210Pbex Measurements Research Articles

Using radiotracers 137Cs and 210Pbex to document climate change in mountain areas through the estimate of soil erosion rates

Abstract. During the last few decades, a general increase in heavy rainfall events has been documented in many areas of the world. These events have caused changes in soil erosion rates and strongly affected the human activities in mountain areas by reducing the national income obtained from cultivated land. In this context, the use of fallout radiotracers can be an important tool for better understanding the consequences of climate change in these areas and proposing effective countermeasures in order to reduce soil loss. In this contribution, plot experiments carried out in southern Italy that involve the use of 137Cs and 210Pbex measurements were performed to estimate soil erosion rates during the last few decades. The overall results indicate an increase in soil erosion rates during the last 15–20 years and suggest the use of this technique to detect climate change in mountain areas.

A model on changes in 210Pbex depth distribution for non-eroded abandoned farmland

Fallout radionuclides such as 137Cs and 210Pbex have been successfully used to quantify rates of soil and sediment redistribution in many areas of the world in recent years. However, little attention has been given to the assessment of soil erosion rate in abandoned farmland using the 210Pbex tracer technique. The artificially derived 137Cs is still basically uniformly distributed in the soil after farmland abandonment, while the depth distribution of the naturally derived 210Pbex in the soil of the abandoned farmland will be continuously changed by the combined effects of its continuous atmospheric deposition, infiltration and radioactive decay within 100 years after farmland abandonment. At present, there is no model to represent this change of 210Pbex distribution after the farmland abandonment, and the existing steady-state 210Pbex model is not suitable for soil erosion assessment in the abandoned farmland. It is necessary to develop a model on the changes of 210Pbex depth distribution in the soil of abandoned farmland. In this study, the redistribution process of 210Pbex in the soil after farmland abandonment was decomposed and theoretically deduced on basis of analyzing the physical mechanisms of 210Pbex infiltration and decay in the soil. The expression of 210Pbex decay in the plow layer on the initially abandoned farmland and the expression of infiltration of the new fallout 210Pbex in the soil after farmland abandonment were incorporated to develop the model on changes in 210Pbex depth distribution for the abandoned farmland. The parameters such as the plow depth and the diffusion coefficient required for the model were obtained according to the measured 137Cs and 210Pbex depth distributions from the typical abandoned farmlands in Sichuan Province, southwest China. The result showed that the modeled curves of 210Pbex depth distribution in the farmland abandoned for 19, 15 and 8 years matched each other with the measured curves. In addition, the Nash-Sutcliffe efficiency coefficient (ENS) test showed that the ENS of the three abandoned farmlands were 0.975, 0.961 and 0.889, respectively, indicating the modeled results are reliable. The present study has an important theoretical significance for the development of the models for calculating the soil erosion amount from 210Pbex measurements on the abandoned farmland and further provides an effective method for the evaluation of the soil erosion response driven by abandonment.

A Preliminary Study of the Impacts of Shelter Forest on Soil Erosion in Cultivated Land: Evidence from integrated 137Cs and 210Pbex Measurements

The Three-North Shelter Forest Program (TNSFP) has played an important role in increasing the forest coverage and decreasing the wind erosion rate. Fallout radionuclides (FRNs), such as caesium-137 (137Cs) and excess lead-210 (210Pbex), have extensively been used as fast and economical tools to estimate erosion rates over a broad range of spatial and temporal scales. However, the 137Cs and 210Pbex conversion models used to estimate annual soil erosion rates under steady state conditions have not been used to predict corresponding rates following reforestation due to the land-use changes that have occurred since 1963 in China. This study investigated the influence of shelter forest on soil erosion of cultivated land (CL) by using 137Cs and 210Pbex in northern China. Opposing trends in the spatial variation were found between the 137Cs and 210Pbex inventories, which were due to their differing sources and mass balances within the soil profile. Exploiting this finding, we propose a conceptual 137Cs and 210Pbex variation model to detect depth variations between before and after reforestation. Wind erosion rate was 29.11 ± 14.42 Mg ha-1 yr-1 in the CL when estimated with 137Cs. However, estimation by the revised 210Pbex mass balance model showed that wind erosion rates were 68.55 ± 22.11 and -8.52 ± 47.32 Mg ha-1 yr-1 before and after the surrounding forest matured, respectively. The spatial variation in the 137Cs inventories mainly reflects the soil erosion patterns before the surrounding shelter forest matured, while the spatial variation in the 210Pbex inventories mainly reflects the soil erosion patterns after the surrounding shelter forest matured. Furthermore, the soil erosion rates that were deduced from the 210Pbex conversion model confirmed that the TNSFP played an important role in decreasing the soil erosion rates and intercepting sandstorms in northern China. Thus, the advantages and limitations associated with the use of FRNs for assessing wind erosion in the study area were also proposed. More attention should also be paid to the limitation of estimating soil erosion rates by using FRNs measurements in the TNSFP region of China.

