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International audience; Waste generation and management is a global issue receiving increasing attention. Construction and Demolition (C&D) debris generate high percentages of a country’s total solid waste, and has been estimated to contribute to 35% of the solid waste generated worldwide. Construction of Technosols is an innovative process based on the association of organic and mineral wastes to construct fertile soils that are favorable environment for plant growth. Such an approach could be a relevant solution to recycle significant amount of C&D materials as these waste could provide valuable properties such as bearing and drainage capacities and buffer capacity to the constructed Technosols. Technosols in various situations around the world are discussed as well as the actual and potential ecosystem services provided by such artificial soils. The presentation focuses on their designs and biotic choice. We explain and predict the assembly and function of Technosols under varieties of environmental conditions. Humans have total control over such soils and play a dominant role on every aspect and stages, providing a lot of opportunities. However, wrong choices can have tremendously negative consequences: every action should be weighted and evaluated carefully when manipulating these systems, to maximize Technosols ecological benefits while minimizing the ecological risk.

PosterFR2116Poster

L’augmentation de la population urbaine, la demande en produits frais de proximité et le besoin croissant de nature en ville stimulent l’engouement pour l’agriculture urbaine, notamment dans les pays industrialisés. De nouvelles formes émergent, telles que les « micro-fermes urbaines », dont l’activité de production alimentaire est étroitement imbriquée avec des activités de loisir, pédagogiques ou à vocation sociale. Elles sont implantées sur des sols urbains remaniés ou non, d’historique très hétérogène ou sur du bâti, en construisant des sols à partir de matériaux divers, en particulier des déchets organiques de la ville. Alors que les attentes sont fortes vis-à-vis de ces composantes d’une trame verte et des services écosystémiques qu’ils pourraient rendre à la ville, ceux-ci ne sont pas connus et évalués.L’objectif de ce projet est d’évaluer les services écosystémiques rendus par les micro-fermes urbaines, en considérant plusieurs catégories de services : support de biodiversité, approvisionnement, régulation et services culturels, afin d’apporter aux acteurs de la ville des éléments pour une meilleure gestion de cette forme d’agriculture urbaine et de leurs sols.Méthodologie : le projet porte sur six micro-fermes illustrant la diversité de cette forme d’agriculture urbaine de par l’importance relative de la production alimentaire et d’autres activités et le type de sols sur lesquelles elles sont développées, localisées à Paris ou en Petite Couronne, unité territoriale du projet. Il s’appuie sur des compétences variées dans une démarche pluridisciplinaire : pédologues, agronomes, écologues, sociologues et paysagistes, et associe différents acteurs : porteurs de projets de micro-fermes, associations dédiées à la nature en ville et personnels de services d’urbanisme. Les services écosystémiques sont appréhendés par une série d’indicateurs.Résultats attendus : (i) Une identification et une quantification d’indicateurs des services rendus par un ensemble de micro-fermes urbaines. Une démarche d’analyse de ces services ; (ii) l’identification de leviers d’optimisation de ces services, via une pratique culturale : l’apport d’intrants organiques au sol sous forme de produits résiduaires organiques ; (iii) l’identification d’outils relatifs aux états du milieu nécessaires aux porteurs de projet, urbanistes ou collectivités locales, pour un développement de l’agriculture urbaine optimisant les services rendus ; (iv) des échanges et un renforcement de la structuration des acteurs de ces micro-fermes urbaines.Organisation en six lots : Le lot 1, fil rouge du projet, mobilise une diversité d’acteurs de l’agriculture urbaine afin de sélectionner six fermes parmi une présélection réalisée en début de projet et de co-organiser les campagnes de prélèvement et observations. Cet ensemble d’acteurs est ensuite mobilisé pour discuter des résultats obtenus dans les autres lots, identifier les outils nécessaires pour mieux insérer les micro-fermes dans le métabolisme urbain, en minimiser les externalités négatives et en optimiser les services écosystémiques rendus. Cela permettra d’étudier la place actuelle et potentielle des micro-fermes dans des documents d’urbanisme. Le lot 2 est une caractérisation des micro-fermes au plan biophysique et de leurs pratiques. Le lot 3 quantifie et qualifie la biodiversité floristique et tellurique (microorganismes, mésofaune, macrofaune du sol). Le lot 4 est consacré au service d’approvisionnement en aliments, en abordant également leur qualité sanitaire (teneur en ETM et HAP). Le lot 5 quantifie des indicateurs de services de régulation du cycle de l’eau (infiltration et capacité de rétention de l’eau), du climat global (stocks de carbone des sols), du climat local (régulation de la température) et du recyclage des déchets (inventaire des pratiques, de la nature et de l’origine géographique des produits résiduaires organiques utilisés). Le lot 6 est consacré aux services sociaux, culturels et paysagers associés aux micro-fermes en mettant l’accent sur les pratiques et représentations des parties prenantes.

Background: Phytoextraction is an in situ technique that can be applied to minerals and mining wastes using hyperaccumulator plants to purposely bio-concentrate high levels of metals or metalloids into their shoots in order to remove them from the substrate, while achieving monetary gain. Phytoextraction can be applied to a limited number of elements depending on the existence of hyperaccumulator plants with suitable characteristics. Although phytoextraction has been trialled in experimental settings, it requires testing at field scale to assess commercial broad-scale potential. Scope: The novelty and purported environmental benefits of phytoextraction have attracted substantial scientific inquiry. The main limitation of phytoextraction with hyperaccumulators is the number of suitable plants with a high accumulation capacity for a target element. We outline the main considerations for applying phytoextraction using selected elemental case studies in which key characteristics of the element, hyperaccumulation and economic considerations are evaluated. Conclusions: The metals cobalt, cadmium, thallium and rhenium and the metalloids arsenic and selenium are present in many types of minerals wastes, especially base metal mining tailings, at concentrations amenable for economic phytoextraction. Phytoextraction should focus on the most toxic elements (arsenic, cadmium, and thallium) or especially valuable elements (selenium, cobalt, and rhenium). The value proposition is in the clean-up of contaminated land in the case of toxic elements, whereas it is in the ‘bio-ore’ generated by the process in the case of valuable elements.

International audience

International audience; Light Non-Aqueous Phase Liquids (LNAPLs) are an important source of soil contamination. When they infiltrate through the unsaturated zone, part of the LNAPLs remains trapped by capillary forces. The others accumulate above the top of the water table, forming a floating ‘free’ phase able to generate a long-term dissolved LNAPL plume. Seasonal variations in the groundwater level lead to significant vertical dispersion of these contaminants at the capillary fringe, favoring their release into the air and water. The IPCC predicts an intensification of these groundwater level variations over the next century in response to variations in rainfall intensity and frequency (related to climate change) and the increasing use of water resources. This context may strongly impact the LNAPL remobilization. It is, therefore, essential to better understand the impact of these groundwater level fluctuations on the remobilization processes of these hydrocarbon contaminants. To this end, an original experimental system combining indirect geophysical (electrical conductivity), in situ physical-chemical (pH, Eh, temperature), and geochemical measurements was developed at the GISFI station (Homécourt, France). This device allows the assessment and the comparison of nature and the amount of LNAPLs release into the atmosphere and water from a contaminated soil during two groundwater level fluctuations scenarios: one corresponding to the ‘actual’ rainfall pattern based on regional climate records; the other based on the most extreme IPCC scenario. This study will be conducted at different scales (laboratory decametric columns and 2 m3 lysimeters) and on soils of different geological complexity. The remobilized hydrocarbons will be collected via porous candles and gas collection chambers and regularly analyzed (GC-MS, FTIR). The complementarity of the monitoring methods will be evaluated and numerical simulations of the LNAPL flow and transport through the contaminated soil will be carried out to identify the processes responsible for the pollutant remobilization. This work is partly funded by the DEEPSURF project ”Lorraine Université d’Excellence”, ANR-15-IDEX-04-LUE”.

International audience; Ecological engineering of degraded ecosystems often manipulates plants, with positive outcomes for their restoration or ecosystem services production. The importance of soil biota for successional plant communities has prompted consideration of direct inoculation (active) or attraction (passive) of soil organisms as a relevant restoration strategy. However, few attempts have manipulated soil invertebrates as part of nature based solutions for ecosystem restoration, despite their major role in many soil ecological processes and in plant-soil feedback processes. In addition, while ecological restoration and ecological engineering approaches successfully incorporate plant traits, soil invertebrate traits remain underused. Exploiting the functional diversity of soil communities by adopting a trait-based approach could enhance restoration of soil chemical, biological and physical properties. Here, we conduct a narrative review and identify a set of soil invertebrate functional traits with great potential in ecosystem restoration. We focus on traits related to four main ecological functions that are often at the core of restoration plans: nutrient cycling and carbon cycling, pollutant detoxification, soil structure arrangement, and biological control agent by prey/pest regulation. This paper further proposes guidelines for stakeholders that need to be addressed to successfully integrate soil organism traits into ecological engineering. Finally, we highlight main knowledge gaps and limitations currently impeding the use of soil invertebrate traits in ecological engineering, and identify avenues for future research. We especially bring out (i) that few studies still use soil invertebrates in restoration, so even fewer are based on traits, (ii) a lack of data about soil invertebrate species role in ecosystems, (iii) a lack of data about attributes from specific traits and groups in existing soil functional trait databases, (iv) the complex relationships between functions and traits and (v) that future studies are needed to demonstrate the benefits of such trait-based approaches compared to approaches relying on emblematic species.

