clarification. This paper describes methods used for assessing organic carbon and nitrogen accumulation rates in six sediment cores collected in the sediment accumulation areas in the Baltic Sea. Mass sediment accumulation rates were based on 210Pb method validated by 137Cs measurements. The organic carbon accumulation rates ranged from 18 to 75 g·C·m−2·yr−1. The C/N ratios and δ13C were used to access sedimentary organic matter provenance. The C/N ratios in the investigated cores vary in the range from 7.4 to 9.6, while δ13C ranged from −24.4‰ to −26.4‰. Results of the terrestrial organic matter contribution in the sedimentary organic matter were calculated basing on δ13C using the end member approach. Large proportion (41–73%) of the sedimentary organic carbon originates on land. The obtained results indicate the Baltic Sea sediments as an important sink for organic carbon. Substantial fraction of the sedimentary load originates on land.

Validating the use of 137Cs and 210Pbex measurements to estimate rates of soil loss from cultivated land in southern Italy

Soil erosion represents an important threat to the long-term sustainability of agriculture and forestry in many areas of the world, including southern Italy. Numerous models and prediction procedures have been developed to estimate rates of soil loss and soil redistribution, based on the local topography, hydrometeorology, soil type and land management. However, there remains an important need for empirical measurements to provide a basis for validating and calibrating such models and prediction procedures as well as to support specific investigations and experiments. In this context, erosion plots provide useful information on gross rates of soil loss, but are unable to document the efficiency of the onward transfer of the eroded sediment within a field and towards the stream system, and thus net rates of soil loss from larger areas. The use of environmental radionuclides, particularly caesium-137 (137Cs) and excess lead-210 (210Pbex), as a means of estimating rates of soil erosion and deposition has attracted increasing attention in recent years and the approach has now been recognised as possessing several important advantages. In order to provide further confirmation of the validity of the estimates of longer-term erosion and soil redistribution rates provided by 137Cs and 210Pbex measurements, there is a need for studies aimed explicitly at validating the results obtained. In this context, the authors directed attention to the potential offered by a set of small erosion plots located near Reggio Calabria in southern Italy, for validating estimates of soil loss provided by 137Cs and 210Pbex measurements. A preliminary assessment suggested that, notwithstanding the limitations and constraints involved, a worthwhile investigation aimed at validating the use of 137Cs and 210Pbex measurements to estimate rates of soil loss from cultivated land could be undertaken. The results demonstrate a close consistency between the measured rates of soil loss and the estimates provided by the 137Cs and 210Pbex measurements and can therefore been seen as validating the use of these fallout radionuclides to document soil erosion rates in that environment. Further studies are clearly required to exploit other opportunities for validation in contrasting environments and under different land use conditions.

Climatic variability and anthropogenic signatures in the Gulf of Salerno (southern-eastern Tyrrhenian Sea) during the last half millennium

The high-resolution study of sediment core C90-1 m collected at the continental shelf of the Gulf of Salerno (southern Tyrrhenian Sea) provides an excellent opportunity to show paleoenvironmental changes during the last 500 years induced by natural variability and human impact. Based on 210Pb and 137Cs measurements, the sedimentation rate results 0.20 cm/year for the last 100 years. The high sampling resolution (1 cm sample spacing) of core C90-1 m, 105 cm long, provides a time resolution of approximately 5 years/cm. Quantitative changes in the planktonic and benthonic foraminiferal assemblages combined with δ18O G.ruber variations allow to identify regional climatic and oceanographic signals. A significant turnover between herbivorous and opportunistic species and carnivorous planktonic foraminifera after the Maunder event suggests changes in river runoff and/or an increase in coastal flooding events in the studied area. Variations in the microfauna since 1940 yAD document environmental changes induced by the construction of a dam in the Sele River.

Estimating Soil Erosion in Northeast China Using 137Cs and 210Pb ex

Evaluation of soil erosion in agricultural fields is valuable to develop conservation practices for reducing agricultural nonpoint source pollution. Soil erosion rates were quantified using the fallout radionuclide tracer technique in Mojiagou Basin located on the outskirts of Changchun in Northeast China. The calculated soil erosion rates in the study area were 1.99 and 1.85 mm year −1 using 137Cs and excess 210Pb ( 210Pb ex) measurements, respectively. Both fallout radionuclides showed a similar tendency at downslope sites. All measured sites have experienced net erosion during the past 50 to 100 years. 137Cs and 210Pb ex measurements were useful to quantify soil erosion rates on field and small basin scales. At this rate of erosion, the current fertile topsoil layer would be entirely removed within 70 years.

