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10 páginas, 4 figuras, 1 tabla, Lindane and other 1,2,3,4,5,6-hexachlorocyclohexane (HCH) isomers are persistent organic pollutants highly hydrophobic, which hampers their availability and biodegradation. This work aimed at (i) investigating genes encoding enzymes involved in HCH degradation in the bacterium Sphingobium sp. D4, (ii) selecting strains, from a collection of environmental isolates, able to mobilize HCHs from contaminated soil, and (iii) analysing the biodegradation of HCHs by strain D4 in co-culture with HCH-mobilizing strains or when cultivated with root exudates. Fragments of the same size and similar sequence to linA and linB genes were successfully amplified. Two isolates, Streptomyces sp. M7 and Rhodococcus erythropolis ET54b able to produce emulsifiers and to mobilize HCH isomers from soil were selected. Biodegradation of HCH isomers by strain D4 was enhanced when co-inoculated with HCH mobilizing strains or when cultivated with root exudates. The degrader strain D4 was able to decompose very efficiently HCHs isomers, reducing their concentration in soil slurries by more than 95% (from an average initial amount of 50 ± 8 mg HCH kg soil) in 9 days. The combination of HCH-degrading and HCH-mobilizing strains can be considered a promising inoculum for future soil bioremediation studies using bioaugmentation techniques or in combination with plants in rhizodegradation assays., The research was supported by Ministerio de Economía y Competitividad (Spain) the FEDER program of the EU (CTM2012–39904- C02–01), the Interreg SUDOE Programme (PhytoSUDOE and Phy2SUDOE projects) and the Agencia Nacional de Promocion ´Científica y Tecnologica´ (Argentina, PICT 2018–2706).

Farmyard manure, an amendment traditionally used for improving the fertility of sandy soils in arid climates, is becoming scarce and expensive. Its shortage makes it necessary to evaluate, at field scale, the suitability and medium-term performance of other cheap, highly available substitutes. A field trial was established to analyze the effects of a single application of three organic residues on barley yield and nutrient uptake and selected soil properties after two consecutive harvests. Municipal solid waste compost (MSWC), sewage sludge compost (SSC) and farmyard manure (FYM) were tested at rates of 0, 20, 40 and 60 t ha−1. Adding all three organic amendments increased organic matter, cation exchange capacity and available P, Ca, Mg and K in the soil, the grain yield (up to 51%), and the barley plants’ nutrient contents. After the second harvest, a positive residual effect of the amendment was observed in plant yield (up to 77%) and nutrient contents. MSWC and SSC induced slight increases on the extractable fractions (BCR protocol) of Co, Cu and Ni, relative to the unamended soil. The results demonstrate the positive immediate and residual effect of the amendments evaluated as fertilizers for agricultural purposes., We are grateful to the staff at the Eremology and Combating Desertification Laboratory, IRA at the Arid Regions Institute (IRA) (Medenine) (LR16IRA01)

The diversity of cultivable bacteria associated with plants from phytomanaged soils with mixed trace metal (TM) and polycyclic aromatic hydrocarbon (PAH) contamination in Pierrelaye (France) was evaluated. The emphasis was on the cultivable bacterial community since the overall objective is to obtain inoculants to improve the remediation of this type of contaminated site. Root endophytic and rhizosphere soil bacterial counts were determined, and isolates were pooled by amplified rDNA restriction analysis and identified by 16S rDNA sequencing. Isolates were further characterized for the production of plant growth-promoting (PGP) substances, and resistance to TM. The selected strains were evaluated for their ability to degrade PAHs. The potential of cell-free microbial supernatant to increase the mobilisation of PAHs from the polluted soil of Pierrelaye was also evaluated. Proteobacteria and Actinobacteria dominated the collection of isolates, and differences in taxonomic diversity were observed between plant species (Populus or Zea mays) and depending on the remediation treatment (Populus inoculation with mycorrhizae or Populus intercropping with Alnus). The majority of isolates exhibited at least one of the tested PGP traits, as well as resistance to more than one TM. Several rhizosphere, endophyte and even one bulk soil isolate showed high rates of fluoranthene and pyrene reduction. The endophyte Rhizobium strain MR28 isolated from maize and degrading pyrene produced bioemulsifying molecules capable of improving the availability of PAHs from the soil of Pierrelaye. A selection of the most interesting strains was made for further re-inoculation experiments in order to assess their potential in rhizoremediation processes., This work was supported by the Agence Nationale de la Recherche (ANR) under the PRECODD (ANR-06-ECOT-O15-01- PHYTOPOP) and the Blanc International (ANR-10-INTB-1703-01- BIOFILTREE) projects.

Phytomining can be limited by low biomass productivity by plants or limited availability of soil metals. Ongoing research attempts to overcome these potential constraints and to make phytomining a successful commercial technique in the recovery of metals from polluted or naturally metal-rich soil by (hyper) accumulating plants. Recently, the benefits of combining phytoremediation with bioremediation, which uses beneficial microorganisms such as endophytic or rhizosphere bacteria and fungi for metal removal from soils, have been demonstrated. Metal-resistant microorganisms play an important role in enhancing plant survival and growth in these soils by alleviating metal toxicity and supplying nutrients. Furthermore, these beneficial microorganisms are able to enhance metal bioavailability in the rhizosphere of plants. An increase in plant growth and metal uptake increases the effectiveness of phytoremediation processes coupled with bioremediation. Here, we discuss how abiotic factors, such as the presence of metals in polluted sites or in naturally metal-rich (ultramafic) soils modulate activities of soil microbial communities. Then we introduce the concept of microbe-assisted phytomining and underline the role of plant-associated microorganisms in metal bioavailability and uptake by host plants that has attracted growing interest over the last decade. Finally, we present various techniques, including phenotypic, genotypic, and metagenomic approaches, which allow for characterizing soil microbial community structure and diversity and endophytic community in polluted or naturally metal-rich soils.

Initial experiments using Mediterranean Ni-hyperaccumulator plants for the purpose of phytomining were carried out in the 1990s. In order to meet commercial phytoextraction requirements, a technology has been developed using hyperaccumulator species with adapted intensive agronomic practices on naturally Ni-rich soils. Ultramafic soils in the Balkans and other parts of Europe display a great variability in Ni concentrations and available Ni levels. In Albania, Vertisols are currently being used for low-productivity agriculture (pasture or arable land) on which phytomining could be included in cropping practices. In northwestern Greece (Pindus and Vourinos mountain regions), agricultural soils may occur on ultramafic Cambisols. In Spain and Austria, these soils are much more erratically distributed and are seldom used for crops and pastures. In the Balkans, Odontarrhena chalcidica (synonym Alyssum murale) occurs widely on these ultramafic soils and is a spontaneous weed that grows among other crops. Field studies across Europe have now been carried out outside Mediterranean areas and have evaluated the Ni-hyperaccumulator O. chalcidica, as well as two other species native to northwestern Greece (Bornmuellera emarginata and B. tymphaea). At each site, local hyperaccumulator plants were tested for comparison (Noccaea goesingense in Austria and Odontarrhena serpyllifolia s.l. in Spain), in the context of two recent EUfunded projects (by Agronickel and LIFEAgromine). Soil and crop management practices are being developed in order to optimize the Ni agromining process. Field studies have evaluated the potential benefits of fertilization regimes, crop selection, and cropping patterns (introducing agroecological practices), and bioaugmentation using plant-associated microorganisms.

