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The stabilizing properties of mineral–organic carbon (OC) interactions have been studied in many soil environments (temperate soils, podzol lateritic soils, and paddy soils). Recently, interest in their role in permafrost regions is increasing as permafrost was identified as a hotspot of change. In thawing ice-rich permafrost regions, such as the Yedoma domain, 327–466 Gt of frozen OC is buried in deep sediments. Interactions between minerals and OC are important because OC is located very near the mineral matrix. Mineral surfaces and elements could mitigate recent and future greenhouse gas emissions through physical and/or physicochemical protection of OC. The dynamic changes in redox and pH conditions associated with thermokarst lake formation and drainage trigger metal-oxide dissolution and precipitation, likely influencing OC stabilization and microbial mineralization. However, the influence of thermokarst processes on mineral–OC interactions remains poorly constrained. In this study, we aim to characterize Fe, Mn, Al, and Ca minerals and their potential protective role for OC. Total and selective extractions were used to assess the crystalline and amorphous oxides or complexed metal pools as well as the organic acids found within these pools. We analyzed four sediment cores from an ice-rich permafrost area in Central Yakutia, which were drilled (i) in undisturbed Yedoma uplands, (ii) beneath a recent lake formed within Yedoma deposits, (iii) in a drained thermokarst lake basin, and (iv) beneath a mature thermokarst lake from the early Holocene period. We find a decrease in the amount of reactive Fe, Mn, Al, and Ca in the deposits on lake formation (promoting reduction reactions), and this was largely balanced by an increase in the amount of reactive metals in the deposits on lake drainage (promoting oxidation reactions). We demonstrate an increase in the metal to C molar ratio on thermokarst process, which may indicate an increase in metal–C bindings and could

Arctic warming and permafrost degradation are modifying northern ecosystems through changes in microtopography, soil water dynamics, nutrient availability, and vegetation succession. Upon permafrost degradation, the release of deep stores of nutrients, such as nitrogen and phosphorus, from newly thawed permafrost stimulates Arctic vegetation production. More specifically, wetter lowlands show an increase in sedges (as part of graminoids), whereas drier uplands favor shrub expansion. These shifts in the composition of vegetation may influence local mineral element cycling through litter production. In this study, we evaluate the influence of permafrost degradation on mineral element foliar stocks and potential annual fluxes upon litterfall. We measured the foliar elemental composition (Al, Ca, Fe, K, Mn, P, S, Si, and Zn) of ∼ 500 samples of typical tundra plant species from two contrasting Alaskan tundra sites, i.e., an experimental sedge-dominated site (Carbon in Permafrost Experimental Heating Research, CiPEHR) and natural shrub-dominated site (Gradient). The foliar concentration of these mineral elements was species specific, with sedge leaves having relatively high Si concentration and shrub leaves having relatively high Ca and Mn concentrations. Therefore, changes in the species biomass composition of the Arctic tundra in response to permafrost thaw are expected to be the main factors that dictate changes in elemental composition of foliar stocks and maximum potential foliar fluxes upon litterfall. We observed an increase in the mineral element foliar stocks and potential annual litterfall fluxes, with Si increasing with sedge expansion in wetter sites (CiPEHR), and Ca and Mn increasing with shrub expansion in drier sites (Gradient). Consequently, we expect that sedge and shrub expansion upon permafrost thaw will lead to changes in litter elemental composition and therefore affect nutrient cycling across the sub-Arctic tundra with potential implications for fur