Using 137Cs and 210Pbex to trace soil erosion rates for a small catchment in the mid-hills of Nepal

Soil erosion is a major threat to agricultural sustainability in the hills of Nepal. However, little is known about the soil erosion rates at a small catchment scale in this region. In this study, the soil redistribution rates in a typical small hilly catchment in the Ramechhap District of Nepal were evaluated using the 137Cs and 210Pbex tracer techniques. Nine representative slopes under three land uses and a reference site from the gentle sloping forest land within the catchment were selected as sample plots. A downhill transect was built in each sample plot, and soil samples were collected at 5-m intervals along the transects. The results showed that the spatial variations in radionuclide inventory and soil erosion rates measured by 137Cs measurements were highly consistent with equivalent estimates from 210Pbex measurements, suggesting the potential for using 137Cs and 210Pbex measurements to estimate soil redistribution rates. All 137Cs and 210Pbex inventories on the slopes were less than the reference values, indicating that net soil loss has occurred at all of the sampling points. The net erosion rates from sloping farmland (37.08 t ha???1 year???1) and shrub land (32.52 t ha???1 year???1) were significantly higher than those from forest land (14.91 t ha???1 year???1). Furthermore, the soil erosion rates obtained from 210Pbex measurements were higher than those obtained from 137Cs measurements, which implies that soil erosion in the catchment was accelerated during the last two decades. The net soil loss from the study catchment was estimated to be 31.29 t ha???1 year???1, which is mainly contributed by shrub land (55.08%) and sloping farmland (37.68%). These results indicate that shrub land and sloping farmland are vulnerable to erosion, which should be specifically considered in the sustainable management of small agricultural catchments in the mid-hills of Nepal, especially in dry valley regions.

Livestock grazing significantly accelerates soil erosion more than climate change in Qinghai-Tibet Plateau: Evidenced from 137Cs and 210Pbex measurements

Livestock grazing and climate change accelerate soil erosion in the grassland of Qinghai-Tibet Plateau (QTP), China. However, the linkage of the two factors to accelerated erosion in the region has never been separated. Thus, this study was set up to determine the contribution of livestock grazing and climate change to soil erosion in the grassland of QTP. Five sites (Tuotuohe, Maduo, Maqin Dongqinggou (MQDQG), Maqin Junmuchang (MQJMC), and Maqin Jungongzhen (MQJGZ)) across 1100-km East-West transect in the Three-River Headwaters Region (TRHR) of QTP were selected for this study. The 137Cs and 210Pbex techniques were used to determine soil redistribution rates, covering a time scale of 50 and 100 years, respectively. In the last 100 years, soil accumulation was obvious in four sites (Tuotuohe, Maduo, MQDQG and MQJMC) except one site (MQJGZ), where soil erosion occurred along the transect. In the entire transect, almost no soil erosion but soil accumulation (0.25 t ha−1 yr−1) occurred over a period of 100 years. In contrast, soil erosion significantly increased by 75 times at a rate of 18.68 t ha−1 yr−1 in the last 50 years. Net soil redistribution varied significantly from −99 t ha−1 yr−1 in MQJGZ to 14.2 t ha−1 yr−1 in MQDQG over a period of last 50 years. Accelerated soil erosion across QTP significantly correlated with livestock numbers and intensive grazing activities but not significantly correlated with precipitation. Our results suggest that livestock grazing play a key role in accelerating soil erosion more than climate change in the grassland of Qinghai-Tibet Plateau.