Different definitions for the concepts of information, information transfer, i.e. communication and its effect and efficiency of false, but also correct information, especially from the environmental sector, are given. "THE TEN ECOLOGICAL COMMANDMENTS" developed by Menke-Glückert at the end of the 1960s and the 9th commandment "Do not pollute information", in particular, are examined in more detail and understood practically as a currently unchanging law in our existing world societies. The "Ethics Consensus", derived from "THE TEN ECOLOGICAL COMMANDMENTS" and developed by Markert at the end of the 1990s, reflects both theoretical and practical levels of action that many people in our highly diverse world societies can support. From a scientific point of view, this article deals in particular with the so-called B & B technologies, i.e. bioindication and biomonitoring of chemical elements, their chemical speciation as well as organic substances.In particular, B & B technologies, which deal with the biological detection of atmospheric deposition of chemical substances on a regional, national and international level, are taken into account. From both an academic and a practical point of view, mosses have prevailed here in the last decades in addition to lichens. The use of mosses is a major focus of international air monitoring, especially in Europe. Furthermore, the phytoremediation of chemical substances in water, soil and air is described as a biological and sustainable biological process, which does not "yet" have the full scope as it is used in bioindication and biomonitoring, as shown in the example of mosses. However, the phytoremediation considers to be an excellent tool to have the leading role in the sustainable pollutant "fight". In the future qualitative and quantitative approaches have been further on developed to fit scientifically and practically B&B Technologies as well the different form of phytotechnological approaches. Finally, the example of lithium, which is optionally derived from the Biological System of Chemical Elements (BSCE), becomes a chemical example that the administration of lithium to ALL mentally conditioned diseases such as manic depression up to smoking of cigarettes become one of the most valuable service for the recovery of our human society on a global level.As a conclusion of these tremendous effects of lithium can be considered: pulled out, in order to make clear that only this chemical element beside a psychiatric care and the involvement of family members, friends, physicians, psychologists and psychiatrists. In addition it is a must, that there is a strong relationship in between patient, psychiatrist(s) and strongly related persons to the patient. First an intensive information transfer via communication has to be guaranteed. After it a psychological support by doctors and, only if it seems necessary Lithium is to be given in a patient specific dose.Keywords. Bioindication, Biomonitoring, B&B Technology, Phytotechnology, The Biological System of Chemical Elements (BSCE), Lithium. Neurological diseases, Functional Food.

The role of endophytic fungi isolated from different populations of European Ni hyperaccumulators was investigated in regard to the microorganisms' ability to enhance the hyperaccumulation of Ni in Noccaea caerulescens. Effects of particular species of endophytic fungi on adaptation of N. caerulescens to excess Ni were tested by co-cultivation with single strains of the fungi. Seven of these had a positive effect on plant biomass production, whereas two of the tested species inhibited plant growth; biomass production of inoculated plants was significantly different compared to non-inoculated control. Inoculation with six fungal strains: Embellisia thlaspis, Pyrenochaeta cava, Phomopsis columnaris, Plectosphaerella cucumerina, Cladosporium cladosporioides and Alternaria sp. stimulated the plant to uptake and accumulate more Ni in both roots and shoots, compared to non-inoculated control. P. columnaris was isolated from all plant species sampled. Strains isolated from Noccaea caerulescens and Noccaea goesingensis increased Ni root and shoot accumulation of their native hosts (compared to non-inoculated control). Inoculation of different populations of Noccaea with P. columnaris of foreign origin did not cause its host to accumulate more Ni, with the exception of the Ni-unadapted ecotype of N. goesingensis. Inoculation with P. columnaris from N. caerulescens significantly improved Ni uptake, but the effect of the fungus was not as prominent as in the case of N. caerulescens. By comparing the transcriptomes of N. caerulescens and N. goesingensis from Flatz inoculated with P. columnaris, we showed that enhanced uptake and accumulation of Ni in the plants is accompanied by an upregulation of several genes mainly involved in plant stress protection and metal uptake and compartmentation.

To investigate the effects of fertilization and bacterial inoculation on the growth, health and Ni phytoextraction capacity of three Ni-hyperaccumulators, Odontarrhena bracteata, O. inflata and O. serpyllifolia. Plants were grown for three months in serpentine soil fertilized with inorganic NPK or amended with cow manure and inoculated with five rhizobacterial strains (previously isolated from O. serpyllifolia). Shoot and root dry weight (DW) yields, Ni accumulation and removal, nutritive status and stress indicators were determined. Plants grown in manure-amended soil showed significantly higher DW yields, improved nutritive status and higher total Ni phytoextracted. Some bacterial inoculants enhanced Ni removal due to the stimulation in growth and/or increase in shoot Ni concentration but this depended on the plant species, soil type and inoculant. Pseudoarthrobacter oxydans strain SBA82 enhanced shoot DW yield of all three Odontarrhena spp. in at least one soil type. Paenarthrobacter sp. strain LA44 and Stenotrophomonas sp. strain MA98 promoted growth of O. serpyllifolia and O. bracteata. Inoculated plants showing growth promotion presented lower activities of antioxidative enzymes, and concentrations of malondialdehyde (MDA) and H2O2, indicating a protective effect of these inoculants on the plants. Rhizobacterial inoculants applied in combination with manure can improve plant growth and health, and Ni phytoextraction, in some hyperaccumulating Odontarrhena spp.

To improve the efficiency of Ni phytoextraction, the metal hyperaccumulator N. goesingensis was subject to treatment with a combination of a Ni uptake stimulating microorganism and the commercially available, IAA- based biostimulating seaweed extract - Kelpak. Additionally, we compared the plant growth promoting and Ni uptake capabilities of the two biofertilizers. Treatment with the Kelpak alone had no significant effect on plant growth or Ni accumulation. Inoculation of N. goesingensis with Phomopsis columnaris significantly improved the biomass of the hyperaccumulating plant and Ni yield per plant and improved several plant biometric features such as fresh and dry weight and several others related to leaf and root size. However, the combination of the two treatments yielded the best results; plants treated with the two growth promoting agents yielded 85% more biomass compared to not treated plants and accumulated 48% more Ni per plant. To verify plant inoculation with the fungus we generated a GFP expressing strain of P. columnaris and visualized the fungus in both plant leaves and roots. To trace the development of the fungus in planta and to evaluate the effect of biostimulant treatment on mycelium development fungal translational elongation factor 1α (tef1α) DNA was quantified with qPCR. Upon biofertilizer the abundance P. columnaris in plant leaves increased nearly 5-fold. The utilization of plant growth stimulating microorganisms, endophytic fungi in particular, can significantly improve Ni phytoextraction in hyperaccumulator N. goesingensis., This work was supported by The National Centre for Research and Development, Poland, project AGRONICKEL (contract No. FACCE SURPLUS/I/AGRONICKEL/02/2016).

Bioremediation of polluted soils is a promising technique with low environmental impact, which uses soil organisms to degrade soil contaminants. In this study, 19 bacterial strains isolated from a diesel-contaminated soil were screened for their diesel-degrading potential, biosurfactant (BS) production, and biofilm formation abilities, all desirable characteristics when selecting strains for re-inoculation into hydrocarbon- contaminated soils. Diesel-degradation rates were determined in vitro in minimal medium with diesel as the sole carbon source. The capacity to degrade diesel range organics (DROs) of strains SPG23 (Arthobacter sp.) and PF1 (Acinetobacter oleivorans) reached 17-26% of total DROs after 10 days, and 90% for strain GK2 (Acinetobacter calcoaceticus). The amount and rate of alkane degradation decreased significantly with increasing carbon number for strains SPG23 and PF1. Strain GK2, which produced BSs and biofilms, exhibited a greater extent, and faster rate of alkane degradation compared to SPG23 and PF1. Based on the outcomes of degradation experiments, in addition to BS production, biofilm formation capacities, and previous genome characterizations, strain GK2 is a promising candidate for microbial-assisted phytoremediation of diesel-contaminated soils. These results are of particular interest to select suitable strains for bioremediation, not only presenting high diesel-degradation rates, but also other characteristics which could improve rhizosphere colonization. This research was supported by ERDF Interreg Sudoe Program (PhytoSU-DOE-SOE1/P5/E0189); by the Galician government Agrupacion Estratexica CRETUS Strategic Partnership (AGRUP2015/02); and by the University of Hasselt (BOF project 06G02 and Methusalem project 08M03VGRJ).