Using 210Pb measurements to estimate sedimentation rates on river floodplains

Growing interest in the dynamics of floodplain evolution and the important role of overbank sedimentation on river floodplains as a sediment sink has focused attention on the need to document contemporary and recent rates of overbank sedimentation. The potential for using the fallout radionuclides 137Cs and excess 210Pb to estimate medium-term (10–10 2 years) sedimentation rates on river floodplains has attracted increasing attention. Most studies that have successfully used fallout radionuclides for this purpose have focused on the use of 137Cs. However, the use of excess 210Pb potentially offers a number of advantages over 137Cs measurements. Most existing investigations that have used excess 210Pb measurements to document sedimentation rates have, however, focused on lakes rather than floodplains and the transfer of the approach, and particularly the models used to estimate the sedimentation rate, to river floodplains involves a number of uncertainties, which require further attention. This contribution reports the results of an investigation of overbank sedimentation rates on the floodplains of several UK rivers. Sediment cores were collected from seven floodplain sites representative of different environmental conditions and located in different areas of England and Wales. Measurements of excess 210Pb and 137Cs were made on these cores. The 210Pb measurements have been used to estimate sedimentation rates and the results obtained by using different models have been compared. The 137Cs measurements have also been used to provide an essentially independent time marker for validation purposes. In using the 210Pb measurements, particular attention was directed to the problem of obtaining reliable estimates of the supported and excess or unsupported components of the total 210Pb activity of sediment samples. Although there was a reasonable degree of consistency between the estimates of sedimentation rate provided by the 137Cs and excess 210Pb measurements, some differences existed and the various models used to interpret excess 210Pb measurements could produce different results. By using the 137Cs measurements to provide independent validation of the estimates of sedimentation rate provided by the different models used with the excess 210Pb measurement it was shown that the CICCS and Composite CRS models appeared to generally provide the best results.

METHOD FOR SIMULTANEOUS 90SR AND 137CS IN-VIVO MEASUREMENTS OF SMALL ANIMALS AND OTHER ENVIRONMENTAL MEDIA DEVELOPED FOR THE CONDITIONS OF THE CHERNOBYL EXCLUSION ZONE

To perform in vivo simultaneous measurements of the 90Sr and 137Cs content in the bodies of animals living in the Chernobyl Exclusion Zone (ChEZ), an appropriate method and equipment were developed and installed in a mobile gamma beta spectrometry laboratory. This technique was designed for animals of relatively small sizes (up to 50 g). The 90Sr content is measured by a beta spectrometer with a 0.1-mm-thick scintillation plastic detector. The spectrum processing takes into account the fact that the measured object is "thick-layered" and contains a comparable quantity of 137Cs, which is a characteristic condition of the ChEZ. The 137Cs content is measured by a NaI scintillation detector that is part of the combined gamma beta spectrometry system. For environmental research performed in the ChEZ, the advantages of this method and equipment (rapid measurements, capability to measure live animals directly in their habitat, and the capability of simultaneous 90Sr and 137Cs measurements) far outweigh the existing limitations (considerations must be made for background radiation and the animal size, skeletal shape, and body mass). The accuracy of these in vivo measurements is shown to be consistent with standard spectrometric and radiochemical methods. Apart from the in vivo measurements, the proposed methodology, after a very simple upgrade that is also described in this paper, works even more accurately with samples of other media, such as soil and plants.

Long-term variations of 14C and 137Cs in the Bratislava air – implications of different atmospheric transport processes

This study summarizes measurements of atmospheric 14C and 137Cs in the Bratislava air since 1976. Higher 14C levels observed in spring and early summer months until the 1980’s confirm injection of the stratospheric air into the troposphere. Later, deep winter minima were observed in 14C concentrations, probably due to the depletion of the atmospheric 14C levels in winter months by the injection of large quantities of fossil CO2. Presently observed 14C maxima in summer and minima in winter were caused by the depletion of the atmospheric 14C in winter months, amplified by temperature inversions during winter, rather than by the injection of the stratospheric air into the troposphere. The observed 137Cs activity concentrations also showed an impact of the stratospheric air on the 137Cs levels until the early 1980’s, documented by typical spring/early summer maxima and winter minima. The global fallout 137Cs record was then disturbed by the Chernobyl accident (1986) when large quantities of 137Cs were released to the atmosphere. The recent 137Cs variations observed in the atmosphere, characterised by winter maxima and summer minima, are assumed to be mainly due to the resuspension of 137Cs from the soil. A correlation was found between the 137Cs activity concentration and the dust level in the air (the correlation coefficient r = 0.74), as well as an anticorrelation with the temperature (r = −0.56).

