Estimating soil aggregate stability with infrared spectroscopy and pedotransfer functions

International audienceSoil aggregate stability is an important indicator of soil condition and is directly related to soil degradation processes such as erosion and crusting. Aggregate stability is conventionally measured by testing the aggregate resistance to water disturbance mechanisms. Such measurements, however, are costly and time-consuming, which make them difficult to implement at a regional or country scale. In this study, we explore two different approaches to estimate soil aggregate stability by means of commonly-measured soil properties or mid-infrared spectroscopy measurements. The first approach relies on land use and soil properties. In the second approach aggregate stability is estimated by a model fitted with mid-infrared spectroscopic data. We tested the two approaches with a dataset composed of 202 soil samples from mainland France, in which aggregate stability was measured with a fast wetting test. We found that simple linear models based on common soil properties and models based on mid-infrared spectral data yielded similar results. Interpretation of the models revealed wellknown relationships: land use had a major role in predicting aggregate stability, followed by organic carbon and clay content. Overall, we conclude that both approaches offer a reliable, cheap and time-efficient alternative to estimating soil aggregate stability. These approaches offer a tool to estimate aggregate stability over large geographical areas, which can support the development of erosive risk management plans and the implementation of adaptive management strategies to mitigate threats to soil and improve the overall soil condition

A review of worldwide sediment core dating research including fallout radionuclides to reconstruct erosion and sedimentation processes

International audienceDating recent sediment archives (<150 years) constitutes a prerequisite for reconstructing soil erosionand deposition processes during the last several decades. Radiocesium ($^{137}$Cs) emitted duringthermonuclear bomb testing ($^-$1950 - $^-$1980) and nuclear accidents (1986 and 2011) was generally used for identifying sediment sources or for establishing sediment core chronology based on discrete time markers. Although this method has been widely used during the last several decades, there is a lack of structured and comprehensive worldwide synthesis of both natural and artificial fallout radionuclidesused for dating sediment cores in environmental and Earth sciences. The current literature overview wasbased on 573 articles published between 1977 and 2020, reporting the collection of 1351 individualsediment cores. This synthesis led to the identification of the worldwide distribution of discrete timemarkers associated with the thermonuclear bomb testing peak in 1963, the Chernobyl fallout, theFukushima fallout, and the identification of 25 events induced by local accidents or nuclear tests (e.g.,Sellafield, la Hague accidents, Chinese nuclear tests). With a growing number of studies focusing on the analysis of recent sediment cores and the increasinginterest in sediment fingerprinting techniques, this spatialized synthesis provides a unique worldwide foridentifying the distribution of $^{137}$Cs sources across the globe. The potential associated with the analysis of other fallout radionuclides, including excess-lead-210 ($^{210}$Pb$_{xs}$) and plutonium atom ratios ($^{240}$Pu/$^{239}$Pu), is also discussed to improve the dating of environmental archives for reconstructing soil erosion and sedimentation processes

A review of worldwide sediment core dating research including fallout radionuclides to reconstruct erosion and sedimentation processes

International audienceDating recent sediment archives (<150 years) constitutes a prerequisite for reconstructing soil erosionand deposition processes during the last several decades. Radiocesium ($^{137}$Cs) emitted duringthermonuclear bomb testing ($^-$1950 - $^-$1980) and nuclear accidents (1986 and 2011) was generally used for identifying sediment sources or for establishing sediment core chronology based on discrete time markers. Although this method has been widely used during the last several decades, there is a lack of structured and comprehensive worldwide synthesis of both natural and artificial fallout radionuclidesused for dating sediment cores in environmental and Earth sciences. The current literature overview wasbased on 573 articles published between 1977 and 2020, reporting the collection of 1351 individualsediment cores. This synthesis led to the identification of the worldwide distribution of discrete timemarkers associated with the thermonuclear bomb testing peak in 1963, the Chernobyl fallout, theFukushima fallout, and the identification of 25 events induced by local accidents or nuclear tests (e.g.,Sellafield, la Hague accidents, Chinese nuclear tests). With a growing number of studies focusing on the analysis of recent sediment cores and the increasinginterest in sediment fingerprinting techniques, this spatialized synthesis provides a unique worldwide foridentifying the distribution of $^{137}$Cs sources across the globe. The potential associated with the analysis of other fallout radionuclides, including excess-lead-210 ($^{210}$Pb$_{xs}$) and plutonium atom ratios ($^{240}$Pu/$^{239}$Pu), is also discussed to improve the dating of environmental archives for reconstructing soil erosion and sedimentation processes

