Earthworm’s influence on phytoavailability and Human gastric bioaccessibility of metals

►Introduction : Le développement d’entreprises de recyclage des métaux comme la Société de Traitement Chimique des Métaux (STCM) participe à l’économie circulaire. Cependant, ces activités de recyclage ont durant plusieurs décennies également engendré des émissions de polluants dans l’environnement induisant une augmentation de sites pollués par les retombées atmosphériques de particules fines enrichies en métaux et métalloïdes. Par ailleurs, le ver de terre, organisme clé de l’écosystème sol, apparait comme un ingénieur physique et mécanique des sols, et fait désormais l’objet de nombreuses études environnementales. Pour cette étude, notre objectif était d’évaluer l’influence de la bioturbation des vers de terre sur la phytodisponibilité des métaux et les mécanismes en jeu en lien avec leur compartimentation, leur spéciation et leur écotoxicité. ►Mise en œuvre : Dans ce contexte, une expérience de 25 jours a été menée en microcosmes, avec ou sans vers de terre dans le sol et avec un gradient d’Eléments Traces Inorganiques (ETI) dû aux retombées des particules atmosphériques. L’influence de l’activité des vers de terre sur les transferts sol-plante des métaux a été étudiée au moyen de microcultures de laitues (dispositif RHIZOtests®) réalisées sur 3 conditions différentes de sols : sols non bioturbés (SNB), sols bioturbés (SB) et turricules (T, déjections des vers). Les concentrations en ETI dans les sols, les vers et les salades ont été mesurées et la bioaccessibilité gastrique humaine a été déterminée à partir du test in vitro BARGE. Par ailleurs, des analyses de spéciation chimique du plomb dans divers compartiments abiotiques (sols et turricules) et biotiques (divers organes du vers de terre) ont été réalisées par spectroscopie EXAFS au synchrotron de l’ESRF à Grenoble. ►Résultats & Discussions : L’activité des vers de terre n’est pas significativement impactée par les concentrations en ETI appliquées dans les sols. Mais, la bioturbation des vers augmente la concentration en ETI présents dans les feuilles de laitues (parties consommées par l’homme). La concentration en ETI dans les feuilles de salades peut augmenter avec l’activité des vers de terre, de plus de 45% et 36 % pour le Pb et le Zn respectivement. Généralement, dans les sols et les plantes, les concentrations mesurées en ETI pour les différentes conditions sont classées ainsi : SNB < SB et T. La bioaccessibilité gastrique humaine est fonction de la nature des ETI et augmente pour SB et T, dans le cas du Zn et du Cu notamment. Des changements de spéciation du plomb mettant en évidence l’effet des vers de terre sur le sol ont été observés par spectroscopie EXAFS, en comparant les sols SNB et T, et les tissus des vers de terre. La figure 1 présente les voies d’exposition des ETI pour les vers, et les mécanismes proposés pour expliquer l’augmentation de phytodisponibilité induite par la bioturbation. Figure 1. Voies d’exposition des vers de terre aux ETI et mécanismes potentiellement impliqués dans l’augmentation de phytodisponibilité du fait de la bioturbation. ►Conclusion : La bioturbation des vers de terre modifie le devenir des ETI dans les sols par des changements de spéciation pouvant augmenter la mobilité des métaux, et certainement aussi en raison de modifications de la distribution des matières organiques présentes dans le sol

Exposure to cerium dioxide nanoparticles differently affect swimming performance and survival in two daphnid species

