Experimental evidence of colloids and nanoparticles presence from 25 waste leachates.

International audienceThe potential colloids release from a large panel of 25 solid industrial and municipal waste leachates, contaminated soil, contaminated sediments and landfill leachates was studied. Standardized leaching, cascade filtrations and measurement of element concentrations in the microfiltrate (MF) and ultrafiltrate (UF) fraction were used to easily detect colloids potentially released by waste. Precautions against CO(2) capture by alkaline leachates, or bacterial re-growth in leachates from wastes containing organic matter should be taken. Most of the colloidal particles were visible by transmission electron microscopy with energy dispersion spectrometry (TEM-EDS) if their elemental MF concentration is greater than 200 μgl(-1). If the samples are dried during the preparation for microscopy, neoformation of particles can occur from the soluble part of the element. Size distribution analysis measured by photon correlation spectroscopy (PCS) were frequently unvalid, particularly due to polydispersity and/or too low concentrations in the leachates. A low sensitivity device is required, and further improvement is desirable in that field. For some waste leachates, particles had a zeta potential strong enough to remain in suspension. Mn, As, Co, Pb, Sn, Zn had always a colloidal form (MF concentration/UF concentration>1.5) and total organic carbon (TOC), Fe, P, Ba, Cr, Cu, Ni are partly colloidal for more than half of the samples). Nearly all the micro-pollutants (As, Ba, Co, Cr, Cu, Mo, Ni, Pb, Sb, Sn, V and Zn) were found at least once in colloidal form greater than 100 μgl(-1). In particular, the colloidal forms of Zn were always by far more concentrated than its dissolved form. The TEM-EDS method showed various particles, including manufactured nanoparticles (organic polymer, TiO(2), particles with Sr, La, Ce, Nd). All the waste had at least one element detected as colloidal. The solid waste leachates contained significant amount of colloids different in elemental composition from natural ones. The majority of the elements were in colloidal form for wastes of packaging (3), a steel slag, a sludge from hydrometallurgy, composts (2), a dredged sediment (#18), an As contaminated soil and two active landfill leachates. These results showed that cascade filtration and ICP elemental analysis seems valid methods in this field, and that electronic microscopy with elemental detection allows to identify particles. Particles can be formed from dissolved elements during TEM sample preparation and cross-checking with MF and UF composition by ICP is useful. The colloidal fraction of leachate of waste seems to be a significant source term, and should be taken into account in studies of emission and transfer of contaminants in the environment. Standardized cross-filtration method could be amended for the presence of colloids in waste leachates

Composites of biopolymers and ZnO NPs for controlled release of zinc in agricultural soils and timed delivery for maize

Zinc deficiency is a widespread micronutrient deficiency problem affecting crops worldwide. Unlike conventional ionic fertilizers (Zn as salt or chelated forms), Zn-based engineered nanomaterials (ENMs) have the potential to release Zn in a controlled manner, reducing Zn losses through leaching upon application to soil. In this work, composites made of biopolymers (microcrystalline cellulose, chitosan and alginate) and ZnO nanoparticles (4-65% Zn w/w) were prepared. Their potential for Zn controlled release was tested in four agricultural soils of distinct pH and organic matter content over 30 days. While conventionally used Zn salts leached from the soil resulting in very low CaCl2-extractable Zn concentration, Zn in ZnO NPs was less labile, and ZnO-biopolymers maintained a better constant supply of CaCl2-extractable Zn than all other treatments. ZnO NPs/alginate beads prepared by crosslinking with CaCl2 presented the slowest Zn release kinetics. As assessed with maize plants grown in poor Zn acidic soil (LUFA 2.1, pH=5.2), this constant Zn release from ZnO NPs/alginate beads resulted in a steadier Zn concentration in the soil pore water over time. These results further indicate that ZnO NPs/alginate beads could meet the maize Zn needs while avoiding the early stage Zn toxicity induced by conventional Zn supplies, demonstrating that these ENMs are a sustainable way to supply Zn in a controlled manner in acidic soils. The impact of plant exudates on Zn bioavailability in the soil under maize-root influence (rhizosphere) is also discussed, underlying the need to study the fate of micronutrients in the rhizosphere to better predict its long-term bioavailability in bulk soils.publishe

Engineered Nanoparticles Interact with Nutrients to Intensify Eutrophication in a Wetland Ecosystem Experiment

Despite the rapid rise in diversity and quantities of engineered nanomaterials produced, the impacts of these emerging contaminants on the structure and function of ecosystems have received little attention from ecologists. Moreover, little is known about how manufactured nanomaterials may interact with nutrient pollution in altering ecosystem productivity, despite the recognition that eutrophication is the primary water quality issue in freshwater ecosystems worldwide. In this study, we asked two main questions: (1) To what extent do manufactured nanoparticles affect the biomass and productivity of primary producers in wetland ecosystems? (2) How are these impacts mediated by nutrient pollution? To address these questions, we examined the impacts of a citrate‐coated gold nanoparticle (AuNPs) and of a commercial pesticide containing Cu(OH)2 nanoparticles (CuNPs) on aquatic primary producers under both ambient and enriched nutrient conditions. Wetland mesocosms were exposed repeatedly with low concentrations of nanoparticles and nutrients over the course of a 9‐month experiment in an effort to replicate realistic field exposure scenarios. In the absence of nutrient enrichment, there were no persistent effects of AuNPs or CuNPs on primary producers or ecosystem productivity. However, when combined with nutrient enrichment, both NPs intensified eutrophication. When either of these NPs were added in combination with nutrients, algal blooms persisted for \u3e 50 d longer than in the nutrient‐only treatment. In the AuNP treatment, this shift from clear waters to turbid waters led to large declines in both macrophyte growth and rates of ecosystem gross primary productivity (average reduction of 52% ± 6% and 92% ± 5%, respectively) during the summer. Our results suggest that nutrient status greatly influences the ecosystem‐scale impact of two emerging contaminants and that synthetic chemicals may be playing an under‐appreciated role in the global trends of increasing eutrophication. We provide evidence here that chronic exposure to Au and Cu(OH)2 nanoparticles at low concentrations can intensify eutrophication of wetlands and promote the occurrence of algal blooms

Relating structure, reactivity and cellular interactions of inorganic nanotubes : case of imogolites

Aujourd’hui, les difficultés pour établir des liens entre caractéristiques des nanomatériaux et réponses biologiques sont principalement issues du manque de contrôle de la synthèse des nanomatériaux, ne permettant pas de faire varier leurs paramètres physico-chimiques clés une à une.Pour identifier certains mécanismes gouvernant la toxicité des nanomatériaux nous avons utilisé un nanotube inorganique modèle dont la synthèse est bien contrôlée : les Ge-imogolites. Les effets de la longueur, du nombre de parois, de la cristallinité et de la composition chimique des Ge-imogolites ont été étudiés sur une bactérie des sols: Pseudomonas brassicacearum. Il a été identifié que la présence de sites réactifs (en bordure de tubes) induit une toxicité due à une interaction forte des nanotubes avec les cellules bactériennes, ainsi que la génération d’espèces réactives de l’oxygène. Ajouter des sites réactifs via la présence de défauts structuraux augmente la dégradation des tubes ainsi que la rétention d’éléments nutritifs essentiels, ce qui augmente leur toxicité. Enfin, l’ajout de fer dans leur structure transforme les Ge-imogolites en source de fer, qui sont dégradées et deviennent promoteurs de croissance. Dans tous ces cas, les interactions entre nanomatériaux et cellules ont été identifiées comme cruciales pour comprendre et prévenir les effets des nanomatériaux. Ce travail de thèse a également permis de mettre en avant la capacité de nouveaux outils pour le suivi de l’internalisation de nanomatériaux dans les organismes.Only a few studies of (eco)toxicology linked the physico-chemical properties of nanoparticles to the toxicity mechanisms or the stress they induce. Moreover, no clear conclusions can be drawn at present because of the variability of nanoparticles used in studies. The present study used the inorganic Ge-imogolite nanotubes as a model compound. The toxic effects of length, number of walls, structural defects, and chemical composition were assessed towards the soil bacteria Pseudomonas brassicacearum. Several mechanisms modulating the toxicity of Ge-imogolite were then identified. Indeed, reactive sites at the tube ends induce a slight toxicity via a strong cell interaction and the generation of reactive oxygen species. Creating vacant sites on the surface of Ge-imogolite (ant thus increasing the number of reactive sites), appears to cause a deficiency of nutrients in the culture media correlated with a higher degradation of the tubes, leading to a high bacterial growth decrease. Finally, structural iron incorporation into Ge-imogolite transforms them into an iron source, being degraded and becoming growth promoters. In this work, the new tools capacities for the study of nanomaterials/cells interaction have been studied

Effect of Initial Speciation of Copper- and Silver-Based Nanoparticles on Their Long-Term Fate and Phytoavailability in Freshwater Wetland Mesocosms

International audienc

Opportunities and challenges for nanotechnology in the agri-tech revolution

International audienc

Organic contaminants in marine sediments and seawater: A review for drawing environmental diagnostics and searching for informative predictors

International audienc

An experimental test of the transmission-virulence trade-off hypothesis in a plant virus

BGPI : équipe 2International audienceThe transmissionvirulence trade-off hypothesis is one of the few adaptive explanations of virulence evolution, and assumes that there is an overall positive correlation between parasite transmission and virulence. The shape of the transmissionvirulence relationship predicts whether virulence should evolve toward either a maximum or to an intermediate optimum. A positive correlation between each of these traits and within-host growth is often suggested to underlie the relationship between virulence and transmission. There are few experimental tests of this hypothesis; this study reports on the first empirical test on a plant pathogen. We infected Brassica rapa plants with nine natural isolates of Cauliflower mosaic virus and then estimated three traits: transmission, virulence, and within-host viral accumulation. As predicted by the trade-off hypothesis, we observed a positive correlation between transmission and virulence, suggestive of the existence of an intermediate optimum. We discovered the unexpected existence of two groups of within-host accumulation, differing by at least an order of magnitude. When accumulation groups were not accounted for, within-host accumulation was correlated neither to virulence nor transmission, although our results suggest that within each group these correlations exist

Comprehensive framework for overcoming scientific challenges related to assessing radioactive ultra-fine (nano/micro) particles transfer at the atmosphere-leaf interface

International audienceFood products are prone into contamination after a nuclear emission of radionuclides. While the mechanisms of emission and deposition of ultrafine radioactive particles are well documented, the transfer of these species from the atmosphere into plants is poorly assessed. This is evident in the lack of quantification of particles distributed within plants, especially regarding particles physical-chemical criteria to plant of different properties. Such knowledge gaps raise the concern about the representativeness of risk assessment tools designed for the transfer evaluation of ionic/soluble species to be qualified for simulating insoluble species exposure and proposes a possible underestimation. This highlights the possible need for special particle codes development to be implemented in models for future emissions. In addition, the later tools utilize transfer factors aggregating relevant sub-processes, suggesting another weak point in their overall reliability. As researchers specialized in the nuclear safety and protection, we intend in this perspective, to develop a compressive analysis of the interaction of ultrafine particles with plants of different specificities at different level processes starting from particles retention and gradual translocation to sink organs. This analysis is leveraged in providing insights for possible improvements in the current modeling tools for better real-life scenarios representation