Oxidant selection to treat an aged PAH contaminated soil by in situ chemical oxidation.

International audienceThis work is a part of the OXYSOL project aiming at the conception of a global treatment pathway including In Situ Chemical Oxidation to clean up soils of former metallurgical sites. It deals with the selection of the most adapted oxidants. Batch experiments were performed with aged contaminated soil samples of a former steel-making plant to degrade the 16 US EPA PAHs. In this research, hydrogen peroxide, modified Fenton's reaction, potassium permanganate, sodium percarbonate and sodium persulfate were compared at high and moderate doses. Hydrogen peroxide, modified Fenton's reagent, percarbonate and activated persulfate led to a maximum degradation ratio of 45%. A higher ratio (70%) was obtained with a high dose of permanganate. Except for permanganate, increasing oxidant dose did not improve degradation rates, especially with radical-based oxidative systems probably due to radical scavenging. Oxidant doses had an effect on pH that drastically increased or dropped in some cases, which was a drawback. Permanganate efficacy was mainly assigned to its persistence. In all cases, the low availability of PAHs, partly sequestrated in the aged soil, was identified as the most limiting factor for degradation performance. Oxidants were ranked according to their efficiency for PAH oxidation in soils. Efficiency was not correlated to the doses

Ennoyage des mines de fer lorraines : impact sur la qualité de l'eau

International audienceThe flooding of the abandoned ironmines of Lorraine leads to a degradation of the groundwater quality. Laboratory experiments allowed us to build a kinetic chemical model based on simple chemical mechanisms. During mining operations, pyrite oxidation and carbonate dissolution lead to the precipitation of gypsum. The local decrease of pH favours local dissolutions of minerals and releases ions that are fixed on cationic exchange sites. During the flooding of the mine workings, the dissolution of the newly precipitated gypsum, the precipitation of carbonates and cationic exchange reactions are responsible for the increase of the concentrations of sulphate, magnesium, sodium, potassium and strontium in water. Thereafter, these concentrations would decrease with the natural leaching of the mining reservoir.L’ennoyage des mines de fer abandonnées de Lorraine entraîne une dégradation de la qualité de l’eau souterraine. Des expériences en laboratoire ont permis la construction d’un modèle chimique cinétique, basé sur des schémas réactionnels simples. Lors de l’exploitation, l’oxydation de la pyrite et la dissolution des carbonates conduisent à la précipitation de gypse. Les baisses locales de pH favorisent des dissolutions ponctuelles de minéraux et libèrent des ions qui se fixent sur des sites d’échanges cationiques. Lors de l’ennoyage, la dissolution du gypse néoformé, la précipitation des carbonates et des réactions d’échanges cationiques entraînent une hausse des concentrations de l’eau en sulfate, magnésium, sodium, potassium et strontium qui devraient ensuite diminuer au fur et à mesure du lessivage naturel du réservoir

Mitochondrial DNA and trade data support multiple origins of Helicoverpa armigera (Lepidoptera, Noctuidae) in Brazil

The Old World bollworm Helicoverpa armigera is now established in Brazil but efforts to identify incursion origin(s) and pathway(s) have met with limited success due to the patchiness of available data. Using international agricultural/horticultural commodity trade data and mitochondrial DNA (mtDNA) cytochrome oxidase I (COI) and cytochrome b (Cyt b) gene markers, we inferred the origins and incursion pathways into Brazil. We detected 20 mtDNA haplotypes from six Brazilian states, eight of which were new to our 97 global COI-Cyt b haplotype database. Direct sequence matches indicated five Brazilian haplotypes had Asian, African, and European origins. We identified 45 parsimoniously informative sites and multiple substitutions per site within the concatenated (945 bp) nucleotide dataset, implying that probabilistic phylogenetic analysis methods are needed. High diversity and signatures of uniquely shared haplotypes with diverse localities combined with the trade data suggested multiple incursions and introduction origins in Brazil. Increasing agricultural/horticultural trade activities between the Old and New Worlds represents a significant biosecurity risk factor. Identifying pest origins will enable resistance profiling that reflects countries of origin to be included when developing a resistance management strategy, while identifying incursion pathways will improve biosecurity protocols and risk analysis at biosecurity hotspots including national ports