Rhizodegradation is the breakdown of organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) using plants and rhizospheric microorganisms. The influence of two phytoremediating plants, Miscanthus × giganteus (M × G) and Trifolium repens L., was studied on a PAH-contaminated technosol composed of soil and sediments. More specifically, microbial density and diversity were studied along with the density of the population of PAH-degrading bacteria. M × G and white clover were tested in mono- and co-culture on the technosol in a mesocosm over 263 days (life cycle of M × G until its senescence). At the beginning and the end of the phytoremediation experiment, microbial density was measured by real-time PCR, targeting bacteria (16S rDNA), fungi (18S rDNA), and PAH-degrading bacteria (PAH-RHDα GP). Bacterial and fungal diversity were determined by metagenomic analysis. The M × G monoculture appeared to increase bacterial diversity compared to non-planted technosol, in contrast to other planting patterns, while fungal diversity appeared to decrease in the presence of any of the plants. Overall, the plants increased the bacterial density in the technosol, while only white clover and the co-culture increased the fungal density, with the latter having a greater impact. Concerning the degrading bacteria, only the co-culture stimulated the PAH-degrading bacterial population. This is remarkable for the PAH rhizodegradation. Even though the co-culture seemed to decrease the microbial diversity in the technosol, this condition was the most interesting with respect to the increase of the bacterial and fungal density as well as the enhancement of the PAH-degrading bacteria in the technosol.

International audience; Despite its importance for human activities, soil biodiversity remains largely unknown. This gap of knowledge is a strong limit for studies including it such as in the agricultural field. Particularly, in France, no large-scale monitoring of soil biodiversity exist for the moment except for microorganisms (bacteria and fungi). Aware to this need, with the support of OFB, we studied the feasibility to add a soil biodiversity survey (RMQS-Biodiversity) to the already existing French soil quality monitoring network (RMQS). It is a systemic monitoring based on a 16*16 km grid where the sampling is done on a plot at the center of the mesh, which could belong to different land use types (forest, crops, urban gardens and wastelands, vines, orchards, pastures, meadows and other natural habitats). The sampling occurs throughout the year, every 15 years since 2000. The advantages to lean the new survey on an already existing one compared to establish an independent survey are that 1) field teams are already operational, 2) it reduces costs and 3) different data types (in our case, with pedologic and management practices ones) can be crossed at the country scale with a high statistical power to infer spatial and temporal variations and drivers. The objective of this new monitoring is to cover almost the whole soil biodiversity. With this aim, we gathered experts on soil microflora, microfauna, mesofauna and macrofauna and soil functions. We ask them if the RMQS sampling strategy could fit with a soil biodiversity survey. We together choose the taxons and functions to be surveyed, the associated protocols and estimate the related financial, material and human needs. According to the experts, the sampling design of RMQS fits with a soil biodiversity survey. We select sampling protocols for i) bacteria and fungi, ii) protists, iii) nematodes, iv) mesofauna (particularly springtails), v) below-ground macrofauna (earthworms), vi) surface macrofauna (beetles and spiders), and considering functions, vii) soil porosity, viii) enzymatic activity and ix) organic matter degradation. Before starting at National scale, we tested on several sites the selected sampling protocols and various sampling strategies in order to optimize the temporal sequence, the spatial arrangement of the protocols, the time spent on the field and to reduce the effect of disturbances on the soil organisms. The RMQS-biodiversity is a promising project that will help to fill the knowledge gap of soil biodiversity in France. The data would be used to assess the distribution of soil organisms and monitor the changes in soil biodiversity at the scale of the French territory. In addition, coupling data provided by biodiversity survey with data from RMQS will allow deciphering links between biodiversity, physical-chemical characteristics of the soil and human activities (practices, heavy metal loading, and pesticide residues for instance). Moreover, the RMQS-Biodiversity could serve as a model for other countries to establish a large-scale integrative soil monitoring including both pedologic and biodiversity data.

The consumption of vegetables grown on soils polluted by trace elements can cause a serious threat for animal and human health and disturb the functioning of the ecosystem. The aim of this work is to determine the concentrations of As, Cd, Co, Cr, Cu, Ni, Pb, Mn, and Zn in soils and different vegetables from market gardens of urban areas in Marrakech city in order to investigate human health risk through ingestion of contaminated vegetables. Plant transfer factor (TF), daily intake of metals (DIM), and health risk index (HRI) were calculated. The concentrations of all metals studied in the garden top soils were within the threshold values. The Cu, Zn, Co, Mn, and As concentration in the edible parts of vegetables were within the safe limits. However, Cd and Pb in Malva parviflora and Cd in Brassica rapa, and Cr and Ni in Coriandrum sativum exceeded their permissible limits. The TF for these nine metals varied between 0.01 and 1.35. The classification of TEs according to their TF is as follows: Cu > Zn > Cd > Ni > Cr > Pb > Mn > Co > As. The maximum value was recorded in Coriandrum sativum while the minimum value was recorded in Cynara cardunculus. The HRI values were within the safe limit (

International audience; Partitioning of metals between the soil solid phase and the solution is an important topic in environmental sciences because it determines the metal transfers to aquifers and biological organisms. Complexation of metals with ligands in the soil solution strongly influences the sorption/desorption (SD) of metals, in particular that of the free ion. Because the latter is the metal species principally absorbed by biological organisms, the bioavail-ability of a metal is better reflected by the soil-solution distribution coefficients of the free ion as compared to that of the total metal (sum of the free ion and of the complexes). The present work proposes a modeling approach to determine the distribution coefficients for the free ion and for the metal complexes from SD experiments. The method does not require estimating the mobile pool of the metal sorbed onto the solid phase by any chemical extraction as the modeling relies on the variation of the sorbed metal, which is experimentally exactly estimated from the variation of the amount of metal in solution during the SD experiment. Tested for cadmium (Cd), the model reproduced very well the SD curves observed for the total metal. For any solution:soil ratio including that at field soil moisture, the model gives estimates of important variables including the distribution coefficient for the free ion, the complex, the ligands and the total metal, the concentration of these species in the soil solution and onto the solid phase. The model can be applied as long as the range of the concentration investigated allows to assume a linear sorption of the metal.

Aims: Dicranopteris linearis is a fern that accumulates unusually high concentrations (up to 0.3% dry weight) of rare earth elements (REEs) in China. Previously, we reported that D. linearis accumulates high concentrations of aluminium (Al) and silicon (Si) in the fronds, but the interactions between these elements and REEs were unknown. Methods: In this study, a range of analytical techniques, including chemical extractions, Scanning-Electron Microscopy with Energy-Dispersive Spectroscopy (SEM-EDS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) were used to study the association of REEs with Al and Si. Results: The results show that D. linearis accumulates high concentrations of REEs (up to 3830 mg kg−1), Al (up to 9660 mg kg−1) and Si (up to 20,300 mg kg−1), with concentrations increasing with age and frond order of pinna. The extraction patterns suggest the existence of REEs-Si and Al-Si complexes. The SEM-EDS analysis confirmed the existence of phytoliths (Al) deposits in the protoplast and apoplast of the pinna cells. The upper epidermis of the pinnule and the pericycle of the midvein are more concentrated in phytoliths (Al) particles. The LA-ICP-MS analysis revealed that REEs and Al are preferentially compartmentalized within bio-inactive tissues of the pinnules, e.g. necrotic tissues (REEs) and in the margins (Al). Conclusions: Co-deposition of Si with REEs and Al may be a mechanism for dealing with the high concentrations of REEs and Al in D. linearis fronds.

International audience; In Albania, ultramafic outcrops cover 11% of the surface and have the potential to support nickel phytomining. In a large-scale in-situ experiment on an ultramafic Vertisols in Pojske we are studying the influence of agronomical practices on Ni phytoextraction yield of Odontarrhena chalcidica (syn. Alyssum murale). Three cropping systems were compared in three plots in 2016-2017; POJ-1 Plot (0.3 ha) was established with plants that had germinated spontaneously without any treatments; POJ-2 plot (0.3 ha) was covered by plants that had germinated spontaneously and was treated with mineral fertilizer (N50P50K50 kg ha(-1)); and POJ-3 Plot (400 m(2)) was divided in four sub plots, where O. chalcidica was planted at a density of 4 plants m(-2) on which, we neither applied fertilizer, nor NPK fertilizer (N65P65K65), pig (FPM; N260:P105:K260 + 15 kg ha(-1)N, P, K) or chicken manure (FCHM; N260:P390:K260 +15 kg ha(-1) N, P, K. Irrigation and mechanical control of weeds was done on POJ-3. After 8 months, shoot Ni concentration, biomass, and Ni yields were higher in O. chalcidica treated with manure and the cost of biomass production was smaller. Nickel yield was more promising (145 kg ha(-1)) than in previous field trials. This study highlights that, using manure, the Ni yield increases Ni phytomining net values, thus agromining can become an economically justifiable agricultural cropping system.

