Globally carbon nanoparticles are increasingly utilized, yet it is not known if these nanoparticles pose a threat to the environment or human health. This investigation examined 'as-prepared', and acid cleaned carbon nanoparticle physicochemical characteristics (by FTIR, TEM, FESEM, UV-VIS and X-ray microanalysis), and whether these characteristics changed following 2.5-7 yr exposure to pH neutral saline or fresh water. To determine if these aqueous aged nanotubes were cytotoxic, these nanotubes were incubated with human epithelial monolayers and analyzed for cell viability (vital staining) and ultrastructural nanoparticle binding/localization (TEM, FESEM). The presence of Ni and Y catalyst, was less damaging to cells than CNT lattice surface oxidation. Extended fresh water storage of oxidized CNTs did not reduce surface reactive groups, nor lessen cell membrane destruction or cell death. However storing oxidized CNTs in saline or NOM significantly reduced CNT-induced cell membrane damage and increased cell survival to control levels. Oxidized SWCNTs in pH neutral fresh and saline water showed no reduction in surface oxidation with time, yet exposure of these nanotubes to saline and NOM reduced human cell toxicity markedly.

Soil humic substances (HS) stabilize carbon nanotube (CNT) dispersions, a mechanism we hypothesized arose from the surfactive nature of HS. Experiments dispersing multi-walled CNT in solutions of dissolved Aldrich humic acid (HA) or water-extractable Catlin soil HS demonstrated enhanced stability at 150 and 300 mg L-1 added Aldrich HA and Catlin HS, respectively, corresponding with decreased CNT mean particle diameter (MPD) and polydispersivity (PD) of 250 nm and 0.3 for Aldrich HA and 450 nm and 0.35 for Catlin HS. Analogous trends in MPD and PD were observed with addition of the surfactants Brij 35, Triton X-405, and SDS, corresponding to surfactant sorption maximum. NEXAFS characterization showed that Aldrich HA contained highly surfactive domains while Catlin soil possessed a mostly carbohydrate-based structure. This work demonstrates that the chemical structure of humic materials in natural waters is directly linked to their surfactive ability to disperse CNT released into the environment. Suspensions of multi-walled carbon nanotubes are stabilized by relatively low concentrations of dissolved humic substances in solution through surfactive mechanisms.

The diffusive oxygen uptake (DOU) of sediments inhabited by Chironomus riparius and Tubifex tubifex was investigated using a planar oxygen optode device, and complemented by measurements of bioturbation activity. Additional experiments were performed within contaminated sediments to assess the impact of uranium on these processes. After 72 h, the two invertebrate species significantly increased the DOU of sediments (13-14%), and no temporal variation occurred afterwards. Within contaminated sediments, it was already 24% higher before the introduction of the organisms, suggesting that uranium modified the sediment biogeochemistry. Although the two species firstly reacted by avoidance of contaminated sediment, they finally colonized it. Their bioturbation activity was reduced but, for T. tubifex, it remained sufficient to induce a release of uranium to the water column and an increase of the DOU (53%). These results highlight the necessity of further investigations to take into account the interactions between bioturbation, microbial metabolism and pollutants. This study highlights the ecological importance of bioturbation in metal-contaminated sediments.

The correlations among arsenic (As) accumulation in grains and straw, rates of radial oxygen loss (ROL), and porosity of roots using 25 rice cultivars were investigated based on two pot experiments: (1) soil with addition of 100 mg As kg⁻¹ for analysis of As in grains and straw, and (2) deoxygenated solution for analyzing rates of ROL and porosity of roots. The results showed that there were great differences in grain As (0.71-1.72 mg kg⁻¹) and straw As (15.6-31.7 mg kg⁻¹), rates of ROL (7.40-13.24 mmol O2 kg⁻¹ root d.w. h⁻¹), and porosity (20.91-33.08%) among the cultivars. There were significant negative correlations between As in grains or straw and ROL and porosity, and significant positive correlations between rates of ROL and porosities, respectively. Rice cultivars with high porosities tended to possess higher rates of ROL, and had higher capacities for limiting the transfer of As to aboveground tissues. Rice with high radial oxygen loss and porosity of root accumulates low As in grains.

