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Ferromanganese (Fe-Mn) deposits constitute a ubiquitous mineral type in oceanic settings, with metal (Cu, Ni, Zn, Co, Pt) and rare earth element (REE) enrichments of potential economic interest. Routine analysis of trace elements by ICP-MS has advanced our understanding of the impact of hydrogenetic, diagenetic and hydrothermal processes on the mobility and interaction of high field strength elements (HFSE: Zr and Ti) and REE and yttrium (REY) with Fe-Mn oxyhydroxides. Recent discoveries in the French exclusive economic zone (EEZ) of Wallis and Futuna (southwest Pacific Ocean) have brought new insight into the formation of low temperature (LT) hydrothermal Mn deposits and lead us to reconsider the classification and discrimination diagrams for Fe-Mn deposits and ore-forming processes. Using a suite of LT hydrothermal Fe-Mn crusts from Wallis and Futuna, we investigate how contrasting genetic processes influence the distribution of metals (Mn, Fe, Cu, Ni, and Co), HFSE and REY in hydrogenetic, diagenetic, hydrothermal and mixed-type deposits from different environments in the global ocean. The interaction of the different metal oxide-forming processes indicates that: (i) enrichment of Co, HFSE and REY is favored by hydrogenetic precipitation, (ii) diagenetic processes produce higher Mn, Cu, and Ni concentrations with oxic remobilization in the sedimentary column, while suboxic conditions promote greater Mn and Fe remobilization that competes with the incorporation of Cu and Ni ions in nodules. HFSE and REY derived from seawater are usually low in diagenetic precipitates, which discriminate between hydrogenetic and diagenetic inputs within nodules, (iii) hydrothermal Fe-Mn deposits show strong depletion in HFSE and REY due to rapid formation and high contents of either Fe or Mn oxides. We present a new discrimination scheme for the genetic types of Fe-Mn deposits using a 10 ∗ (Cu + Ni + Co) − 100 ∗ (Zr + Y + Ce) − (Fe + Mn) / 4 ternary diagram. The use of HFSE and REY in the classification allows for a more robust discrimination of: (i) each ore-forming process with well-delimited fields, without overlap of metal-rich hydrothermal samples and hydrogenetic samples, (ii) oxic and suboxic diagenesis within nodules, (iii) trends between hydrogenetic and diagenetic end-members forming a continuum, and (iv) mixed genetic types such as the presence of hydrothermal particles within hydrogenetic crust layers. Alternatives are also explored to adapt our discriminative diagram to elements measurable by on-board instruments to aid in exploration at sea.

International audience; To assess the influence of the composition of dissolved organic matter (DOM) on metal speciation, two models have been used: Model VI and NICA-Donnan. The speciation of Cu, Ni, Pb and Zn in the soil solution of 36 samples characterized by alkaline pH and different contamination levels has been determined. Four assumptions about DOM composition have been tested: (i) 100% of humic substances (HS) are fulvic acids (FA), (ii) 100% are humic acids (HA), (iii) 35% are HA and 65% FA and (iv) 84% are HA and 16% FA. The results obtained with the two distinct models are of the same order of magnitude; however, few differences have been highlighted regarding the description of the non-specific interactions, the Zn–FA interactions and the lowest free ion concentrations. The main result of this study is that the free ion concentrations calculated with the two models may differ by one order of magnitude depending on whether HA and/or FA are used to represent DOM. This work demonstrates the impact of the assumptions made about the DOM nature for metal speciation modelling.

International audience; Metal and metalloid (As, Cd, Co, Cu, Pb and Zn) distribution in soils from the Katanga Copperbelt (Democratic Republic of Congo) is investigated in order to characterize the environmental impacts of mining and smelting activities in that area. The concentrations of Cu, Co, As, Zn, Pb and Cd in soils from mining sites are higher than in non-metalliferous sites and above permissible metal and metalloid concentrations in soils. Moreover, the fractionation and mobility of Co, and Cu in such environment is assessed using the application of both ammonium acetate-EDTA extraction and speciation modeling (WHAM 6). The resulting data set covers wide range of environmental conditions (pH, trace metals concentration, natural soils and soils affected by mining and ore processing). These extractions show that only a small fraction of Cu and Co is mobile, with variation depending on sites: mobility is higher in soils affected by mining and ore processing. The strong affinity of Mn-oxides for Co may explain lower Co mobility in Mn-rich soils. The high Mn and Fe contents of Cu–Co soils from Katanga may actually exert a protective effect against the toxic effects of Co. Finally, Cu–Co speciation modeling of contaminated sites emphasizes that organic matter strongly sorb Cu whereas Co speciation is mostly by Mn content. This type of study leads to a better understanding of metal fractionation and can guide to define different practices of phytoremediation.