Non-Darcian flow experiments of shear-thinning fluids through rough-walled rock fractures

Understanding non-Darcian flow of shear-thinning fluids through rough-walled rock fractures is of vital importance in a number of industrial applications such as hydrogeology or petroleum engineering. Different laws are available to express the deviations from linear Darcy law due to inertial pressure losses. In particular, Darcy’s law is often extended through addition of quadratic and cubic terms weighted by two inertial coefficients depending on the strength of the inertia regime. The relations between the effective shear viscosity of the fluid and the apparent viscosity in porous media when inertial deviations are negligible were extensively studied in the past. However, only recent numerical works have investigated the superposition of both inertial and shear-thinning effects, finding that the same inertial coefficients obtained for non-Darcian Newtonian flow applied in the case of shear-thinning fluids. The objective of this work is to experimentally validate these results, extending their applicability to the case of rough-walled rock fractures. To do so, flow experiments with aqueous polymer solutions have been conducted using replicas of natural fractures, and the effects of polymer concentration, which determine the shear rheology of the injected fluid, have been evaluated. Our findings show that the experimental pressure loss-flow rate data for inertial flow of shear-thinning fluids can be successfully predicted from the empirical parameters obtained during non-Darcian Newtonian flow and Darcian shear-thinning flow in a given porous medium

Variabilité écophysiologique et enzymatique de Cydia pomonella L en fonction de l'origine géographique et de la plante hôte

Plusieurs caractères écophysiologiques et enzymatiques ont été étudiés chez des populations de Cydia pomonella, prélevées dans des localités géographiquement éloignées et sur des plantes hôtes différentes (pommier, poirier, cognassier, noyer, abricotier). Des seuils photopériodiques d'induction de la diapause et thermiques de réactivation post-diapause différents sont observés entre localités mais non entre plantes hôtes. L'analyse enzymatique de 7 loci polymorphes ne fait apparaître qu'une faible différenciation génétique, aussi bien entre les échantillons issus de localités différentes (Fst = 0,0294) qu'entre ceux prélevés sur les diverses plantes hôtes dans une même localité (Fst = 0,0385). On observe cependant, entre localités, des différences significatives de fréquences alléliques. L'hypothèse est avancée de populations locales, essentiellement inféodées au pommier, dont une partie émigre, plus ou moins régulièrement, vers des hôtes plus occasionnels, en fonction de coïncidences spatio-temporelles. Toutefois, cette dispersion des adultes ne peut constituer un «effet fondateur» que temporaire, car l'arrêt de développement hivernal et le décalage des stades phénologiques sensibles des plantes hôtes concourent au brassage régulier des sous-populations.Ecophysiological and enzymatic variability of Cydia pomonella L according to geographical origin and host plant. Simultaneous ecophysiological and enzymatic investigations were performed on Cydia pomonella populations from distant areas and from various host plants (apple, pear, quince, walnut and apricot). Different photoperiodic thresholds for diapause induction and temperature thresholds for post-diapause reactivation were observed according to areas but not host plants. The enzymatic analysis of 7 polymorphic loci exhibits only a weak genetic differentiation between populations from different localities (Fst = 0.0294) and different host plants (Fst = 0.0385). However, significant differences of allelic frequencies were noted. We put forward the hypothesis of local populations, mostly apple pests, some of which emigrate to occasional hosts, according to spatio-temporal synchronisms. Nonetheless, this dispersion does not constitute a 'foundation effect', since arrested winter development and the non-coincidence of the sensitive phenological stages of host-plants lead to a regular mixing of subpopulations