As many contaminated agricultural soils can no longer be used for food crops, lignocellulosic energy crops matter due to their ability to grow on such soils and to produce biomass for biosourced materials and biofuels, thereby reducing the pressure on the limited arable lands. Sorghum bicolor (L.) Moench, can potentially produce a high biomass suitable for producing bioethanol, renewable gasoline, diesel, and sustainable aircraft fuel, despite adverse environmental conditions (e.g. drought, contaminated soils). A 2-year field trial was carried out for the first time in the northern France for assessing sorghum growth on a Cd, Pb and Zn-contaminated agricultural soil amended with humic/fulvic acid, alone and paired with arbuscular mycorrhizal fungi. Sorghum produced on average (in t DW ha−1): 12.4 in year 1 despite experiencing a severe drought season and 15.3 in year 2. Humic/fulvic acids (Lonite 80SP®) and arbuscular mycorrhizal fungi did not significantly act as biostimulants regarding the shoot DW yield and metal uptake of sorghum. The annual shoot Cd, Pb and Zn removals averaged 0.14, 0.20 and 1.97 kg ha−1, respectively. Sorghum cultivation and its metal uptake induced a significant decrease in 0.01M Ca(NO3)2-extractable soil Cd, Pb and Zn concentrations by 95%, 73% and 95%, respectively, in year 2. Soluble and exchangeable soil Cd, Pb and Zn would be progressively depleted in subsequent crops, which should result in lower pollutant linkages and enhanced ecosystem services. This evidenced sorghum as a relevant plant species for phytomanaging the large area (750 ha) with metal-contaminated soil near the former Pb/Zn Metaleurop Nord smelter, amidst ongoing climate change. The potential bioethanol yield of the harvested sorghum biomass was 5589 L ha-1. Thus sorghum would be a promising candidate for bioethanol production, even in this northern French region.

The need of biofuels from biomass, including sustainable aviation fuel, without using agricultural land dedicated to food crops, is in constant demand. Strategies to intensify biomass production using mycorrhizal fungi, biostimulants and their combinations could be solutions for improving the cultivation of lignocellulosic plants but still lack well-established validation on metal-contaminated soils. This study aimed to assess the yield of Miscanthus x giganteus J.M. Greef & Deuter and Cannabis sativa L. grown on a metal-contaminated agricultural soil (11 mg Cd, 536 mg Pb and 955 mg Zn kg-1) amended with biostimulants and/or arbuscular mycorrhizal fungi, and the shoot Cd, Pb and Zn uptake. A pot trial was carried out with soil collected from a field near a former Pb/Zn smelter in France and six treatments: control (C), protein hydrolysate (a mixture of peptides and amino acids, PH), humic/fulvic acids (HFA), arbuscular mycorrhizae fungi (AMF), PH combined with AMF (PHxAMF), and HFA combined with AMF (HFAxAMF). Metal concentrations in the soil pore water (SPW), pH and electrical conductivity were measured over time. Miscanthus and hemp shoots were harvested on day 90. Both PH and PHxAMF treatments increased SPW Cd, Pb, and Zn concentrations (e.g. by 26, 1.9, and 22.9 times for miscanthus and 9.7, 4.7, and 19.3 times for hemp in the PH and PHxAMF treatments as compared to the control one, respectively). This led to phytotoxicity and reduced shoot yield for miscanthus. Conversely, HFA and HFAxAMF treatments decreased SPW Cd and Zn concentrations, increasing shoot yields for hemp and miscanthus. Shoot Cd, Pb, and Zn uptakes peaked for PH and PHxAMF hemp plants (in μg plant-1, Cd: 310-334, Pb: 34-38, and Zn: 232-309 for PHxAMF and PH, respectively), while lowest values occurred for PH miscanthus plants mainly due to low shoot yield. Overall, this study suggested that humic/fulvic acids can be an effective biostimulant for increasing shoot biomass production in a metal-contaminated soil. These results warrant further investigations of the HFAxAMF in field trials.

