International audience | AbstractThis study addresses the spatio-temporal dynamics of per and polyfluoroalkyl substances (PFASs) in a highly urbanized freshwater hydrosystem, the Seine River (NW France). The distribution of PFASs between water, sediment, and periphytic biofilm was investigated at three sampling sites along a longitudinal gradient upstream and downstream from the Paris urban area. Seasonal variability was assessed through four sampling campaigns performed under contrasting hydrological conditions. In the dissolved phase, ∑PFASs fluctuated between 2 and 9 ng L−1 upstream and 6–105 ng L−1 downstream from Paris. Negative correlations between dissolved PFAS levels and river flow rate were generally observed, corroborating the predominance of point-source PFAS inputs at these sites. 18/19 target PFASs were detected, with a predominance of PFHxS and PFOS (20% of ∑PFASs each), except for the farthest downstream site where 6:2 FTSA was prevalent (35 ± 8% of ∑PFASs), likely reflecting industrial and urban inputs. In biofilms, ∑PFASs fell in the 4–32 ng g−1 dw range, and substantial bioconcentration factors (BCFs) were reported for PFNA, PFDA, and PFOS (log BCF 2.1–4.3), higher than those of PFHxS or PFOA. BCFs varied inversely with dissolved PFAS levels, potentially pointing to concentration-dependent bioaccumulation. Biofilm community characteristics (C/N ratio) may also be an influential determinant of PFAS bioaccumulation.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED | International audience | CWs for combined sewer overflow treatment (CSO CWs) are vertical flow filters with detention basin and fixedoutflow rate. They receive stochastic loadsinduced by urban runoff and protect natural waters against pollutants and streambed erosion.However, due to the stochastic nature of flows, concentrations and periodicity, optimizing CSO CW design requires a dynamic approach.Computational tools are available but process-based models are difficult to handle [1].Moreover, the absence of user interface in design-oriented tools (e.g. RSF_Sim [2]) demands manual data handling and simulations of multiple designs. Therefore, a new tool called Orage was developed. Orage relies on a core model similar to RSF_Sim.Long-term hydraulics, COD and NH4-N were simulated with good accuracy. Filter material selection and scaling is based on inflow data series and a low number of inputs. The iterative shell calls for simulations repeatedly to (1) optimize hydraulics; (2) select the simplest material which isnecessary to satisfy emission requirements on NH4-N and (3) determine the minimalfilter area at which legislative thresholds can be met. A design is optimized if the maximum of moving average on simulated effluent concentrations (Peak_MA_cc) is at the legislative threshold (NH4N) or below (COD). Fig. 1 shows an example of the iteration process.

