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Graphical abstract The ability of tobacco (Nicotiana tabacum L. cv. Badischer Geudertheimer) for phytomanaging and remediating soil ecological functions at a contaminated site was assessed with a potted soil series made by fading an uncontaminated sandy soil with a contaminated sandy soil from the Borifer brownfield site, Bordeaux, SW France, at the 0%, 25%, 50%, 75%, and 100% addition rates. Activities of sandblasting and painting with metal-based paints occurred for decades at this urban brownfield, polluting the soil with metal(loid)s and organic contaminants, e.g., polycyclic aromatic hydrocarbons, in addition to past backfilling. Total topsoil metal(loid)s (e.g., 54,700 mg Zn and 5060 mg Cu kg−1) exceeded by seven- to tenfold the background values for French sandy soils, but the soil pH was 7.9, and overall, the 1M NH4NO3 extractable soil fractions of metals were relatively low. Leaf area, water content of shoots, and total chlorophyll (Chl) progressively decreased with the soil contamination, but the Chl fluorescence remained constant near its optimum value. Foliar Cu and Zn concentrations varied from 17.8 ± 4.2 (0%) to 27 ± 5 mg Cu kg−1 (100%) and from 60 ± 15 (0%) to 454 ± 53 mg Zn kg−1 (100%), respectively. Foliar Cd concentration peaked up to 1.74 ± 0.09 mg Cd kg−1, and its bioconcentration factor had the highest value (0.2) among those of the metal(loid)s. Few nutrient concentrations in the aboveground plant parts decreased with the soil contamination, e.g., foliar P concentration from 5972 ± 1026 (0%) to 2861 ± 334 mg kg−1 (100%). Vulnerability to drought-induced embolism (P50) did not differ for the tobacco stems across the soil series, whereas their hydraulic efficiency (Ks) declined significantly with increasing soil contamination. Overall, this tobacco cultivar grew relatively well even in the Borifer soil (100%), keeping its photosynthetic system healthy under stress, and contaminant exposure did not increase the vulnerability of the vascular system to drought. This tobacco had a relevant potential to annually phytoextract a part of the bioavailable soil Zn and Cd, i.e., shoot removals representing here 8.8% for Zn and 43.3% for Cd of their 1M NH4NO3 extractable amount in the potted Borifer soil. Supplementary Information The online version contains supplementary material available at 10.1007/s11356-021-16411-y.

In situ stabilization of Cd, Pb, and Zn in an Austrian agricultural soil contaminated by atmospheric depositions from a smelter plant was assessed with a pine bark chip-derived biochar, alone and in combination with either compost or iron grit. Biochar amendment was also trialed in an uncontaminated soil to detect any detrimental effect. The pot experiment consisted in ten soil treatments (% w/w): untreated contaminated soil (Unt); Unt soil amended with biochar alone (1%: B1; 2.5%: B2.5) and in combination: B1 and B2.5 + 5% compost (B1C and B2.5C), B1 and B2.5 + 1% iron grit (B1Z and B2.5Z); uncontaminated soil (Ctrl); Ctrl soil amended with 1 or 2.5% biochar (CtrlB1, CtrlB2.5). After a 3-month reaction period, the soil pore water (SPW) was sampled in potted soils and dwarf beans were grown for a 2-week period. The SPW Cd, Pb, and Zn concentrations decreased in all amended-contaminated soils. The biochar effects increased with its addition rate and its combination with either compost or iron grit. Shoot Cd and Zn removals by beans were reduced and shoot Cd, Pb, and Zn concentrations decreased to common values in all amended soils except the B1 soil. Decreases in the SPW Cd/Pb/Zn concentrations did not improve the root and shoot yields of plants as compared to the Ctrl soil.