The stabilizing properties of mineral-organic carbon interactions have been studied in many soil environments (temperate soils, podzol lateritic soils, paddy soils). Recently, interest in their role in permafrost regions is increasing as permafrost was identified as a hotspot of change. In thawing ice-rich permafrost regions, such as the Yedoma domain, 327-466 Gt of frozen organic carbon (OC) is buried in deep sediments. Interactions between minerals and OC are important since the OC is located in close contact with the mineral matrix. Mineral surfaces and elements could mitigate recent and future greenhouse gas emissions through physical and/or physico-chemical protection of OC. The dynamic changes of redox and pH conditions associated with thermokarst lake formation and drainage, trigger metal-oxide dissolution and precipitation, likely influencing OC stabilization and microbial mineralization. However, the influence of thermokarst processes on mineral-OC interactions remains poorly constrained. In this study, we aim to characterize Fe, Mn, Al and Ca minerals and their potential protective role for OC. Total and selective extractions were used to assess the crystalline and amorphous oxides or complexed metal pools as well as the organic acids found within these pools. We analyzed four sediment cores from an ice-rich permafrost area in Central Yakutia, which were drilled i) in undisturbed Yedoma uplands, ii) beneath a recent lake formed within Yedoma deposits, iii) in a drained thermokarst lake basin, and iv) beneath a mature thermokarst lake from the early Holocene period. We find a decrease in the amount of reactive Fe, Mn, Al and Ca in the deposits upon lake formation (promoting reduction reactions), and this was largely balanced by an increase in the amount of reactive metals in the deposits upon lake drainage (promoting oxidation reactions). We demonstrate an increase in the metal:C molar ratio upon thermokarst process, which may indicate an increase of metal

A healthy soil is able to perform many ecosystem services, such as plant production, water cycle regulation, biodiversity support, or climate regulation. An accurate assessment of soil health is an important step in implementing soil conservation and improvement practices for policy makers, soil professionals, and citizens. Many soil health indices have been developed for this purpose. They consist of a soil health score resulting from the aggregation of different types of soil parameters (chemical, physical, or biological). Most soil health indices, however, are tailored to a particular land use and pedoclimatic region that are not relevant to the Belgian context. Moreover, these indices often depend on complex and expensive measurements, making them poorly operational. Here, we propose a methodology that aims to develop a soil health diagnostic tool tailored for Belgian soils by capitalizing on the strengths of existing soil health indices. The proposed approach consists in a review of existing indices to select some to be applied and tested in the field. Based on the critical analysis of the application results, we will be able to develop a tool that would estimate ecosystem services provided by soils of various land uses in Belgium. This tool will be based, as far as possible, on inexpensive, rapid, and accessible measurement protocols. First, the literature review will identify the parameters, protocols, and ecosystem services assessed by existing approaches. To date, few land uses are covered, most existing indices having been developed for agricultural soils. Despite that some indices include only one type of parameter, recent indices (11 out of 23 indices considered) target a more comprehensive understanding by combining chemical, physical, and biological parameters. Indeed, soil health indices tend to encompass the soil in all its complexity, sometimes including indicators of soil functioning highlighting the proper functioning of soil processes, such as or

With permafrost thaw, significant amounts of organic carbon (OC) previously stored in frozen deposits are unlocked and become potentially available for microbial mineralization. This is particularly the case in ice-rich regions such as the Yedoma domain. Excess ground ice degradation exposes deep sediments and their OC stocks, but also mineral elements, to biogeochemical processes. Interactions of mineral elements and OC play a crucial role for OC stabilization and the fate of OC upon thaw, and thus regulate carbon dioxide and methane emissions. In addition, some mineral elements are limiting nutrients for plant growth or microbial metabolic activity. A large ongoing effort is to quantify OC stocks and their lability in permafrost regions, but the influence of mineral elements on the fate of OC or on biogeochemical nutrient cycles has received less attention and there is an overall lack of mineral element content analyses for permafrost sediments. Here, we combine portable X-ray fluorescence (pXRF) with a bootstrapping technique to provide i) the first large-scale Yedoma domain Mineral Concentrations Assessment (YMCA) dataset, and ii) estimates of mineral element stocks in never thawed (since deposition) ice-rich Yedoma permafrost and previously thawed and partly refrozen Alas deposits. The pXRF method for mineral element quantification is non-destructive and offers a complement to the classical dissolution and measurement by optical emission spectrometry (ICP-OES) in solution. Using this method, mineral element concentrations (Si, Al, Fe, Ca, K, Ti, Mn, Zn, Sr and Zr) were assessed on 1,292 sediment samples from the Yedoma domain with lower analytical effort and lower costs relative to the ICP-OES method. The pXRF measured concentrations were calibrated using alkaline fusion and ICP-OES measurements on a subset of 144 samples (R2 from 0.725 to 0.996). The results highlight that i) the mineral element stock in sediments of the Yedoma domain (1,387,000 km2) is higher