Purpose: Journal of Soils and Sediments publishes the main outcomes of SUITMA 9 Conference in its Special Issue. SUITMA (Soils of Urban, Industrial, Traffic, Mining and Military Areas) working group organizes conferences biannually all over the world. The ninth conference organized in Moscow in May 2017 involved more than 215 speakers from 25 countries, whose presentations focused on challenges and opportunities of urbanization for soil functions and ecosystem services. Materials and methods: The main outcomes of SUITMA 9 were analyzed in comparison to the previous SUIMTA conferences and the main topics were distinguished. Manuscripts accepted for publishing in the Special Issue were reviewed and presented. Results and discussion: Comparison of the topics highlighted in different special issues highlighted the evolution of the SUITMA studies from fundamental morphological descriptions and classifications to applied studies on soil engineering, assessment of SUITMA functions and ecosystem services. Conclusions: The manuscripts accepted to the Special Issue covered included various case studies of SUITMA ecosystem services (e.g. global and local climate regulation, biodiversity maintenance and improvement, nutrients balance and recreation) and disservices (e.g. pollution by heavy metals, polycyclic aromatic hydrocarbons and sulfur). The increasing role of SUITMA studies for urban management and decision making was concluded.

Light Non-Aqueous Phase Liquids (LNAPLs) are one of the most important sources of soil and groundwater contamination worldwide. When they infiltrate through the unsaturated zone, part of the LNAPLs remains trapped by capillary forces. The others accumulate above the top of the water table, forming a floating ‘free’ phase able to generate a long-term dissolved LNAPL plume that durably alters the quality of the water resource. Seasonal variations in the groundwater level lead to significant vertical spreading of these light petroleum hydrocarbon contaminants at the capillary fringe, favoring their release into the air and groundwater. In the climate change context, the IPCC predicts an intensification of these groundwater level variations over the next century in response to variations in rainfall intensity and frequency, whose effects are increased by the use of water resources. This context may strongly impact the mobilization of these organic contaminants and their release to the environment. To study these phenomena, it is, therefore, essential to better understand the impact of the groundwater level fluctuation patterns on the LNAPLs mobilization processes. To this end, an original experimental system combining indirect geophysical (complex electrical conductivity, permittivity), in-situ physical-chemical (pH, Eh, temperature), and geochemical measurements was developed at the GISFI station (Homécourt, France). This device allows the assessment and the comparison of the amount and nature of LNAPLs release into the atmosphere and water from contaminated soil during two groundwater level fluctuations scenarios: one corresponding to the ‘actual’ rainfall pattern based on regional climate records; the other based on the predictions of the most extreme IPCC scenario. This study will be conducted at different scales (laboratory decametric columns and 2 m3 lysimeters) and on soils of different geological complexity. The remobilized hydrocarbons will be collected via suction cups and gas collection chambers as the groundwater table fluctuates and will be regularly analyzed (GC-MS, FTIR). The complementarity of the monitoring methods aims to provide a better understanding of the fate of these organic pollutants at contaminated sites and the evolution of the associated environmental risks in the coming years, under the expected effect of climate change. Preliminary results concerning the hydrocarbon pollution migration through the unsaturated zone and the distribution of the LNAPL will be presented to illustrate the capacity of this new instrumental system.This work is partly funded by the DEEPSURF project "Lorraine Université d’Excellence", ANR-15-IDEX-04-LUE".

L'auteur a souhaité limiter l'accès aux membres de l'Enseignement supérieur français jusqu'au 12 juillet 2022; Hyperaccumulation is a phenomenon that was only discovered 45 years ago, it has been the focused of very intensive research because of the unusual behaviour of metals in the ecosystem and also because it offers a vast potential for nature-based solutions. Describing the Ni biogeochemical cycle within the soil-hyperaccumulator plants ecosystem is necessary to elucidate the ecological role of hyperaccumulator plants in their natural environment, but also to understand their potential behaviour under tropical agromining systems. Agromining and exporting Ni rich-biomass will interrupt the cycle. It is therefore important to understand the mechanisms which govern the Ni biogeochemical cycle in both natural and agromining systems: What are the Ni cycles (internal and external) and their impact on the ecological functioning of tropical hyperaccumulator forest? How rapid are the Ni fluxes across the soil-plant compartments, and what is the turnover of Ni in a hyperaccumulator tropical system? How fast can a tropical Agromining crop deplete Ni in soil? How can we manage soil fertilisation for a sustainable tropical Ni agromining crop? Therefore, the objectives were: (i) to study the biogeochemical cycling of a natural forest of Phyllanthus rufuschaneyi in order to assess and evaluate the natural fluxes of Ni in the ecosystem; (ii) to manipulate such an ecosystem in order to perform a sensitivity test of the ecosystem for the following flux: litter return to the soil; (iii) to optimize the cropping system of P. rufuschaneyi for Ni agromining. Two parallel stands of P. rufuschaneyi were instrumented, monitored and compared over two years (2018 and 2019), (i) a natural secondary 100-m2 forest and (ii) a densely planted field in which litter returns to the soil were calibrated; from no return (export) to a doubling of the return.This study did not prove allelopathy of tropical hyperaccumulator plants, despite the extreme influence of Ni hyperaccumulators in building up available Ni stocks in topsoils. Nickel cycle was mainly driven by internal fluxes, i.e. degradation and recycling of the hyperaccumulator biomass. The percentage of Ni recycled by litterfall tended to decrease with increasing litter addition to the soil and was not influenced by coppicing, at least in the short term. Major nutrient (NPK) fertilisation did not affect Ni yield (i.e. 75kg Ni ha-1 yr-1) in the short term either, even if N fertilisation reduced Ni concentrations in leaves and plant biomass production. Nickel turnover should be taken into account when designing tropical agromining crops and natural secondary forests are a good surrogate to evaluate the long term impacts of agromining. Further study of the weathering processes would help to precise the contribution of bedrock and soil mineral horizons in the Ni and nutrient budgets of the system.; L'hyperaccumulation est un phénomène qui a été découvert il y a 45 ans seulement, il a fait l'objet de nombreuses recherches, en raison du comportement inhabituel des métaux dans l'écosystème et en raison du potentiel de solutions fondées sur la nature qui en découle. La description du cycle biogéochimique du Ni des plantes hyperaccumulatrices est nécessaire pour élucider leur rôle écologique dans leur environnement naturel, mais aussi pour comprendre leur comportement potentiel dans des cultures tropicales d’agromine. L'exploitation agricole et l'exportation de la biomasse riche en Ni interrompront le cycle du Ni. Il est donc important de comprendre les mécanismes qui régissent le cycle biogéochimique du Ni dans les systèmes naturels et de cultures : Quels sont les cycles du Ni et leur impact sur le fonctionnement écologique des forêts tropicales d’hyperaccumulateurs ? Quelle est la vitesse des flux de Ni à travers les compartiments sol-plante et quelle est la dynamique et le renouvellement du Ni dans un système tropical d'hyperaccumulateurs ? À quelle vitesse une culture tropicale Agromine peut-elle épuiser le Ni dans le sol ? Comment pouvons-nous gérer la fertilisation des sols pour une culture d’agromine tropicale de Ni durable ? Les objectifs de ce doctorat étaient donc les suivants (i) d'étudier le cycle biogéochimique d'une forêt naturelle de Phyllanthus rufuschaneyi afin d'évaluer les flux de Ni dans l'écosystème ; (ii) de manipuler un tel écosystème afin d'effectuer un test de sensibilité de l'écosystème pour le flux suivant : retour de la litière au sol ; de l'absence de retour (exportation) à un doublement du retour ; (iii) d'optimiser le système de culture de P. rufuschaneyi pour l'agromine du Ni. Deux peuplements parallèles de P. rufuschaneyi ont été instrumentés, surveillés et comparés pendant deux ans (2018 et 2019), (i) une forêt secondaire naturelle de 100 m2 et (ii) un champ densément planté dans lequel les retours de litière au sol ont été calibrés ; de l'absence de retour (exportation) à un doublement du retour. Cette étude n'a pas révélé l'allopathie des plantes hyperaccumulatrices tropicales. Les plantes hyperaccumulatrices de Ni influent sur la constitution des stocks de Ni disponibles dans les couches arables. Le cycle du Ni est principalement régi par des flux internes, notamment la dégradation et le recyclage de la litière. Ce pourcentage de renouvellement du Ni ne semble pas être influencé par le taillis à court terme mais par la présence initiale de litière sur le sol. La fertilisation NPK n'a aucun effet sur le rendement en Ni à court terme (75 kg Ni ha-1 an-1), même si la fertilisation en azote a tendance à réduire le rendement en Ni de P. rufuschaneyi. Il convient de tenir compte du renouvellement du nickel lors de la conception des cultures d’agromine tropicales. Une étude plus approfondie de l’altération permettrait de préciser son rôle dans la reconstitution des stocks de Ni disponible et de nutriments.