Using 137Cs and 210Pbex measurements to explore the effectiveness of soil conservation measures in semi-arid lands: a case study in the Kouhin region of Iran

One of the most fragile agro-ecosystems in Iran is represented by dry farming lands on steep hillslopes that occupy ca. 54% of the national agricultural lands. Therefore, in order to reduce loss of fertile soil from these lands, it is important to apply effective soil conservation strategies. This study used cesium-137 (137Cs) and excess lead-210 (210Pbex) measurements to assess the effectiveness of soil conservation practices in controlling soil erosion in Kouhin, Qazvin Province of Iran. Soil samples were collected from two adjacent hillslopes with and without conservation agriculture practices. The managed site benefited from conservation practices, including controlled grazing, terraces, and contour farming for 50 years. The unmanaged site was under cultivation without agricultural conservation practices. At the managed site, both 137Cs and 210Pbex activities were measured. Only 137Cs activity was measured for the unmanaged site. Conservation practices performed at the managed site were effective in minimizing soil erosion, i.e., net soil erosion rates provided by 137Cs measurements were only 4.6 Mg ha−1 year−1 at the managed site, compared to 12 Mg ha−1 year−1 for the unmanaged site. By using the 210Pbex approach, net soil loss and sediment delivery ratio in the managed site were 12.3 Mg ha−1 year−1 and 60%, respectively. Soil redistribution magnitudes established from 137Cs inventories are associated with a period extending from 1963 to the time of sampling, while those obtained from 210Pbex measurements are related to the past 100 years. However, 210Pbex measurements are expected to be more sensitive to erosive events that occurred during the last 15 to 20 years and this could reflect the higher estimate of erosion rate provided by this radionuclide for the managed site. The increasing trend seems to suggest a possibility that the higher soil losses estimated by the 210Pbex measurements are a result of increasing climate variability during the last two decades. However, further investigation would be needed to confirm this hypothesis.

Exploring the potential for using 210Pbex measurements within a re-sampling approach to document recent changes in soil redistribution rates within a small catchment in southern Italy

In recent years, the fallout radionuclides caesium-137 (137Cs) and unsupported lead-210 (210Pbex) have been successfully used to document rates of soil erosion in many areas of the world, as an alternative to conventional measurements. By virtue of their different half-lives, these two radionuclides are capable of providing information related to different time windows. 137Cs measurements are commonly used to generate information on mean annual erosion rates over the past ca. 50–60 years, whereas 210Pbex measurements are able to provide information relating to a longer period of up to ca. 100 years. However, the time-integrated nature of the estimates of soil redistribution provided by 137Cs and 210Pbex measurements can be seen as a limitation, particularly when viewed in the context of global change and interest in the response of soil redistribution rates to contemporary climate change and land use change. Re-sampling techniques used with these two fallout radionuclides potentially provide a basis for providing information on recent changes in soil redistribution rates. By virtue of the effectively continuous fallout input, of 210Pb, the response of the 210Pbex inventory of a soil profile to changing soil redistribution rates and thus its potential for use with the re-sampling approach differs from that of 137Cs. Its greater sensitivity to recent changes in soil redistribution rates suggests that 210Pbex may have advantages over 137Cs for use in the re-sampling approach. The potential for using 210Pbex measurements in re-sampling studies is explored further in this contribution. Attention focuses on a small (1.38 ha) forested catchment in southern Italy. The catchment was originally sampled for 210Pbex measurements in 2001 and equivalent samples were collected from points very close to the original sampling points again in 2013. This made it possible to compare the estimates of mean annual erosion related to two different time windows. This comparison suggests that mean annual rates of net soil loss had increased during the period between the two sampling campaigns and that this increase was associated with a shift to an increased sediment delivery ratio. This change was consistent with independent information on likely changes in the sediment response of the study catchment provided by the available records of annual sediment yield and changes in the annual rainfall documented for the local area.