Ice-rich permafrost is subject to abrupt thaw, during past and present global warming. Ice-rich domains encompass Yedoma Ice Complex deposits that have never thawed since deposition and Alas deposits that have undergone previous thermokarst processes during the Late glacial and Holocene warming periods. Upon thaw of these deep ice-rich deposits, organic carbon (OC) and minerals are unlocked and OC is exposed to mineralization. A portion of this OC is associated with iron (Fe), that provides physico-chemical protection of OC or drives the mineralization of OC by redox processes. We hypothesize that post-depositional thaw processes induce changes in redox conditions in Alas deposits and so affect the role that Fe plays in mediating present day OC mineralization. To test this hypothesis, we quantify the vertical distribution of Fe concentrations and Fe mineralogy in unthawed Yedoma and previously thawed Alas deposits from the Yedoma domain (Alaska, the Kolyma region, the Indigirka region, the New Siberian Archipelago, the Laptev Sea coastal region, and Central Yakutia). Portable XRF-measured concentrations trueness were calibrated from alkaline fusion and inductively coupled plasma optical emission spectrometry (ICP-OES) measurement method on a subset of 144 samples (R² = 0.95). Iron extractions of unthawed and previously thawed deposits show that, ~25% of the total iron is a reactive species, composed of crystalline or amorphous oxides, or complexed with OC, with no significant difference between Yedoma and Alas deposits. We observe a consistenttotal Fe concentration in Yedoma deposits, but a depletion or accumulation of total Fe in Alas deposits, which experienced previous thaw and/or flooding events. These results suggest that redox driven processes during the Lateglacial and Holocene thermokarst formation impact the present-day distribution of reactive Fe and its association with OC in ice-rich permafrost.

Abrupt permafrost thaw leads to changing redox conditions (Figure 1), thereby affecting manganese forms and their potential role in organic carbon stabilization. We analyzed four sediment cores from Central Yakutia (Russia) representing progressive thermokarst processes, from continuously frozen Yedoma deposits (Windirsch et al., 2020) to an Alas lake in a Holocene thermokarst basin that underwent multiple lake generations (Jongejans et al, 2021). We analyzed total manganese concentrations and manganese selectively extracted with dithionite-citrate-bicarbonate (DCB), oxalate and pyrophosphate. In addition, we analyzed organic carbon selectively extracted by oxalate and pyrophosphate. We also determined the main crystalline minerals by X-ray diffraction analyses. We found that i) selective extractions by DCB, oxalate and pyrophosphate are valid for quantifying manganese phases, and ii) thermokarst processes influence interactions between manganese and organic carbon in ice-rich permafrost.

Vegetable gardening in urban soils increases food security and offers a wide range of social and ecosystem benefits. However, elevated soil trace metal element concentrations in urban and industrial areas may pose a health hazard, limiting the development of urban gardening. Such a situation is encountered in Wallonia where former industrial activities have substantially increased trace metal topsoil content. To provide appropriate recommendations for users of contaminated vegetable gardens in Wallonia, we developed a web tool, called SANISOL, which is described in this work. SANISOL provides recommendations concerning (1) the health risks posed by the presence of As, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb and Zn in soil and (2) the products that can be cultivated safely in the vegetable garden. The recommendations concerning health risks are provided from a health risks assessment model. The gardener’s exposure is estimated based on the gardener’s profile (age, garden products consumed, etc.) and the garden’s soil trace metal contents. If there is a potential health risk, SANISOL tool reports information on the health risk causes and provides recommendations to reduce the gardener’s exposure. The quality of garden produce is provided for 14 fruits and vegetables based on the expected trace metal content in the products calculated from soil-to-plant transfer models. SANISOL tool indicates if a specific garden product is likely to have trace metal contents higher than a commercially purchased product, or than the maximum level in foodstuffs. In conclusion, while this work demonstrates that it is possible to develop a tool that provides appropriate and tailored recommendations for gardeners living in areas with high trace metal content in soil, it also highlights the uncertainties and progress that needs to be made to properly manage the human health risks associated with soil trace metals such as As, Cd and Pb.

