Trace metal fractionation as a mean to improve on the management of contaminated sediments from runoff water infiltration basins

The management of stormwater sediment is a key issue for local authorities due to their pollution load and important tonnages. In view of reuse, e.g. for embankment, the environmental evaluation of these highly aggregated sediments requires studying trace metals fractionation and mobility. The distribution of trace metals (Cd, Cr, Cu, Ni, Pb, Zn) and their level of lability in three French stormwater sediments was determined using sequential and kinetic extractions (EDTA reagent) associated with mineralogical analysis and SEM observations. Using microanalysis, new data were acquired on the evolution of aggregate state during extractions and on its significant role in trace metals retention. Trace metals were, in particular, observed to be very stable in small aggregates (10-50 µm). The comparison of the two extraction methods pointed out that EDTA extraction was not convenient to evaluate the stable fraction of Cr, Ni and Zn. Moreover, the results were relevant for basins presenting similar trace metals sources, whatever the physicochemical conditions in basins. The results suggest that the management of stormwater sediments could be improve by a better knowledge of metal mobility, as far as chemical extractions could highlight the localisation of the mobile trace metals fraction. Treatment could be therefore avoided or specific treatment could be applied to a reduced volume of sediments

Conditions and mechanism for the formation of iron-rich Montmorillonite in deep sea sediments (Costa Rica margin): Coupling high resolution mineralogical characterization and geochemical modeling

International audienceIron-rich smectite is commonly described in the diagenetic fraction of deep-sea sediment, as millimeter to centimeter aggregates dispersed in the sediment, or as a coating on sedimentary particles or nodules. This study examines several factors to elucidate formation mechanisms of a particular iron-rich smectite and its potential transformation to glauconite. The study combines a detailed mineralogical investigation on natural samples and a chemical modeling approach to assess mineralogical reactions and pathways. Transmission electron microscopy (TEM) observations and analytical electron microscopy (TEM-AEM) analyses were conducted on microtomed samples of millimeter- to centimeter-long green grains. These grains are widespread in pelagic calcareous sediment from the Costa Rica margin. They are composed of pyrites that are partially dissolved and are surrounded by amorphous or very poorly crystallized iron-rich particles. Iron-rich montmorillonite grows from an amorphous precursor and its formation requires the input of Si, O, Mg, K, Na and Ca; our results suggest that these inputs are supported by the dissolution of sedimentary phases such as volcanic glasses, siliceous fossils and silicates. Thermodynamic modeling of fluid-sediment interactions was conducted with the geochemical computer code PhreeqC, using mineralogical and pore fluid compositions from sediment samples and calculated estimates for thermodynamic constants of smectites that are not maintained by the computer code. Simulations confirm the possibility that the green grains are the product of pyrite alteration by seawater under oxidizing conditions. The extent of smectite production is controlled by the kinetics of pyrite dissolution and fluid migration. The absence of aluminum in the Costa Rica margin system explains the formation of an iron-rich montmorillonite instead of glauconite, whereas the presence of calcite that buffers the system explains the formation of an iron-rich montmorillonite instead of iron oxides

O teor de montmorilonite é um parâmetro influente do desenvolvimento e rendimento da videira no Sul do Uruguai