International audience; Brownfield surface is expanding in Europe, but as often abandoned or underused, these areas become refuge for microbial, faunal and floral biodiversity. However, brownfield sites are generally contaminated, likely posing severe environmental risks. At a former wood preservation site contaminated with Cu, we evaluated the efficiency of compost and dolomitic limestone incorporation into the soil, followed by revegetation with Cu-tolerant grassy species, as a phytomanagement option to increase vegetation cover and plant diversity while reducing pollutant linkages. 7 years of phytomanagement enhanced natural revegetation through the improvement of soil physicochemical properties, particularly with compost-based amendments. The compost incorporation increased soil Cu solubility; however, no increment in Cu availability and a reduction in Cu-induced phytotoxicity were observed with the compost. The improved soil nutrient availability and the soil phytotoxicity mitigation in compost-amended soils facilitated over the 7 years the growth of beneficial plant colonists, including leguminous species, which can potentially promote essential soil functions. Soil treatments did not affect Cu uptake and translocation by plants and shoot Cu levels indicated no risk for the food chain. Overall, a long-term phytomanagement combining an initial amendment of compost and dolomitic limestone with the cultivation of Cu-tolerant grassy populations can ameliorate such Cu-contaminated soils, by mitigating risks induced by Cu excess, ultimately allowing the development of a meadow that can provide ecological and economic benefits in terms of ecosystem services.Agrostis capillaris; Agrostis gigantea; Metal pollution; Organic amendments; Phytotoxicity; Phytoremediation

The rapid increase of the world population constantly demands more food production fromagricultural soils. This causes conflicts, since at the same time strong interest arises on novel bio-based products from agriculture, and newperspectives for rural landscapes with their valuable ecosystemservices. Agriculture is in transition to fulfill these demands. In many countries, conventional farming, influenced by post-war food requirements, has largely been transformed into integrated and sustainable farming. However, since it is estimated that agricultural production systems will have to produce food for a global population that might amount to 9.1 billion by 2050 and over 10 billion by the end of the century, we will require an even smarter use of the available land, including fallow and derelict sites. One of the biggest challenges is to reverse non-sustainable management and land degradation. Innovative technologies and principles have to be applied to characterize marginal lands, explore options for remediation and re-establish productivity. With view to the heterogeneity of agricultural lands, it is more than logical to apply specific crop management and production practices according to soil conditions. Cross-fertilizing with conservation agriculture, such a novel approach will provide (1) increased resource use efficiency by producing more with less (ensuring food security), (2) improved product quality, (3) ameliorated nutritional status in food and feed products, (4) increased sustainability, (5) product traceability and (6) minimized negative environmental impacts notably on biodiversity and ecological functions. A sustainable strategy for future agriculture should concentrate on production of food and fodder, before utilizing bulk fractions for emerging bio-based products and convert residual stage products to compost, biochar and bioenergy. The present position paper discusses recent developments to indicate how to unlock the potentials of marginal land. The authors are partners in the FACCE-SURPLUS project INTENSE and gratefully acknowledge financial support by the FACCE-JPI Programme SFS-05-2015: Strategies for crop productivity, stability and quality, grant number 652515.

Gentle remediation options (GRO), i.e. in situ stabilisation, (aided) phytoextraction and (aided) phytostabilisation, were implemented at ten European sites contaminated with trace elements (TE) from various anthropogenic sources: mining, atmospheric fallout, landfill leachates, wood preservatives, dredged-sediments, and dumped wastes. To assess the performance of the GRO options, topsoil was collected from each field trial, potted, and cultivated with lettuce (Lactuca sativa L.) for 48 days. Shoot dry weight (DW) yield, photosynthesis efficiency and major element and TE concentrations in the soil pore water and lettuce shoots were measured.GRO implementation had a limited effect on TE concentrations in the soil pore water, although use of multivariate Co-inertia Analysis revealed a clear amelioration effect in phytomanaged soils. Phytomanagement increased shoot DW yield at all industrial and mine sites, whereas in agricultural soils improvements were produced in one out of five sites. Photosynthesis efficiency was less sensitive than changes in shoot biomass and did not discriminate changes in soil conditions.Based on lettuce shoot DW yield, compost amendment followed by phytoextraction yielded better results than phytostabilisation; moreover shoot ionome data proved that, depending on initial soil conditions, recurrent compost application may be required to maintain crop production with common shoot nutrient concentrations.