International audience; Nanoparticles refer to very small size elements less than 100 nm. These particles have a large surface area to volume ratio with enhanced reactivity. One nanomaterial very interesting for remediation activities is nano zero valent iron (nZVI) estimated to be 10 to 1000 times more reactive than granular ZVI, thereby creating a greater reductive capacity per gram. Thus smaller amounts of iron would be needed to treat a contaminated plume at a faster rate, which would further reduce costs. nZVI also has the potential to treat recalcitrant pollutants such as chlorinated organic compounds, nitrates and hexavalent chromium. But the high reactivity of nZVI alone is not enough to make it an effective remediation agent, the nano iron particles should also be able to form stable dispersions and migrate to contaminated plumes. These expected additional properties are seen to be missing as the nZVI quickly agglomerates and oxidizes once released into the environment. This study looks at the challenges associated with the use of nZVI and the different transporters or carriers that have sought to overcome these shortfalls. Further attention is focused on how these nZVI particles are synthesized on carriers and the results obtained when used to treat pollutants.

Plant functional traits on serpentine degraded areas in Sabah (Malaysia). A potential tool for its reclamation. International Conferences on Serpentine Ecology (ICSE)

International audience; Oligogalacturonides (OGs) are known for their powerful ability to stimulate the plant immune system but little is known about their mode of action in pea (Pisum sativum). In the present study, we investigated the elicitor activity of two fractions of OGs, with polymerization degrees (DPs) of 2–25, in pea against Aphanomyces euteiches. One fraction was nonacetylated (OGs − Ac) whereas the second one was 30% acetylated (OGs + Ac). OGs were applied by injecting the upper two rachises of the plants at three- and/or four-weeks-old. Five-week-old roots were inoculated with 105 zoospores of A. euteiches. The root infection level was determined at 7, 10 and 14 days after inoculation using the quantitative real-time polymerase chain reaction (qPCR). Results showed significant root infection reductions namely 58, 45 and 48% in the plants treated with 80 µg OGs + Ac and 59, 56 and 65% with 200 µg of OGs − Ac. Gene expression results showed the upregulation of genes involved in the antifungal defensins, lignans and the phytoalexin pisatin pathways and a priming effect in the basal defense, SA and ROS gene markers as a response to OGs. The reduction of the efficient dose in OGs + Ac is suggesting that acetylation is necessary for some specific responses. Our work provides the first evidence for the potential of OGs in the defense induction in pea against Aphanomyces root rot.

Aided phytostabilization using coal fly ashes (CFAs) is an interesting technique to clean-up polluted soils and valorizing industrial wastes. In this context, our work aims to study the effect of two CFAs: silico-aluminous (CFA1) and sulfo-calcic (CFA2) ones, 10 years after their addition, on the phytostabilization of a highly Cd (cadmium), Pb (lead) and Zn (zinc) contaminated agricultural soil, with four forest tree species: Robinia pseudoacacia , Alnus glutinosa , Acer pseudoplatanus and Salix alba . To assess the effect of CFAs on trees, leaf fatty acid composition, malondialdehyde (MDA), oxidized and reduced glutathione contents ratio (GSSG: GSH), 8-hydroxy-2′-deoxyguanosine (8-OHdG), Peroxidase (PO) and Superoxide dismutase (SOD) activities were examined. Our results showed that CFA amendments decreased the CaCl 2- extractable fraction of Cd and Zn from the soil. However, no significant effect was observed on metal trace element (MTE) concentrations in leaves. Fatty acid percentages were only affected by the addition of sulfo-calcic CFA. The most affected species were A. glutinosa and R. pseudoacacia in which C16:0, C18:0 and C18:2 percentages increased significantly whereas the C18:3 decreased. The addition of sulfo-calcic CFA induced the antioxidant systems response in tree leaves. An increase of SOD and POD activities in leaves of trees planted on the CFA2-amended plot was recorded. Conversely, silico-aluminous CFA generated a reduction of lipid and DNA oxidation associated with the absence or low induction of anti-oxidative processes. Our study evidenced oxidative stress alleviation in tree leaves due to CFA amendments. MTE mobility in contaminated soil and their accumulation in leaves differed with the nature of CFA amendments and the selected tree species.