Using fallout radionuclides to investigate recent overbank sedimentation rates on river floodplains: an overview

Abstract. Information on rates of overbank sedimentation on river floodplains is needed for a variety of purposes. Use of 137Cs and 210Pbex measurements provides an effective means of estimating medium-term floodplain sedimentation rates and that approach has now been successfully used in many areas of the world. This contribution reviews the use of 137Cs and 210Pbex measurements in floodplain sedimentation investigations and discusses some of the important sampling requirements and key issues associated with interpreting the measurements, and subsequently deriving reliable estimates of sedimentation rates. The potential use of other radionuclides, including 241Am, 238,239+240Pu, and 7Be is considered, and the advantages of using two or more radionuclides, in combination, is highlighted.

Wind erosion on Deliblato (the largest European continental sandy terrain) studied using 210Pbex and 137Cs measurements

The objective of this paper is to estimate the difference in wind erosion between two extreme situations: sandy soil permanently covered by grass and the nearby frequently ploughed area highly susceptible to wind erosion. The spatial pattern of soil erosion rate was investigated using 137 Cs and 210 Pbex tracing technique. The spatial pattern of erosion rate obtained within the studied area reveal influence of topography as well as direction of prevailing winds on mobilization and transport of the soil particles.

Use of 7Be measurements to estimate rates of soil loss from cultivated land: Testing a new approach applicable to individual storm events occurring during an extended period

AbstractThe techniques available for documenting rates and patterns of soil redistribution in the landscape have many limitations and the value of those employing fallout radionuclides (FRNs), including caesium‐137 (137Cs) and excess lead‐210 (210Pbex) is being increasingly recognized. However, the use of 137Cs and 210Pbex measurements is best suited to investigations of longer‐term soil redistribution rates (i.e., ∼50–60 years for 137Cs and ∼100 years for 210Pbex). For many purposes, a much shorter timeframe is required. Beryllium‐7 (7Be), another FRN (half‐life 53 days), offers the potential to document soil redistribution associated with individual events or short periods of heavy rainfall. However, existing approaches for using 7Be possess important limitations related to both the timing of the study period and its length. This contribution reports the development of a new approach that permits estimation of the soil loss associated with all individual events or short periods of rainfall occurring during a study period extending over a year or more. The approach was validated using data collected from an erosion plot located in southern Italy. The close agreement of the measured and estimated values demonstrates the validity of the new approach which has the potential to greatly increase the scope for using 7Be measurements to document short‐term soil redistribution associated with individual storm events.

Using 137Cs and 210Pbex measurements and conventional surveys to investigate the relative contributions of interrill/rill and gully erosion to soil loss from a small cultivated catchment in Sicily

In many cultivated areas in semiarid Mediterranean regions, soil erosion is responsible for problems related to both on-site and off-site impacts, including reduced crop productivity, water quality, and degradation of freshwater ecosystems. In some areas of Sicily, where intense short duration rainfall events are common, soil erosion is a very serious problem, especially on land subjected to continuous tillage operations. The rates of soil loss in these areas and their impact differ according to the dominant type of erosion. Several existing studies have focused on the impacts of either linear (gully- or ephemeral gully-erosion) or interrill–rill erosion, but to date the relative magnitude of these two different types of erosion, has rarely been assessed. This paper reports the results of a study aimed at comparing the relative contribution of interrill–rill erosion and gully erosion to soil loss from a small cultivated catchment located in Sicily (Italy). Surveys of ephemeral gullies (EG) in the study catchment carried out at the event scale since 1999 are used to quantify soil loss attributable to EG erosion. 137Cs and 210Pbex measurements are used to quantify the net soil loss from the catchment attributable to interrill–rill (IRR) erosion. The study demonstrates that EG formation occurred 7 years out of 10, with a mean soil loss averaged over a 10-year period equal to 26.5tha−1yr−1. The rates of IRR erosion estimated using 137Cs and 210Pbex measurements provided values of mean annual net soil loss of 38.8tha−1yr−1 and 34.2tha−1yr−1, respectively. The resulting ratios of soil loss attributable to EG to total soil loss (IRR+EG) were 0.41 and 0.44 for the 137Cs and 210Pbex measurements, respectively. The results suggest that the contributions of EG and IRR erosion are of a similar magnitude in semiarid regions of Sicily, although the precise value of the ratio is likely to vary both spatially and temporally in response to catchment morphology, soil erodibility and land use and inter-annual variability of rainfall magnitude and erosivity. The findings are consistent with those of other studies that have attempted to compare the relative efficacy of the two erosion types. The use of 137Cs and 210Pbex measurements in the study area provided important insights into the relative importance of IRR and EG erosion and the same approach could be employed in other locations where both forms of erosion occur and there is a need to quantify their relative importance.