L'outil SANISOL, financé par le Service public de Wallonie et réalisé par l’Université de Liège (ULiège-GxABT), SPAQuE, l’ISSeP, l’Université catholique de Louvain (UCLouvain) et l’ASBL Espace Environnement a pour objectif de fournir des informations sur la problématique des métaux lourds dans les potagers de Wallonie et sur les recommandations liées à l'utilisation de ces sols. En répondant à diverses questions concernant la qualité du potager et les modalités d'usage de ce dernier, l'outil SANISOL fournit des recommandations concernant le risque lié au jardinage et à la consommation de fruits et légumes ainsi que des renseignements sur la qualité des fruits et légumes produits. Ce rapport a pour objectif de présenter les méthodes appliquées et les choix réalisés pour déterminer les teneurs dans la plante de l'outil SANISOL, ainsi que les indications données par l'outil SANISOL quant à la qualité des produits du potager.

Vegetable gardening in urban soils increases food security and offers a wide range of social and ecosystem benefits. However, elevated soil trace metal element concentrations in urban and industrial areas may pose a health hazard, limiting the development of urban gardening. Such a situation is encountered in Wallonia where former industrial activities have substantially increased trace metal topsoil content. To provide appropriate recommendations for users of contaminated vegetable gardens in Wallonia, we developed a web tool, called SANISOL, which is described in this work. SANISOL provides recommendations concerning (1) the health risks posed by the presence of As, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb and Zn in soil and (2) the products that can be cultivated safely in the vegetable garden. The recommendations concerning health risks are provided from a health risks assessment model. The gardener’s exposure is estimated based on the gardener’s profile (age, garden products consumed, etc.) and the garden’s soil trace metal contents. If there is a potential health risk, SANISOL tool reports information on the health risk causes and provides recommendations to reduce the gardener’s exposure. The quality of garden produce is provided for 14 fruits and vegetables based on the expected trace metal content in the products calculated from soil-to-plant transfer models. SANISOL tool indicates if a specific garden product is likely to have trace metal contents higher than a commercially purchased product, or than the maximum level in foodstuffs. In conclusion, while this work demonstrates that it is possible to develop a tool that provides appropriate and tailored recommendations for gardeners living in areas with high trace metal content in soil, it also highlights the uncertainties and progress that needs to be made to properly manage the human health risks associated with soil trace metals such as As, Cd and Pb.

With permafrost thaw, significant amounts of organic carbon (OC) previously stored in frozen deposits are unlocked and become potentially available for microbial mineralization. This is particularly the case in ice-rich regions such as the Yedoma domain. Excess ground ice degradation exposes deep sediments and their OC stocks, but also mineral elements, to biogeochemical processes. Interactions of mineral elements and OC play a crucial role for OC stabilization and the fate of OC upon thaw, and thus regulate carbon dioxide and methane emissions. In addition, some mineral elements are limiting nutrients for plant growth or microbial metabolic activity. A large ongoing effort is to quantify OC stocks and their lability in permafrost regions, but the influence of mineral elements on the fate of OC or on biogeochemical nutrient cycles has received less attention and there is an overall lack of mineral element content analyses for permafrost sediments. Here, we combine portable X-ray fluorescence (pXRF) with a bootstrapping technique to provide i) the first large-scale Yedoma domain Mineral Concentrations Assessment (YMCA) dataset, and ii) estimates of mineral element stocks in never thawed (since deposition) ice-rich Yedoma permafrost and previously thawed and partly refrozen Alas deposits. The pXRF method for mineral element quantification is non-destructive and offers a complement to the classical dissolution and measurement by optical emission spectrometry (ICP-OES) in solution. Using this method, mineral element concentrations (Si, Al, Fe, Ca, K, Ti, Mn, Zn, Sr and Zr) were assessed on 1,292 sediment samples from the Yedoma domain with lower analytical effort and lower costs relative to the ICP-OES method. The pXRF measured concentrations were calibrated using alkaline fusion and ICP-OES measurements on a subset of 144 samples (R2 from 0.725 to 0.996). The results highlight that i) the mineral element stock in sediments of the Yedoma domain (1,387,000 km2) is higher

