Multimetallic contamination from Zn-ore smelter: solid speciation and potential mobility in riverine floodbank soils of the upper Lot River (SW France)

International audienceThe former Zn-ore smelting activity in Viviez (Aveyron, France) resulted in multimetallic contamination of the upper Lot River system (SW France). This study addresses for the first time the metals/metalloids mobility in impacted riverside fluvial soils due to reducing conditions during long-term flooding events. Six impacted riverside fluvio-soils were sampled along the Riou Mort and Lot rivers. Their levels of contamination decrease with the distance from the contamination source. Higher enrichment factors (EF) relative to French average soil metallic content occur 1 km far from the contamination source and vary from 3 for Sn, to 5 for As, 9 for Sb, 27 for Pb, 40 for Zn and 63 for Cd. At 20 km downstream from the contamination source, EF still reach a value of 3 for Cd and Zn. A micro-physical mineralogical characterisation of contaminated soils revealed a variety of metal-bearing phases: metallic compounds, oxides and sulphides, Fe oxides, glass and silicates as well as coke. Sequential chemical extraction experiments were conducted on the most contaminated soil in order to identify which mineral phases were the best candidates to release metals/metalloids. At the end of experiments more than 70% of total Cd and As, 55% of Zn and Sb, and 40% of Pb and Sn were extracted from the soil. Only Cd appeared as readily mobilised, with 33% of its total amount being extracted in the first steps of experiments. Under reducing conditions, iron oxyhydroxides, franklinite and multimetallic oxides are the best candidates, in decreasing order of importance, for metals/metalloids release from the soi

BioMareau-II : Dynamique temporelle des saulaies-peupleraies en Loire moyenne

National audienceLe projet « BioMareau-II : Dynamique de recolonisation de la biodiversité après travaux d'entretien du lit de la Loire » s'intéresse aux interactions entre le fonctionnement sédimentaire et la dynamique des saulaies-peupleraies, dans le cadre des travaux d'entretien du lit en Loire moyenne, et à leurs conséquences sur plusieurs compartiments de la biodiversité (végétation, entomofaune, avifaune, castor). Après une présentation du projet BioMareau-II, l'intervention ciblera le propos sur la dynamique temporelle des saulaies-peupleraies en Loire moyenne en décrivant le dispositif « Flore de Loire moyenne » qui constitue l'une des 11 actions du volet biodiversité du projet. A cet effet 158 peuplements de salicacées, principalement à base de peuplier noir, ont été échantillonnés tout au long de la Loire moyenne suivant un gradient de succession allant de l'installation des jeunes arbres aux peupleraies sauvages adultes en transition vers les forêts à bois durs. En complément, certains facteurs d'anthropisation ont été pris en compte tels que les travaux d'entretien du lit pour les premiers stades et l'envahissement de l'érable négondo pour les stades âgés. Les mesures et notations portent sur la hauteur des sédiments accumulés, les cortèges dendrologiques, la flore vasculaire et la bryoflore épiphyte. Les dernières observations ayant été réalisées en octobre 2018, nous présenterons seulement les premiers retours d'expérience des campagnes de terrain qui se sont succédées depuis 2016, notamment les difficultés pour constituer l'échantillonnage, informatives des réalités du terrain. La reconstitution de l'historique des peupleraies âgées depuis 1950 sera aussi présentée avec, pour chaque peuplement étudié, la réponse à 3 questions : (1) s'agit-il d'une succession primaire de salicacées ? (2) quel âge ont les plus vieux arbres ? (3) la forêt s'est-elle installée de façon uniforme ou par cumul de plusieurs cohortes hétérogènes ? Ces premiers résultats seront examinés suivant l'objectif du projet BioMareau-II, c'est-à-dire la conséquence des travaux d'entretien du lit sur la biodiversité, ici au regard de la bonne représentation des différents stades de la succession primaire à salicacées, nécessaire pour la conservation durable de l'habitat Natura 2000 prioritaire de forêt alluviale (91E0*) en Loire moyenne

Atmospheric nitrogen deposition is related to plant biodiversity loss at multiple spatial scales

Due to various human activities, including intensive agriculture, traffic, and the burning of fossil fuels, in many parts of the world, current levels of reactive nitrogen emissions strongly exceed pre‐industrial levels. Previous studies have shown that the atmospheric deposition of these excess nitrogen compounds onto semi‐natural terrestrial environments has negative consequences for plant diversity. However, these previous studies mostly investigated biodiversity loss at local spatial scales, that is, at the scales of plots of typically a few square meters. Whether increased atmospheric nitrogen deposition also affects plant diversity at larger spatial scales remains unknown. Here, using grassland plant community data collected in 765 plots, across 153 different sites and 9 countries in northwestern Europe, we investigate whether relationships between atmospheric nitrogen deposition and plant biodiversity are scale‐dependent. We found that high levels of atmospheric nitrogen deposition were associated with low levels of plant species richness at the plot scale but also at the scale of sites and regions. The presence of 39% of plant species was negatively associated with increasing levels of nitrogen deposition at large (site) scales, while only 1.5% of the species became more common with increasing nitrogen deposition, indicating that large‐scale biodiversity changes were mostly driven by “loser” species, while “winner” species profiting from high N deposition were rare. Some of the “loser” species whose site presence was negatively associated with atmospheric nitrogen deposition are listed as “threatened” in at least some EU member states, suggesting that nitrogen deposition may be a key contributor to their threat status. Hence, reductions in reactive nitrogen emissions will likely benefit plant diversity not only at local but also at larger spatial scales