Soil physical and chemical characteristics play a key role on vine growth and yield. The soils of South Uruguay display high content of montmorillonite or illite. The proportion of these minerals deserves special attention as they influence the soil structure and its hydrological properties. The present study was conducted in a 1.1 ha vineyard of this region (Canelones), characterized by a high heterogeneity of plant vigour. It was aimed to determine and map the physical and chemical properties of the soil and their relations with plant vigour and yield. The cation exchange capacity (CEC) and the clay and organic matter contents were measured in 84 locations within this vineyard to calculate the montmorillonite and illite contents of the soil. In addition, the type and abundance of clays was corroborated by X-ray diffractometry analysis. The CEC and montmorillonite contents were positively correlated with vine vigour, expressed by the Normalized Vegetation Index (NDVI), trunk diameter, pruning weight, leaf area, and with yield. Thus, the within vineyard distribution of the ratio montmorillonite/illite conditioned the heterogeneity of vine growth and yield at the field level. The impact of those minerals on water and mineral supply to the plant is discussed.Las características físicas y químicas del suelo desempeñan un papel fundamental en el crecimiento y el rendimiento de la vid. Los suelos del sur de Uruguay presentan un alto contenido de montmorillonita o illita. Las proporciones de estos minerales merecen especial atención ya que influyen en la estructura del suelo y en sus propiedades hídricas. El presente estudio se realizó en un viñedo de 1,1 ha de esta región (Canelones), caracterizado por una alta heterogeneidad de vigor de las plantas. El objetivo fue determinar y cartografiar las propiedades físicas y químicas del suelo, y su relación con el vigor de las plantas y el rendimiento. La capacidad de intercambio catiónico (CEC) y los contenidos de arcilla y materia orgánica se midieron en 84 lugares de este viñedo para calcular los contenidos de montmorillonita e illita del suelo. Además, se corroboró el tipo y la abundancia de arcillas mediante análisis de difractometría de rayos X. Los contenidos de CEC y de montmorillonita se correlacionaron positivamente con el vigor de la vid, expresado por el índice de vegetación normalizado (NDVI), el diámetro del tronco, el peso de la poda, el área foliar y con el rendimiento. Así, la distribución dentro del viñedo de la relación montmorillonita/ilita condicionó la heterogeneidad del crecimiento de la vid y del rendimiento a nivel de campo. Se discute el impacto de estos minerales en el suministro de agua y minerales a la planta.As características físicas e químicas do solo desempenham um papel fundamental no crescimento e rendimento da vinha. Os solos do Sul do Uruguai apresentam um elevado teor de montmorilonite ou illite. As proporções destes minerais merecem especial atenção, uma vez que influenciam a estrutura do solo e as propriedades hídricas. O presente estudo foi realizado numa vinha de 1,1 ha desta região caracterizada por uma elevada heterogeneidade de vigor vegetal. O seu objetivo era determinar e mapear as propriedades físicas e químicas do solo e as suas relações com o vigor e rendimento das plantas. A capacidade de troca catiônica (CEC) e os teores de argila e matéria orgânica foram medidos em 84 locais dentro desta vinha para calcular os teores de montmorilonite e illite do solo. Além disso, o tipo e abundância de argilas foram corroborados pela análise difractométrica de raios X. Os teores de CEC e montmorillonite foram positivamente correlacionados com a vigor da vinha, expresso pelo Índice de Vegetação Normalizada (NDVI), diâmetro do tronco, peso da poda, área foliar, e com o rendimento. Assim, a distribuição dentro da vinha da razão montmorilonite/ilite condicionou a heterogeneidade do crescimento da vinha e o rendimento ao nível do campo. O impacto desses mineraisminerais na água e no fornecimento de minerais à planta é discutido

How soil and climate variability within a vineyard can affect the heterogeneity of grapevine vigour and production

This study aimed to determine how within-plot soil heterogeneity combined with yearly climate variability can promote the heterogeneity of vine growth at plot level, and which soil-climate parameters influence final yield and berry composition the most. An 8-year experiment was conducted on grapevine in two zones of a vineyard (1 ha) differentiated according to grapevine vigour as determined by NDVI: high vigour (HV) and low vigour (LV). The heterogeneity of the soil properties (depth, texture and composition), plant growth (shoots and roots) and plant production (yield components and berry composition) were determined at plot level. Compared to the LV zone, the HV zone was associated with deeper soils, higher soil water and nitrogen availability, CEC and montmorillonite/illite ratio. More extended root systems, higher vegetative growth and higher yield were observed in the HV zone compared to the LV zone. Drier and warmer vintages increased the difference in heterogeneity of vine growth and yield between the two zones. Berry composition (primary and secondary metabolites) also differed between HV and LV zones but seemed unconnected to vigour and mainly depended on soil-climate-plant interactions over the years. The heterogeneity of plant vigour within the vineyard mainly resulted from differences in root exploration, soil profile and composition (notably montmorillonite/illite ratio). The present study identified soil and crop factors that, depending on weather conditions, can be drivers for reducing the heterogeneity of plant development and improving productivity at vineyard level