Erratum to “Applicability study of using in-situ gamma ray spectrometry technique for 137Cs and 210Pbex inventories measurement in grassland environments” [Applied Radiation and Isotopes 68 (2010), 1143–1149

Erratum to “Applicability study of using in-situ gamma ray spectrometry technique for 137Cs and 210Pbex inventories measurement in grassland environments” [Applied Radiation and Isotopes 68 (2010), 1143–1149

Disaggregating measurement uncertainty from population variability and Bayesian treatment of uncensored results

In making low-level radioactivity measurements of populations, it is commonly observed that a substantial portion of net results is negative. Furthermore, the observed variance of the measurement results arises from a combination of measurement uncertainty and population variability. This paper presents a method for disaggregating measurement uncertainty from population variability to produce a probability density function (PDF) of possibly true results. To do this, simple, justifiable and reasonable assumptions are made about the relationship of the measurements to the measurands (the 'true values'). The measurements are assumed to be unbiased, that is, that their average value is the average of the measurands. Using traditional estimates of each measurement's uncertainty, a likelihood PDF for each individual's measurand is produced. Then using the same assumptions and all the data from the population of individuals, a prior PDF of measurands for the population is produced. The prior PDF is non-negative, and the average is equal to the average of the measurement results for the population. Using Bayes's theorem, posterior PDFs of each individual measurand are calculated. The uncertainty in these bayesian posterior PDFs appears to be all Berkson with no remaining classical component. The method is applied to baseline bioassay data from the Hanford site. The data include (90)Sr urinalysis measurements of 128 people, (137)Cs in vivo measurements of 5337 people and (239)Pu urinalysis measurements of 3270 people. The method produces excellent results for the (90)Sr and (137)Cs measurements, since there are non-zero concentrations of these global fallout radionuclides in people who have not been occupationally exposed. The method does not work for the (239)Pu measurements in non-occupationally exposed people because the population average is essentially zero relative to the sensitivity of the measurement technique. The method is shown to give results similar to classical statistical inference when the measurements have relatively small uncertainty.

Comparison of the soil losses from 7Be measurements and the monitoring data by erosion pins and runoff plots in the Three Gorges Reservoir region, China

The potential for using 7Be measurements to document soil redistribution associated with a heavy rainfall was estimated using 7Be method on a bare purple soil plot in the Three Gorges Reservoir region of China. The results were compared with direct measurement from traditional approaches of erosion pins and runoff plots. The study shows that estimation of soil losses from 7Be are comparable with the monitoring results provided by erosion pins and runoff plots, and are also in agreement with the existing knowledge provided by 137Cs measurements. The results obtained from this study demonstrated the potential for using 7Be technique to quantify short-term erosion rates in these areas.

Measuring 137Cs, 40K and decay products of 226Ra and 232Th in samples of different nature by a multidetector spectrometer

A coincidence method for measuring 137Cs, 40K, 226Ra and 232Th decay products activity in soil, vegetation and fish samples, was applied to the six-crystal gamma-coincidence spectrometer PRIPYAT-2M. In this way, some problems appeared in simultaneous measurement of 137Cs, 226Ra and 232Th by NaI(Tl) detectors and the PRIPYAT-2M spectrometer were solved. The obtained results were agreeable with the HPGe spectrometer ones.

Reorientational Dynamics of the Dodecahydro-closo-dodecaborate Anion in Cs2B12H12

Rapid reorientational motions of the B(12)H(12)(2-) icosahedral anion, a key intermediate in borohydride dehydrogenation, are revealed by quasielastic neutron scattering (QENS) measurements of Cs(2)B(12)H(12) between 430 and 530 K. At 430 K, over the range of momentum transfers collected, the elastic incoherent structure factor (EISF) is consistent with a model for reorientational jumps about a single molecular axis. At temperatures of 480 K and higher, however, the EISF suggests the emergence of multiaxis reorientation by dynamically similar, independent jumps about two axes, on average, preserving crystallographic order. Alternatively, if one assumes that the anions are undergoing temperature-dependent rotational trapping, then the EISF is also consistent with a jump model involving a temperature-dependent mobile fraction of anions statistically tumbling between discrete crystallographic sites. Although neutron vibrational spectra demonstrate that the anion torsional modes soften dramatically with increasing temperature, the QENS-derived activation energy of 333 meV for reorientation clearly shows that the anions are not undergoing isotropic rotational diffusion.