La présentation porte sur le travail de cartographie des concentrations de fond dans les sols qui a été réalisée dans le cadre de la convention POLLUSOL 2. Cette cartographie se base sur un modèle prédictif prenant en compte l'occupation du sol, le type de substrat pédogéologique, les retombées atmosphériqueset les propriétés de dépendance spatiale des concentrations entre elles. Afin d'établir le modèle prédictif, un jeu de données contenant des résultats d'analyse géoréférencés représentatifs des concentrations de fond en Wallonie a été constitué à partir des points d'échantillonnage des projets POLLUSOL 1 et 2. Les outliers univariés, multivariés et spatiaux ont été supprimés de ce jeu de données. L'application du modèle prédictif a l'ensemble de la Wallonie a permis de réaliser des cartes de concentration attendues dans les sols et des cartes d'incertitudes sur la prédiction en tout point de la Wallonie. Les cartes d'incertitudes renseignent la concentration qui a une probabilité inférieure à 5 chances sur 100 d'être dépassée. Le modèle prédictif établi donne des très bons résultats pour les ETM suivants : As, Ba, Be, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, Zn. Pour ces éléments, les données se prêtent à une très bonne prédiction spatiale : l'erreur absolue moyenne d'estimation est de l'ordre de 25% de la moyenne des points connus. Le modèle de prédiction spatiale présente un gain en précision d'environ 100% en terme d'erreur absolue moyenne d'estimation par rapport à l'utilisation de la valeur de la moyenne régionale comme prédiction en tout point. Pour les HAP, Sn, le toluène, les cyanures et l'indice phénol, le modèle donne de bons résultats : les données se prêtent à une assez bonne prédiction spatiale. L'erreur absolue moyenne d'estimation est de l'ordre de 50% de la moyenne des points connus, et le modèle de prédiction spatiale présente un gain en précision d'environ 60% en terme d'erreur absolue moyenne d'estimation par rapport à l'utilisation de la valeur de la

Iron (Fe) plays a key role in mediating organic carbon (OC) decomposition rates in permafrost soils. Fe-bearing minerals stabilize OC through complexation, co-precipitation or aggregation processes and thus hinder degradation of OC. In addition, Fe(III) reduction can inhibit methanogenesis and decrease warming potential of greenhouse gases release. Ice-rich permafrost is subject to abrupt thaw and thermokarst formation, which unlocks OC and minerals from deep deposits and exposes OC to mineralization. These ice-rich domains include Yedoma sediments that have never thawed since deposition and Alas sediments that have undergone previous thermokarst processes during the Lateglacial and Holocene warming periods. The post-depositional history of these sediments may affect the distribution and reactivity of Fe-bearing minerals and the role Fe plays in mediating present day OC mineralization. Here we quantify Fe concentrations, Fe spatial and depth distribution, and Fe mineralogy in unthawed Yedoma and previously thawed Alas deposits from the Yedoma domain (West Siberia, Laptev Sea region, Kolyma region, New Siberian Islands and Alaska). Total Fe concentrations of ice-rich Yedoma deposits and previously thawed Alas deposits were determined using a portable X-ray fluorescence (XRF) device. This non-destructive method allowed a total iron concentration assessment of Yedoma domain deposits based on 1292 sediment samples. Portable XRF-measured concentrations trueness were calibrated from alkaline fusion and inductively coupled plasma optical emission spectrometry (ICP-OES) measurement method on a subset of 144 samples (R² = 0.81). Fe extractions of unthawed and previously thawed deposits display that, on average, 25% of the total iron is considered as reactive species, either as crystalline or amorphous oxides, or complexed with OC, with no significant difference between Yedoma and Alas deposits. We observe a constant total Fe concentration in Yedoma deposits, but a depletion