A review of worldwide sediment core dating research including fallout radionuclides to reconstruct erosion and sedimentation processes

International audienceDating recent sediment archives (<150 years) constitutes a prerequisite for reconstructing soil erosionand deposition processes during the last several decades. Radiocesium ($^{137}$Cs) emitted duringthermonuclear bomb testing ($^-$1950 - $^-$1980) and nuclear accidents (1986 and 2011) was generally used for identifying sediment sources or for establishing sediment core chronology based on discrete time markers. Although this method has been widely used during the last several decades, there is a lack of structured and comprehensive worldwide synthesis of both natural and artificial fallout radionuclidesused for dating sediment cores in environmental and Earth sciences. The current literature overview wasbased on 573 articles published between 1977 and 2020, reporting the collection of 1351 individualsediment cores. This synthesis led to the identification of the worldwide distribution of discrete timemarkers associated with the thermonuclear bomb testing peak in 1963, the Chernobyl fallout, theFukushima fallout, and the identification of 25 events induced by local accidents or nuclear tests (e.g.,Sellafield, la Hague accidents, Chinese nuclear tests). With a growing number of studies focusing on the analysis of recent sediment cores and the increasinginterest in sediment fingerprinting techniques, this spatialized synthesis provides a unique worldwide foridentifying the distribution of $^{137}$Cs sources across the globe. The potential associated with the analysis of other fallout radionuclides, including excess-lead-210 ($^{210}$Pb$_{xs}$) and plutonium atom ratios ($^{240}$Pu/$^{239}$Pu), is also discussed to improve the dating of environmental archives for reconstructing soil erosion and sedimentation processes

A review of worldwide sediment core dating research including fallout radionuclides to reconstruct erosion and sedimentation processes

International audienceDating recent sediment archives (<150 years) constitutes a prerequisite for reconstructing soil erosionand deposition processes during the last several decades. Radiocesium ($^{137}$Cs) emitted duringthermonuclear bomb testing ($^-$1950 - $^-$1980) and nuclear accidents (1986 and 2011) was generally used for identifying sediment sources or for establishing sediment core chronology based on discrete time markers. Although this method has been widely used during the last several decades, there is a lack of structured and comprehensive worldwide synthesis of both natural and artificial fallout radionuclidesused for dating sediment cores in environmental and Earth sciences. The current literature overview wasbased on 573 articles published between 1977 and 2020, reporting the collection of 1351 individualsediment cores. This synthesis led to the identification of the worldwide distribution of discrete timemarkers associated with the thermonuclear bomb testing peak in 1963, the Chernobyl fallout, theFukushima fallout, and the identification of 25 events induced by local accidents or nuclear tests (e.g.,Sellafield, la Hague accidents, Chinese nuclear tests). With a growing number of studies focusing on the analysis of recent sediment cores and the increasinginterest in sediment fingerprinting techniques, this spatialized synthesis provides a unique worldwide foridentifying the distribution of $^{137}$Cs sources across the globe. The potential associated with the analysis of other fallout radionuclides, including excess-lead-210 ($^{210}$Pb$_{xs}$) and plutonium atom ratios ($^{240}$Pu/$^{239}$Pu), is also discussed to improve the dating of environmental archives for reconstructing soil erosion and sedimentation processes