Using 137Cs measurements to investigate the influence of erosion and soil redistribution on soil properties

Information on the interaction between soil erosion and soil properties is an important requirement for sustainable management of the soil resource. The relationship between soil properties and the soil redistribution rate, reflecting both erosion and deposition, is an important indicator of this interaction. This relationship is difficult to investigate using traditional approaches to documenting soil redistribution rates involving erosion plots and predictive models. However, the use of the fallout radionuclide (137)Cs to document medium-term soil redistribution rates offers a means of overcoming many of the limitations associated with traditional approaches. The study reported sought to demonstrate the potential for using (137)Cs measurements to assess the influence of soil erosion and redistribution on soil properties (particle size composition, total C, macronutrients N, P, K and Mg, micronutrients Mn, Mo, Fe, Cu and Zn and other elements, including Ti and As). (137)Cs measurements undertaken on 52 soil cores collected within a 7 ha cultivated field located near Colebrooke in Devon, UK were used to establish the magnitude and spatial pattern of medium-term soil redistribution rates within the field. The soil redistribution rates documented for the individual sampling points within the field ranged from an erosion rate of -12.9 t ha(-1) yr(-1) to a deposition rate of 19.2 t ha(-1) yr(-1). Composite samples of surface soil (0-5 cm) were collected immediately adjacent to each coring point and these samples were analysed for a range of soil properties. Individual soil properties associated with these samples showed significant variability, with CV values generally lying in the range 10-30%. The relationships between the surface soil properties and the soil redistribution rate were analysed. This analysis demonstrated statistically significant relationships between some soil properties (total phosphorus, % clay, Ti and As) and the soil redistribution rate, but for most properties there was no significant relationship. This suggests that other factors, in addition to soil erosion and soil redistribution, are also important in causing spatial variability in soil properties, or that, because of the relatively deep soils, soil properties are relatively insensitive to soil redistribution processes. The importance of the erosional history of the field was explored using a simple model to predict changes in soil properties in response to the magnitude of the erosion or deposition rate and the length of the period during which the field had been subject to soil erosion and soil redistribution.

Deviations from Beta Radioactivity Exponential Drop

At long-term count rate measurements of beta sources 3H, 56Mn, 32Si, 36Cl, 60Co, 137Cs, 90Sr-90Y and decay products of 226Ra the rhythmic changes with amplitude 0.1% 0.3% from average magnitude and period 1 year, and up to 0.01 % with period about one month are detected. Magnitude of diurnal oscillations did not exceed 0.003%. Analysis of measurements data for alpha radioactive sources 238Pu and 239Pu did not reveal any statistically reliable periodic patterns. Sporadic drops in the count rate were detected while registering the activity of 54Mn, 60Co and 90Sr-90Y sources. Bursts in the count rate were registered when scanning the celestial sphere by a reflecting telescope with 60Co or 40K radioactive sources at the focus point. Possible factors underlying these deviations in beta-radioactivity are discussed.

137Cs Redistribution in Thin Stony Soil of a Carbonate Rock Slope in Southwest China

The fallout radionuclide cesium-137 ( 137Cs) has been widely employed as a tracer for assessment of soil loss from thick uniform soils; however, few studies have been conducted on thin stony soils on slopes underlain by carbonate rocks which are widely distributed in karst areas. Information derived from 137Cs measurement of soil samples collected along a carbonate rock slope with thin stony soil where neither soil erosion nor deposition occurred was used to investigate the characteristics of 137Cs redistribution in a karst area of Southwest China. The results indicated that the 137Cs inventories of the surface soil on the slope studied were much lower than that of the local 137Cs reference inventory and the 137Cs activities were much higher than those on slopes with thick uniform soils. The spatial distribution of 137Cs inventories was characterized by considerable variation. The high 137Cs depletion in the stony soil of the slope studied was mainly because a considerable proportion of the fallout input of 137Cs could be lost with runoff and the dissolution of carbonate particles in the soil promoted the loss of 137Cs. These demonstrated that the rates of soil loss could not be estimated from the degree of depletion of the 137Cs inventory relative to the local reference inventory for the thin stony soil of the rocky slope underlain by carbonate rocks in the study area in the way that has been widely used in areas with thick uniform soils.

