Valorisation agronomique des sédiments fins de retenues hydroélectriques en construction d’Anthroposols fertiles

Fine sediments naturally accumulate upstream of hydropower facilities. For technical or environmental reasons, they occasionally have to be dredged and land managed. Using dredged sediment to construct fertile soils and set up green spaces or rehabilitate degraded land is one the ways dredged sediment can be valorized. This use of sediment as an alternative soil-building material helps preserve the topsoil resource, but its agronomical value and environmental safety first has to be demonstrated. We used an experimental approach (a 3-month greenhouse trial and a 24-month in situ lysimeter test) to assess the physical, chemical, and biological parameters of soil fertility from 6 sediments that were either pure or mixed with 40 % (v:v) of green waste compost.The results showed that sediment aggregation capacity is a key factor of their fertility. The monitoring of vegetation cover development on the constructed soil demonstrated that all six sediments could support vegetation. High organic matter (OM) content sediments (> 30 g kg-1) are suitable to grow plants with potentially high water and nutrient requirements. Low OM content sediments (30 g kg-1) sont adaptés aux végétaux des espaces végétalisés ayant potentiellement des exigences hydriques et trophiques élevées. Les sédiments pauvres en MO (<30 g kg-1), semblent davantage adaptés à une utilisation pour des opérations de restauration où les exigences des végétaux sont généralement moindres. Ce travail aboutit à la proposition de critères environnem

BD interrégionale (harmonisation)

Objectifs :- Construire une carte à 1/250000 des sols en France associée à une base de données en format Donesol- Etre « économe » en termes de construction de la nouvellebase de données France entière.- Construire cette base en concertation avec les auteurs des RRP

Potential use of dam sediment for soil construction in urban greening: agronomic fertility and environmental harmlessness

International audienceThere is today a growing demand to develop green spaces in city, as they provide a support for biodiversity and can contribute to ecological connectivity with surroundings. Greening urban areas requires large amounts of arable soil that is a non-renewable resource. The purpose of our study is todetermine whether river dam sediments can be used as alternative materials to preserve soil resource in urban greening. Indeed, sediments are natural materials coming mainly from soils erosion available in large volumes. Sediments are composed of elementary mineral and organic particles. Each year in France, several hundred thousand cubic meters of sediments are dredged from EDF hydraulic power installations to ensure their correct operation, and returned to the river to respect the sedimentary continuity. In some cases, sediments may not be returned to water. Then, ways of valorization are sought. Most often they do not contain anthropic contaminants, in relation with their origin, far fromhuman activities (Brochier et al., 2016), but in some cases, they could contain traces of heavy metalscoming from the natural geochemical backgrounds

Agronomic fertility of dam sediment for soil construction in urban greening

International audienceThere is today a growing demand to develop green spaces in city, as they provide asupport for biodiversity and can contribute to ecological connectivity with surroundings.Greening urban areas requires large amounts of arable soil that is a non-renewable resource.The purpose of our study is to determine whether river dam sediments can be used as alter-native materials to preserve soil resource. Indeed, sediments are natural materials comingmainly from soils erosion available in large volumes (several hundred thousand cubic meterseach year in France coming from EDF hydraulic power installations).We studied four sediments coming from four hydroelectric plant dams showing differences intexture, mineral composition and initial organic matter content, that were compared withan agricultural loam soil. The sediments and the control soil were used alone or mixedwith green waste compost. Each substrate was put into individual instrumented lysimeters(350L) in July 2015 sown withLolium perenneand placed under natural outdoor conditionsover a three-year period. Experiments in greenhouse under controlled conditions were alsoconducted to understand fine process.In both experiments following parameters were measured:Physical properties: aggregate stability, bulk density, hydraulic conductivity at saturation,porosity; chemical properties: pH, CEC, organic matter content, nutriments contents; bio-logical properties: potential of mineralization of C, microbial and fungal biomasses, plantbiomasses.First results show that after six month, all sediments with or without compost favored plantdevelopment with differences in grass development depending on the sediments properties.Compost addition seems improve micro-organism performance in substrates

Fertility of Technosols constructed with dam sediments for urban greening and land reclamation

International audienceFine sediment accumulates upstream of hydroelectric dams. To ensure that dams can operate properly, part of the sediment has to be dredged and land managed. In parallel, using topsoil from agricultural parcels for urban greening or land restoration is currently controversial because arable surface areas are decreasing. An alternative idea for protecting these natural resources consists in reusing fine dredged sediment to construct multifunctional soils. This agronomic use is only possible if sediment can provide acceptable physical and chemical properties for plant growth

Early structural stability of fine dam sediment in soil construction

International audienceFine sediments accumulate upstream of hydroelectric dams. To ensure that dams can operate properly, most sediments are returned downstream reaches, but a portion of them have to be dredged and land managed. In parallel, using topsoil from agricultural parcels for urban greening is currently controversial because arable surface areas are decreasing. An alternative idea for protecting these natural resources consists in reusing fine dredged sediment to construct functional soils. The agronomical use of fine dredged sediment raises the question of its ability to provide acceptable physical properties for plant growth