Seed endophytic bacterial (SEB) communities have been little studied to date, although these microorganisms may assist seeds and seedlings to cope with environmental stresses. Hyperaccumulators have become models for studying plant adaptation to extreme environments, such as metalliferous soils. This work aims to characterize the endophytic bacterial communities associated with hyperaccumulating seeds collected from their native ecosystems (nonmetalliferous or calamine soils). Using 16S rRNA metabarcoding, endophytic bacterial communities were characterized for seeds from 14 Noccaea caerulescens populations. Plant genomes and environmental properties of the sites had previously been described. In all plant populations the metabarcoding revealed a large SEB core microbiome composed of the main phyla and sub-phyla: ɣ-Proteobacteria (56.56%) > α-Proteobacteria (32.23%) > Actinobacteria (7.93%) > Firmicutes (3.78%). According to the literature, some operational taxonomic units (OTUs) found in the core microbiome may be related to “plant growth promoting endophytes” (PGPE). The changes in the relative abundance of phyla/subphyla were correlated to altitude, pH, and soil exchangeable elements (Al, Mg, Cd, Mn, Zn), yet the main parameters observed to drive SEB diversity were the plants’ genetics. The distinction between populations based on calamine soils and nonmetalliferous soils failed to explain the SEB communities’ structural dissimilarities. In fact, the factor that best explained these dissimilarities was the plant’s genetic subunit. Future research, based on transcriptomic approaches, should study the ecological roles of the SEB communities and their involvement in the adaptation of hyperaccumulators to metalliferous soils.

International audience; Purpose Assessments of urban soil organic carbon stock (SOCS) are scant because citywide data are scarce. Moreover, we do not know which factors mostly explain SOCS spatial and temporal variations in urban open soils.Methods To fill these knowledge gaps, the present study focused on Paris (France): two periods (1993-2007 and 2008-2016) were compared to better understand SOCS changes at 0-30 cm depth. The effects of anthropic factors (land use, management intensity, cover type, site age and size, city district, and indirectly, resource material used for the site establishment) and soil properties (e.g., soil nutrient contents) on SOCS were studied over the more recent period (2008-2016) on 810 soil samples.Results The changes in green space management methods between both periods resulted in an additional storage of + 43.5 Gg SOC in Paris open soils in 2008-2016 compared to 1993-2007. During 2008-2016, SOCS was still influenced by city history and particularly by the type of resource material used for landscaping, which has changed since the 1950s. SOCS differed significantly among city districts, which represent a combination of all studied anthropic factors: each district has its own history (i.e., soil resource material, green space age), specific number and size of green spaces, current management methods, and plant cover types. Paris green space SOCS was also influenced by soil nitrogen, sand, and magnesium contents as well as pH.Conclusions Modifications of local landscape management methods are a main driver of SOCS changes. Moreover, citywide SOCS distribution tends to depend on city history.

Biocrust-mediated in situ bioremediation could be an alternative strategy to mitigate metal(loid) pollution in aquatic habitats. To better understand the roles of biocrusts in regulating the fate of metal(loid)s, we examined the morphology, composition and structure of biological aqua crusts (BAC) developed in the mine drainage of a representative Pb/Zn tailing pond, and tested their effectiveness for immobilizing typical metal(loid)s. Unlike terrestrial biocrusts, BAC results from an assembly of compounds produced by the strong microbial activity and mineral compounds present in the aquatic environment. The BAC exhibited a unique flexible, spongy and porous structure with a specific surface area of 12-22 m2 g-1, and was able to effectively concentrate various metal(loid)s (e.g. Cd, 0.26-0.60 g kg-1; Pb, 0.52-0.66 g kg-1; As, 10.4-24.3 g kg-1). The concentrations of metal(loid)s (e.g. Cd and As) in the BAC were even three to seven times higher than those in the source tailings, and more than 98% of immobilized metal(loid)s were present as the highly stable non-EDTA-exchangeable fraction. Adsorption on the well distributed micro-particles of the clay minerals (e.g. kaolinite) and the organic matters (2.0-2.7 wt.%) were found to be the major mechanisms for BAC to bind metal cations, whereas adsorption and coprecipitation on Fe/Mn oxide (e.g. FeOOH), was proposed to be the dominant pathway for accumulating metal(loid)s, especially As. The decrease in aqueous concentrations of the metal(loid)s along the drainage could be attributed in part to the scavenging effects of the BAC. These findings therefore provide new insights into the possible and efficient strategy for metal(loid) removal from water bodies, and highlighted the important role of BAC as a nature-based solution to benefit the bioremediation of mining area.

The aim of this study was to assess the potential of the woody nickel hyperaccumulator species Blepharidium guatemalense (Standl.) Standl. for agromining in southeastern Mexico. Pot trials consisting of nickel dosing (0, 20, 50, 100, and 250 mg Ni kg−1), and synthetic and organic fertilization were conducted. Field trials were also undertaken with different harvesting regimes of B. guatemalense. Foliar nickel concentrations increased significantly with rising nickel additions, with a 300-fold increase at 250 mg Ni kg−1 treatment relative to the control. Synthetic fertilization strongly increased nickel uptake without any change in plant growth or biomass, whereas organic fertilization enhanced plant shoot biomass with a negligible effect on foliar nickel concentrations. A 5-year-old stand which was subsequently harvested twice per year produced the maximum nickel yield tree−1yr−1, with an estimated total nickel yield of 142 kg ha−1yr−1. Blepharidium guatemalense is a prime candidate for nickel agromining on account of its high foliar Ni concentrations, high bioconcentration (180) and translocation factors (3.3), fast growth rate and high shoot biomass production. Future studies are needed to test the outcomes of the pot trials in the field. Extensive geochemical studies are needed to identify potential viable agromining locations. Novelty Statement Our research team is a pioneer in the discovery of metal hyperaccumulator plants in Mesoamerica with at least 13 species discovered in the last 2 years. This study is the first to assess the potential of nickel agromining (phytomining) in Mexico (and in all the American continent), using one of the strongest nickel hyperaccumulators reported so far. The promising results of this study are the basis for optimal agricultural management of Blepharidium guatemalense.

Texte intégral accessible uniquement aux membres de l'Université de Lorraine jusqu'au 1er janvier 2022.; Agromining technology involves the recovery of strategic metals from metalliferous soils through the cultivation of metal(loid) hyperaccumulator plants. The impetus of this research was to evaluate the potential of Mexican plant resources for the future development of agromining. The main objectives were then to identify and to study some metal hyperaccumulator plant species in Mexico, and to assess the agronomy of one promising “metal crop” for agromining. We first undertook field explorations in three nickel-rich ultramafic regions of central and southern Mexico. Despite the availability of soil and climatic conditions, no nickel (Ni) hyperaccumulation was found in any of these regions. A second strategy based on plant phylogeny as a prediction tool for metal hyperaccumulation was followed. In total, ten plant metal hyperaccumulator species were identified during this research (Rubiaceae and Violaceae) in Ni-enriched soils influenced by volcanic activity in Southeastern Mexico; most of them were priorly unknown. Our studies revealed two of the strongest hypernickelophores reported so far (>4%wt Ni) and two new Ni hyperaccumulator genera (Orthion and Mayanaea). Special focus was given to the hypernickelophore tree Blepharidium guatemalense. The phloem on leaves, roots, stems and petioles of this plant are the richest in Ni suggesting an unusual re-distribution mechanism via the phloem. Different agronomic practices were tested for this plant. Synthetic fertilization strongly increased nickel uptake without any change in plant growth or biomass, whereas organic fertilization enhanced plant shoot biomass with a negligible effect on foliar Ni concentrations. A 5-year-old stand which was subsequently harvested twice per year produced the maximum Ni yield tree⁻¹ yr⁻¹, with an estimated total nickel yield of 142 kg ha⁻¹ yr⁻¹. Blepharidium guatemalense is a prime candidate for Ni agromining on the account of its valuable traits: extremely efficient Ni uptake, high biomass production, fast growth rate, and easy to reproduce.; L’agromine concerne la récupération de métaux stratégiques dans les sols métallifères par la culture de plantes hyperaccumulatrices de métaux (et metalloïdes). Le moteur de cette recherche était d'évaluer le potentiel des ressources végétales mexicaines pour le développement de l'agromine. Les principaux objectifs étaient d'identifier et d'étudier quelques espèces de plantes hyperaccumulatrices de métaux au Mexique, et d'évaluer l'agronomie d'une de ces espèces avec des caractéristiques prometteuses pour l’agromine. Nous avons d'abord effectué des explorations dans trois régions ultramafiques riches en nickel (Ni) du centre et du sud du Mexique. Malgré la disponibilité du nickel dans le sol et les conditions climatiques, aucune hyperaccumulation de Ni n'a été trouvée dans ces régions. Une deuxième stratégie basée sur la phylogénie végétale comme outil de prédiction de l'hyperaccumulation des métaux a été suivie. Au total, dix espèces hyperaccumulatrices de métaux ont été identifiées au cours de cette recherche (Rubiaceae et Violaceae) dans des sols riches en Ni influencés par l'activité volcanique, dans le sud-est du Mexique ; la majorité d’entre elles n’était pas identifiée comme hyperaccumulatrices. Nos études ont révélé deux des hypernickelophores les plus puissants détectés jusqu'à présent (>4% wt Ni) et deux nouveaux genres hyperaccumulateurs de nickel (Orthion et Mayanaea). Une attention particulière a été accordée à l'hypernickelophore Blepharidium guatemalense. Le phloème des feuilles, des racines, des tiges et des pétioles de cette plante est très riche en Ni, ce qui suggère un mécanisme de redistribution via le phloème. Différentes pratiques agronomiques ont été testées pour cette plante. La fertilisation inorganique a fortement augmenté l'absorption du Ni sans modifier la croissance ou la biomasse de la plante, tandis que la fertilisation organique a augmenté la biomasse de la plante avec un effet négligeable sur les concentrations de Ni dans les parties aériennes. Une parcelle avec une culture de 5 ans, qui a ensuite été récolté deux fois par an, produit le rendement maximal en Ni de 142 kg ha⁻¹ an⁻¹. Blepharidium guatemalense est un candidat de choix pour l'agromine du Ni en raison de ses caractéristiques appréciables : absorption extrêmement efficace du Ni, production élevée de biomasse, taux de croissance rapide, et facilité de reproduction