Sensitivity of source sediment fingerprinting to tracer selection methods

International audienceAbstract. In a context of accelerated soil erosion and sediment supply to water bodies, sediment fingerprinting techniques have received an increasing interest in the last 2 decades. The selection of tracers is a particularly critical step for the subsequent accurate prediction of sediment source contributions. To select tracers, the most conventional approach is the three-step method, although, more recently, the consensus method has also been proposed as an alternative. The outputs of these two approaches were compared in terms of identification of conservative properties, tracer selection, modelled contributions and performance on a single dataset. As for the three-step method, several range test criteria were compared, along with the impact of the discriminant function analysis (DFA). The dataset was composed of tracer properties analysed in soil (three potential sources; n = 56) and sediment core samples (n = 32). Soil and sediment samples were sieved to 63 µm and analysed for organic matter, elemental geochemistry and diffuse visible spectrometry. Virtual mixtures (n = 138) with known source proportions were generated to assess model accuracy of each tracer selection method. The Bayesian un-mixing model MixSIAR was then used to predict source contributions on both virtual mixtures and actual sediments. The different methods tested in the current research can be distributed into three groups according to their sensitivity to the conservative behaviour of properties, which was found to be associated with different predicted source contribution tendencies along the sediment core. The methods selecting the largest number of tracers were associated with a dominant and constant contribution of forests to sediment. In contrast, the methods selecting the lowest number of tracers were associated with a dominant and constant contribution of cropland to sediment. Furthermore, the intermediate selection of tracers led to more balanced contributions of both cropland and forest to sediments. The prediction of the virtual mixtures allowed us to compute several evaluation metrics, which are generally used to support the evaluation of model accuracy for each tracer selection method. However, strong differences or the absence of correspondence were observed between the range of predicted contributions obtained for virtual mixtures and those values obtained for actual sediments. These divergences highlight the fact that evaluation metrics obtained for virtual mixtures may not be directly transferable to models run for actual samples and must be interpreted with caution to avoid over-interpretation or misinterpretation. These divergences may likely be attributed to the occurrence of a not (fully) conservative behaviour of potential tracer properties during erosion, transport and deposition processes, which could not be fully reproduced when generating the virtual mixtures with currently available methods. Future research should develop novel metrics to quantify the conservative behaviour of tracer properties during erosion and transport processes. Furthermore, new methods should be designed to generate virtual mixtures closer to reality and to better evaluate model accuracy. These improvements would contribute to the development of more reliable sediment fingerprinting techniques, which are needed to better support the implementation of effective soil and water conservation measures at the catchment scale

Radionuclide, organic matter, geochemical and colorimetric properties of potential source material and target sediment for conducing sediment fingerprinting approaches in the Dzoumogné reservoir, Mayotte Island, France

&lt;p&gt;The current dataset was compiled to study sediment fingerprintings practices, i.e tracer selection and contribution modelling. Colorimetric properties analysed with a portable diffuse reflectance spectrophotometer (Konica Minolta CM-700d) and geochemical contents obtained with an energy dispersive X-ray fluorescence spectrometer (ED-XRF Epsilon 4), organic matter and stable isotopes were analysed by EA-IRMS and radionuclides using coaxial N- and P- type HPGe detectors (Canberra/Ortec). These properties &nbsp;were analysed in potential source material that may supply sediment to the Dzoumogné reservoir, Mayotte island, France. Three potential soil source materials (n = 57) were considered: cropland (n = 29), forest (n = 13) and subsurface material originating from channel bank collapse, landslides, badlands (n = 16). A sediment core was collected in the Dzoumogné reservoir (Target) on the 8th October 2021 and 20 layers were sampled.&lt;/p&gt;&lt;p&gt;The current dataset comprises two Excel files including the metadata description and the data itself.&lt;/p&gt

Temporal evolution of plutonium concentrations and isotopic ratios in the Ukedo - Takase Rivers draining the Difficult-To-Return zone in Fukushima, Japan (2013–2020)

International audienc

Temporal evolution of plutonium concentrations and isotopic ratios in the Ukedo - Takase Rivers draining the Difficult-To-Return zone in Fukushima, Japan (2013–2020)

International audienc

Uncontrolled deforestation and population growth threaten a tropical island’s water and land resources in only 10 years

International audienceRapid demographic growth in tropical islands can exacerbate conflicts and pressures on natural resources, as illustrated by the French island of Mayotte where resources are limited. In only 10 years, uncontrolled migration and population growth (+80% of population between 2002 and 2021) have led to a pronounced 3600% increase in deforestation rates (2010–2014) and an intensification of agricultural practices, escalating conflicts over limited land, water, and biodiversity resources. Implementing an original multi-proxy approach to sediment cores, our study reveals a staggering 300% acceleration in erosion during the first wave of migration (2011–2015), followed by a further 190% increase (2019–2021) under sustained migratory and demographic pressures. Sedimentary DNA analysis provided insights into increased connectivity and community changes. By 2050, the population of this region will increase by 74 and 103%, in Comoros and Madagascar islands, respectively. Urgent conservation measures are needed to avoid major socio-environmental crises and to protect resources for future generations