Soils from arid and semi-arid ecosystems are generally very low in organic matter content, poor in nutrients and typically with sandy texture. The application of different organic amendments has been proposed as an adequate approach to improve the quality of these soils for their use in agriculture. The use of organic wastes of different origins (agricultural, industrial, urban, etc.) as soil amendments has a dual goal: i) improving soil fertility and quality, ii) reducing the environmental problem that poses the disposal of these residues. However, despite of the beneficial effects of these residues, undesirable changes may also occur in agricultural soils after their addition. For example, the presence of various pollutants of anthropogenic origin in organic wastes may cause adverse effects on soil microbiota. Generally, the arid and semi-arid soils of Tunisia are well characterised. However, the use of organic amendments to improve the quality of these soils has been scarcely investigated. Soil biochemical properties, and specifically soil enzyme activities, have been often used to investigate the impact of different amendments on soil quality, because they are highly sensitive to human or environmental perturbations. In this work, the results of a field trial established for investigating the effectiveness of three organic residues (composted municipal solid waste, composted sewage sludge and farmyard manure) to improve the quality of one agricultural soil from Tunisia are reported. The soil had a sandy texture, alkaline pH (pH 8.3) and was very poor in organic matter (0.21 and 0.03% of total C and N, respectively). Each of the organic residues was applied in triplicate at three different doses in nine sub-plots randomly distributed; three untreated sub-plots were also established for comparison. One, 6 and 18 months after the soil amendments, surface (0-20 cm) soil samples were collected from all the treated and untreated subplots. The soil samples were analysed for the enzyme activities of four hydrolases involved in the C, N, P and S cycles and for an oxidoreductase (dehydrogenase) reflecting soil microbial activity. All the soil samples were also characterised for their main physicochemical properties. Addition of the three organic amendments induced slight increases of the total organic carbon and nutrients content; however, the improvements observed were generally not related with the amount of applied residue. The activity of the enzymes increased after the application of the three residues, but these increments were not correlated with the dose of residue and did not consistently varied with the time elapsed after residue application. Generally, the highest increases in absolute values were observed for manure-amended soils, but when the activities were considered in relation to the total organic C of the soils, the sludge amended soils appeared to be the most favoured. The results are discussed with regards to their implications for improving very poor agricultural soils., This research was financially supported by the Xunta de Galicia (IN607A 2017/6), UE Interreg-Sudoe program (SOE1/P5/E0189) and the Tunisian Ministry of Higher Education and Scientific Research. H. Oueriemmi thanks founding support of Erasmus plus program for her stay at the IIAG-CSIC.

Our aim was to assess the efficacy of four different bioremediation strategies applied to soil treated with urban sediments for alleviating soil phytotoxicity (examined using Lepidium sativum), by removing polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), and mitigating the toxic effect on plants by the applied sediment: (1) Natural attenuation, (2) phytoremediation with the use of two plants Tagetes patula L. and Festuca arundinacea, (3) rhizobacterial inoculation with Massilia niastensis p87 and Streptomyces costaricanus RP92 strains, (4) rhizobacteria-assisted phytoremediation with both plants and strains. The applied sediment had a positive influence on L. sativum growth (90% higher than in the unamended soil), mostly due to its high content of nutrients, mainly Ca and Fe, which immobilize pollutants. The positive effect of sediments continued for up to 10-week duration of the experiment; however, the rhizobacterial inoculated samples were characterized by higher growth of L. sativum. The application of rhizobacteria-assisted phytoremediation further increased the growth of L. sativum, and was also found to improve the efficiency of PCDD/PCDF removal, resulting in a maximum 44% reduction of its content. This strategy also alleviated the negative impact of urban sediments on T. patula and F. arundinacea biomass, and had a beneficial effect on protein and chlorophyll content in the studied plants., The pot experiment was a part of Greenland project (FP7-KBBE-266124) financed by the European Commission under the Seventh Framework Programme for Research; the research was also conducted as a part of the Project IP2014 049273 financed by the Ministry of Science and Higher Education programme under the name ‘‘Iuventus Plus’’ for the years 2015–2017.

Plants and their associated microbiota can have a significant impact on the behaviour of soil contaminants. Particularly, root exudation is one of the most important plant-associated processes in this respect, as it may have a substantial effect on the bioavailability of soil contaminants, specially of hydrophobic contaminants strongly sorbed by soil. The aim of the present study was to evaluate the effect of root exudates (natural and artificial) on the desorption of α-, β-, δ- and γ-isomers of hexachlorocyclohexane (HCH) from contaminated soil, using batch experiments. Natural root exudates were obtained from Holcus lanatus plants growing in the same (contaminated) area. Fifteen compounds (mainly organic acids and phenolic compounds) usually found in root exudates were also tested, individually or as mixtures (1 and 10 mM). Both natural and artificial exudates favoured the mobilization of sorbed HCH in soil. The effect was highly significant for α-, β- and γ-HCH isomers, for which the desorption rates increased by 23.0, 26.8 and 15.5% in the presence of natural root exudates and by 40.1, 25.9 and 25.6% in the presence of the artificial mixture (at 10 mM). The δ-HCH desorption rates increased by less than 10%. The effect of individual exudate components was very variable, but increased with the carbon content, reflecting the significance of hydrophobic interactions between the exudates and HCH molecules in the desorption of these last from soil. These findings indicate that plants may significantly influence the bioavailability of persistent contaminants, with major implications for improving phyto- and bioremediation procedures., Dr Balseiro-Romero was in receipt of a postdoctoral fellowship(Programa de axudas á etapa posdoutoral; ED481B 2017/073) by the Consellería de Cultura, Educación e Ordenación Universitaria(Xunta de Galicia, Spain). M. Balseiro-Romero and C. Monterrosobelong to the Galician Competitive Research Group GRC-ED431C2018/12 and to the CRETUS Strategic Partnership (ED431E 2018/01). All of these programmes are co-funded by ERDF (UE).

Bioremediation is a soil clean-up technique which exploits the metabolic capacity of microorganisms to degrade soil contaminants. A model was developed to simulate the ex situ bioremediation of a diesel-contaminated soil in a bio-slurry reactor inoculated with a diesel-degrading bacterial strain. Mass transfer processes involving desorption of diesel from soil to water and volatilization of diesel from water, and biodegradation by the bacterial inoculant were included in the model by using Weibull sigmoid kinetics and logistic/Monod kinetics respectively. Model parameters were estimated in batch-based abiotic and biodegradation experiments. Sensitivity analysis revealed the importance of maintaining a high bacterial density in the system for maximum bioremediation efficiency. The model was validated using a pilot bioreactor monitored for 528 h, which removed almost 90% of the diesel present in the system. The results revealed the capacity of the model to predict the bioremediation efficiency under different scenarios by adapting the input parameters to each system.