Assessment of soil redistribution and spatial pattern for a small catchment in the black soil region, Northeastern China: Using fallout 210Pbex

Soil erosion greatly reduces soil fertility. Quantification of soil erosion is required to effectively implement soil conservation practices. This study used the 210Pbex measurements to assess long-term rates and spatial pattern of soil redistribution in an agricultural catchment in the black soil region, Northeastern China. A total of 61 sampling cores were collected from the catchment, where 137Cs has been previously used to study medium-term soil redistribution rates. The potential use of 210Pbex was validated through using 137Cs measurements in our previous study and other methods. 210Pbex-based soil redistribution rates ranged from −106.5 to 166.9tha−1yr−1 with a mean value of −3.9tha−1yr−1. The net erosion rate for the entire catchment was −8.3tha−1yr−1, which is much higher than the tolerable soil erosion rate. The spatial pattern of soil redistribution was investigated based on the 210Pbex measurements. The correlations between the rates of soil redistribution and slope gradient and curvature were not significant at the 0.05 risk level. Although the shelterbelts could greatly affect spatial pattern of soil redistribution, ca. 78% of the eroded soils were lost per year from the agricultural catchment and soil erosion has accelerated in the last few decades. Integrated soil conservation measures are urgently required to effectively control soil loss in the black region of Northeastern China.

Using 210Pbex measurements to quantify soil redistribution along two complex toposequences in Mediterranean agroecosystems, northern Spain

Information on soil redistribution rates associated with the intricate patterns of Mediterranean agroecosystems is a key requirement for assessing both soil degradation, and off-site sediment problems that can affect downstream water bodies. Excess lead-210 (210Pbex) measurements provide a very effective means of documenting spatial patterns of rates of soil redistribution in different landscapes, but to date the approach has not been widely used in mountain Mediterranean landscapes. This research aims to use 210Pbex measurements to estimate soil redistribution rates on slopes uncultivated and under cultivation, within two complex toposequences located in the vicinity of Estaña Lake, characterized by an intricate mosaic of land use, steep slopes and anthropogenic modification (e.g. terraces and tracks), which are typical of these agroecosystems in northeastern Spain. A perceptual model is developed to account for the soil redistribution dynamics along both toposequences. This provides a simple and novel methodology adapted to Mediterranean agroecosystems, which besides using information on soil redistribution rates provided by 210Pbex measurements, also takes into account variations in land use and the presence of linear landscape elements, which modify runoff and soil redistribution processes and sediment connectivity along the toposequences. The results show that erosion predominated on the steep cultivated slopes, but lower soil redistribution rates were found on the uncultivated slopes. On the flat areas at the bottom of both transects, deposition was dominant. Variations in land use and the presence of linear landscape elements control soil redistribution processes. Such elements can perform the role of Ecological Focus Areas (EFAs), proposed within ‘The Green’ Common Agricultural Policy for 2014, in which at least 7% of a farmer's land should comprise EFAs, which can include terraces, landscape features, buffer strips and afforested areas.

Introduction to the special issue ‘Tracer Applications in Sediment Research’

Introduction to the special issue ‘Tracer Applications in Sediment Research’

Modeling the vertical soil organic matter profile using Bayesian parameter estimation