International audience; A 2-year pot experiment was carried out to examine the aging effect of biochar (B), alone or combined with iron grit (Z), on Cu stabilization and plant growth in a contaminated soil (964 mg Cu kg− 1) from a wood preservation site. The experiment consisted in 3 soil treatments, either planted with Arundo donax L. (Ad) or Populus nigra L. (Pn): (1) untreated Cu-contaminated soil (Ad, Pn); (2) Unt + 1% (w/w) B (AdB, PnB), and (3) Unt + 1% B + 1% Z (AdBZ, PnBZ). After 22 months, the soil pore water (SPW) was sampled and roots and shoots were harvested. The SPW compositions at 3 and 22 months were compared, showing that the SPW Cu2 + concentration increased again in the PnB and PnBZ soils. Cultivation of A. donax enhanced the dissolved organic matter concentration in the SPW, which decreased its Cu2 + concentration but promoted its total Cu concentration in the Ad and AdB soils. Adding Z with B reduced both SPW Cu2 + and Cu concentrations in the pots cultivated by A. donax and P. nigra as compared to B alone. The B and BZ treatments did not enhance root and shoot yields of both plant species as compared to the Unt soil but their shoot Cu concentrations were in the range of common values.

International audience; Two biochars, a green waste compost and iron grit were used, alone and in combination, as amendment to improvesoil properties and in situ stabilize Cu in a contaminated soil (964 mg Cu kg−1) from a wood preservationsite. The pot experiment consisted in 9 soil treatments (% w/w): untreated Cu-contaminated soil (Unt); Unt soilamended respectively with compost (5%, C), iron grit (1%, Z), pine bark-derived biochar (1%, PB), poultry-manure-derived biochar (1%, AB), PB or AB + C (5%, PBC and ABC), and PB or AB + Z (1%, PBZ and ABZ). After a3-month reaction period, the soil pore water (SPW) was sampled in potted soils and dwarf beans were grownfor a 2-week period. In the SPW, all amendments decreased the Cu2+ concentration, but total Cu concentrationincreased in all AB-amended soils due to high dissolved organic matter (DOM) concentration. No treatment improvedroot and shoot DWyields, which even decreased in the ABC and ABZ treatments. The PBZ treatment decreasedtotal Cu concentration in the SPWwhile reducing the gap with common values for root and shoot yieldsof dwarf bean plants. A field trial is underway before any recommendation for the PB-based treatments.

Background and aims 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. Methods 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. Results 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. Conclusions 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.

During the past decades a number of field trials with gentle remediation options (GRO) have been established on trace elements (TE) contaminated sites throughout Europe. Each research group selects different methods to assess the remediation success making it difficult to compare efficacy between various sites and treatments. This study aimed at selecting a minimum risk assessment battery combining chemical and ecotoxicological assays for assessing and comparing the effectiveness of GRO implemented in seven European case studies. Two test batteries were pre-selected; a chemical one for quantifying TE exposure in untreated soils and GRO-managed soils and a biological one for characterizing soil functionality and ecotoxicity. Soil samples from field studies representing one of the main GROs (phytoextraction in Belgium, Sweden, Germany and Switzerland, aided phytoextraction in France, and aided phytostabilisation or in situ stabilization/phytoexclusion in Poland, France and Austria) were collected and assessed using the selected test batteries. Extractable TE concentrations generally decreased more significantly in soils managed by in situ stabilisation combined with phytoexclusion, phytostabilisation or phytoextraction than in soils only managed with phytoextraction. Pseudo-total TE concentrations did not change in the phytomanaged sites, except for one case, which was attributed to the dilution by the amendments. Among the single chemical extractions, the NH4NO3- and EDTA-extractions showed most frequently the differences in the extracted TE concentrations between the treated and untreated soils, while the most frequent correlations with the biological responses occurred for NH4NO3, followed by NaNO3-extractable TE. Pseudo-total (aqua regia extractable) concentrations showed weak correlation with the biological responses. Out of the bioindicators (plants, earthworms, and nematodes), dwarf beans, especially through root mass, followed by shoot length, and stress enzyme activities, were the most responsive indicators to the soil treatments. Even though the selective chemical extractions did not always show statistically significant changes in TE extractability, dwarf beans and stress enzymes developed a stronger response to the tested GRO options. Generally, the plant growth decreased with higher extractable TE concentrations in soil, while bean stress enzymes reacted in the opposite way, i.e. increased with increasing TE extractability. It is suggested that a minimum risk assessment battery to compare or monitor the sites phytomanaged by GROs might consist of the NH4NO3-extraction and the dwarf bean Plantox test including the stress enzyme activities. Validation of this assessment battery as a potential indicator of successful remediation should be further implemented for a broader range of soils and long-term treatments.