The skyrmion switch: turning magnetic skyrmion bubbles on and off with an electric field

Nanoscale magnetic skyrmions are considered as potential information carriers for future spintronics memory and logic devices. Such applications will require the control of their local creation and annihilation, which involves so far solutions that are either energy consuming or difficult to integrate. Here we demonstrate the control of skyrmion bubbles nucleation and annihilation using electric field gating, an easily integrable and potentially energetically efficient solution. We present a detailed stability diagram of the skyrmion bubbles in a Pt/Co/oxide trilayer and show that their stability can be controlled via an applied electric field. An analytical bubble model, with the Dzyaloshinskii-Moriya interaction imbedded in the domain wall energy, account for the observed electrical skyrmion switching effect. This allows us to unveil the origin of the electrical control of skyrmions stability and to show that both magnetic dipolar interaction and the Dzyaloshinskii-Moriya interaction play an important role in the skyrmion bubble stabilization

The bZIP transcription factor SPA Heterodimerizing Protein represses glutenin synthesis in Triticum aestivum

The quality of wheat grain is mainly determined by the quantity and composition of its grain storage proteins (GSPs). Grain storage proteins consist of low- and high-molecular-weight glutenins (LMW-GS and HMW-GS, respectively) and gliadins. The synthesis of these proteins is essentially regulated at the transcriptional level and by the availability of nitrogen and sulfur. The regulation network has been extensively studied in barley where BLZ1 and BLZ2, members of the basic leucine zipper (bZIP) family, activate the synthesis of hordeins. To date, in wheat, only the ortholog of BLZ2, Storage Protein Activator (SPA), has been identified as playing a major role in the regulation of GSP synthesis. Here, the ortholog of BLZ1, named SPA Heterodimerizing Protein (SHP), was identified and its involvement in the transcriptional regulation of the genes coding for GSPs was analyzed. In gel mobility shift assays, SHP binds cis-motifs known to bind to bZIP family transcription factors in HMW-GS and LMW-GS promoters. Moreover, we showed by transient expression assays in wheat endosperm that SHP acts as a repressor of the activity of these gene promoters. This result was confirmed in transgenic lines overexpressing SHP, which were grown with low and high nitrogen supply. The phenotype of SHP-overexpressing lines showed a lower quantity of both LMW-GS and HMW-GS, while the quantity of gliadin was unchanged, whatever the nitrogen availability. Thus, the gliadin/glutenin ratio was increased, which suggests that gliadin and glutenin genes may be differently regulated

Neuronal Cholesterol Accumulation Induced by Cyp46a1 Down-Regulation in Mouse Hippocampus Disrupts Brain Lipid Homeostasis

Impairment in cholesterol metabolism is associated with many neurodegenerative disorders including Alzheimer's disease (AD). However, the lipid alterations underlying neurodegeneration and the connection between altered cholesterol levels and AD remains not fully understood. We recently showed that cholesterol accumulation in hippocampal neurons, induced by silencing Cyp46a1 gene expression, leads to neurodegeneration with a progressive neuronal loss associated with AD-like phenotype in wild-type mice. We used a targeted and non-targeted lipidomics approach by liquid chromatography coupled to high-resolution mass spectrometry to further characterize lipid modifications associated to neurodegeneration and cholesterol accumulation induced by CYP46A1 inhibition. Hippocampus lipidome of normal mice was profiled 4 weeks after cholesterol accumulation due to Cyp46a1 gene expression down-regulation at the onset of neurodegeneration. We showed that major membrane lipids, sphingolipids and specific enzymes involved in phosphatidylcholine and sphingolipid metabolism, were rapidly increased in the hippocampus of AAV-shCYP46A1 injected mice. This lipid accumulation was associated with alterations in the lysosomal cargoe, accumulation of phagolysosomes and impairment of endosome-lysosome trafficking. Altogether, we demonstrated that inhibition of cholesterol 24-hydroxylase, key enzyme of cholesterol metabolism leads to a complex dysregulation of lipid homeostasis. Our results contribute to dissect the potential role of lipids in severe neurodegenerative diseases like AD