This text focuses on the identification, efficiencies, classification and management of landscape features having a potential buffer function regarding diffuse phosphorus, because of their specific structure (vegetation-soil) and of their location at the interface between sources (farm infrastructures, emitting fields…) and surface water bodies. These buffers are very diverse and correspond to natural landscape features (wetlands, riparian areas…) as well as manmade structures (constructed buffer strips or intermediate cases such as field margins, hedgerows). Their role and efficiency depends on the local factors controlling the retention processes (internal organisation and properties of the buffer), on the position within the watershed, and on the landscape context which reciprocally determines the overall buffer capacity of a watershed. On that basis, we recognize the diversity of the buffers in structure and functioning and thus in the way they attenuate the signal, their limitations (sustainability, side effects) and their hierarchic organisation at the watershed scale.

International audience | Expansion of aquaculture has increased concern over its environmental impact. The composition of effluents from intensive aquaculture is well documented, but few data on extensive aquaculture are available. During 12 draining operations, 523 water samples were collected downstream from six extensively-managed fishponds in northeastern France. Study ponds had surface areas of 2–620 ha and were managed for production of Cyprinids and Percids. Concentrations of total suspended solids, total phosphorus, and Kjeldahl nitrogen in effluents from the ponds were greatest during the final stage of draining. Loads of phosphorus were higher than those reported for effluents of more intensive aquaculture ponds in the USA, but the source of the potential pollutants was catchments and sediment rather than feeds and fertilizer. It will be necessary to reduce the water drawdown rate during the fishing stage and possibly implement other best management practices to prevent the TSS concentration from exceeding 1 g/L. Effluent phosphorus loads were higher than those reported for more intensive aquaculture ponds, but the pollutant source was catchments rather than feeds and fertilizers.

Constructed Wetlands receiving treated wastewater (CWtw) have recently become attractive in France under the perception that they would increase water quality of the WWTP effluent. This study focuses on the fate of phosphorus (P) in 2 pilot-scale CWtw after 2 years of operation considering the 3 components: water, soil and plants. P mass balance was estimated by measures of water balance (inflow outflow and infiltration), flow composite samples, grab samples, water in soil, deposits, soil and plants samples. When considering inlet/outlet an efficiency of 83% and 39 % P removal was observed respectively in M1 and M2. Since the plant uptake was of 15-25 % of total P removal in both systems, the remaining fraction was either retained in the soil or infiltrated. Removal of P by harvesting of aboveground biomass is relevant in that case because of a lightly load system and confirms the need for a harvesting per year to avoid the release of up to 7 kg of P.

Phosphorus removal in constructed wetlands have received particular attention last decades by using specific materials promoting adsorption/precipitation mechanisms. Recent studies have shown interest in using apatite materials to promote P precipitation onto the particle surface. As previous trials were mainly done by lab experiments, this present study aims to evaluate the real potential of apatites to remove P from wastewater in pilots and a full-scale plant. Two different apatites have been studied in 1.5 m² pilots fed with wastewater from the outlet of a trickling filter. They were monitored to follow inlet/oulet flows, hydraulic gradient, meteorological conditions, pH, temperature, and redox potential. Treatment performances were evaluated by regular complete analysis (COD, BOD, SS, nitrogen and phosphorus forms, Ca) as well as PO4-P by a WTW online analyser. At the same time a full-scale experiment study have been done to point out P retention properties in real conditions over a 2 years period. P retention kinetics of two qualities of apatites are presented and discussed according to the temperature dependence. In this work apatite appears to have high retention capacity and is still an interesting way for P removal in constructed wetlands. However, other qualities of apatite must be studied for a better reliability of treatment.

[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCA [ADD1_IRSTEA]Systèmes aquatiques soumis à des pressions multiples | International audience | Gammarus fossarum is an often-abundant crustacean detritivore that contributes importantly to leaf litter breakdown in oligotrophic, mainly heterotrophic, headwater streams. This species requires large amounts of Ca to moult, thus allowing growth and reproduction. Because resource quality is tightly coupled to the organism's growth and physiological status, we hypothesised that low Ca concentration [Ca] and low food resource quality (low phosphorus [P] and/ or reduced highly unsaturated fatty acid [HUFA] contents) would interactively impair molecular responses (gene expression) and reproduction of G. fossarum. To investigate the effects of food resources quality, we experimentally manipulated the P content of sycamore leaves and also used diatoms because they contain high amounts of HUFAs. Three resource quality treatments were tested: low quality (LQ, unmanipulated leaves: low P content), high quality 1 (HQ1; P-manipulated leaves: high P content), and high quality 2 (unmanipulated leaves supplemented with a pellet containing diatoms: high P and HUFA content). Naturally, demineralised stream water was supplemented with CaSO4 to obtain three Ca concentrations (2, 3.5, and 10.5 mg Ca L