Les travaux de la présente convention intitulée « Optimisation des modèles de transfert sol-plante en Wallonie pour l’aide à la détermination de recommandations concernant la production de biomasse alimentaire sur un sol contaminé » ont été réalisés par l'équipe de recherche de l'Earth and Life Institute de l'UCLouvain et financés par la Direction Générale Opérationnelle Agriculture, Ressources Naturelles et Environnement (DGO3) du Service Public de Wallonie. Les missions confiées à l’UCLouvain dans le cadre de la convention sont dans le prolongement des travaux de la subvention SANISOL, et plus particulièrement du développement d'un outil informatique pilote (appelé « outil SANISOL ») visant à définir les recommandations particulières à suivre pour la consommation des productions végétales et l’utilisation des sites de production dont elles sont issues. En particulier, la présente convention a pour objectif l’amélioration (1) des équations de transfert sol-plante de l’outil SANISOL et (2) du code informatique de l'outil SANISOL. Le modèle S-Risk, à partir duquel est basé l’outil SANISOL, comporte un grand nombre d’équations de transfert sol-plante (22 modèles ou facteurs de bioconcentration pour 10 éléments traces métalliques). Ces équations ne sont pas nécessairement adaptées aux sols wallons. Dans le cadre de la subvention SANISOL, une base de données d'analyses de sols et de plante a été constituée par l'équipe de recherche de l'ULg-GxABTLa base de données est documentée dans le délivrable 1.2 de la subvention SANISOL réalisé par Amandine Liénard et Gilles Colinet (ULg-GxABT). Cette base de données contient plus de 3000 enregistrements correspondant à des analyses d’éléments traces métalliques dans les végétaux consommables (As, Cd, Cr, Cu, Co, Hg, Mn, Mo, Ni, Pb et Zn) et du sol correspondant (paramètres pédologiques et teneurs en éléments traces métalliques). Dans ce travail, pour chaque élément trace et chaque catégorie de végétaux, une proposition est réalis

Le projet SANISOL, à travers la mise en œuvre d’un outil informatique pilote sur Internet, vise à fournir des recommandations particulières de gestion et d’utilisation à tout producteur de biomasse alimentaire (notamment légumes et fruits) sur sols contaminés en Wallonie. Caractère innovant du sujet proposé L’originalité de cette étude repose sur le caractère multidisciplinaire et multi-acteurs de l’approche. Elle mobilise des compétences en matière d’échantillonnage et d’analyses de sols, de légumes et de fruits ainsi qu’un biomonitoring avec prélèvements d’échantillons biologiques (cheveux, sang, urine), le tout en concertation avec les acteurs régionaux et locaux. Les objectifs poursuivis étant de livrer des recommandations adaptées à la production potagère et à la fréquentation des potagers pour les personnes réalisant une activité de jardinage en vue d’une autoconsommation sur sol contaminé. En outre, elle rassemble des acteurs d’horizons différents : des scientifiques (Université de Liège et Université Catholique de Louvain), des organismes d’intérêt public (SPAQuE, ISSeP, Espace Environnement), le secteur associatif et les pouvoirs publics. Résumé Le projet SANISOL s’articule autour de cinq volets : l’étude des transferts sols-plantes en métaux en jardins potagers, le diagnostic du modèle S-Risk© pour la production végétale, un programme d’action Environnement-Santé à l’aide d’un biomonitoring, la configuration d’un outil informatique pilote et une gestion de la communication avec production d’un contenu « Sols potagers pollués » diffusable au grand public. L’association de ses différentes approches permettra la détermination de teneurs limites en polluants dans le sol en vue d’assurer la qualité commerciale des productions végétales en Wallonie et la gestion des risques pour les producteurs et les jardiniers. En effet, la pratique du jardinage est en recrudescence et elle démontre plusieurs bienfaits physiques, sociaux, psychiques, etc. Cependant, l’autoprod

