Efficiency of source control systems for reducing runoff pollutant loads: Feedback on experimental catchments within Paris conurbation.

International audience: Three catchments, equipped with sustainable urban drainage systems (SUDS: vegetated roof, underground pipeline or tank, swale, grassed detention pond) for peak flow mitigation, have been compared to a reference catchment drained by a conventional separate sewer system in terms of hydraulic behaviour and discharged contaminant fluxes (organic matter, organic micropollutants, metals). A runoff and contaminant emission model has been developed in order to overcome land use differences. It has been demonstrated that the presence of peak flow control systems induces flow attenuation even for frequent rain events and reduces water discharges at a rate of about 50% depending on the site characteristics. This research has also demonstrated that this type of SUDS contributes to a significant reduction of runoff pollutant discharges, by 20%-80%. This level of reduction varies depending on the considered contaminant and on the design of the drainage system but is mostly correlated with the decrease in runoff volume. It could be improved if the design of these SUDS focused not only on the control of exceptional events but also targeted more explicitly the interception of frequent rain events

Using conducting polymers as active agents for marine antifouling paints

Antifouling coatings were prepared with paints containing polyaniline (PAni) and derivatives as active pigment, and evaluated by antifouling performance on metallic or polyvinyl chloride substrates. The paints, PAni and its derivatives were characterized by FT-IR spectrophotometry, thermogravimetric analysis, electrical conductivity and scanning electron microscopy. Coatings were also characterized by salt spray, leaching and erosion tests. Antifouling coatings’ performance was evaluated by immersion tests in a marine environment or in fresh water. Paints containing PAni-ES, PAni/DBSA and SPAN, and a co-biocide PyZn, showed antifouling performance similar to a commercial antifouling paint

Synthesis of hybrid TiO2 nanoparticles with well-defined poly(methyl methacrylate) and poly(tert-butyldimethylsilyl methacrylate) via the RAFT process

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Behaviour of flooding source control systems for frequent rain events: effect on pollutant loads.

International audienceThe aims of this work are to evaluate the hydrological behaviour of source control systems used to regulate runoff discharges in sewer, for current events which contribute to the major part of the annual pollutants loads. These systems are based on various types of upstream storage systems (more or less integrated into the urban landscape) and fitted with a flow limitation system at the outlet. Four catchments (one with conventional stormwater system and three with source control systems) have been monitored during one year and compared with regards to flow dynamic and to discharged runoff volumes. Significant effects of source control systems have been shown. These observations had allowed establishing some recommendations for the conception of source control systems if the objective is improving water quality

Synthesis of ZnO nanoparticles with tunable size and surface hydroxylation

International audienceZinc oxide (ZnO) is an important metal oxide for hybrid inorganic–organic devices in which the surface properties can dictate the overall characteristics of the system. The particle size and the amount of hydroxyl groups’ density at the surface are key parameters to promote further bonding of organic phase on metal oxide. The precipitation method was used to successfully prepare ZnO nanoparticles at room temperature with a wurtzite structure and a controlled surface hydroxylation. Spherical nanoparticles with diameters around 6–8 nm were synthesized in ethanolic solutions whereas the addition of water in the reaction mixture led to bigger particles within the range of 20–50 nm together with a change in morphology. The X-ray diffraction data revealed that a high crystal quality of ZnO with hexagonal (wurtzite-type) crystal structure could be obtained with increasing the amount of water and the annealing temperature. Transmission electronic microscopy images demonstrated the presence of two populations of particles size synthesized in an ethanol/water reaction mixture together with the presence of a zinc dihydroxide amorphous layer surrounding the well-crystallized grains in water solution. The amount of physically and chemically adsorbed water on to ZnO particles was determined through thermogravimetric analysis. The surface hydroxylation of ZnO particles and the hydrophilic character of the particles surface were shown to be modulated by the solvent, the time, and the annealing temperature of the precipitated particles. In ethanol/water solutions, the use of a reactive silane capping agent such a 3-(trimethoxysilyl)propylmethacrylate was shown to limit the growth of ZnO particles with diameters around 5 nm to switch their wetting characteristics from a hydrophilic to a hydrophobic surface

Fragmentation pathways of methacrylic homopolymers with labile trialkylsilyl ester side-groups-A mass spectrometric investigation of the RAFT process

International audienceFragmentation pathways of methacrylic polymers containing labile silyl ester pendant groups were characterized upon collisional activation of electrosprayed oligomer adducts. Dissociation of lithiated oligomers mainly generated low mass product ions containing the a end-group and arising from backbone bond homolytic cleavages, as typically observed for poly(alkylmethacrylate)s. Combined with the sum of the end-group masses as determined from MS data, this main reaction allowed both end-groups to be validated. In contrast, loss of HCOOR (with R = triisopropylsilyl) or elimination of alkene species from alkylsilyl groups, such as reported from poly(butylmethacrylate), was not observed here, probably due to steric hindrance of the pendant moieties. Activation of ammonium oligomer adducts was found to provide highly complementary information, since they exhibited a similar behavior as compared to poly(methacrylic acid), with serial eliminations of a triisopropylsilanol neutral conducting to the determination of the polymerization degree of the dissociating precursor ion. It should be noted however that this useful pathway was not always observed to efficiently compete with dissociation of reactive omega end-groups. Based on these fragmentation rules, five poly(triisopropylsilyl methacrylate)s were identified in a sample obtained via reversible addition-fragmentation chain transfer (RAFT) polymerization using cyanoisopropyl dithiobenzoate as the chain transfer agent. Their structure could be rationalized with regards to RAFT processes: (i) dormant chains initiated by a cyanoisopropyl group and terminated by a dithiobenzoate group, as the main species: (ii) proton- and (iii) vinyl-terminated dead chains produced by disproportionation termination events: (iv) alpha,omega-cyanoisopropyl-terminated polymer chains arising from a combination termination between two macromolecular propagating radicals, and (v) dormant chains containing methacrylic acid monomer units within the chain. (C) 2011 Elsevier B.V. All rights reserved

Micropolluants organiques dans les eaux de ruissellement urbaines -Effets de différents modes de gestion des eaux pluviales

International audienceRésumé Les concentrations en certains micropolluants organiques (HAP, PCB, alkylphénols) ont été mesurées dans les retombées atmosphériques, dans les eaux de ruissellement d'un petit bassin versant résidentiel amont drainé par un réseau séparatif et à l'exutoire de trois bassins versants dont les eaux pluviales sont contrôlées à la source. Les concentrations mesurées sur le petit bassin versant en amont du réseau séparatif apparaissent faibles par rapport à ce qui a été trouvé dans la littérature pour des bassins versants plus grands, ce qui montre l'intérêt, pour des objectifs de qualité, de gérer les eaux pluviales dès l'amont, afin d'éviter les contaminations par mélange ou dans le réseau. De plus, à l'aide d'outils de modélisation, nous avons montré que les systèmes de contrôle à la source permettaient une réduction importante des masses de contaminants dans les eaux pluviales. Le niveau d'abattement est lié au type de substances considérées, au type et au fonctionnement de l'ouvrage, et est surtout fortement lié à la réduction des volumes d'eau de ruissellement, les résultats ne mettant pas systématiquement en évidence la réduction des concentrations mais la réduction des masses rejetées