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Five mesofauna communities varying in both structure and composition were exposed to phenanthrene in mesocosms for up to four months. Effects of phenanthrene were assessed on mesofauna population dynamics, fungal biomass (ergosterol concentrations), and litter decomposition (litter mass loss, nitrogen concentration). The effects of each community on the fate of phenanthrene were also assessed. We hypothesize that phenanthrene affects the population dynamics of mesofauna and soil biological functioning depending on exposure duration, type of community, or both. Results show that phenanthrene exerted an effect on mesofauna and that the effects on some species, like Folsomia fimetaria, were influenced by the species composition in the mesocosms, the soil layer, and the sampling date. However, the effects of phenanthrene on ergosterol content and organic matter decomposition were not significantly influenced by community composition. These results demonstrate that interspecific relationships are needed to assess the toxicity of pollutants and should be taken into account in ecotoxicological risk assessment. Furthermore, this work does not support the hypothesis of a direct link between toxic effects of organic pollutants on mesofauna species and soil biological functioning. Five mesofauna communities varying in both structure and composition were exposed to phenanthrene in mesocosms for up to four months. Effects of phenanthrene were assessed on mesofauna population dynamics, fungal biomass (ergosterol concentrations), and litter decomposition (litter mass loss, nitrogen concentration). The effects of each community on the fate of phenanthrene were also assessed. We hypothesize that phenanthrene affects the population dynamics of mesofauna and soil biological functioning depending on exposure duration, type of community, or both. Results show that phenanthrene exerted an effect on mesofauna and that the effects on some species, like Folsomia fimetaria, were influenced by the species composition in the mesocosms, the soil layer, and the sampling date. However, the effects of phenanthrene on ergosterol content and organic matter decomposition were not significantly influenced by community composition. These results demonstrate that interspecific relationships are needed to assess the toxicity of pollutants and should be taken into account in ecotoxicological risk assessment. Furthermore, this work does not support the hypothesis of a direct link between toxic effects of organic pollutants on mesofauna species and soil biological functioning. Five mesofauna communities varying in both structure and composition were exposed to phenanthrene in mesocosms during up to four months. Effects of phenanthrene were assessed on mesofauna population dynamics, fungal biomass (ergosterol concentrations) and litter decomposition (litter mass loss, nitrogen concentration). The effects of each community on the fate of phenanthrene were also assessed. We hypothesize that phenanthrene affects the population dynamics of mesofauna and soil biological functioning depending on exposure duration and/or type of community. Results show that phenanthrene exerted an effect on mesofauna and that the effects on some species, like Folsomia fimetaria, were influenced by the species composition in the mesocosms, the soil layer and the sampling date. However the effects of phenanthrene on ergosterol contents and organic matter decomposition were not significantly influenced by community composition. These results demonstrate that interspecific relationships are needed to assess the toxicity of pollutants, and should be taken into account in ecotoxicological risk assessment. Furthermore, this work does not support the hypothesis of a direct link between toxic effects of organic pollutants on mesofauna species and soil biological functioning.

Rhizosphere pH is the consequence of numerous, complex processes and is a key factor of biogeochemistry at the soil-root interface. This work aimed at evaluating the impact of nutrient root absorption on rhizosphere pH using a mechanistic model formalizing major nutrient cation and anion transport, under the influence of concentration, electric potential gradients and of convection. The electrical neutrality of the system was maintained through a H+ root efflux or influx (or equivalent opposite OH− fluxes). The model outputs were compared to the rhizosphere pH of maize (Zea mays L.), ryegrass (Lolium perenne L.) and Alpine pennycress (Noccaea caerulescens (J. & C. Presl) F. K. Mey.) grown in three different soils, determined with planar optodes. A global sensitivity analysis was carried out in order to highlight the dominating factors. The composition of 37 soil solutions from the literature was used to predict rhizosphere pH. The model most of the time predicts the alkalinisation of the rhizosphere by up to +3.3 pH units, given that in aerobic soils, nitrate is the most absorbed nutrient and its internalization is equilibrated by H+ root absorption (or equivalent OH− excretion). This alkalinisation is close to that observed in the rhizosphere of ryegrass and Alpine pennycress. The rhizosphere pH predictions are very sensitive to the initial composition of the soil solution and quite insensitive to root absorption kinetics and soil buffer power for the various nutrients. Because it favours nitrate diffusion, water content is positively correlated with rhizosphere alkalinisation. Moreover, the lower the root density, the lower the effect of the root uptake on both ion concentrations and on rhizosphere pH. Convection has little influence on rhizosphere pH. This study confirms the prominent role of mineral nutrition in the determination of rhizosphere pH. The model therefore constitutes a tool for understanding and predicting rhizosphere pH.

International audience; Clay-sized soil minerals are known to protect organic carbon (OC) from mineralisation by formation of organo-mineral associations limiting its availability to microorganisms. The impact of soil fauna on these processes is poorly known. The aim of this study was to investigate the effect of earthworms on organic matter (OM) decomposition and association with minerals during a laboratory experiment. We used a model system consisting of fresh OM incubated with and without epigeic earthworms (Eisenia andrei and foetida) in presence of different types and amounts of phyllosilicates (kaolinite, montmorillonite) and an iron oxide (goethite) and combinations of these minerals. Our experimental setup included a high OM:mineral ratio to represent the soil-litter interphase. We monitored OC mineralisation during 196 days. Additionally, we investigated physicochemical parameters and chemical OM characteristics of decomposition products by determination of water-soluble OC (WSOC) and acquisition of solid-state 13C NMR spectra. We also analysed microscale organisation of the organo-mineral associations produced with and without earthworms by transmission electron microscopy (TEM).Earthworms enhanced OC mineralisation in all treatments. They also led to greater reductions of OC emissions in the presence of minerals as compared to the mineral-free control, depending on the type and amount of minerals added. The presence of earthworms affected microbial biomass, the concentration of WSOC and increased the contribution of aromatic compounds to OM decomposition products. Microscale analyses by TEM showed that earthworms favoured association of minerals with partly degraded OM along with completely degraded material, while in absence of earthworms only completely degraded OM was associated with minerals. We conclude that earthworms impact OM decomposition through (1) their effect on microbial biomass and the physicochemical parameters of microbial habitat and (2) the formation of OM associations by changing the OM types associated to minerals and possibly by creating closer association of partly degraded OM and iron oxides. The stability of these associations remains to be investigated.

