Détermination, distribution spatiale et évolution dans le temps des plantes sur des sédiments contaminés de bassins d’infiltration urbains

Colloque avec actes et comité de lecture. internationale.International audienceWe identified over a decade the evolution of species richness of flora and its abundance on two types of vegetated basins: Minervewherethe vegetation was originally planted, and the other naturally colonized (called Django). In Minerve, we observed a gradient from upstream (near the water entry) to downstream (farthest from this water entry) for parameters like organiccontent, height oflayer and trace element contents. In Django, the distribution is less clear, but we also observed zones with contrasting contents in organic matter and heavy metal. The regression of helophytes communities on Minerve for the benefit of ruderals pioneer species marks the evolution of the site. Since 1999, over 93% of implanted species have disappeared, but the diversity of helophytes seems to have stabilized since 2008withonly 12.5% of variation for the number of such species. On the basin of Django, the number of species remained stable since 2008. But, the decrease of almost 50% of macrophytes recovery rate, reduced to Phalaris arundinacea, Typha latifoliaand Schoenoplectus tabernamontanii, emphasizes a change in entering water flow rates. The dominant flora found in infiltration basins evolves over time with euryece species of pseudo-metallophytes macrophyte group (Typha latifolia, Phragmites australis, Iris pseudacorus, Phalaris arundincea), ruderal species typical of dry grasslands (Asteraceae, Poaceae, Brassicaceae) and wetland species (Rumex sp.). But before all, these plants are mainly divided/distributed in theses basins according to hydrological factors, i.e. water availability among other

The potential of ryegrass (Lolium perenne L.) to clean up multi-contaminated soils from labile and phytoavailable potentially toxic elements to contribute into a circular economy

International audienceAided phytoremediation was studied for 48 weeks with the aim of reducing extractable and phytoavailable toxic elements and producing potential marketable biomass. In this sense, biomass of ryegrass was produced under greenhouse on two contaminated garden soils that have been amended with two successive additions of phosphates. After the first addition of phosphates, seeds of ryegrass were sown and shoots were harvested twice. A second seedling was performed after carefully mixing the roots from the first production (used as compost), soils and phosphates. Forty-eight weeks after starting the experiments, the concentrations of Cd, Pb, Zn, Cu, Fe, and Mn extracted using the rhizosphere-based method were generally lower than those measured before the addition of phosphates and cultivation (except for Pb and Fe in the most contaminated soil). The concentrations of metals in the shoots of ryegrass from the second production were lower than those from the first (except for Al). The best results were obtained with phosphates and were the most relevant in the lowest contaminated soil, demonstrating that the available metal concentrations have to be taken into account in the management of contaminated soils. In view of the concentration of metals defined as carcinogens, mutagens, and reprotoxics (e.g., Cd, Pb) and those capable to be transformed into Lewis acids (e.g., Zn, Fe), the utilization of ryegrass in the revegetation of contaminated soils and in risk management may be a new production of marketable biomass. The development of phytomanagement in combination with this type of biomass coincided with the view that contaminated soils can still represent a valuable resource that should be used sustainably. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature

Effects of Calcium Phosphates on the (Im)Mobilization of Metals and Nutrients, on the Biological Activity and on the Plant Health from Multi-contaminated Urban Soils

International audienceTwo smelters in the North of France emitted potentially toxic metals for more than a century and today, the resulting contamination represents a risk to human health and affects also the biodiversity. To limit health risks and to improve the soil quality, a study using calcium phosphates (monocalcium phosphate, dicalcium phosphate and a mixture of both salts) and Lolium perenne L was conducted. Through this preliminary investigation, we will try to shed some light about (i) the effects of a sustainable amount of calcium phosphates on the agronomic, biological (microbial and fungi communities) and physiological parameters (chlorophyll a and b, antocyanins, carotenoids) as well as the phytoavailability of potentially toxic metals and nutrients in time, and (ii) the potential use of contaminated biomass from ryegrass as a source of new valorisation ways instead of using it as contaminated compost by gardeners. Although slight variations in pH and significant increases of assimilable phosphorus after adding calcium phosphates were registered, the physiology of plants and the biological parameters were statistically unchanged. The germination of the ryegrass seeds was favoured with calcium phosphates regardless the contamination level of the studied soils. No clear effects of calcium phosphates on the microbial and fungi communities were detected. In contrast, results indicated relationships between the physicochemical parameters of soils, their contamination level and the composition of fungal communities. Indeed, for one of the soils studied, calcium could limit the transport of nutrients, causing an increase in fungi to promote again the transfer of nutrients. Surprisingly, the phytoavailability of Pb increased in the most contaminated soil after adding dicalcium phosphate and the mixture of phosphates whereas a slight decrease was highlighted for Cd and Mn. Although minor changes in the phytoavailability of potentially toxic metals were obtained using calcium phosphates, the ability of ryegrass to accumulate Zn and Ca (up to 600 and 20,000 mg kg−1, respectively) make possible to qualify this plant as a bio ‘ore’ resource. © 2019, Springer Nature Switzerland AG