This study was carried out in shrimp ponds from New Caledonia, in order to determine the cause of the exceptional proportion of abnormal tests (FAI) (often >50%, sometimes >80%). FAI was positively correlated to the quantity of easily oxidized material (EOM) deposited on the bottom of the ponds and to the sediment oxygen demand, and negatively correlated to redox. These results suggest that a very high FAI is a potential indicator for great accumulations of native organic matter, leading to a high sediment oxygen demand. When studying ancient sediments in core samples, exceptional abundances of abnormal tests may indicate periods of high accumulation of EOM, and therefore of oxygen depletion. This finding should help in better management of aquaculture ponds, but should also allow new insight into the interpretation of sedimentary records, providing a useful proxy for paleoenvironmental reconstructions.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SYNERGIE | International audience | The strategy of CLIMB is aiming to employ and integrate advan¬ced field monitoring techniques, remote sensing ana-lyses and retrievals, climate models auditing and integra¬ted hydrologic modeling and socioeconomic factor assess¬ment in a new conceptual framework to significantly reduce exist-ing uncertainties in climate change impact analysis. It will create an integrated risk assessment tool for adaptive water resources management and best agricultural practice under climate change conditions. The risk and vulnerability analysis tool will also enable the assess¬ment of risks for conflict-inducing actions. The impro¬ved models, new assessment tools, and their results will be evaluated against current methodologies. Improvements will be communicated to stakeholders and decision makers in a transparent, easy-to-understand form, enabling them to utilize the new findings in regional water resource and agricultural management initiatives as well as in the design of mechanisms to reduce potential for conflict CLIMB is embedded in a cluster of independent EU- projects with WASSERMed and CLICO, focused on climate induced changes in water resources as a threat to security. | L'objectif de la stratégie du projet CLIMB est d'utiliser et d'intégrer des techniques de suivi avancées sur le terrain, des analyses et des recherches de données faisant appel à la télédétection, de vérification de modèles d'évolution climatique et de modélisation par l'intégration hydrologique, et d'évaluation des facteurs socio-économiques dans un cadre conceptuel nouveau afin de réduire de façon significative les incertitudes existantes au sein des analyses des impacts du changement climatique. Ce projet créera un outil intégré d'évaluation du risque qui servira à gérer d'une façon adaptée les ressources en eau et à mettre en ½uvre les meilleures pratiques agricoles possibles dans les conditions du changement climatique. Cet outil d'analyse du risque et de la vulnérabilité permettra aussi l'évaluation des risques dans le cas d'actions conflictuelles. On comparera les modèles améliorés, les nouveaux outils d'évaluation, et leurs résultats aux méthodologies couramment utilisées. On diffusera les progrès obtenus aux parties prenantes et aux décideurs sous une forme transparente et facile à comprendre, leur permettant d'une part d'utiliser les résultats fraichement produits, tant dans les initiatives relatives à la ressource régionale en eau et à la gestion de l'agriculture, et d'autre part de réduire la source de conflit potentiel.

Protecting geotextiles are used in the design of watertight bottom liners at landfill sites, above the géomembrane, to protect it against puncture during the installation of the drainage layer and, during the service life, to the weight of the waste to be put in place. To date, the results of the 2 standard tests (static and dynamic tests) given by the technical sheets for the protecting geotextiles are not sufficient to choose the good geotextile. The development of an experimental procedure to simulate in the lab the waste loading conditions is presented here; this procedure uses large size static damage tests and follows a previous study concerning the implementation dynamic conditions (Budka & al., 2006). | Les géotextiles sont utilisés dans la constitution des étanchéités des installations de stockage de déchets (ISD) pour protéger la géomembrane contre les effets du poinçonnement liés à la mise en oeuvre de la couche de drainage puis, en service, au poids des déchets sus jacents. À ce jour, les deux essais normalisés de poinçonnement, statique et dynamique, figurant sur les fiches techniques des géotextiles de protection ne permettent pas directement le choix du produit adapté. La mise au point d'une procédure d'étude des effets des sollicitations en service est présentée ici ; elle s'appuie sur des essais d'endommagement de grandes dimensions et fait suite à une étude déjà publiée sur l'effet des sollicitations de mise en oeuvre (Budka et al., 2006).

The paper presents parts of the recent guide of recommendations "Mountain reservoirs". It makes a synthesis of a feedback on the behaviour and the pathology of geomembrane lining systems and gives the strong recommendations of the guide relative to these systems, in particular onto the structure support, the drainage inherent to the DEG and the covering structure. A general description of the guide ends the article. | L'article présente, à travers le récent guide de recommandations « Retenues d'altitude », la synthèse d'un retour d'expérience sur le comportement et la pathologie des dispositifs d'étanchéité par géomembrane (DEG) en altitude. Il donne les recommandations fortes du guide relatives à ces dispositifs, en particulier sur la structure support, le drainage inhérent au DEG et la structure de recouvrement. Un descriptif général du guide termine l'article.