Pregnant hamsters were treated by topical application of formaldehyde solution on day 8, 9, 10 or 11 of gestation. Fetuses recovered on day 15 were weighed, measured, and examined for teratogenic effects of formaldehyde exposure. The resorption rate was increased in the treated groups, but formaldehyde treatment did not significantly affect weight or length, nor did any malformations which could be related to treatment appear. It was concluded that fetal risk due to maternal topical exposure to formaldehyde is minimal in this model system.

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.

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.

At a former wood preservation site contaminated with Cu, various phytomanagement options have been assessed in the last decade through physicochemical, ecotoxicological and biological assays. In a field trial at this site, phytomanagement with a crop rotation based on tobacco and sunflower, combined with the incorporation of compost and dolomitic limestone, has proved to be efficient in Cu-associated risk mitigation, ecological soil functions recovery and net gain of economic and social benefits. To demonstrate the long-term effectiveness and sustainability of phytomanagement, we assessed here the influence of this remediation option on the diversity, composition and structure of microbial communities over time, through a metabarcoding approach. After 9 years of phytomanagement, no overall effect was identified on microbial diversity; the soil amendments, notably the repeated compost application, led to shifts in soil microbial populations. This phytomanagement option induced changes in the composition of soil microbial communities, promoting the growth of microbial groups belonging to Alphaproteobacteria, many being involved in N cycling. Populations of Nitrososphaeria, which are crucial in nitrification, as well as taxa from phyla Planctomycetacia, Chloroflexi and Gemmatimonadetes, which are tolerant to metal contamination and adapted to oligotrophic soil conditions, decreased in amended phytomanaged plots. Our study provides an insight into population dynamics within soil microbial communities under long-term phytomanagement, in line with the assessment of soil ecological functions and their recovery. (C) 2019 Elsevier B.V. All rights reserved.

Since the emergence of phytoremediation, much research has focused on its development for (i) the removal of metals from soil and/or (ii) the reduction of metal bioavailability, mobility, and ecotoxicity in soil. Here, we review the lights and shades of the two main strategies (i.e., phytoextraction and phytostabilization) currently used for the phytoremediation of metal contaminated soils, irrespective of the level of such contamination. Both strategies face limitations to become successful at commercial scale and, then, often generate skepticism regarding their usefulness. Recent innovative approaches and paradigms are gradually establishing these phytoremediation strategies as suitable options for the management of metal contaminated soils. The combination of these phytotechnologies with a sustainable and profitable site use (a strategy called phytomanagement) grants value to the many benefits that can be obtained during the phytoremediation of metal contaminated sites, such as, for instance, the restoration of important ecosystem services, e.g. nutrient cycling, carbon storage, water flow regulation, erosion control, water purification, fertility maintenance, etc.

Mining sites shelter a characteristic biodiversity with large potential for the phytoremediation of metal contaminated soils. Endophytic plant growth-promoting bacteria were isolated from two metal-(hyper)accumulator plant species growing in a metal contaminated mine soil. After characterizing their plant growth-promoting traits, consortia of putative endophytes were used to carry out an endophyte-assisted phytoextraction experiment using Noccaea caerulescens and Rumex acetosa (singly and in combination) under controlled conditions. We evaluated the influence of endophyte-inoculated plants on soil physicochemical and microbial properties, as well as plant physiological parameters and metal concentrations. Data interpretation through the grouping of soil properties within a set of ecosystem services was also carried out. When grown together, we observed a 41 and 16% increase in the growth of N. caerulescens and R. acetosa plants, respectively, as well as higher values of Zn phytoextraction and soil microbial biomass and functional diversity. Inoculation of the consortia of putative endophytes did not lead to higher values of plant metal uptake, but it improved the plants' physiological status, by increasing the content of chlorophylls and carotenoids by up to 28 and 36%, respectively, indicating a reduction in the stress level of plants. Endophyte-inoculation also stimulated soil microbial communities: higher values of acid phosphatase activity (related to the phosphate solubilising traits of the endophytes), bacterial and fungal abundance, and structural diversity. The positive effects of plant growth and endophyte inoculation on soil properties were reflected in an enhancement of some ecosystem services (biodiversity, nutrient cycling, water flow regulation, water purification and contamination control).