Transport of 137Cs to the Southern Hemisphere in an ocean general circulation model

137Cs originating from global fallout is transported into the ocean interior by advection and diffusion, and the 137Cs concentration is reduced by radioactive decay. 137Cs concentrations in the global ocean can be simulated by global integration of the coarse-resolution Parallel Ocean Program to understand the mechanism of material transport in the ocean. We investigated the transport mechanism of 137Cs to the Southern Hemisphere using an ocean general circulation model (OGCM) and compared the simulated results with observations of 137Cs concentrations in the Southern Hemisphere. 137Cs was deposited on the ocean surface mainly as global fallout originating from atmospheric nuclear weapons testing since 1945, and the global distribution of cumulative 137Cs deposition has been reconstructed from global measurements of 137Cs in rain, seawater, and soil. We estimated the global distribution of 137Cs deposition from 1945 to 2003 using these distribution data, 137Cs deposition data observed at the Meteorological Research Institute, Tsukuba, Japan, from 1958 to 2003, and 137Cs deposition data for 1945–1957 estimated from ice-core data. We compared the simulated results with 137Cs sections from the South Pacific, Indian, and South Atlantic Oceans obtained during the BEAGLE2003 cruise in 2003. The simulated 137Cs sections were in good agreement with the observations, except for the effects of mesoscale eddies, which not be simulated by the model because of its coarse resolution. OGCMs can simulate the general pattern of 137Cs distribution in the world’s oceans and improve our understanding of the transport mechanism leading to those 137Cs distributions on a time scale of several decades. The model simulation results suggest that the 137Cs deposited in the North Pacific advected to the South Pacific and Indian Ocean, and then to the South Atlantic over about four decades. The North Pacific is thus an important source area of 137Cs to the Southern Hemisphere.

Particulate organic carbon (POC) in surface sediments of the Baltic Sea

In this study, particulate organic carbon (POC) contents and their distribution pattern in surficial sediments of the Baltic Sea are presented for 1,471 sampling stations. POC contents range from approx. 0.1% in shallow sandy areas up to 16% in deep muddy basins (e.g. Gotland Basin). Some novel relationships were identified between sediment mass physical properties (dry bulk density (DBD), grain size) and POC levels. Notably, the highest POC concentrations (about 10–17 mg cm–3) occur in sandy mud to mud (60–100% mud content) with intermediate POC contents of about 3–7% and DBDs of 0.1–0.4 g cm–3. Areas with this range in values seem to represent the optimum conditions for POC accumulation in the Baltic Sea. The maximum POC contents (8–16%) are found in fluid mud of the central Baltic Sea characterized by extremely low DBDs (<0.1 g cm–3) and moderate POC concentrations (4–7 mg cm–3). Furthermore, sediment mass accumulation rates (MAR), based on 210Pb and 137Cs measurements and available for 303 sites of the Baltic Sea, were used for assessing the spatial distribution of POC burial rates. Overall, these vary between 14 and 35 g m–2 year–1 in the mud depositional areas and, in total, at least 3.5 (±2.9) Mt POC are buried annually. Distribution patterns of POC contents and burial rates are not identical for the central Baltic Sea because of the low MAR in this area. The presented data characterize Baltic Sea sediments as an important sink for organic carbon. Regional differences in organic carbon deposition can be explained by the origin and transport pathways of POC, as well as the environmental conditions prevailing at the seafloor (morphology, currents, redox conditions). These findings can serve to improve budget calculations and modelling of the carbon cycle in this large brackish-water marginal sea.

Comparing the use of the traditional and repeated-sampling-approach of the 137Cs technique in soil erosion estimation

Two approaches have been used in the literature to estimate soil erosion using 137Cs measurements. The traditional-approach requires only one set of samples and uses a single reference 137Cs level, determined off-site, for the whole site. The repeated-sampling-approach requires two sets of samples and uses point-specific values, the 137Cs inventories of the first set of samples, as the reference 137Cs levels. No study has been carried out to investigate the advantages and limitations of these two approaches. In this study, a hay-pasture site, located in Ontario, Canada, with a short period of corn ( Zea mays L.) production was examined. Total erosion was estimated using both the traditional- and repeated-sampling-approach. Water and tillage erosion were assessed using established models. The sum of water and tillage erosion served as the model-predicted total soil erosion, assuming negligible wind erosion. The site was classified into five landform elements and the 137Cs-estimated and model-predicted erosion rates were grouped into the landform elements. It was determined that when the reference 137Cs level is accurate, the traditional-approach can produce accurate soil erosion rates, providing that errors due to the conversion models are negligible. However, when there is a large error in the reference 137Cs level, the estimated erosion rates are biased. The repeated-sampling-approach eliminates the bias of reference 137Cs level but has higher random errors. However, the random errors can be reduced by taking multiple samples and using the spatially averaged erosion rate for data interpretation. Landscape segmentation based on topography provides a useful landform division for describing erosion processes and, therefore, practical units for grouping the sampling points. In addition, repeated-sampling-approach also has many advantages due to a shortened time period. In particular, the uncertainties of simple conversion models can be greatly reduced.