The impact of contaminated bottom sediments on plant growth and soil enzyme activities was evaluated in a greenhouse pot study. The sediments were moderately contaminated with zinc and heavily contaminated with polycyclic aromatic hydrocarbons and polychlorinated dibenzo-p-dioxins and furans. The sediments were mixed with soil and planted with either Festuca arundinacea or Tagetes patula. The capacity of two rhizobacterial strains (Massilia niastensis P87 and Streptomyces costaricanus RP92), previously isolated from contaminated soils, to improve plant growth under the chemical stress was tested. Application of sediments to soil was severely phytotoxic to T. patula and mildly to F. arundinacea. On the other hand, the addition of sediments enhanced the soil enzymatic activity. Inoculation with both bacterial strains significantly increased shoot (up to 2.4-fold) and root (up to 3.4-fold) biomass of T. patula. The study revealed that the selected plant growth-promoting bacterial strains were able to alleviate phytotoxicity of bottom sediments to T. patula resulting from the complex character of the contamination.

In Galicia (NW Spain), ultramafic outcrops represent approximately 5% of the land surface and several mining and quarrying activities take place in these areas. Resulting mine-soils present physical, chemical and biological properties which limit plant growth and soil functioning. Nickel phytomining, an eco-friendly strategy for metal recovery, could potentially be applied to these areas. A one-year field experiment was carried out in a serpentine quarry to evaluate the performance of four Ni hyperaccumulating plant species, comparing the Mediterranean spp. Bornmuellera emarginata and Odontarrhena muralis with the native populations of Noccaea caerulescens and Odontarrhena serpyllifolia. Field plots were established and amended with inorganic NPK fertilisers or composted sewage sludge. Three replicate plots (4 m2) were planted for each plant species and fertilisation regime. Amending with compost reduced pH from 7.8 to 6.6, and increased soil cation exchange capacity (CEC), nutrient concentrations and Ni availability. Moreover, compost-amended mine-soil presented higher microbial density and activity, parameters which were further stimulated by plant growth. Plant biomass production of all plant species was significantly higher in compost-amended soils than that after NPK fertilisation, being most pronounced for O. muralis and B. emarginata. Despite the reduction in shoot Ni concentrations observed in plants (except O. muralis) grown in compost-amended plots, the increased biomass production led to significantly higher Ni yields (in kg ha−1) in B. emarginata (2.9), N. caerulescens (1.9) and O. muralis (2.3). All plant species were able to establish and grow in the mine-soil (with the Mediterranean species showing a higher capacity for adaptation) and to generate moderate Ni yields. Nonetheless, the results highlight the need for further optimisation in order to enhance the Ni phytoextraction efficiency. Finally, the improvement in soil quality after compost amendment and plant growth support the idea that phytomining systems can be effective approaches for the rehabilitation of soils affected by quarrying operations after mine closure.

Phytomining techniques based on metal-hyperaccumulating plants can be implemented in serpentine quarry wastes for Ni recovery. However, strategies must be developed to overcome the unfavourable plant growth conditions that these substrates present and to optimize Ni yields. In this study, the Ni hyperaccumulators Alyssum serpyllifolium, Alyssum inflatum, and Alyssum bracteatum were evaluated for their Ni phytoextraction efficiency from quarry tailings. Effects of two organic amendments, composted municipal sewage sludge and cow manure, on plant growth and physiological status and Ni removal were determined. Organic amendments were incorporated at two addition rates (5% and 20% w/w). The best-performing hyperaccumulators were A. inflatum and A. serpyllifolium. Organic amendments improved plant biomass production, photosynthetic efficiency and nutrition, but reduced shoot Ni concentrations. However, the stimulation in biomass resulted in significantly enhanced Ni yields. The most promising results were found using low addition rates and after manure incorporation.

Less than half of anthropogenic carbon dioxide emissions remain in the atmosphere. While carbon balance models imply large carbon uptake in tropical forests, direct on-the-ground observations are still lacking in Southeast Asia. Here, using long-term plot monitoring records of up to half a century, we find that intact forests in Borneo gained 0.43 Mg C ha−1 per year (95% CI 0.14–0.72, mean period 1988–2010) in above-ground live biomass carbon. These results closely match those from African and Amazonian plot networks, suggesting that the world’s remaining intact tropical forests are now en masse out-of-equilibrium. Although both pan-tropical and long-term, the sink in remaining intact forests appears vulnerable to climate and land use changes. Across Borneo the 1997–1998 El Niño drought temporarily halted the carbon sink by increasing tree mortality, while fragmentation persistently offset the sink and turned many edge-affected forests into a carbon source to the atmosphere., The existence of a pan-tropical forest carbon sink remains uncertain due to the lack of data from Asia. Here, using direct on-the-ground observations, the authors confirm remaining intact forests in Borneo have provided a long-term carbon sink, but carbon net gains are vulnerable to drought and edge effects.

International audience; Nickel (Ni) agromining of ultramafic soils has been proposed as an eco-friendly option for metal recovery, which can also improve the fertility and quality of these low productive soils. The selection of adequate plant species and the analysis of their performance under the different climatic conditions are of interest for optimising the process and evaluating its full viability. A one-year field experiment was carried out to evaluate the viability of the two Ni-hyperaccumulating Mediterranean species, Alyssum murale and Leptoplax emarginata, for agromining purposes in ultramafic soils under a humid-temperate climate. Field plots of 50 m(2) were established and the soil was fertilised with gypsum and inorganic NPK fertilisers prior to cropping. Alyssum murale produced a slightly higher Ni yield than L. emarginata, but Ni bioaccumulation was dependent on the plant phenological stage for both species, being maximal at mid-flowering (4.2 and 3.0 kg Ni ha(-1), respectively). In both species, Ni was mainly stored in the leaves, especially in leaves of vegetative stems, but also in flowers and fruits in the case of L. emarginata. The main contributors to Ni yield of A. murale were flowering stems and their leaves, while for L. emarginata they were flowering stems and fruits. Implementing the agromining system increased soil nutrient availability, and modified microbial community structure and metabolic activity (due to fertilisation and plant root activity). The soil bacterial communities were dominated by Proteobacteria, Actinobacteria, Acidobacteria and Chloroflexi, and the agromining crops modified the relative abundance of some phyla (increasing Proteobacteria, Bacteroidetes and Nitrospirae and reducing Acidobacteria and Planctomycetes). Cultivating A. murale increased the densities of total culturable bacteria, while L. emarginata selected Ni-tolerant bacteria in its rhizosphere. In summary, both species showed great potential for their use in Ni agromining systems, although optimising soil and crop management practices could improve the phytoextraction efficiency. (C) 2018 Elsevier B.V. All rights reserved.

Soil is an essential, nonrenewable resource providing vital supporting, regulating, provisioning, and cultural ecosystem services. Contamination of soils by inorganic and organic pollutants can result in a decline in soil quality and its capability to support ecosystem functions. Remediation strategies can assist in halting or reversing the loss of soil quality, thus restoring its functionality, with attendant consequences to the bioavailability of contaminants. This chapter will focus on practical current soil remediation techniques including combinations (1) soil amendments (adding materials to soils to improve their quality) and (2) phytoremediation (remediation of soils using plants). Case study examples will be presented and discussed in relation to these remediation techniques, specifically focusing on environmental risk reduction. The main environmental policies and sustainable management systems for soil protection existing at national and international levels will also be briefly reviewed in order to emphasis the need for a common soil policy framework.