Atmospheric nitrogen deposition is related to plant biodiversity loss at multiple spatial scales

Due to various human activities, including intensive agriculture, traffic, and the burning of fossil fuels, in many parts of the world, current levels of reactive nitrogen emissions strongly exceed pre‐industrial levels. Previous studies have shown that the atmospheric deposition of these excess nitrogen compounds onto semi‐natural terrestrial environments has negative consequences for plant diversity. However, these previous studies mostly investigated biodiversity loss at local spatial scales, that is, at the scales of plots of typically a few square meters. Whether increased atmospheric nitrogen deposition also affects plant diversity at larger spatial scales remains unknown. Here, using grassland plant community data collected in 765 plots, across 153 different sites and 9 countries in northwestern Europe, we investigate whether relationships between atmospheric nitrogen deposition and plant biodiversity are scale‐dependent. We found that high levels of atmospheric nitrogen deposition were associated with low levels of plant species richness at the plot scale but also at the scale of sites and regions. The presence of 39% of plant species was negatively associated with increasing levels of nitrogen deposition at large (site) scales, while only 1.5% of the species became more common with increasing nitrogen deposition, indicating that large‐scale biodiversity changes were mostly driven by “loser” species, while “winner” species profiting from high N deposition were rare. Some of the “loser” species whose site presence was negatively associated with atmospheric nitrogen deposition are listed as “threatened” in at least some EU member states, suggesting that nitrogen deposition may be a key contributor to their threat status. Hence, reductions in reactive nitrogen emissions will likely benefit plant diversity not only at local but also at larger spatial scales

Outcomes of surgical resection in microsatellite instable colorectal cancer after immune checkpoint inhibitor treatment

International audienc

Identification of cis- and trans-regulatory variation modulating microRNA expression levels in human fibroblasts

MicroRNAs (miRNAs) are regulatory noncoding RNAs that affect the production of a significant fraction of human mRNAs via post-transcriptional regulation. Interindividual variation of the miRNA expression levels is likely to influence the expression of miRNA target genes and may therefore contribute to phenotypic differences in humans, including susceptibility to common disorders. The extent to which miRNA levels are genetically controlled is largely unknown. In this report, we assayed the expression levels of miRNAs in primary fibroblasts from 180 European newborns of the GenCord project and performed association analysis to identify eQTLs (expression quantitative traits loci). We detected robust expression for 121 miRNAs out of 365 interrogated. We have identified significant cis- (10%) and trans- (11%) eQTLs. Furthermore, we detected one genomic locus (rs1522653) that influences the expression levels of five miRNAs, thus unraveling a novel mechanism for coregulation of miRNA expression

Transcriptional and post-transcriptional profile of human chromosome 21

Recent studies have demonstrated extensive transcriptional activity across the human genome, a substantial fraction of which is not associated with any functional annotation. However, very little is known regarding the post-transcriptional processes that operate within the different classes of RNA molecules. To characterize the post-transcriptional properties of expressed sequences from human chromosome 21 (HSA21), we separated RNA molecules from three cell lines (GM06990, HeLa S3, and SK-N-AS) according to their ribosome content by sucrose gradient fractionation. Polyribosomal-associated RNA and total RNA were subsequently hybridized to genomic tiling arrays. We found that ∼50% of the transcriptional signals were located outside of annotated exons and were considered as TARs (transcriptionally active regions). Although TARs were observed among polysome-associated RNAs, RT-PCR and RACE experiments revealed that ∼40% were likely to represent nonspecific cross-hybridization artifacts. Bioinformatics discrimination of TARs according to conservation and sequence complexity allowed us to identify a set of high-confidence TARs. This set of TARs was significantly depleted in the polysomes, suggesting that it was not likely to be involved in translation. Analysis of polysome representation of RefSeq exons showed that at least 15% of RefSeq transcripts undergo significant post-transcriptional regulation in at least two of the three cell lines tested. Among the regulated transcripts, enrichment analysis revealed an over-representation of genes involved in Alzheimer's disease (AD), including APP and the BACE1 protease that cleaves APP to produce the pathogenic beta 42 peptide. We demonstrate that the combination of RNA fractionation and tiling arrays is a powerful method to assess the transcriptional and post-transcriptional properties of genomic regions

Charged impurity scattering and mobility in gated silicon nanowires

We study the effects of charged impurity scattering on the electronic transport properties of -oriented Si nanowires in a gate-all-around geometry, where the impurity potential is screened by the gate, gate oxide and conduction band electrons. The electronic structure of the doped nanowires is calculated with a tight-binding method and the transport properties with a Landauer-Buttiker Green functions approach and the linearized Boltzmann transport equation (LBTE) in the first Born approximation. Based on our numerical results we argue that: (1) There are large differences between Phosphorous (P) and Boron (B) doped systems, acceptors behaving as tunnel barriers for the electrons, while donors give rise to Fano resonances in the transmission. (2) As a consequence, the mobility is much larger in P- than in B-doped nanowires at low carrier density, but can be larger in B-doped nanowires at high carrier density. (3) The resistance of a single impurity is strongly dependent on its radial position in the nanowire, especially for acceptors. (4) As a result of subband structure and screening effects, the impurity-limited mobility can be larger in thin nanowires embedded in HfO2 than in bulk Si. Acceptors might, however, strongly hinder the flow of electrons in thin nanowires embedded in SiO2. (5) The perturbative LBTE largely fails to predict the correct mobilities in quantum-confined nanowires.Comment: Submitted to Phys. rev.