Temporal variation of accumulation rates on a natural salt marsh in the 20th century — The impact of sea level rise and increased inundation frequency

Salt marshes are potentially threatened by sea level rise if sediment supply is unable to balance the rising sea. A rapid sea level rise is one of the pronounced effects of global warming and global sea level is at present rising at an elevated rate of about 3.4mm y−1 on average. This increasing rate of sea level rise should make it possible to study the effect of rapidly rising sea level on salt marsh accumulation. However, such an understanding is generally hampered by lack of available data with sufficient precision. Here we present a high-precision dataset based on detailed radiometric measurements of 137Cs in 10 sediment cores retrieved at a natural and unmanaged micro tidal salt marsh. Two distinct 137Cs-peaks were found in all cores, one peak corresponding to the 1963-maximum caused by testing of nuclear weapons in the atmosphere and the other to the Chernobyl accident in 1986. Salt marsh accretion has generally kept pace with sea level rise since 1963 but comparison of the accumulation rates of minerogenic material in the period 1963–1986 and 1986–2003 revealed a slight decrease in accumulation with time in spite of an observed increase in inundation frequency. The observed decrease in sediment deposition is significant and gives reason for concern as it may be the first sign of a sedimentation deficiency which could be threatening this and other salt marshes in the case of a rapidly rising sea level. Our work demonstrates that the assumption of a constant relationship between salt marsh inundation and sediment deposition is not necessarily valid, even for a salt marsh that receives most of its allocthonous sediment from the adjacent sea. The apparent decrease in sediment deposition indicates that the basic assumption of sufficient sediment supply used in contemporary models dealing with salt marsh accretion is most probably not valid in the present case study and it may well be that this is also the case for many other salt marshes, especially if sea level continues to rise rapidly as indicated by some climate change scenarios.

Using 137Cs measurements to establish catchment sediment budgets and explore scale effects

AbstractGrowing awareness of the wider environmental significance of fine sediment transport by rivers and associated sediment problems linked to sediment–water quality interactions, nutrient and contaminant transfer, and the degradation of aquatic habitats has resulted in the need for an improved understanding of the mobilization and transfer of sediment in catchments to support the development of effective sediment management strategies. The sediment budget provides a key integrating concept for assembling information on the internal functioning of a catchment in terms of its sediment dynamics by providing information on the mobilization, transfer, storage and output of sediment. One key feature of a catchment sediment budget is the relationship between the sediment yield at the catchment outlet and rates of sediment mobilization and transfer within the catchment, which is commonly represented by the sediment delivery ratio. To date, most attempts to derive estimates of this ratio have been based on a comparison of the measured sediment yield from a catchment with an estimate of the erosion occurring within the catchment, derived from an erosion prediction procedure, such as the Universal Soil Loss Equation (USLE) or its revised version, RUSLE. There is a need to obtain more direct and spatially distributed evidence of the erosion rates occurring within a catchment and to characterize the links between sediment mobilization, transfer, storage and output more explicitly. In this context, fallout radionuclides have proved particularly useful as sediment tracers. This paper reports the results of a study aimed at exploring the use of caesium‐137 (137Cs) measurements to establish sediment budgets for three catchments of different sizes and contrasting land use located in Calabria, southern Italy. Long‐term measurements of sediment output were available for the catchments, and, by using the estimates of gross and net rates of soil loss within the catchments provided by 137Cs measurements, it was possible to establish the key components of the sediment budget for each catchment. By documenting the sediment budgets of three catchments of different sizes, the study provides a basis for exploring the effects of scale on catchment sediment budgets and, in particular, the increasing importance of catchment storage as the size of the catchment increases. The results of this study demonstrate a reduction in the sediment delivery ratio from 98 to 2% as catchment area increases from 1·47 ha to 31·2 km2. Copyright © 2010 John Wiley &amp; Sons, Ltd.