International audience | Barrage fishponds may represent a significant surface water area in some French regions. Knowledge on their effect on water resources is therefore necessary for the development of appropriate water quality management plans at the regional scale. Although there is much information on the nutrient removal capacity of these water bodies, little attention has been paid to other agricultural contaminants such as pesticides. The present paper reports the results of a 1-year field monitoring of pesticide concentrations and water flows measured upstream and downstream from a fishpond in North East France to evaluate its capacity in reducing pesticide loads. Among the 42 active substances that had been applied on the fishpond's catchment, seven pesticides (five herbicides, two fungicides) were studied. The highest concentration in the inflow to the pond was 26.5 mu g/L (MCPA), while the highest concentration in pond outflow was 0.54 mu g/L (prosulfocarb). Removal rates of dissolved pesticides in the fishpond ranged from 0-8 % (prosulfocarb) to 100 % (clopyralid). Although not primarily designed for the treatment of diffuse sources of pesticides, the studied fishpond had the potential to do so.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED | International audience | Gas emissions of Vertical Flow Constructed Wetlands (VFCW) treating raw wastewater have been poorly investigated. One of the main issue measuring gas emissions on such systems is related to their high heterogeneity of flow conditions (surface water distribution, feeding/resting periods etc). It is thus of importance to develop a specific methodology to be able first to determine representative gas emission fluxes and then to decide how filter‘s operation can affect these emissions. This study investigates greenhouse gas emissions from a full-scale VFCW for raw wastewater treatment. The plant designed for 800 population equivalents combines two stages of vertical subsurface flow filters planted with Phragmites. Australis. Gaseous emissions were continuously monitored during three weeks representing an overall feeding/resting period (1/3 weeks). Several automatic closed chambers connected to an infrared analyzer were placed at different strategic positions of the filters and allowed the measurement of tens of gaseous fluxes per day and per position. Dissolved N2O concentration was measured in the inlet and the outlet of each filtration stage using N2O micro-sensors. A combination of on-line sensors for NH4+ and NO3- and 24-h composite samples was used to characterize the process performances of each filtration stage. Finally, O2concentration was regularly measured in the air phase of the porous media in order to evaluate the aerobic conditions of the filters. Ammonium removal was on average of 94% during the monitoring period. The continuous measurement highlighted strong spatial and temporal variability of gaseous fluxes. This latter was observed at different time scales (day, week, feeding/resting cycle) and was linked to: (i) the intermittent feeding of the filters, (ii) oxygen content in the porous media and (iii) environmental conditions such as the ambient temperature. Dissolved N2O flux represented about 20% of the total flux (gas + liquid) which indicates the importance of accounting the dissolved flux in the N2O budget. The two filtration stages exhausted contrasted fluxes of methane and nitrous oxide in relation to carbon load and oxygen availability for carbon removal and nitrification. From a methodological point of view, this study indicates that: (i) continuous monitoring of greenhouse gas fluxes during at least an overall filtration cycle and (ii) appropriate spatial sampling strategy are decisive for a reliable determination of emission factors in VFCWs. The overall N2O emission factor estimated during the monitoring period was of 0.78% of the influent total nitrogen which is 28 times higher than the default IPCC factor (0.023% of the TN load). As N2O emissions were strongly correlated to the oxygen concentration within the porous media, it is suspected that nitrification was the main contributor to N2O production in the VFCW studied.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED | International audience | This simulation study investigates the treatment performance of a French style single stage vertical flow constructed wetland using a zeolite layer in order to increase ammonia removal. For the modelling exercise, the CW"2D biokinetic model of the HYDRUS Wetland Module is used. The calibrated model is able to determine the effect of different depths of the zeolite layer on ammonia removal in order to optimize the design of the system. For calibration of the model, hydraulic effluent flow rates as well as influent and effluent concentrations of COD and NH4-N have been measured. To model the adsorption capacity of zeolite, Freundlich isotherms are used. The results present the simulated treatment performance within three different depths of the zeolite layer, 10 cm (default), 15 cm and 20 cm respectively. The increase of the zeolite layer depth leads to a decrease of the simulated NH4-N effluent concentration.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED | International audience | The classic design of French constructed wetlands (CW) consists in two successive stages of vertical flow filters (VFFs). While this configuration permits full nitrification, it also needs a large surface area (> 2 m²/pe). Therefore high ammonium removal efficiencies are of interest for compact systems such as single stage CW.The use of zeolite as filtrating medium could fix the problem thanks to itsexchange capacity and its high affinity for ammonium. Indeed, the ammonium is adsorbed during the feeding cycle then nitrified during the rest period.This study aims to assess the feasibility of ammonium removal by zeolite in a first stage VFF fed with raw sewage. Seven columns (40 cm-depth, 107 cm²) filled with zeolite under a gravel layer and one control without zeolitewere studied over four months. All columns, except a zeolite-control, were packed with inoculated media froma treatment plant. The columns have been operated in a sequential mode of feeding and rest periods of 3.5d and 7d, respectively, with synthetic solution of ammonium (100mgNH4-N/L). Two columns were fed with different concentrations of ammonium while two others were also fed sodium in order to assess the impact of the ammonium concentration and the presence of competitive species, respectively. The nitrogen concentrations (ammonium, nitrite and nitrate) were measured at the inlet and the outlet.

Adding fertiliser to sediments is an established way of studying the effects of eutrophication but a lack of consistent methodology, reporting on enrichment levels, or guidance on application rates precludes rigorous synthesis and meta-analysis. We developed a simple enrichment technique then applied it to 28 sites across an intertidal sandflat. Fertiliser application rates of 150 and 600 g N m−2 resulted in pore water ammonium concentrations respectively 1–110 and 4–580 × ambient, with greater elevations observed in deeper (5–7 cm) than surface (0–2 cm) sediments. These enrichment levels were similar to eutrophic estuaries and were maintained for at least seven weeks. The high between-site variability could be partially explained by the sedimentary environment and macrofaunal community (42%), but only at the high application rate. We suggest future enrichment studies should be conducted in situ across large environmental gradients to incorporate real world complexity and increase generality of conclusions.

Despite being generally located far from contamination sources, deep marine ecosystems are impacted by chemicals like PCB. The PCB contamination in five fish and shark species collected in the continental slope of the Gulf of Lions (NW Mediterranean Sea) was measured, with a special focus on intra- and interspecific variability and on the driving factors. Significant differences occurred between species. Higher values were measured in Scyliorhinus canicula, Galeus melastomus and Helicolenus dactylopterus and lower values in Phycis blennoides and Lepidorhombus boscii. These differences might be explained by specific abilities to accumulate and eliminate contaminant, mostly through cytochrome P450 pathway. Interindividual variation was also high and no correlation was observed between contamination and length, age or trophic level. Despite its major importance, actual bioaccumulation of PCB in deep fish is not as documented as in other marine ecosystems, calling for a better assessment of the factors driving individual bioaccumulation mechanisms and originating high variability in PCB contamination.