Simultaneous simulations of uptake in plants and leaching to groundwater of cadmium and lead for arable land amended with compost or farmyard manure.

he water budget of soil, the uptake in plants and the leaching to groundwater of cadmium (Cd) and lead (Pb) were simulated simultaneously using a physiological plant uptake model and a tipping buckets water and solute transport model for soil. Simulations were compared to results from a ten-year experimental field study, where four organic amendments were applied every second year. Predicted concentrations slightly decreased (Cd) or stagnated (Pb) in control soils, but increased in amended soils by about 10% (Cd) and 6% to 18% (Pb). Estimated plant uptake was lower in amended plots, due to an increase of Kd (dry soil to water partition coefficient). Predicted concentrations in plants were close to measured levels in plant residues (straw), but higher than measured concentrations in grains. Initially, Pb was mainly predicted to deposit from air into plants (82% in 1998); the next years, uptake from soil became dominating (30% from air in 2006), because of decreasing levels in air. For Cd, predicted uptake from air into plants was negligible (1–5%)

Structure, Function, and Evolution of the Thiomonas spp. Genome

Bacteria of the Thiomonas genus are ubiquitous in extreme environments, such as arsenic-rich acid mine drainage (AMD). The genome of one of these strains, Thiomonas sp. 3As, was sequenced, annotated, and examined, revealing specific adaptations allowing this bacterium to survive and grow in its highly toxic environment. In order to explore genomic diversity as well as genetic evolution in Thiomonas spp., a comparative genomic hybridization (CGH) approach was used on eight different strains of the Thiomonas genus, including five strains of the same species. Our results suggest that the Thiomonas genome has evolved through the gain or loss of genomic islands and that this evolution is influenced by the specific environmental conditions in which the strains live

Potential use of dam sediment for soil construction in urban greening: Agronomic fertility and soil structuration

International audienceSediments are natural materials coming mainly from watershed soils and rocks erosion. They 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.In order to find a way to reuse the dredged sediments and to preserve natural soil resources, a research program to use sediments, and particularly fine sediments (< 2 mm) as fertile constructed soils in urban green spaces has been developed. Soils built from sediments could be at the same time a way to restore soils functions and ecosystem services in urban areas and a way to prevent natural soil resource destruction andscarcity. Then the potential fertility of such sediments, and particularly their ability to form aggregates is studied.The objective of the present study is to assess the agronomic fertility of dam sediments located in different geological environments by (i) following the early pedogenesis of constructed soil from sediment mixed or not with exogenous organic material and (ii) understanding the involved aggregation dynamics, leading to soil structuration.Four sediments contrasted in texture (from sandy loam to silty loam), mineral composition and initial organic matter content (from 29.1 to 224.3 g kg-1) were studied and compared to an agricultural loam soil used as control. The sediments were dredged from hydropower plant reservoirs, air-dried and sieved with a 40 mm screen to eliminate the coarse organic debris and stones.An in situ experiment started in July 2015 where the four sediments and the control soil were put into 50 individual 350-L containers, sown with ray grass (Lolium perenne) and placed under natural conditions over a 3-yr period. The sediments and the control soil were used alone or mixed with 40% v/v of a green waste compost. The hydraulic properties (water content and soil matric potential) of the substrates were continuously monitored using dataloggers. Moreover, after 6 (April 2016), 12 (October 2016) and 18 (April 2017) months, we measured the evolution of substrates chemical properties (pH, CEC, OM content, nutrients contents), biological properties (C-mineralization potential, microbial C biomass, plant biomassproduction) and physical properties (aggregate stability, bulk density, hydraulic conductivity at saturation (Ks), porosity, available water). The aggregate stability was assessed according to Le Bissonnais (1996) to distinguish three breakdown mechanisms: slaking, mechanical breakdown and microcracking and calculate the mean weight diameter (MWD (mm)) index.Studied sediments presented good initial agronomic properties that allowed plant growth. After 12 months we observed contrasted cumulated plant biomass production, depending on the sediment and on the compost addition, from 522 g DM m-2 to 1637 g DM m-2. These results are mainly explained by the different physical properties of the constructed soils and more precisely by the low aggregate stability (MWD Fourvel G.- 121 - under 1 mm whereas a stable aggregate MWD is above 2 mm) of certain sediments leading to slaking crusts and poor hydrodynamic behavior. The addition of compost in sediment changed the soil structure organization by slightly increasing the soil total porosity by 2.5 % to 13 % v/v, increasing the macroporosity (34 % v/v on average) and decreasing the microporosity (10 % v/v on average).From a chemical point of view, the addition of compost leads to a lower aerial biomass production than for pure sediments after 12 months (from 17% to 89%). These results can be mainly explained by the low nitrogen content of the mixed sediment-compost soil after 6 months (from 2.34 to 16.9 mg N kg-1) and after 12 months (from 0.2 to 11.16 mg N kg-1), leading to nitrogen organization by the microbial communities to the detriment of plant nutrition. Nevertheless, the development of roots is important for all the modalities, which suggests a plant growth potential for next months.In conclusion, the four studied sediments have contrasted aggregation and plant biomass production capacities but all of them showed a potential use for urban greening of high interest. Results on sediment aggregation showed that some sediments are already mature with strong aggregates that resist to external aggressions and that other sediments with lower maturity should be improved with treatment, such as high organic matter content material addition.In situ experiment gave interesting results about aggregation dynamics but the main factors favoring sediment structuration (addition of a high organic matter content material, wetting-drying cycles and microbial community dynamics) need to be investigated during a controlled conditions experiment to understand more accurately the aggregation processes in such constructed soils. In parallel, the remaining 18 months of the in situ experiments should confirm over time physical properties improvement or conservation and they will allow to assess the impact of the structuration on the hydrodynamic behavior of constructed soils (soil water retention and aeration, and soil water drainage)

A decision support tool to reuse fine dam sediments as fertile constructed soils

International audienc

A decision support tool to reuse fine dam sediments as fertile constructed soils

International audienc

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

PCBs uptake by carrots after sludge composts application: worst-case and operational practice in greenhouse conditions

Polychlorinated biphenyls (PCBs) are classified as priority pollutants by American and European environmental agencies. The most important problem with PCBs is their potential for transmission within the food chain. In France, sewage sludge composts which answer to the French norm NFU 44-095 are applied on arable crops and could be applied on market gardening. A study on PCBs behaviour in a sand/soil - plant system was conducted with the reclamation of sewage sludge compost for market gardening in mind. It was carried out in a temperature and humidity regulated greenhouse. Soil, compost and carrot samples were analyzed. PCBs uptake was followed into carrots core, peel and leaves. First, carrot plants (Daucus carota var. Amsterdam Bejo) were grown on sand + PCBs pure substances in order to study transfer pathways. Two pathways by which PCBs can enter a carrot were identified: (1) uptake and transport in oil channels (2) foliar uptake of vapour from surrounding air. Secondly, carrot plants were grown on amended sand and sandy soil under operational practice. No PCBs uptake was observed from the real operational practice experiment. Indeed, PCBs levels in carrots were lower than the limit of quantification in all cases

Capacité d'un sédiment à se substituer à la terre végétale en construction de sol

International audienc

Capacité d'un sédiment à se substituer à la terre végétale en construction de sol

International audienc

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