• Energy Research

Rapeseed (Brassica napus L.) is a Cd/Zn-accumulator whereas soil conditioners such as biochars may immobilize trace elements. These potentially complementary soil remediation options were trialed, singly and in combination, in a pot experiment with a metal(loid)-contaminated technosol.The technosol [total content in mg kg(-1) Zn 6089, Cd 9.4, Cu 110, and Pb 956] was either amended (2% w/w) or not with a poultry manure-derived biochar. Rapeseed was cultivated for both soil treatments during 24 weeks up to harvest under controlled conditions.Biochar incorporation into the technosol promoted the As, Cd, Cu, Mo, Ni, Pb and Zn solubility. It decreased foliar B, Cu and Mo concentrations, and Mo concentration in stems, pericarps and seeds. But, it did not impact neither the biomass of aerial rapeseed parts (except a decrease for seeds), nor their C (except a decrease for stems), seed fatty acid, seed starch and soluble sugar contents, and antioxidant capacity in both leaves and seeds. Biochar amendment increased the phytoextraction by aerial plant parts for K, P, and S, reduced it for N, Ca, B, Mo, Ni and Se, whereas it remained steady for Mg, Zn, Fe, Mn, Cu, Cd and Co.The biochar incorporation into this technosol did not promote Cd, Cu and Zn phytoextraction by rapeseed and its potential oilseed production, but increased the solubility of several metal(loid)s. Here Zn and Cd concentrations in the soil pore water were decreased by rapeseed, showing the feasibility to strip available soil Zn and Cd in combination with seed production.

AbstractPolluted sites are ubiquitous worldwide but how plant partition their biomass between different organs in this context is unclear. Here, we identified three possible drivers of biomass partitioning in our controlled study along pollution gradients: plant size reduction (pollution effect) combined with allometric scaling between organs; early deficit in root surfaces (pollution effect) inducing a decreased water uptake; increased biomass allocation to roots to compensate for lower soil resource acquisition consistent with the optimal partitioning theory (plant response). A complementary meta-analysis showed variation in biomass partitioning across published studies, with grass and woody species having distinct modifications of their root: shoot ratio. However, the modelling of biomass partitioning drivers showed that single harvest experiments performed in previous studies prevent identifying the main drivers at stake. The proposed distinction between pollution effects and plant response will help to improve our knowledge of plant allocation strategies in the context of pollution.

Contamination of soil with trace elements, such as Cu, is an important risk management issue. A pot experiment was conducted to determine the effects of three biochars and compost on plant growth and the immobilisation of Cu in a contaminated soil from a site formerly used for wood preservation. To assess Cu mobility, amended soils were analysed using leaching tests pre- and post-incubation, and post-growth. Amended and unamended soils were planted with sunflower, and the resulting plant material was assessed for yield and Cu concentration. All amendments significantly reduced leachable Cu compared to the unamended soil, however, the greatest reductions in leachable Cu were associated with the higher biochar application rate. The greatest improvements in plant yields were obtained with the higher application rate of biochar in combination with compost. The results suggest joint biochar and compost amendment reduces Cu mobility and can support biomass production on Cu-contaminated soils.

Abstract Rinsing tanks of crop sprayers produce significant volumes of Cu-rich Bordeaux mixture effluents (BME) that can be treated by rhizofiltration in constructed wetlands (CWs). A pilot-scale CW (6 × 600 L) was developed to jointly rhizofiltrate such BME, produce Cu-rich root mat for ecocatalysis and provide usable shoot biomass with low Cu concentration. Three CW units were unplanted control (Ctrl) while three others were planted with Arundo donax L. ( Ad ) in floating racks. The rhizofiltration was carried out during 30 days in the early growing season. Total Cu concentration in the BME was 4.4 mg Cu L −1 . Copper removal peaked within the 48 first hours after Bordeaux mixture addition in the Ad and Ctrl units (i.e. 92 and 81% respectively). The BME Cu concentration met the requirement for indirect discharge of chemical industry effluents (i.e. 0.5 mg Cu L −1 ) at T 48h (0.4 ± 0.2) and T 21days (0.4 ± 0.1) for the Ad and Ctrl units, respectively. At day 30, in the Ad units, Cu concentration remaining in the water and distributed between A. donax roots, shoots was respectively 3.5, 33 and 0.5% of the initial Cu input. In the Ctrl units, Cu remaining in water was low (7%) and Cu removal (93%) could be partly explained by its immobilization in the Cu-rich biofilm (i.e. 207210 ± 18516 mg Cu kg −1 ) coating the vat wall. Foliar chlorophyll (i.e. a, b and total) and carotenoid contents decreased at day 30 but root and shoot dry weight (DW) yields increased by 23% and 47% per Ad unit, respectively. The shoot Cu concentration remained in the common range (i.e. 3–20 mg Cu kg −1 ) while the root Cu concentration reached 623 ± 140 mg kg −1 allowing 786 mg Cu removal by the root mat. Higher Cu concentration in BME or subsequent repetitions of treatment cycle must be tested to achieve at least 1000 mg Cu kg −1 DW in roots (threshold value for Cu-ecocatalyst) whereas the biofilm role must deserve more attention.