Most of the research dedicated to agromining has focused on cultivating a single hyperaccumulator plant, although plant diversity has been shown to positively modify soil characteristics. Hence, we compared the effect of cropping a nickel-hyperaccumulator Alyssum murale with a legume (Vicia sativa) to A. murale's mono-culture, on the bacterial diversity and physico-chemical characteristics of an ultramafic soil. A pot experiment with 5 replicates was conducted in controlled conditions for 11 months. The treatments studied were: co-cropping and rotation vs. mineral fertilization controls and bare soil. The introduction of legumes induced a clearly positive effect on the soil's microbial biomass carbon and nitrogen. Arylsulfatase and urease activities tended to be enhanced in the co-cropping and rotation treatments and to be lessened in the mineral fertilization treatments. However, β-glucosidase and phosphatase activities were seen to decrease when legumes were used. Our results showed that the rotation treatment induced a higher organic matter content than the fertilized control did. Actinobacteria was the most-represented bacterial phyla and had lower relative abundance in treatments associating legumes. Conversely, the relative abundance of Acidobacteria and Gemmatimonadetes phyla increased but not significantly in treatments with legumes. The relative abundance of Chloroflexi phylum was shown to be significantly higher for the fertilized rotation control. The relative abundance of β-Proteobacteria subphylum increased but not significantly in treatments with legumes. NMDS analysis showed a clear separation between planted treatments and bare soil and between co-cropping and rotation and fertilized controls. Shannon index showed reduction in microbial diversity that was mainly due to chemical inputs in the soil. This study showed that these new cropping systems influenced both the bacterial diversity and the physico-chemical characteristics of an ultramafic soil. In addition, this study provides evidence that mineral fertilization can negatively impact bacterial communities and some of their functions linked to biogeochemical cycles.

Agromining aims to rehabilitate contaminated or natural metal-rich soils (ultramafic soils) by extracting metals of high economic importance, such as nickel (Ni), using hyperaccumulator plants and then to recover these metals for industrial purposes. Ultramafic soils are characterized by low fertility levels and this can limit yields of hyperaccumulators and metal phytoextraction. Here, we characterized the potential benefits for phytoextraction efficiency of co-cropping two plants: a Ni-hyperaccumulator (Alyssum murale; Brassicaceae) and a legume (Vicia sativa; Fabaceae). A field experiment with 3 replicates was set up in an ultramafic zone in North West Spain. Four treatments were tested: co-cropping (“Co”), fertilized mono-culture (“FMo”), non-fertilized mono-culture (“NFMo”) and bulk soil (“BS”). “FMo” and “Co” treatments increased the biomass yields of A. murale by 453% and 417% respectively, compared to “NFMo”. “Co” treatment generated 35% and 493% higher Ni-yields than “FMo” and “NFMo”, respectively. Most of the microbial analyses showed that introducing V. sativa (“Co” treatment) into the cropping system had beneficial effects. “Co” treatment significantly modified the phenotypical structure of bacterial communities and raise the relative abundance of the phylum Bacteroidetes and reduced that of Actinobacteria. In addition, non-metric multidimensional scaling analysis of the operational taxonomic units (OTUs) showed that “Co” was clearly separate from all other treatments. Thus, this study showed that co-cropping a hyperaccumulator with a legume in Ni-agromining systems not only improves plant biomass and Ni-yields, but also enhanced some soil microbial enzymatic activities. Ameliorating agromining by replacing fertilizers would combine eco-efficient or sustainable metal recovery with soil fertility/quality improvement.

Phytomining can be limited by low biomass productivity by plants or limited availability of soil metals. Ongoing research attempts to overcome these potential constraints and to make phytomining a successful commercial technique in the recovery of metals from polluted or naturally metal-rich soil by (hyper)accumulating plants. Recently, the benefits of combining phytoremediation with bioremediation, which consists in the use of beneficial microorganisms such as endophytes or rhizosphere bacteria and fungi, for metal removal from soils have been demonstrated. Metal-resistant microorganisms play an important role in enhancing plant survival and growth in these soils by alleviating metal toxicity and supplying nutrients. Furthermore, these beneficial microorganisms are able to enhance the metal bioavailability in the rhizosphere of plants. An increase in plant growth and metal uptake increases the effectiveness of phytoremediation processes coupled with bioremediation. Herein, we highlight the specificity of the rhizosphere and the critical roles in soil nutrient cycling and provision of ecosystem services that can be brought by rhizosphere microorganisms. We discuss how abiotic factors, such as the presence of metals in polluted sites or in naturally rich (ultramafic) soils modulate activities of soil microbial communities. Then we introduce the concept of microbe-assisted phytomining, and underline the role of plant-associated microorganisms in metal bioavailability and uptake by host plants that has attracted a growing interest over the last decade. Finally, we present various techniques, including phenotypic, genotypic, and metagenomic approaches, which allow for characterising soil microbial community structure and diversity in polluted or naturally metal-rich soils.

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.

Waste incineration bottom ash is considered a secondary resource for valuable trace elements (TE), which is currently neglected in most European countries. Phytomining could potentially recover valuable TE from such waste materials but is still at an exploratory stage with many challenges. The use of bioaugmentation to improve plant growth and TE accumulation of metal-tolerant high biomass plants growing on waste incineration bottom ash was evaluated. Bacterial strains that were previously isolated from rhizosphere, roots and contaminated soil were selected according to their plant growth promoting characteristics and tolerance to the bottom ash substrate. Those selected bacterial strains were tested for their beneficial effects on Nicotiana tabacum and Salix smithiana with regards to phytomining. The rhizobacterial strain Rhodococcus erythropolis P30 enhanced the shoot dry weight of N. tabacum by on average 57% compared to the control plants. Several bacterial inoculants enhanced biomass production and the nutritional status of S. smithiana. Moreover, those bacterial strains previously described to enhance biomass production of N. tabacum and members of the Salicaceae on TE-contaminated soils, also enhanced biomass production of these species on bottom ash. However, bacterial inoculants could not enhance trace element accumulation in plants.

Bottom sediments accumulate rapidly in urban reservoirs and should be periodically removed. Their high organic matter content makes them valuable fertilizers, but they often contain toxic substances. The present study compares the responses of the dicotyledonous Tagetes patula and monocotyledon Festuca arundinacea to the presence of such sediments in soil and to soil inoculation with two rhizobacterial strains (Massilia niastensis p87 and Streptomyces costaricanus RP92) isolated from contaminated soil. Total soluble protein, total chlorophyll content, as well as chlorophyll a/b ratio, degree of lipid peroxidation (TBARS), α-tocopherol content, total phenolic compounds (TPC) content and anthocyanins content were examined in the leaves of investigated plants. T. patula was more sensitive to the toxic substances in the sediments than F. arundinacea. Rhizobacterial inoculation reduced the toxic effect of the sediment. RP92 has a more favorable effect on the condition of T. patula than p87. F. arundinacea was not adversely affected by the addition of sediments or inoculation with the p87 or RP92 strains. Both tested plant species are suitable for planting on soils enriched with urban sediments, and the addition of bacterial inoculums promote plant growth and reduce the damage caused by the xenobiotics contained in the sediments., This research was supported by the European Commission under the Seventh Framework Program for Research (FP7-KBBE-266124, Greenland) and University of Lodz Grant No. B17 11 000 000 052.01.

The performance of Cytisus striatus in association with different microbial inoculant treatments on the dissipation of the insecticide hexachlorocyclohexane (HCH) was studied. Two soils with different organic matter (A and B soil) content were spiked with 0 or 65 mg HCH kg−1. Plants were either not inoculated (NI), or inoculated with the endophyte Rhodococcus erythropolis ET54b and the HCH-degrader Sphingomonas sp. D4 separately or in combination (ET, D4 and ETD4). Unplanted pots were also established. HCH phytotoxicity was more pronounced in the B soil. Soil HCH concentrations in unplanted pots were similar to initial concentrations, whereas concentrations were reduced after plant growth: by 20% and 8% in A and B soil, respectively. Microbial inoculants also modified HCH dissipation, although effects were soil-dependent. Inoculation with the combination of strains (ETD4) led to a significant enhancement in HCH dissipation: up to 53% in the A soil and 43% in the B soil.