International audience; Amendments of biochar, the residual solid of biomass pyrolysis, have been shown to enhance metal phytoextraction from contaminated soils with hyperaccumulating plants in specific situations. In order to investigate this phenomenon over successive harvests in field conditions, two identical undisturbed soil cylinders (1-m2 section × 1.85-m height) were excavated from a contaminated agricultural plot and monitored with instrumented lysimeters. Wood-derived biochar was added at a rate of 5% (w/w) in the first 30 cm of one of the two lysimeters. The Cd/Zn-hyperaccumulator Noccaea caerulescens was then grown for the next four years on both lysimeters. Our results showed that the hyperaccumulating plant was able to remove about 2 g m−2 of Cd and 12–16 g m−2 of Zn within four years, representing about 40% and 4% of the initial Cd and Zn soil contamination, respectively. Biochar amendment improved plant germination and survival and increased root surface density. However, no significant effect of biochar on shoot metal content of N. caerulescens was observed. Mass balances suggested that up to 10% the metal contamination moved from the disturbed Ap horizon to the deeper horizons, particularly in the biochar-amended soil profile. Furthermore, shoot Cd and Zn concentration generally decreased over the successive harvests, together with soil metal availability. Depending on the way to account for this progressive decrease in efficiency, our estimations of the time necessary to remove the excess of metals in the topsoil in these conditions ranged from 11 to 111 years for Cd and from 97 years to an infinite time for Zn. In conclusion, the simultaneous use of N. caerulescens and biochar amendment can lead to a significant removal of specific metallic elements from the topsoil, but the risk of metal movement down the soil profile and the observed decrease in phytoextraction efficiency over time deserve further investigations.

Selenium (Se), a trace element essential for human and animal biological processes, is deficient in many agricultural soils. Some extremely rare plants can naturally accumulate extraordinarily high concentrations of Se. The native legume Neptunia amplexicaulis, endemic to a small area near Richmond and Hughenden in Central Queensland, Australia, is one of the strongest Se hyperaccumulators known on Earth, with foliar concentrations in excess of 4000 μg Se g−1 previously recorded. Here, we report on the Se distribution at a whole plant level using laboratory micro X-ray Fluorescence Microscopy (μXRF) and scanning electron microscopy (SEM-EDS), as well as on chemical forms of Se in various tissues using liquid chromatography-mass spectrometry (LC-MS) and synchrotron X-ray absorption spectroscopy (XAS). The results show that Se occurs in the forms of methyl-selenocysteine and seleno-methionine in the foliar tissues, with up to 13 600 μg Se g−1 total in young leaves. Selenium was found to accumulate primarily in the young leaves, flowers, pods and taproot, with lower concentrations present in the fine-roots and stem and the lowest present in the oldest leaves. Trichomes were not found to accumulate Se. We postulate that Se is (re)distributed in this plant via the phloem from older leaves to newer leaves, using the taproot as the main storage organ. High concentrations of Se in the nodes (pulvini) indicate this structure may play an important a role in Se (re)distribution. The overall pattern of Se distribution was similar in a non-Se tolerant closely related species (Neptunia gracilis), although the prevailing Se concentrations were substantially lower than in N. amplexicaulis.

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Seed germination represents the first crucial stage in the life cycle of a plant, and the seed must contain all necessary transition elements for the development and successful establishment of the seedling. Problematically, seed development and germination are often hampered by elevated metal(loid) concentrations in industrially polluted soils, making their revegetation a challenging task. Biscutella laevigata L. (Brassicaceae) is a rare perennial pseudometallophyte that can tolerate high concentrations of trace metal elements. Yet, the strategies of this and other plant species to ensure reproductive success at metalliferous sites are poorly understood. Here we characterized several parameters of germination and used synchrotron X-ray fluorescence microscopy to investigate the spatial distribution and concentration of elements within B. laevigata seeds from two metallicolous and two non-metallicolous populations. We find that average germination time was shorter and the seed weight was lower in the metallicolous compared to the non-metallicolous populations. By allowing for at least two generations within one growth season, relatively fast germination at metalliferous sites accelerates microevolutionary processes and likely enhances the potential of metallicolous accessions to adapt to environmental stress. We also identified different strategies of elemental accumulation within seed tissues between populations. Particularly interesting patterns were observed for zinc, which was found in 6-fold higher concentrations in the endosperm of metallicolous compared to non-metallicolous populations. This indicates that the endosperm protects the seed embryo from accumulating toxic concentrations of metal(loid)s, which likely improves reproductive success. Hence, we conclude that elemental uptake regulation by the seed endosperm is associated with enhanced metal tolerance and adaptation to metalliferous environments in B. laevigata.

International audience; Hyperaccumulator plants have the ability to efficiently concentrate metallic elements, e.g. nickel, from low-grade sources into their living biomass. Although the majority of nickel hyperaccumulator plant species restrict cobalt uptake, some species are able to co-accumulate cobalt when growing in ultramafic soils. The asteraceous perennial herb Berkheya coddii from South Africa is one of the most promising agromining crops known globally. It may accumulate nickel in excess of 30 000 mg g À1 in dry leaves, while co-accumulating up to 600 mg g À1 cobalt. This study aimed to elucidate the interactions between nickel and cobalt for uptake by and translocation into B. coddii through a pot experiment including various cobalt/nickel treatment combinations in soil, after which uptake and localisation were recorded. Cobalt in the substrate limits nickel uptake by B. coddii plants and is mainly retained in the basal leaves in contrast to Ni that is rapidly transferred to the top of the plant. B. coddii was more tolerant to high Ni concentration, whether in the substrate or internally but remains a promising crop which could be used, with suitable agronomic measures and practices, for cobalt agromining in areas with high soil cobalt but low soil nickel. A yield of 77 kg ha À1 nickel and 16.5 kg ha À1 cobalt may be attainable under optimum conditions. Significance to metallomics The hyperaccumulator plant Berkheya coddii from South Africa is one of the most promising 'agromining crops' known globally. This article reports on the interactions between cobalt and nickel for uptake and translocation in this species. Cobalt in the substrate inhibits nickel uptake in plants, and while nickel is rapidly transferred to the top of the plant, cobalt is mainly retained in the basal leaves.

Growing lignocellulosic crops on marginal lands could compose a substantial proportion of future energy resources. The potential of poplar was explored, by devising a field trial of two hectares in 2007 in a metal-contaminated site to quantify the genotypic variation in the growth traits of 14 poplar genotypes grown in short-rotation coppice and to assess element transfer and export by individual genotypes. Our data led us to conclusions about the genotypic variations in poplar growth on a moderately contaminated site, with the Vesten genotype being the most productive. This genotype also accumulated the least amounts of trace elements, whereas the Trichobel genotype accumulated up to 170 mg Zn kg−1 DW in the branches, with large variation being exhibited among the genotypes for trace element (TE) accumulation. Soil element depletion occurred for a range of TEs, whereas the soil content of major nutrients and the pH remained unchanged or slightly increased after 10 years of poplar growth. The higher TE content of bark tissues compared with the wood and the higher proportion of bark in branches compared with the wood led us to recommend that only stem wood be harvested, instead of the whole tree, which will enable a reduction in the risks encountered with TE-enriched biomass in the valorization process.

Plant and soil 455, 289 ��� 303 (2020). doi:10.1007/s11104-020-04629-7, $Aims$Knowledge on the ecophysiology of cobalt hyperaccumulator species is limited. The nickel hyperaccumulator Rinorea cf. bengalensis from Borneo can accumulate high concentrations of cobalt in nature. This study investigates the cobalt accumulation potential of Rinorea cf. bengalensis in relation to nickel concentrations in soils and the subsequent tissue and cellular-level distributions of cobalt, nickel and major cations.$Methods$Seedlings of Rinorea cf. bengalensis were grown in mixed treatments on ultramafic soil containing a high concentration of available nickel. Cobalt and nickel salts were then added to the soil to study their interactions. The tissue and cellular-level distributions of cobalt, calcium, nickel, and potassium were investigated using synchrotron-based X-ray fluorescence microscopy.$Results$The maximum foliar cobalt concentration reached 1200 ��g g$^{���1}$. Accumulation of cobalt competed with nickel accumulation although nickel seems to stimulate cobalt phloem translocation. Plants suffered toxicity in the treatment with the highest soil cobalt concentration. Cobalt and nickel have contrasting distribution patterns in the leaves of Rinorea cf. bengalensis, with cobalt mainly excreted on the surface of the leaves, whereas nickel is localised in foliar epidermal cells.$Conclusions$Rinorea cf. bengalensis can accumulate high concentrations of cobalt, but is intrinsically more tolerant to nickel. It does not rely on a similar sequestration mechanism for both metals, which could explain the lesser tolerance for cobalt. Nickel appears to be essential for the plant to tolerate high cobalt concentrations. Further studies intending to develop agronomic practices are needed to determine the viability of Rinorea cf. bengalensis for nickel-cobalt agromining., Published by Springer Science + Business Media B.V, Dordrecht [u.a.]