Abstract. The vertical distribution of soil organic matter (SOM) in the profile may constitute an important factor for soil carbon cycling. However, the formation of the SOM profile is currently poorly understood due to equifinality, caused by the entanglement of several processes: input from roots, mixing due to bioturbation, and organic matter leaching. In this study we quantified the contribution of these three processes using Bayesian parameter estimation for the mechanistic SOM profile model SOMPROF. Based on organic carbon measurements, 13 parameters related to decomposition and transport of organic matter were estimated for two temperate forest soils: an Arenosol with a mor humus form (Loobos, the Netherlands), and a Cambisol with mull-type humus (Hainich, Germany). Furthermore, the use of the radioisotope 210Pbex as tracer for vertical SOM transport was studied. For Loobos, the calibration results demonstrate the importance of organic matter transport with the liquid phase for shaping the vertical SOM profile, while the effects of bioturbation are generally negligible. These results are in good agreement with expectations given in situ conditions. For Hainich, the calibration offered three distinct explanations for the observations (three modes in the posterior distribution). With the addition of 210Pbex data and prior knowledge, as well as additional information about in situ conditions, we were able to identify the most likely explanation, which indicated that root litter input is a dominant process for the SOM profile. For both sites the organic matter appears to comprise mainly adsorbed but potentially leachable material, pointing to the importance of organo-mineral interactions. Furthermore, organic matter in the mineral soil appears to be mainly derived from root litter, supporting previous studies that highlighted the importance of root input for soil carbon sequestration. The 210Pbex measurements added only slight additional constraint on the estimated parameters. However, with sufficient replicate measurements and possibly in combination with other tracers, this isotope may still hold value as tracer for SOM transport.

Using 137Cs and 210Pbex measurements to investigate the sediment budget of a small forested catchment in southern Italy

AbstractConcern for the sustainability of the soil resource and for the detrimental impacts of fine sediment on downstream river systems and aquatic ecosystems has directed attention to the need for information on the suspended sediment loads of rivers. However, traditional measurement programmes focus primarily on quantifying the sediment load at a catchment outlet. Such information, although useful, may be of limited value in establishing rates of soil degradation, because much of the sediment mobilized within a catchment may be deposited before reaching the catchment outlet. Furthermore, it may also be of limited value in the design and implementation of sediment management and control programmes, because this requires an understanding of the key sources of mobilized sediment, the transport pathways involved and the importance of storage within the catchment. Information on the sediment budget of a catchment must be seen as an increasingly important requirement. However, such information is difficult to obtain using conventional traditional monitoring techniques. Fallout radionuclides, including caesium‐137 (137Cs) and unsupported or excess lead‐210 (210Pbex), have been shown to offer considerable potential for use as sediment tracers in sediment budget investigations. They are able to provide distributed information on rates of soil and sediment redistribution within the catchment, which represents a valuable complement to information on sediment output. This contribution reports the results of a study aimed at exploring the use of both 137Cs and 210Pbex measurements to establish the sediment budget for the small (1.39 km2) forested Bonis catchment, located in southern Italy. The results confirm that 137Cs and 210Pbex measurements can provide a valuable tool for quantifying both erosion and sediment redistribution within a catchment and therefore for establishing its sediment budget. Copyright © 2012 John Wiley & Sons, Ltd.

Using plot experiments to test the validity of mass balance models employed to estimate soil redistribution rates from 137Cs and 210Pbex measurements

Information on rates of soil loss from agricultural land is a key requirement for assessing both on-site soil degradation and potential off-site sediment problems. Many models and prediction procedures have been developed to estimate rates of soil loss and soil redistribution as a function of the local topography, hydrometeorology, soil type and land management, but empirical data remain essential for validating and calibrating such models and prediction procedures. Direct measurements using erosion plots are, however, costly and the results obtained relate to a small enclosed area, which may not be representative of the wider landscape. In recent years, the use of fallout radionuclides and more particularly caesium-137 (137Cs) and excess lead-210 (210Pbex) has been shown to provide a very effective means of documenting rates of soil loss and soil and sediment redistribution in the landscape. Several of the assumptions associated with the theoretical conversion models used with such measurements remain essentially unvalidated. This contribution describes the results of a measurement programme involving five experimental plots located in southern Italy, aimed at validating several of the basic assumptions commonly associated with the use of mass balance models for estimating rates of soil redistribution on cultivated land from 137Cs and 210Pbex measurements. Overall, the results confirm the general validity of these assumptions and the importance of taking account of the fate of fresh fallout. However, further work is required to validate the conversion models employed in using fallout radionuclide measurements to document soil redistribution in the landscape and this could usefully direct attention to different environments and to the validation of the final estimates of soil redistribution rate as well as the assumptions of the models employed.

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.

210Pbex depth distribution in soil and calibration models for assessment of soil erosion rates from 210Pbex measurements

210Pbex depth distribution in soil and calibration models for assessment of soil erosion rates from 210Pbex measurements