International audience; Research on biochar has increased, but its long-term effect on the fertility of temperate agricultural soil remains unclear. In Wallonia, Belgium, pre-industrial charcoal production affected former forested areas that were cleared for cultivation in the nineteenth century. The sites of traditional charcoal kilns, largely enriched in charcoal residues, are similar to soil amended with hardwood biochar more than 150 years ago. We sampled 17 charcoal kiln sites to characterize their effect on soil properties compared with adjacent reference soils. Charcoal-C content was estimated by differential scanning calorimetry. The kiln soil contains from 1.8 to 33.1 g kg−1 of charcoal-C, which markedly increases organic C:N and C:P ratios. It also contains slightly more uncharred soil organic carbon (SOC) than the reference soil, which accords with larger total N content. We measured a small increase in nitrates in the kiln soil that might relate to greater mineralization and nitrification of organic N. Frequent application of lime raised the pH to values close to neutral, which offset the residual effect of charcoal production on soil acidity. A cation exchange capacity (CEC) of 414 cmolc kg−1 was estimated for charcoal-C, whereas that of uncharred SOC was 213 cmolc kg−1. Despite the large CEC of the kiln soil, exchangeable K+ content was no different from the adjacent soil, whereas exchangeable Ca2+ and Mg2+ contents were considerably larger. Charcoal enrichment has little effect on available, inorganic and total P, but it can form strong complexes with Cu, which reduces the availability of the metal. Biochar is very persistent in soil; therefore, long-term implications should not be overlooked.

International audience

Background: Chemical soil factors play an important role in generating and maintaining plant diversity. Naturally metal-enriched habitats support highly distinctive plant communities consisting of many rare and endemic species. Species of these plant communities possess remarkable physiological adaptations and are now being considered key elements in the implementation of green technologies aimed at phytoremediation of contaminated soils and post-mined soils. Several studies have emphasised that industrial mineral extraction results in serious damage to ecosystems and serious threats to human health and leads to the extinction of metallophyte species. In the southeastern Democratic Republic of the Congo (DRC), mining activities represent a threat to the long-term persistence of communities located on metalliferous copper and cobalt outcrops and their associated endemic metallophytes, which are currently considered some of the most critically endangered plants in the world. Scope: Plant diversity conservation of metal-rich soils must assess soil-plant relationships at different scales (ecosystems, communities, and populations) to define in-situ and ex-situ conservation and restoration projects. This paper proposes a review of soil-plant relationships involved in plant diversity and endemism and their implications for biodiversity conservation and restoration., SCOPUS: ar.j, info:eu-repo/semantics/published

International audience; The influence of Fe oxides, Mn oxides and organic matter (OM) on the Cu and Co mobility in soil and accumulation in the metallophyte Anisopappus chinensis (Ac), as compared with Helianthus annuus (Ha), was experimentally investigated. Growth and accumulation response when increasing the exchangeable Cu and Co concentrations in soil were also investigated. Plants were cultivated on soil where concentrations of Cu, Co, Fe oxides, Mn oxides and OM content were varied according to 36 treatments. The OM supply decreased the Cu mobility and increased the Co mobility, resulting in decreasing the foliar Cu of Ac and increasing the foliar Co of Ha. The Fe oxides supply could increase the Cu accumulation for Ac, but was not verified for Ha. Compared with Ha, Ac increasingly accumulated Cu and Co without negative effect on plant growth while increasing Cu and Co mobility to phytotoxic concentrations. The results revealed promising perspectives for the use of Ac in Cu-contaminated environment phytoremediation applications.

Background and aims – In Katanga (D. R. Congo), outcrops of bedrocks naturally enriched in Cu and Co ("copper hills"), host unique plant communities. The spatial variation of vegetation has long been attributed almost exclusively to variation in Cu concentration in the soil, but this assumption has not been experimentally tested. We analysed the variation in plant communities and the niches of selected species in relation to edaphic factors within a copper hill. Methods – Forty-eight 1 m 2 plots were sampled for plant community and soil mineral element composition, and classified with Unweighted Pair Group Method with Arithmetic mean (UPGMA) using the Bray-Curtis distance. Plant-edaphic relationships were examined using a Canonical Correspondence Analysis (CCA). Species niches were modelled with Generalized Additive Model (GAM). Mean edaphic factors between the soil of plant communities were compared with one-way Kruskal-Wallis non-parametric ANOVA. Key results – The diversity of communities at the site scale was higher than observed in previous studies at a larger scale. Cu was the most discriminating edaphic factor of plant communities. However, detailed comparisons of mean edaphic factors among communities revealed individual combinations of edaphic parameters for each community, as well as differences in soil Cu content. High covariation appears to be an essential trait of the edaphic factor variation of Katangan Cu-rich soils. This makes it difficult to examine separately the effect of these factors on plant community structures. A bimodal pattern of niche distribution was found for Cu and pH. For physical parameters, niche optima were normally distributed. Conclusions – Global variation in edaphic factors associated with variation in combinations of edaphic parameters generates a highly heterogeneous environment favourable to a high diversity of plant communities over limited areas. Conservation strategies or restoration actions to limit the impact of mining activities on Cu-enriched ecosystems should pay special attention to recreate heterogeneity, taking into account the covariation of edaphic factors.