International audience; Dans un contexte mondial d’urbanisation croissante et d’intensification des pressions sur les ressources naturelles, la prise en compte des sols dans l’aménagement urbain devient un enjeu incontournable pour rendre les villes plus durables. Cet article se propose de préciser la définition du terme de sol urbain en décrivant la variabilité de ce qu’il recouvre et en le confrontant à ses représentations par les acteurs du monde de l’aménagement. Au travers d’une étude croisée de documents d’urbanisme et la conduite d’entretiens avec ces acteurs, il apparaît que les sols sont un compartiment des écosystèmes urbains dont le potentiel est méconnu et sous-estimé, mais qu’ils sont néanmoins considérés comme une ressource par les maîtres d’ouvrage, les maîtres d’oeuvre et les entreprises de terrassement. Les services écosystémiques qu’ils peuvent rendre apparaissent comme un concept central qui permet de faire le lien entre les experts (pédologues, agronomes, paysagistes) et les décideurs. Sur ces bases, nous formulons un certain nombre de suggestions pour le développement d’outils d’aide à la décision permettant de prendre en compte les potentialités des sols à l’échelle d’un projet d’aménagement. Inspirée de la démarche mise en oeuvre dans le projet Destisol, nos propositions se basent notamment sur l’évaluation des services écosystémiques des sols urbains à partir de l’analyse de leurs caractéristiques physiques, chimiques et biologiques.

Nickel (Ni) is used in numerous industrial processes, with large amounts of Ni-rich industrial wastes produced, which are largely sent to landfill. Nickel recovery from waste materials that would otherwise be disposed is of particular interest. Nickel phytomining represents a new technology in which hyperaccumulator plants are cultivated on Ni-rich substrates for commercial metal recovery. The aim of this study was to investigate the possibility of Ni transfer from industrial waste into plant biomass, to support recovery processes from bio-ores. Different industrial galvanic sludges (containing 85–150 g kg−1 Ni) were converted into artificial substrates (i.e. technosols) and the Ni hyperaccumulator Odontarrhena chalcidica (formerly Alyssum murale) was cultivated on these Ni-rich matrices. A greenhouse pot experiment was conducted for three months including an ultramafic soil control and testing fertilized (NPK) and unfertilized replicates. The results showed that fertilization was effective in improving plant biomass for all the substrates and that O. chalcidica was capable of viably growing on technosols, producing a comparable biomass to O. chalcidica on the control (ultramafic soil). On all technosols, O. chalcidica achieved Ni shoot concentrations of more than >1000 mg Ni kg −1 and maximum Ni uptake was obtained from one of the technosols (26.8 g kg −1 Ni, unfertilized; 20.2 g kg −1 Ni, fertilized). Nickel accumulation from three of the technosols resulted to be comparable with the control ultramafic soil. This study demonstrated the feasibility of transferring Ni from toxic waste into the biomass of Odontarrhena chalcidica and that phytomining from galvanic sludge-derived technosols can provide similar Ni yields as from natural ultramafic soils.

Aims Data on the variability of hyperaccumulation potential of the facultative serpentinophytes Noccaea kovatsii and N. praecox on different geological substrates are scarce. The aim of this study was to assess the accumulation potential of these two species from ultramafic and non-ultramafic substrates, with special emphasis on the hyperaccumulation of Ni, Zn and Cd. Methods Samples of plants and corresponding soils were collected from 16 sites covering a wide range of geochemistry. Elemental concentrations were determined in the roots, shoots and the rhizosphere soils. The pH, particle size distribution and content of organic matter were also determined in the soil samples. Results All ultramafic accessions of both species hyperaccumulated Ni with high intraspecific variability. Only one accession of N. kovatsii from a schist soil hyperaccumulated Zn, with also a high Cd accumulation. Accumulation and translocation of Ni in both species were much higher in the ultramafic accessions, whereas Zn accumulation and translocation was found in both ultramafic and non-ultramafic accessions. Conclusions Ni accumulation and translocation was restricted to ultramafic populations of both species, whereas it is a species-wide trait for Zn. This study provides new and comprehensive information on the natural variation of hyperaccumulation of Ni, Zn and Cd in N. kovatsii and N. praecox.

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Cette etude s’inscrit dans un projet de recherche portant sur l’evaluation des impacts environnementaux et sanitaires de l’orpaillage dans la zone de Komabangou au Niger. L’objectif est de determiner les niveaux de contamination des elements traces dans les sols et d'analyser leur distribution spatiale. Des echantillons des sols ont ete preleves en 2016 dans 27 localites dont 24 sur differents sites de la zone aurifere de Komabangou et 3 sur sites temoins. Les concentrations en elements traces (As, Cd, Co, Cr, Cu, Ni, Pb et Zn) dans les sols ont ete determinees par spectrometrie de masse avec plasma a couplage inductif (ICP-MS). La pollution des sols a ete evaluee en calculant les index de pollution (IP) des sols. Les resultats montrent que les concentrations en elements traces metalliques (ETM) dans les sols different en fonction du site et du metal considere. Les cartes de repartition spatiale montrent une importante concentration des elements traces tels que As, Cd, Pb et Zn au centre de la zone aurifere. Plusieurs de ces teneurs en ETM sont superieures aux seuils reglementaires. Aussi sur les 27 sites etudies, 12 ont des valeurs d’IP superieures a 1 revelant ainsi une contamination des sols par plusieurs elements. Ces resultats montrent une accumulation des metaux dans les sols qui peuvent persister dans l’environnement. Cela peut poser de serieux risques sanitaires pour l’Homme. Pour prevenir tout risque, un plan de surveillance de la contamination des sols devrait etre mis en place et il faudrait envisager de traiter les sites pollues. © 2019 International Formulae Group. All rights reserved. Mots cles : Orpaillage, sols, contamination, elements traces metalliques, valeurs limites, Komabangou, Niger. English Title : Spatial distribution of metallic trace elements in soils of Komabangou gold zone in Niger This study is part of research project on environmental and health impacts of gold mining in Komabangou area of Niger. The objective is to determine pollution levels of trace elements in soils and to analyze their spatial distribution. Soil samples were collected in 2016 at 27 localities, including 24 at different sites in Komabangou gold zone and 3 at control sites. Concentrations of trace elements (As, Cd, Co, Cr, Cu, Ni, Pb and Zn) in soils were determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Soil pollution was assessed by calculating soil pollution index (PI). The results show that metal trace element concentrations in soils differ depending to the site and the metal. Spatial distribution maps show a high concentration of trace elements such as As, Cd, Pb and Zn in the center of the gold zone. Many concentrations of trace elements in soils are above regulatory thresholds. Also, of the 27 sites studied, 12 have PI values greater than 1, revealing soil contamination by several elements. These results show an accumulation of metals in soils, which can persist in the environment. This can pose serious health risks for humans. To prevent any risk, soil contamination monitoring plan should be put in place and consideration should be given to treating polluted sites. Keywords : Gold panning, soils, contamination, trace elements, limit values, Komabangou, Niger.

International audience

The aim of this work is to study and evaluate in situ, the Artemisia herba alba responses to hexavalent chromium stress in the arid and semi-arid steppe Algerian soil. This metallic pollutant was selected to its high toxicity and to its great release from several industrial and agricultural activities emissions in the area of the study region. Artemisia herba alba is a medicinal plant but also a forage species widely used in pasture. It has dominated then adapted to the arid and semi-arid climate of Algerian steppe region, due principally to their morphological and physiological characteristics. To establish this work, A. herba alba species were selected in the Algerian steppe region, and their soils were treated weekly with K

International audience; Purpose Given their increasing importance, soils should be considered as valuable resources by those involved in urban planning. Indeed, soils are expected to be multifunctional in order both to ensure sustainable development of human societies and to resist major environmental issues. Through the study of planning documents, this article describes the way in which political intentions impact the preservation of soil as an urban resource. Materials and methods A lexical analysis was conducted of more than 100 French planning documents. Each of them relates to a specific topic (e.g., soil cover, transport, biodiversity) and to a particular application scale. Tropes (c) software was used to count the number of times the word "soil" occurs in each document. A distinction was made between "soil" written as a surface area (land use, square meters) and a resource (ecosystem, cubic meters). A further statistical analysis was performed by crossing the results with demographic data and the main characteristics of the documents. Results and discussion The results revealed that soil is a subject which is relatively infrequently addressed in French planning documents. Indeed, its index of occurrence reached 0.06% in comparison to "transport" (0.77%). Moreover, "soil" refers both to a surface area (0.035%) and a resource (0.031%). However, this consideration varies from document to another and depends on the given urban area. Finally, the publication date of the document was correlated with the frequency of the use of the word "soil." These results suggest that the level of consideration of soil, as a complex ecosystem, is moderate and relies mainly on the people who drafted the document. Conclusions The frequency of the word "soil" is comparable to those of words as "biodiversity" and "air." Moreover, "soil" is considered as a living resource in the planning documents. It also appears that the services provided by agricultural and forest soils are well known to policy makers and planning operators (e.g., food and non-food biomass provisioning). In contrast, urban soils are predominantly seen as surface areas to be converted or as a potential threat due to their level of contamination or geotechnical properties.

