[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED [Axe_IRSTEA]TED-EPURE | International audience | Oxygen renewal, as a prominent phenomenon for aerobic bacteria activity, deeply impacts VFCW treatment efficiency. We introduce MIGRA, a new model able to simulate oxygen transfer in VFCW. It is based on a realistic two-phase flow module, that allows us to describe various loading sequences, and a transport module. The multi-component transport module is able to deal with convection/diffusion phenomena, inter-phase (air-water) mass exchange, and first-order kinetics. It is validated with analytical solutions and data from an experimental VFCW (column). We show the benefits of a two-phase flow modeling using a comparison with HYDRUS.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED [Axe_IRSTEA]TED-EPURE | International audience | We develop an original solid respirometric method to measure the biodegradation rates of COD and ammonium at different depths of a Vertical Flow Constructed Wetland (VFCW). The method is developed for a matrix operated under unsaturated conditions. The oxygen demand is measured versus time in a gas passing through a reactor containing a mixture of an organic matrix mixed with a bulking agent (wood). For the measurement of the nitrification rate, a solution of ammonia and hydrogenocarbonates is spread on the sample. We ran 15 experiments on different matrices with variable organic matter contents (sludge, VFCW gravels and sand). Within this paper we present the overall methodology, the factors that allow improving the accuracy (number of duplicates, blank, sample volume, bulking agent volume, gas flow, etc.) and the nitrification rates that were obtained.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED [Axe_IRSTEA]TED-EPURE | International audience | On the 2006 IWA International Wetlands Conference in Portugal, two wetland pilot plants in the small tropical island of Mayotte, in the Indian Ocean, were presented. The first pilot plant being a vertical flow filter with recirculation, fed with raw sewage, and the second one a horizontal flow filter after an Imhoff tank. These plants where put into operation the end of 2005 and early 2006, respectively, by SIEAM, which is a syndicate created by the islands authorities who will have the task to operate all water and sewage equipment on the island. The plants have been monitored by SIEAM ever since they went into operation and first results were presented at the 2006 Wetlands conference. In this paper, we present the operation conditions, treatment results and problems encountered during the last 4 years of operation and monitoring of these pilot plants, which will be of particular interest in the aim of finding sustainable treatment solutions for small communities in the tropics, even though the amount of date gathered during this four year period is not as important as we had hoped.

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International audience

The effects of elevated concentrations of atmospheric tropospheric ozone (O3) on DNA damage in five trembling aspen (Populus tremuloides Michx.) clones growing in a free-air enrichment experiment in the presence and absence of elevated concentrations of carbon dioxide (CO2) were examined. Growing season mean hourly O3 concentrations were 36.3 and 47.3 ppb for ambient and elevated O3 plots, respectively. The 4th highest daily maximum 8-h ambient and elevated O3 concentrations were 79 and 89 ppb, respectively. Elevated CO2 averaged 524 ppm (+150 ppm) over the growing season. Exposure to O3 and CO2 in combination with O3 increased DNA damage levels above background as measured by the comet assay. Ozone-tolerant clones 271 and 8L showed the highest levels of DNA damage under elevated O3 compared with ambient air; whereas less tolerant clone 216 and sensitive clones 42E and 259 had comparably lower levels of DNA damage with no significant differences between elevated O3 and ambient air. Clone 8L was demonstrated to have the highest level of excision DNA repair. In addition, clone 271 had the highest level of oxidative damage as measured by lipid peroxidation. The results suggest that variation in cellular responses to DNA damage between aspen clones may contribute to O3 tolerance or sensitivity. Ozone tolerant clones and sensitive Populus tremuloides clones show differences in DNA damage and repair.

In 2006, a controlled infection study was performed in the ‘Kranzberger Forst’ to address the following questions: (1) Will massive artificial inoculation with Apiognomonia errabunda override the previously observed inhibitory effect of chronic ozone? (2) Can biochemical or molecular markers be detected to account for the action of ozone? To this end six adult beech trees were chosen, three ozone fumigated (2× ozone) and three control trees (ambient = 1× ozone). Spore-sprayed branches of sun and shade crown positions of each of the trees, and uninoculated control branches, were enclosed in 100-L plastic bags for one night to facilitate infection initiation. Samples were taken within a five-week period after inoculation. A. errabunda infestation levels quantified by real-time PCR increased in leaves that were not fumigated with additional ozone. Cell wall components and ACC (ethylene precursor 1-amino cyclopropane-1-carboxylic acid) increased upon ozone fumigation and may in part lead to the repression of fungal infection. Chronic sublethal ozone exposure reduces both natural and artificial infestation of beech leaves by the endophytic fungus Apiognomonia errabunda.

Landfill leachates usually need to be treated before discharged, and using soil–plant systems for this has gained substantial interest in Sweden and in the UK. A three-year field study was conducted in central Sweden to quantify plant response, treatment efficiency and impact on groundwater quality of landfill leachate irrigation of short-rotation willow coppice (Salix). Two willow varieties were tested and four irrigation regimes in sixteen 400-m2 plots. The willow plants did not react negatively, despite very high annual loads of nitrogen (≤2160 kg N/ha), chloride (≤8600 kg Cl/ha) and other elements. Mean annual growth was 1.5, 9.8 and 12.6 tonnes DM/ha during years 1–3. For one of two willow varieties tested, relative leaf length accurately predicted growth rate. Irrigation resulted in elevated groundwater concentrations of all elements applied. Treatment efficiency varied considerably for different elements, but was adequate when moderate loads were applied. Short-rotation willow coppice was successfully used for treating a strong landfill leachate in central Sweden over three years.

In this study, we measured via surgical sampling hepatic EROD activity in yellow-legged gulls from oiled and unoiled colonies, 17 months after the Prestige oil spill. We also analyzed stable isotope composition in feathers of the biopsied gulls, in an attempt to monitor oil incorporation into marine food web. We found that yellow-legged gulls in oiled colonies were being exposed to remnant oil as shown by hepatic EROD activity levels. EROD activity was related to feeding habits of individual gulls with apparent consequences on delayed lethality. Capture-recapture analysis of biopsied gulls suggests that the surgery technique did not affect gull survival, giving support to this technique as a monitoring tool for oil exposure assessment. Our study highlights the combination of different veterinary, toxicological and ecological methodologies as a useful approach for the monitoring of exposure to remnant oil after a large oil spill.

Soil, sediment, water, and biota collected from the western coast of Korea were analyzed to determine occurrence and sources of perfluorinated compounds (PFCs). PFCs were significantly concentrations of PFCs were measured in some water and biological samples, while concentrations of PFCs in soils and sediments were relatively low. The most widely detected compound was found to be perfluorooctanesulfonate (PFOS), with a maximum concentration in water of 450 ng/L and in fish of 612 ng/g, dw. PFOS concentrations in water and biota were both less than those thought to cause toxicity. However, in both cases concentrations were within a factor of 10 of the toxicity threshold concentration. Concentrations of PFCs were significantly greater downstream than those upstream on the same river, suggesting point sources. Overall, the detection of PFCs at relatively great concentrations in various environmental matrixes from this region of Korea suggests that further studies characterizing PFCs and their potential risk to both humans and wildlife are needed.