Endophytic plant growth-promoting bacteria (endophytes) were isolated from a variety of (pseudo)metallophytes growing in an abandoned Zn/Pb mine and then characterized according to their plant growth-promoting traits (i.e. ACC deaminase activity, IAA production, siderophore production, phosphate solubilising capacity, metal and salt tolerance and phenotypic characterization). Initially, under growth chamber conditions, an endophyte-assisted aided phytostabilization study was carried out with Festuca rubra plants (native vs. commercial variety) inoculated with a Pseudomonas sp. isolate and cow slurry as organic amendment. The effect of treatments on soil physicochemical and microbial indicators of soil quality, as well as plant physiological parameters and metal concentrations, was assessed. We performed a complementary interpretation of our data through their grouping within a set of ecosystem services. Although the application of cow slurry had the most pronounced effects on soil quality indicators and ecosystem services, the growth of native F. rubra plants reduced soil bioavailability of Cd and Zn by 19 and 22%, respectively, and enhanced several soil microbial parameters. On the other hand, endophyte (Pseudomonas sp.) inoculation improved the physiological status of F. rubra plants by increasing the content of carotenoids, chlorophylls and Fv/Fm by 69, 65 and 37%, respectively, while also increasing the values of several soil microbial parameters. Finally, a consortium of five endophyte isolates was used for an endophyte-assisted aided phytostabilization field experiment, where lower metal concentrations in native excluder plants were found. Nonetheless, the field inoculation of the endophyte consortium had no effect on the biomass of native plants.

•Single- and multi-metal repeated pollution events negatively affected soil quality.•Acid phosphatase was decreased by repeated Cu, Zn and multi-metal treatments.•β-glucosidase activity increased after repeated Pb pollution events.•Fungal gene abundance decreased in all repeated single-metal treatments.•Relative metal bioavailability increased with successive pollution events.

Chemical stabilization is a soil remediation technique based on the incorporation of organic and/or inorganic amendments to metal contaminated soil in order to decrease metal bioavailability and improve soil quality. Consequently, the establishment of follow-up monitoring programmes is essential to ensure the long-term effectiveness of chemical stabilization in terms of both metal bioavailability reduction and soil quality improvement. In this study, three doses (20,40 and 80 t ha(-1)) of a lime-treated sewage sludge, that meets legal standards regarding metal contents, were added to a metalliferous mine soil and a variety of physicochemical and microbial indicators of soil quality were measured over time (immediately before treatment application and one and six months after such application). Soil CaCl2-extractable and plant metal concentrations were also measured. We carried out a complementary interpretation of soil microbial properties through their grouping within a set of ecosystem attributes of ecological relevance: vigour, organization, stability, suppressiveness and redundancy. Sewage sludge addition led to an increase in soil pH, but this beneficial effect was transient. The addition of sewage sludge had a more pronounced effect on parameters used here to estimate soil vigour (dehydrogenase activity, basal and substrate-induced respiration). On the contrary, the addition of sewage sludge did not significantly alter the composition of soil microbial communities, as reflected by PCR-DGGE data. Chemical stabilization was only partly successful: it did improve soil quality but the expected reduction in soil metal bioavailability (as reflected by the values of CaCl2-extractable metal concentration) was clearly observed only for Cd (not for Pb or Zn); however, SL addition led to a significant reduction in shoot metal concentration for the three metals under study. The assessment of soil quality at the attribute level has proven useful for the interpretation of the effect of chemical stabilization on soil functioning. (C) 2013 Elsevier B.V. All rights reserved.