International audience

The enzymatic hydrolysis of lignocellulosic biomass is mainly driven by the action of carbohydrate-active enzymes. By characterizing the gene profiles at the different stages of the anaerobic digestion experiment, we showed that the microbiome retains its hydrolytic functional redundancy even during severe acidosis, despite significant changes in taxonomic composition. By analyzing reconstructed bacterial genomes, we demonstrate that Bacteroidetes hydrolytic gene diversity likely favors the abundance of this phylum in some anaerobic digestion systems. Further, we observe genetic redundancy within the Bacteroidetes group, which accounts for the preserved hydrolytic potential during acidosis. This work also uncovers new polysaccharide utilization loci involved in the deconstruction of various biomasses and proposes the model of acetylated glucomannan degradation by Bacteroidetes. Acetylated glucomannan-enriched biomass is a common substrate for many industries, including pulp and paper production. Using naturally evolved cocktails of enzymes for biomass pretreatment could be an interesting alternative to the commonly used chemical pretreatments., Increased hydrolysis of easily digestible biomass may lead to acidosis of anaerobic reactors and decreased methane production. Previously, it was shown that the structure of microbial communities changed during acidosis; however, once the conditions are back to optimal, biogas (initially CO2) production quickly restarts. This suggests the retention of the community functional redundancy during the process failure. In this study, with the use of metagenomics and downstream bioinformatics analyses, we characterize the carbohydrate hydrolytic potential of the microbial community, with a special focus on acidosis. To that purpose, carbohydrate-active enzymes were identified, and to further link the community hydrolytic potential with key microbes, bacterial genomes were reconstructed. In addition, we characterized biochemically the specificity and activity of selected enzymes, thus verifying the accuracy of the in silico predictions. The results confirm the retention of the community hydrolytic potential during acidosis and indicate Bacteroidetes to be largely involved in biomass degradation. Bacteroidetes showed higher diversity and genomic content of carbohydrate hydrolytic enzymes that might favor the dominance of this phylum over other bacteria in some anaerobic reactors. The combination of bioinformatic analyses and activity tests enabled us to propose a model of acetylated glucomannan degradation by Bacteroidetes. IMPORTANCE The enzymatic hydrolysis of lignocellulosic biomass is mainly driven by the action of carbohydrate-active enzymes. By characterizing the gene profiles at the different stages of the anaerobic digestion experiment, we showed that the microbiome retains its hydrolytic functional redundancy even during severe acidosis, despite significant changes in taxonomic composition. By analyzing reconstructed bacterial genomes, we demonstrate that Bacteroidetes hydrolytic gene diversity likely favors the abundance of this phylum in some anaerobic digestion systems. Further, we observe genetic redundancy within the Bacteroidetes group, which accounts for the preserved hydrolytic potential during acidosis. This work also uncovers new polysaccharide utilization loci involved in the deconstruction of various biomasses and proposes the model of acetylated glucomannan degradation by Bacteroidetes. Acetylated glucomannan-enriched biomass is a common substrate for many industries, including pulp and paper production. Using naturally evolved cocktails of enzymes for biomass pretreatment could be an interesting alternative to the commonly used chemical pretreatments.

International audience; Urban compost application in agroecosystems enhances soil fertility but can also be a source of (micro)plastics, which are not completely removed during the composting process. Knowledge of the fate of these plastics in regularly-amended soils is thus an issue for the environmental management of these soils. The aims of this study were 1) to develop a method combining soil fractionation, microscopic observation and chemical characterization to follow the fate of plastics in soils and 2) to apply this method on a long-term experimental field, where municipal solid waste composts were applied every other year during 10 years. The presence of plastics was investigated within compost and soil fractions using morphological and analytical characterization by transmission electronic microscopy (TEM-EDX) and pyrolysis coupled to gas chromatography and mass spectrometry (Py/GC/MS). Specific features of plastics allowed us to distinguish these polymers from soil organic matter even in the

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARE [ADD1_IRSTEA]Dynamique et fonctionnement des écosystèmes; International audience; Trophic ecology is the study of feeding interactions and food acquisition by organisms. It includes the causes and consequences of those behaviours at all levels of biological organisation. As a field of research, it crosses many disciplinary boundaries and provides knowledge that is pertinent to many other areas of ecology. Here we list and categorise the methods available to trophic ecologists whose toolbox has broadened considerably in recent years. They encompass empirical and numerical approaches with focus ranging from molecules to ecosystems. We further examine the relationship of each method to features such as the scale of observation (from microbes to largest organisms) and organisational level (from individuals to ecosystems) as well as the ecological question the method is capable of answering (from detecting predator-prey relationships to studying implications and consequences at different scales). Our survey reveals a very wide range of methodologies, each more-or-less appropriate for a particular line of research. It also identifies deficits, for example, trophic interactions at microscopic scales, for which empirical methods have hardly been used, as well as trophic models that have failed to consider fluxes at the ecosystem scale. Furthermore, we note that the combination of methodologies remains under-exploited despite great opportunities to solve complex ecological questions and to foster the emergence of new insights and hypotheses regarding organism, population and/or ecosystem properties.

Phytoextraction is a promising technology for decontamination and recovery of rare earth elements (REEs) from REE-rich wastes. However, the improvement of REE phytoextraction efficiency on ion-adsorption REE mine tailings remains a challenge because the substrate can hardly support the growth of hyperaccumulators. In this study, REE phytoextraction using a REE hyperaccumulator, Phytolacca americana, grown on ion-adsorption REE mine tailing materials amended with organic material (OM) and biochar (BC) was explored through a pot experiment. Results show that under 1% OM, 5% OM, 1% BC, and 5% BC treatments, the shoots biomass of P. americana was 4.17, 7.85, 3.41, and 5.14 times higher than the control (without organic amendment) respectively, whereas the REE concentrations in shoots were 2.02, 68.4, 0.16, and 1.98 times lower than the control (524 ± 82.8 mg kg−1) respectively. The highest REE yield was obtained under 1% BC treatment and was 3.56 times that of the control. Both OM and BC treatments largely improved the soil physico-chemical properties. However, compared with OM and 5% BC treatments, 1% BC treatment induced a smaller increase in pH, and the amount of organic carbon and nutrients in the soil solution, thereby minimizing the reduction of REE bioavailability. We conclude that amendment with a low dosage of BC could be a potential way to improve REE phytoextraction efficiency by P. americana on ion-adsorption REE mine tailings.

International audience; Aims This study evaluated the effect of phloem translocation on Ni accumulation in the hyperaccumulator Noccaea caerulescens. Methods The first experiment assessed the metal and organic compound concentrations in phloem sap. Leaves were cut from plants grown in nutrient solutions added with 100 mu M Ni or Zn, and then used for phloem sap extraction by means of the EDTA-stimulated exudation method. In the second experiment, Ni-61(2+) was applied to old leaves as a foliar spray to assess bidirectional movement of Ni in phloem. Results In the first experiment, enrichment of Ni or Zn was found in phloem exudates, indicating high Ni and Zn phloem loading and translocation capacity in N. caerulescens. Amino acids, e.g. nicotianamine and histidine, were present at low concentrations in exudates, which are insufficient for Ni and Zn chelation. On the contrary, concentrations of organic acids, especially malate, were high in all treatments, which may be involved in Ni and Zn chelation in phloem. The second experiment showed that 89 % of Ni-61 exported from old leaves was translocated upward to young leaves, whereas only 11% moved downward to roots. Conclusions Phloem sap of N. caerulescens is enriched in Ni and malate, the majority of which moves upward to young tissues. Phloem translocation may play an important role for Ni accumulation in young leaves of N. caerulescens.

Les sols fournissent des services à la population humaine, appelés services écosystémiques. En vue de répondre aux problématiques environnementales qui se concentrent en milieu urbain, il est attendu que ces services soient facilement appréhendables par les acteurs de l’aménagement. Cet article propose des définitions claires de termes centraux comme « sol urbain », « sol anthropisé » et « couverture de sol » ; il présente également les caractéristiques bio-physico-chimiques des sols urbains. Des analyses bibliométrique et bibliographique de la littérature scientifique sur les services écosystémiques des sols urbains permettent de positionner la place de ce sujet sur les 20 dernières années et de proposer une liste de ces services. Enfin, une analyse critique des perspectives de développement d’outils d’aide à la décision à l’attention des aménageurs pour la prise en compte des sols urbains à chaque étape de l’aménagement est proposée., Soils, as ecosystems provide services that are also called ecosystem services. In the context of natural resources preservation, urban soils are expected to be multifunctional and to provide high level of ecosystem services ( e.g. vegetation support, building support, flood control). Therefore, there is a need for urban planners to take into account the urban soil potentials in urban project development. This article proposes definitions of such crucial terms such as “urban soil”, “anthropized soil” and “sol cover”; it also presents the main bio-physical-chemical characteristics of urban soils. A bibliometric analysis has been conducted to describe the position of ecosystem services provided by urban soils within the frame of actual research. A list and a description of the ecosystem services provided by urban soils is proposed. Finally, this article offers prospects for the development of decision-making tools for planners to encourage them to take into account soil ecosystem at each stage of planning.