An improved understanding of the Ni root-to-shoot translocation mechanism in hyperaccumulators is necessary to increase Ni uptake efficiency for phytoextraction technologies. It has been presumed that an important aspect of Ni translocation and storage involves chelation with organic ligands. It has been reported that exposing several Ni hyperaccumulator species of Alyssum to Ni elicited a large increase in the histidine level of the xylem sap. In later studies it was shown that as time progressed the histidine:Ni ratio dropped considerably. Moreover, previous studies analyzed the relationship between Ni and ligands in plants that were exposed to Ni only for a few hours and therefore obtained results that are unlikely to represent field soils where plants are at steady-state Ni uptake. The aim of this study was to understand the quantitative relationship between Ni and organic ligands in the xylem sap of various Alyssum genotypes or species that reached steady-state Ni uptake after being exposed to Ni in either nutrient solution or serpentine soil for up to 6 weeks. Total Ni concentration, 17 amino acids, 9 organic acids, and nicotianamine were measured in xylem sap of 100-day old plants of Alyssum. Results showed that the concentration of Ni in xylem sap of various Alyssum genotypes was 10–100 fold higher than the concentration of histidine, malate, citrate, and nicotianamine, which were the predominant Ni ligands measured in the sap. When the physiology of the whole plant is taken into account, our results indicate that the concentration of organic chelators is too low to account for the complexation of all the Ni present in the xylem sap of Alyssum at steady-state Ni hyperaccumulation, and suggest that most of the Ni in xylem sap of this species is present as the hydrated cation.

Plants interact closely with microbes and these can enhance plant growth and health by increasing nutrient uptake and improving plant resistance to pathogens and stress. Plant-associated microorganisms are commonly used as ‘biofertilisers’ in agriculture but their incorporation into phytoremediation systems to improve plant establishment and growth, and modify plant metal accumulation, is more recent. This review focuses on the recent advances in the use of plant–bacterial associations to enhance phytoextraction (phytomining) processes in trace element (TE)–contaminated or –enriched sites. Experimental evidence shows that plant-associated bacteria play an important role in plant TE bioaccumulation, and bench level studies suggest bacterial inoculants could enhance phytoextraction efficiency. However, the performance of these bacterial inoculants under natural conditions will have to be investigated under a field scale.

Background and aims Alyssum section Odontarrhena is the largest single clade of Ni-hyperaccumulator plants, most of which are endemic to ultramafic (serpentine) soils. Alyssum serpyllifolium is a facultative hyperaccumulator able to grow both on limestone-derived and ultramafic soils. Analysis of different populations of this species with contrasting phenotypes could allow the identification of genes involved in Ni-hyperaccumulation and serpentine tolerance. Methods A glasshouse pot experiment on compost-amended ultramafic soil was carried out with three ultramafic (U) and two non-ultramafic (NU) populations of A. serpyllifolium. The leaf ionome was determined by elemental analysis and used as a proxy for serpentine adaptation. A Ni-hyperaccumulating phenotype was estimated from leaf Ni concentrations. Cultured plants were genotyped using Amplified Fragment Length Polymorphism (AFLP) markers. Outlier analysis and regressions of leaf ionome over band distribution were applied to detect markers potentially involved in Ni-hyperaccumulation and serpentine tolerance. Results As well as U populations, some plants from NU populations were found to be able to hyperaccumulate Ni in leaves to concentrations exceeding 0.1% (w/w). U populations had a higher Ca/Mg leaf ratio than NU populations, mainly due to Mg exclusion. 374 AFLP markers were amplified and a potential adaptive value was identified in 34 of those markers. Conclusions Phenotype regression analyses were found to be more powerful than outlier analyses and indicated that regulation of foliar concentrations of Ni, Ca, Mg and P are the main factors involved in serpentine adaptation. More research is needed in order to resolve the ancestral or recently -evolved nature of Ni-hyperaccumulation.

Plant growth promoting (PGP) bacterial strains possess different mechanisms to improve plant development under common environmental stresses, and are therefore often used as inoculants in soil phytoremediation processes. The aims of the present work were to study the effects of a collection of plant growth promoting bacterial strains on plant development, antioxidant enzyme activities and nutritional status of Cytisus striatus and/or Lupinus luteus plants a) growing in perlite under non-stress conditions and b) growing in diesel-contaminated soil. For this, two greenhouse experiments were designed. Firstly, C striatus and L. luteus plants were grown from seeds in perlite, and periodically inoculated with 6 PGP strains, either individually or in pairs. Secondly, L luteus seedlings were grown in soil samples of the A and B horizons of a Cambisol contaminated with 1.25% (w/w) of diesel and inoculated with best PGP inoculant selected from the first experiment. The results indicated that the PGP strains tested in perlite significantly improved plant growth. Combination treatments provoked better growth of L. luteus than the respective individual strains, while individual inoculation treatments were more effective for C striatus. L luteus growth in diesel-contaminated soil was significantly improved in the presence of PGP strains, presenting a 2-fold or higher increase in plant biomass. Inoculants did not provoke significant changes in plant nutritional status, with the exception of a subset of siderophore-producing and P-solubilising bacterial strains that resulted in significantly modification of Fe or P concentrations in leaf tissues. Inoculants did not cause significant changes in enzyme activities in perlite experiments, however they significantly reduced oxidative stress in contaminated soils suggesting an improvement in plant tolerance to diesel. Some strains were applied to non-host plants, indicating a non-specific performance of their plant growth promotion. The use of PGP strains in phytoremediation may help plants to overcome contaminant and other soil stresses, increasing phytoremediation efficiency. (C) 2016 Elsevier B.V. All rights reserved. This research was supported by ERDF Interreg Sudoe Program (PhytoSUDOE-SOE1/P5/E0189); by the Galician government (Agrupacion Estratexica CRETUS; AGRU2015/02); and by the University of Hasselt (BOF project 06G02 and Methusalem project 08M03VGRJ).

The association of plants and rhizospheric bacteria provides a successful strategy to clean up contaminated soils. The purpose of this work was to enhance diesel degradation in rhizosphere by inoculation with selected bacterial strains: a diesel degrader (D), plant growth-promoting (PGP) strains, or a combination (D+PGP). Plants were set up in pots with the A or B horizon of an umbric Cambisol (A and B) spiked with diesel (1.25%, w/w). After 1 mo, the dissipation of diesel range organics (DRO) with respect to = 0 (i.e., 1 wk after preparing the pots with the seedlings) concentration was significantly higher in inoculated than in noninoculated (NI) pots: The highest DRO losses were found in A D+PGP pots (close to 15-20% higher than NI) and in B D pots (close to 10% higher). The water-extractable DRO fraction was significantly higher at = 30 d (15-25%) compared with = 0 (

Recent studies have shown that application of phytohormones to shoots of Alyssum murale increased biomass production but did not increase Ni shoot concentration. Increased biomass and Ni phytoextraction efficiency is useful to achieve economically viable phytomining. The objective of this study was to evaluate the effect of two types of phytohormones on the Ni phytoextraction capacity of four Alyssum species. Two different commercially available phytohormones (Cytokin and Promalin) based on cytokinins and/or gibberellins were applied on shoot biomass of four Ni hyperaccumulating Alyssum species (A. corsicum, A. malacitanum, A. murale, and A. pintodasilvae). Cytokin was applied in two concentrations and promalin in one concentration. The application of phytohormones had no clear positive effect on biomass production, Ni accumulation and Ni phytoextraction efficiency in the studied Alyssum species. A. malacitanum was the only species in which a significantly negative effect of these treatments was observed (in Ni uptake). A slightly positive response to promalin treatment was observed in the biomass production and Ni phytoextraction efficiency of A. corsicum. Although this effect was not significant it does indicate a potential application of these approaches to improve phytoextraction ability. Further studies will be needed to identify the most adequate phytohormone treatment as well as the appropriate concentrations and application times.

The plant-microorganism-soil system of three pseudometallophytes (Betula celtiberica, Cytisus scoparius and Festuca rubra) growing in a Pb/Zn mine was characterised. Plant metal accumulation, soil metal fractions (rhizosphere and non-vegetated) and bacterial densities were determined. Total Cd, Pb and Zn in non-vegetated soils was up to 50, 3000 and 20,000 mg kg−1 dry weight, respectively. The residual fraction dominated non-vegetated soils, whereas plant-available fractions became important in rhizosphere soils. All plant species effectively excluded metals from the shoot. F. rubra presented a shoot:root transport factor of ≤0.2 and this population could be useful in future phytostabilisation trials. Culturable bacterial densities and diversity were low (predominantly Actinobacteria). Rhizosphere soils hosted higher total and metal-tolerant bacterial densities. Seventy-four metal-tolerant rhizobacteria were isolated, and characterised genotypically (BOX-PCR, 16S rDNA) and phenotypically [Cd/Zn tolerance, biosurfactant production and plant growth promoting (PGP) traits]. Several isolates resisted high concentrations of Cd and Zn, and only a few presented PGP traits. Fourteen isolates were evaluated for promoting plant growth of two species (Salix viminalis and Festuca pratensis). Thirteen inoculants enhanced growth of F. pratensis, while only three enhanced growth of S. viminalis. Growth enhancement could not always be related to isolate PGP traits. In conclusion, some isolates show potential application in phytostabilisation or phytoextraction techniques., This research was supported by the Ministerio de Ciencia e Innovación ( CTM2009-14576-C02-01 and CTM2009-14576-C02-02 ) and FP7 EC project “Gentle remediation of trace element contaminated land”(Greenland 266124; Theme 2:Food, Agriculture and Fisheries, and Biotechnology).

Free of human interference the soil trace element content is largely dependent on that of the soil parent material and acting weathering processes. An increasingly industrialised society has, however, led to the widespread introduction of trace metals and metalloids into our environment, causing acute and diffuse contamination of soil. The last two decades have seen the emergence of eco-friendly, gentle soil remediation techniques known as phytoremediation. This review focuses on two subtypes of phytoremediation: phytoextraction and phytostabilisation. Phytoextraction aims to remove trace elements from the soil through their uptake and accumulation by plants. In contrast, phytostabilisation aims to establish a vegetation cover and promote in situ inactivation of trace elements by combining the use of metal-tolerant plants and soil amendments. In both these processes the mobility and bioavailability of trace elements in the soil, particularly at the root–soil interface (or rhizosphere) where root uptake or exclusion takes place, is a critical factor affecting their outcome and success. Developing new methods to either enhance (for phytoextraction) or reduce (for phytostabilisation) the bioavailability of metal contaminants in the rhizosphere could significantly improve the efficiency of these remediation techniques. Here we aim to provide an up-to-date review of mechanisms operating in the rhizosphere and their potential role in improving phytoremediation strategies.

Aim Plant -associated bacteria can improve phytoextraction by increasing plant growth and/or metal uptake. This study aimed to characterise the culturable rhizobacterial community associated with two Nihyperaccumulators and to obtain a collection of isolates for application in Ni phytomining. Methods Non-vegetated and rhizosphere soil samples were collected from the Ni-hyperaccumulator Alyssum serpyllifolium ssp. lusitanicum (three populations) and Alyssum serpyllifolium ssp. malacitanum (one population), as well as from non-hyperaccumulating plants (Dactylis glomerata, Santolina semidentata and Alyssum serpyllifolium ssp. serpyllifolium). Rhizobacteria were isolated and characterised genotypically (BOX-PCR, 16S rDNA sequencing) and phenotypically (Ni tolerance, plant growth promoting (PGP) traits, biosurfactant production). Results Hyperaccumulating Alyssum subspecies hosted higher densities of bacteria compared to either nonhyperaccumulators or non-vegetated soil. In some cases hyperaccumulators showed selective enrichment of Nitolerant bacteria. Most bacterial strains belonged to the Actinobacteria phylum and presented Ni resistance. Phosphorus-solubilisers were mostly associated with the hyperaccumulators, siderophore-producers with D. glomerata, and IAA-producers with both these species. Conclusion Taxonomic diversity and phenotypic characteristics were soil-, plant species- and plant population- specific. Moreover, differences were observed between the two Ni-hyperaccumulating subspecies and amongst plant populations. Several strains presented PGP characteristics which could be useful when selecting microorganisms for bioaugmentation trials., This research was supported by the Spanish Ministerio de Economía y Competitividad (CTM2012-39904- C02-01) and FEDER, and by the 7th Framework Program of the European Commission (FP7-KBBE-266124, GREENLAND).

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. This work was supported by the European Community's Seventh Framework Programme through the grant to the budget of the HOMBRE (www.zerobrownfields.eu) and Greenland (www.greenland-project.eu) projects.

Volatile fuel compounds such as fuel oxygenates (FO) (MTBE and ETBE) and BTEX (benzene, toluene, ethylbenzene and xylene) are some of the most soluble components of fuel. Characterizing the leaching potential of these compounds is essential for predicting their mobility through the soil profile and assessing the risk of groundwater contamination. Plant root exudates can play an important role in the modification of contaminant mobility in soil-plant systems, and such effects should also be considered in leaching studies. Artificially spiked samples of A and B horizons from an alumi-umbric Cambisol were leached in packed-columns and batch experiments using Milli-Q water and plant root exudates as leaching agents. The leaching potential and rate were strongly influenced by soil-contaminant interactions and by the presence of root exudates. Organic matter in A horizon preferably sorbed the most non-polar contaminants, lowering their leaching potential, and this effect was enhanced by the presence of root exudates. On the other hand, the inorganic components of the B horizon, showed a greater affinity for polar molecules, and the presence of root exudates enhanced the desorption of the contaminants. Column experiments resulted in a more realistic protocol than batch tests for predicting the leaching potential of volatile organic compounds in dissimilar soils.

Microbacterium spp. isolated from heavy metal (HM)-contaminated environments (soil and plants) can play a role in mobilization processes and in the phytoextraction of HM. Here, we report the whole-genome sequences and annotation of 10 Microbacterium spp. isolated from both HM-contaminated and -noncontaminated compartments.

The genetic diversity of Cistus ladanifer ssp. ladanifer (Cistaceae) growing on ultramafic and non-ultramafic (basic and schists) soils in the NE of Portugal was studied in order to identify molecular markers that could distinguish the metal-tolerant ecotypes of this species. Random Amplified Polymorphic DNA (RAPD) markers were used in order to estimate genetic variation and differences between populations. The RAPD dataset was analysed by means of a cluster analysis and an analysis of molecular variance (AMOVA). Our results indicate a significant partitioning of molecular variance between ultramafic and non-ultramafic populations of Cistus ladanifer, although the highest percentage of this variance was found at the intra-population level. Mantel’s test showed no relationship between inter-population genetic and geographic distances. A series of RAPD bands that could be related to heavy metal tolerance were observed. The identification of such markers will enable the use of Cistus ladanifer in phytoremediation procedures.

The effects of heavy metals on the growth, mineral composition (P, K, Fe and Mn) and metal accumulation of five populations of Cistus ladanifer subsp. ladanifer from NE Portugal were investigated in hydroponic experiments. Plants were exposed to increasing concentrations (0–2000 μM) of one of eight heavy metals: Cd, Co, Cr, Cu, Mn, Ni, Pb or Zn. Populations of C. ladanifer, whose origin was ultramafic soils (S and UB) or soils developed on basic rocks (B), showed a higher tolerance to the metals Cd, Co, Cr, and Mn, and a considerable degree of tolerance to Ni. In contrast, populations originating on acid-rock soils (M and SC) showed higher tolerance to the metals Cu and Zn. Populations showed different patterns of metal accumulation and distribution in the plant parts, suggesting different mechanisms of metal tolerance are used. The more Cd-, Co- and Mn-tolerant populations (S, UB, B and SC (Cd)) showed accumulation of these three metals in the shoots (shoot:root metal concentration ratios (S:R) > 1). Shoot concentrations of up to 309 μg Cd g−1, 2667 μg Co g−1 and 6214 μg Mn g−1 were found in these populations. The populations, UB and M, showed considerable tolerance to Ni and Zn, respectively. These populations accumulated up to 4164 μg Ni g−1 and 7695 μg Zn g−1 in their shoot tissues, and these metals were efficiently transported from the roots to aerial parts (S:R > 3 (Ni), S:R > 1 (Zn)). In contrast, the S and SC populations maintained higher growth rates in the presence of Ni and Zn, respectively, but showed exclusion mechanisms of metal tolerance: reduced Ni and Zn transport to shoots (S:R < 1). Cistus ladanifer was not able to efficiently transport Cr, Cu or Pb from its roots to its aerial parts (S:R ranged from 0–0.4). The more Cu-tolerant populations, M and SC, showed a greater restriction of Cu transport to the shoots than the ultramafic- or basic-rock populations. Significant changes in the plant mineral composition were found, however, concentrations were generally above mineral deficiency levels. Based on these preliminary results the possible usefulness of this plant for phytoremediation technologies is discussed. However, further investigations are necessary to evaluate its growth and metal accumulation under soil and field conditions.

International audience; Endophytic bacteria from roots and crude seed extracts of a Cu-tolerant population of Agrostis capillaris were inoculated to a sunflower metal-tolerant mutant line, and their influence on Cu tolerance and phytoextraction was assessed using a Cu-contaminated soil series. Ten endophytic bacterial strains isolated from surface-sterilized A. capillaris roots were mixed to prepare the root endophyte inoculant (RE). In parallel, surface-sterilized seeds of A. capillaris were crushed in MgSO4 to prepare a crude seed extract containing seed endophytes (SE). An aliquot of this seed extract was filtered at 0.2 μm to obtain a bacterial cell-free seed extract (SEF). After surface sterilization, germinated sunflower seeds were separately treated with one of five modalities: no treatment (C), immersion in MgSO4 (CMg) or SEF solutions and inoculation with RE or SE. All plants were cultivated on a Cu-contaminated soil series (13-1020 mg Cu kg(-1)). Cultivable RE strains were mostly members of the Pseudomonas genera, and one strain was closely related to Labrys sp. The cultivable SE strains belonged mainly to the Bacillus genera and some members of the Rhodococcus genera. The treatment effects depended on the soil Cu concentration. Both SE and SEF plants had a higher Cu tolerance in the 13-517 mg Cu kg(-1) soil range as reflected by increased shoot and root DW yields compared to control plants. This was accompanied by a slight decrease in shoot Cu concentration and increase in root Cu concentration. Shoot and root DW yields were more promoted by SE than SEF in the 13-114 mg Cu kg(-1) soil range, which could reflect the influence of seed-located bacterial endophytes. At intermediate soil Cu (416-818 mg Cu kg(-1) soil), the RE and CMg plants had lower shoot Cu concentrations than the control, SE and SEF plants. At high total soil Cu (617-1020 mg Cu kg(-1)), root DW yield of RE plants slightly increased and their root Cu concentration rose by up to 1.9-fold. In terms of phytoextraction efficiency, shoot Cu removal was increased for sunflower plants inoculated with crude and bacterial cell-free seed extracts by 1.3- to 2.2-fold in the 13-416 mg Cu kg(-1) soil range. Such increase was mainly driven by an enhanced shoot DW yield. The number and distribution of endophytic bacteria in the harvested sunflower tissues must be further examined.

The last few decades have seen the rise of Gentle soil Remediation Options (GRO), which notably include in situ contaminant stabilization ("inactivation") and plant-based (generally termed "phytoremediation") options. For trace element (TE)-contaminated sites, GRO aim to either decrease their labile pool and/or total content in the soil, thereby reducing related pollutant linkages. Much research has been dedicated to the screening and selection of TE-tolerant plant species and genotypes for application in GRO. However, the number of field trials demonstrating successful GRO remains well below the number of studies carried out at a greenhouse level. The move from greenhouse to field conditions requires incorporating agronomical knowledge into the remediation process and the ecological restoration of ecosystem services. This review summarizes agronomic practices against their demonstrated or potential positive effect on GRO performance, including plant selection, soil management practices, crop rotation, short rotation coppice, intercropping/row cropping, planting methods and plant densities, harvest and fertilization management, pest and weed control and irrigation management. Potentially negative effects of GRO, e.g., the introduction of potentially invasive species, are also discussed. Lessons learnt from long-term European field case sites are given for aiding the choice of appropriate management practices and plant species.

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.

Vegetation and its associated microorganisms play an important role in the behaviour of soil contaminants. One of the most important elements is root exudation, since it can affect the mobility, and therefore, the bioavailability of soil contaminants. In this study, we evaluated the influence of root exudates on the mobility of fuel derived compounds in contaminated soils. Samples of humic acid, montmorillonite, and an A horizon from an alumi-umbric Cambisol were contaminated with volatile contaminants present in fuel: oxygenates (MTBE and ETBE) and monoaromatic compounds (benzene, toluene, ethylbenzene and xylene). Natural root exudates obtained from Holcus lanatus and Cytisus striatus and ten artificial exudates (components frequently found in natural exudates) were added to the samples, individually and as a mixture, to evaluate their effects on contaminant mobility. Fuel compounds were analyzed by headspace-gas chromatography-mass spectrometry. In general, the addition of natural and artificial exudates increased the mobility of all contaminants in humic acid. In A horizon and montmorillonite, natural or artificial exudates (as a mixture) decreased the contaminant mobility. However, artificial exudates individually had different effects: carboxylic components increased and phenolic components decreased the contaminant mobility. These results established a base for developing and improving phytoremediation processes of fuel-contaminated soils.

Aluminium (Al) is rhizotoxic and is often present in acidic soils at activities high enough to inhibit root elongation. The objectives of the present study were to assess the level of Al tolerance in different races of Betula pendula Roth (Silver Birch) and to investigate how growth and nutrient acquisition were affected by Al. A solution culture technique was employed which simulated natural soil solutions. Aluminium at low concentrations (2 and 5 mg l(-1)), enhanced the growth of two races of B. pendula originating from soils poor in Al (FM and KP). In contrast, Al, at all concentrations tested, inhibited growth in an Al-sensitive race (KR) whose provenance was a calcareous soil. At concentrations/=10 mg l(-1), Al reduced growth in FM and KP races, while growth increased with increasing Al (up to 25 mg l(-1)) in the Al-tolerant, SMM, race. Aluminium altered both root and leaf architecture. Low Al concentrations (5 mg l(-1)) significantly increased leaf expansion, and high concentrations (25 mg l(-1)) reduced leaf expansion. In the Al-sensitive race, KR, there was a loss of apical dominance, and both lateral and primary roots were stunted and swollen, with increasing Al concentrations. These results demonstrated pronounced racial differences in tolerance to Al by B. pendula that could be predicted from the soil environment of each race.