The CeO2 NPs are increasingly used in industry but the environmental release of these NPs and their subsequent behavior and biological effects are currently unclear. This study evaluates for the first time the effects of CeO2 NPs on the survival and the swimming performance of two cladoceran species, Daphnia similis and Daphnia pulex after 1, 10 and 100 mg.L(-1) CeO2 exposures for 48 h. Acute toxicity bioassays were performed to determine EC50 of exposed daphnids. Video-recorded swimming behavior of both daphnids was used to measure swimming speeds after various exposures to aggregated CeO2 NPs. The acute ecotoxicity showed that D. similis is 350 times more sensitive to CeO2 NPs than D. pulex, showing 48-h EC50 of 0.26 mg.L(-1) and 91.79 mg.L(-1), respectively. Both species interacted with CeO2 NPs (adsorption), but much more strongly in the case of D. similis. Swimming velocities (SV) were differently and significantly affected by CeO2 NPs for both species. A 48-h exposure to 1 mg.L(-1) induced a decrease of 30% and 40% of the SV in D. pulex and D. similis, respectively. However at higher concentrations, the SV of D. similis was more impacted (60% off for 10 mg.L(-1) and 100 mg.L(-1)) than the one of D. pulex. These interspecific toxic effects of CeO2 NPs are explained by morphological variations such as the presence of reliefs on the cuticle and a longer distal spine in D. similis acting as traps for the CeO2 aggregates. In addition, D. similis has a mean SV double that of D. pulex and thus initially collides with twice more NPs aggregates. The ecotoxicological consequences on the behavior and physiology of a CeO2 NPs exposure in daphnids are discussed

Toxicity of CeO2 nanoparticles on a freshwater experimental trophic chain: A study in environmentally relevant conditions through the use of mesocosms

The toxicity of CeO2 NPs on an experimental freshwater ecosystem was studied in mesocosm, with a focus being placed on the higher trophic level, i.e. the carnivorous amphibian species Pleurodeles waltl. The system comprised species at three trophic levels: (i) bacteria, fungi and diatoms, (ii) Chironomus riparius larvae as primary consumers and (iii) Pleurodeles larvae as secondary consumers. NP contamination consisted of repeated additions of CeO2 NPs over 4 weeks, to obtain a final concentration of 1 mg/L. NPs were found to settle and accumulate in the sediment. No effects were observed on litter decomposition or associated fungal biomass. Changes in bacterial communities were observed from the third week of NP contamination. Morphological changes in CeO2 NPs were observed at the end of the experiment. No toxicity was recorded in chironomids, despite substantial NP accumulation (265.8±14.1mg Ce/kg). Mortality (35.3±6.8%) and a mean Ce concentration of 13.5±3.9mg/kg were reported for Pleurodeles. Parallel experiments were performed on Pleurodeles to determine toxicity pathways: no toxicity was observed by direct or dietary exposures, although Ce concentrations almost reached 100 mg/kg. In view of these results, various toxicity mechanisms are proposed and discussed. The toxicity observed on Pleurodeles in mesocosm may be indirect, due to microorganism’s interaction with CeO2 NPs, or NP dissolution could have occurred in mesocosm due to the structural complexity of the biological environment, resulting in toxicity to Pleurodeles. This study strongly supports the importance of ecotoxicological assessment of NPs under environmentally relevant conditions, using complex biological systems

Mesocosm Testing to Address Non Occupational and Exposure Driven Risk Assessment of Advanced Materials

International audienceThe recent years have witnessed an increased interest in developing (pre)-standardized procedures and guidance documents for a harmonized determination of parameters utilized in the risk assessment of nanomaterials. This consists in a variety of exposure- and hazard measurements, including "simple" physical-chemical values (e.g. size, charge) as well as biological end-points. Usually, these are standalone tests developed independently of one another. As a result, these parameters, that often are at the node of risk assessment trees, are determined under a number of experimental conditions. Nevertheless, one might wonder to which extent the non- occupational section of the life cycle of a nanomaterial can be accounted for by a sequence of tests. Indeed in an actual environment, the fate of a nanomaterial is under the control of a multiplicity of simultaneously interacting parameters, and does not necessarily obey the dichotomic process of usual risk assessment schemes. Mesocosm testing is an interesting alternative to performing separate determination of a collection of parameters. Indeed, mesocosms provide exposure and hazard data in a single experiment. The systems are allowed (and even expected) to evolve, as opposed to strictly controlled standards. Robustness of this method for monitoring the environmental effects of nanomaterials has been demonstrated. The critical factor over which theoperator has a control, is the exposure scenario (e.g. pulse vs. chronic contamination, applied dose). Here we show how guidance on how to carefully design this exposure, could translate into a standardized procedure for using mesocosm testing as risk assessment tool