Ce rapport de recherche expose les résultats de l’investigation de la qualité des sols de Bressoux du projet SANISOL 2019. Le Chapitre 1 présente la campagne d'échantillonnage et analyse des sols du potager collectif du Coin de Terre (Bressoux) et de ses alentours. Dans le Chapitre 2, les résultats du Chapitre 1 ont été utilisés afin de déterminer si les teneurs en métaux du potager collectif du Coin de Terre peuvent être considérées comme des concentrations de fond. Pour cela, les procédures du guide intitulé Aide à l'expert pour la proposition de concentrations de fond dans le cadre du Décret wallon relatif à la gestion et à l'assainissement des sols ont été appliquées. Une mise à jour de ce guide suite à cette expérience se trouve en Annexe 1. Dans le Chapitre 3, les résultats de la campagne ont été utilisés afin de cartographier les concentrations de fond à Bressoux. Des cartes ont été produite pour 11 éléments traces métalliques (As, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sn, Zn).

In many countries, large areas where mining and smelting activities took place in the past now exhibit elevated soil metal concentration levels. In Belgium, as in many European countries, soil assays are performed by aqua regia digestion and ICP measurement which is a cost- and time-expensive protocol. The aim of this study is to assess if this protocol could be approximated or replaced by portable XRF measurement as this method is fast, low cost and can be used in situ. This study first focused on the evaluation of the performance of four leading-edge pXRF devices for measuring metal concentrations in a collection of Belgian soil samples from industrial and mining context and non-contaminated areas. Four soil preparation protocols were then tested with one device, involving (1) measurement on fresh soil, (2) in situ sample drying and sieving, (3) in laboratory sample drying and sieving and (4) in laboratory sample drying, sieving and crushing. The comparison of the pXRF devices showed that the performance of each device varies depending on the element measured. The precision of the XRF measurement and correlation with aqua regia measurement protocol both increased for most of the elements when drying and sieving soil samples. However, for Cu and Pb, the four devices provide good measurement results whatever the sample preparation protocol. Finally, we proved the suitability of pXRF devices on a real-world case study by delineating the extent of Pb soil contamination by in situ pXRF measurement on fresh soil.

Ce document présente les résultats de la convention CAPASOL 5 obtenus par l'équipe de chercheurs de l'Earth and Life Institute de l'Université catholique de Louvain. La précédente convention CAPASOL 4 avait permis de réaliser une cartographie de la toxicité des métaux dans les sols wallons pour les organismes terrestres. Cette précédente convention avait également montré l'intérêt et le potentiel de l'utilisation de la fluorescence des rayons X portables pour les sols wallons. Deux thématiques ont été étudiées dans le cadre de la convention CAPASOL 5, qui s'inscrivent dans la continuité des travaux de CAPASOL 4 : La première thématique (partie I de ce rapport) est l'étude de faisabilité de réaliser un outil de prédiction de la concentration limite en métaux admissible dans les sols avant qu'un risque ne se présente pour la santé humaine, les organismes terrestres et la production agricole. La seconde thématique (partie II de ce rapport) reprend les travaux relatifs à la fluorescence des rayons X portable (pXRF) pour les sols wallons. Ces travaux ont permis de déterminer la qualité de mesure des métaux dans les sols par pXRF et les facteurs ayant une influence sur celle-ci pour différents protocoles de préparation d'échantillons, afin d'évaluer la possibilité d'utiliser ces protocoles en complémentarité avec la méthode conventionnelle (extraction à l'eau régale) dans les différents contextes de gestion des métaux dans les sols wallons.