Al oeste de Vitoria-Gasteiz existen zonas industriales cuyo rápido crecimiento provocó la fragmentación ecológicadel territorio circundante. La zona de trabajo (Mendebaldea, 30 ha) se encontraba en estado de abandono y con suelos contaminados antes de la intervención, lo que impedía su uso público y cualquier actividad. Desde el Ayuntamiento de Vitoria-Gasteiz, la Universidad del País Vasco y el Centro de Investigación Neiker-Tecnalia se propuso la restauración del ámbito mediante el empleo de soluciones basadas en la naturaleza para crear una gran infraestructura verde que aportase diversos beneficios ambientales: mitigación del cambio climático, la recuperación de los suelos y la mejora del paisaje. El proyecto se desarrolló en 6 años (10 hectáreas restauradas cada 2 años) incluyendo: sumideros de carbono en suelo y bosques mediante enmiendas orgánicas y plantaciones, balsas artificiales para la biodiversidad, filtros verdes de aguas y red de caminos. Para la descontaminación de suelos se recurrió a la fitorremediación combinando enmiendas y sistemas agroforestales en el marco de los proyectos europeos PhytoSudoe y Phy2Sudoe. Las parcelas de ensayo ejecutadas en dichos proyectos están siendo monitorizadas a largo plazo con participación del público, ofreciendo así un espacio demostrativo para el aprendizaje de estas técnicas de recuperación de suelos. To the west of Vitoria-Gasteiz, there are industrial areas whose rapid growth has led to the ecological fragmentation of the surrounding area. The work area (Mendebaldea, 30 ha) was in a state of abandonment and contaminated soils before the intervention, which prevented its public use and any activity. The Vitoria-Gasteiz City Council, the University of the Basque Country and the Neiker-Tecnalia Research Centre proposed the restoration of the area by using nature-based solutions to create a large green infrastructure that would provide various environmental benefits: climate change mitigation, soil recovery and landscape improvement. The project was developed over 6 years (10 hectares restored every 2 years) including: soil and forest carbon sinks through organic amendments and planting, artificial ponds for biodiversity, green water filters and a network of paths. For soil decontamination, phytoremediation was used combining amendments and agroforestry systems in the framework of the European projects PhytoSudoe and Phy2Sudoe. The test plots implemented in these projects are being monitored in the long term with public participation, thus providing a demonstration area for learning these soil remediation techniques. International audience

Medicago sativa was cultivated at a former harbor facility near Bordeaux (France) to phytomanage a soil contaminated by trace elements (TE) and polycyclic aromatic hydrocarbons (PAH). In parallel, a biotest with Phaseolus vulgaris was carried out on potted soils from 18 sub-sites to assess their phytotoxicity. Total soil TE and PAH concentrations, TE concentrations in the soil pore water, the foliar ionome of M. sativa (at the end of the first growth season) and of Populus nigra growing in situ, the root and shoot biomass and the foliar ionome of P. vulgaris were determined. Despite high total soil TE, soluble TE concentrations were generally low, mainly due to alkaline soil pH (7.8-8.6). Shoot dry weight (DW) yield and foliar ionome of P. vulgaris did not reflect the soil contamination, but its root DW yield decreased at highest soil TE and/or PAH concentrations. Foliar ionomes of M. sativa and P. nigra growing in situ were generally similar to the ones at uncontaminated sites. M. sativa contributed to bioavailable TE stripping by shoot removal (in g ha(-1) harvest(-1)): As 0.9, Cd 0.3, Cr 0.4, Cu 16.1, Ni 2.6, Pb 4, and Zn 134. After 1 year, 72 plant species were identified in the plant community across three subsets: (I) plant community developed on bare soil sowed with M. sativa; (II) plant community developed in unharvested plots dominated by grasses; and (III) plant community developed on unsowed bare soil. The shoot DW yield (in mg ha(-1) harvest(-1)) varied from 1.1 (subset I) to 6.9 (subset II). For subset III, the specific richness was the lowest in plots with the highest phytotoxicity for P. vulgaris.