Safe(r) by Design of Nanomaterials: the Role of Speciation

International audienceTo address concerns about the safety of nanomaterials, the use of the safe(r) by design is attracting increasing interest in the development of these materials. Indeed, to reduce the risk associated with nanomaterials, the strategy consists in reducing the hazard or the exposure or both. While lowering the hazard may not be an option without comprising the functionality, reducing the exposure is usually easier to achieve. This often translates to design materials in which the active (and potentially hazardous) nanoparticle is surrounded by a shell /embedded in a matrix to protect against harmful effects and/or prevent release from the material.The effectiveness of this strategy rest on the stability of the composite, i.e. the strength of the bond between the nanoparticle and its shells as well as the resistance of the shell(s)/matrix during the use and end-of-life phases of the nano-enabled products. The material stability is examined after real/simulated aging with element specific probes. Here we present some examples taken from case studies using off the shelf products on how surface speciation informs about the efficiency of the product formulation in a safe(r) by design perspective

Safe(r) by Design of Nanomaterials: the Role of Speciation

International audienceTo address concerns about the safety of nanomaterials, the use of the safe(r) by design is attracting increasing interest in the development of these materials. Indeed, to reduce the risk associated with nanomaterials, the strategy consists in reducing the hazard or the exposure or both. While lowering the hazard may not be an option without comprising the functionality, reducing the exposure is usually easier to achieve. This often translates to design materials in which the active (and potentially hazardous) nanoparticle is surrounded by a shell /embedded in a matrix to protect against harmful effects and/or prevent release from the material.The effectiveness of this strategy rest on the stability of the composite, i.e. the strength of the bond between the nanoparticle and its shells as well as the resistance of the shell(s)/matrix during the use and end-of-life phases of the nano-enabled products. The material stability is examined after real/simulated aging with element specific probes. Here we present some examples taken from case studies using off the shelf products on how surface speciation informs about the efficiency of the product formulation in a safe(r) by design perspective

Mesocosm Testing to Address Non Occupational and Exposure Driven Risk Assessment of Advanced Materials

International audienceThe recent years have witnessed an increased interest in developing (pre)-standardized procedures and guidance documents for a harmonized determination of parameters utilized in the risk assessment of nanomaterials. This consists in a variety of exposure- and hazard measurements, including "simple" physical-chemical values (e.g. size, charge) as well as biological end-points. Usually, these are standalone tests developed independently of one another. As a result, these parameters, that often are at the node of risk assessment trees, are determined under a number of experimental conditions. Nevertheless, one might wonder to which extent the non- occupational section of the life cycle of a nanomaterial can be accounted for by a sequence of tests. Indeed in an actual environment, the fate of a nanomaterial is under the control of a multiplicity of simultaneously interacting parameters, and does not necessarily obey the dichotomic process of usual risk assessment schemes. Mesocosm testing is an interesting alternative to performing separate determination of a collection of parameters. Indeed, mesocosms provide exposure and hazard data in a single experiment. The systems are allowed (and even expected) to evolve, as opposed to strictly controlled standards. Robustness of this method for monitoring the environmental effects of nanomaterials has been demonstrated. The critical factor over which theoperator has a control, is the exposure scenario (e.g. pulse vs. chronic contamination, applied dose). Here we show how guidance on how to carefully design this exposure, could translate into a standardized procedure for using mesocosm testing as risk assessment tool

Nanoparticules d'oxydes métalliques : relations entre la réactivité de surface et des réponses biologiques

Les nanotechnologies génèrent un engouement assimilable à une révolution technologique. Le domaine de l'environnement est concerné car les nanoparticules (NPs) apportent des solutions à plusieurs problèmes de pollution. Par exemple, nous avons montré la forte capacité de rétention de l'As (8As/nm2) par des NPs d'oxydes de fer (6nm). Ceci est lié à leur grande surface spécifique et à leur forte réactivité de surface due à la présence de sites d'adsorption inédits et à la diminution significative de l'énergie de surface lors de l'adsorption. Mais des questions se posent sur l'impact (éco)toxicologique engendré par la forte production de NPs. Une classification de l'(éco)toxicité des nano-oxydes en fonction de leurs propriétés redox a été proposée. Alors que des NPs chimiquement stables (gFe2O3) en milieux biologiques ne montrent aucune toxicité, des NPs ayant un pouvoir oxydant (CeO2) ou réducteur (Fe) sont cytotoxiques pour Escherichia coli et génotoxiques pour les fibroblastes humains.AIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF