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Soils of abandoned and vacant lands in the periphery of cities are frequently subjected to illegal dumping and can undergo degradation processes such as depletion of organic matter and nutrients, reduced biodiversity, and the presence of contaminants, which may exert an intense abiotic stress on biological communities. Mycorrhizal-assisted phytoremediation and intercropping strategies are highly suitable options for remediation of these sites. A two-year field experiment was conducted at a peri-urban site contaminated with petroleum hydrocarbons and polychlorinated biphenyls, to assess the effects of plant growth (spontaneous plant species, Medicago sativa , and Populus × canadensis , alone vs. intercropped) and inoculation of a commercial arbuscular mycorrhizal and ectomycorrhizal inoculum. Contaminant degradation, plant performance, and biodiversity, as well as a variety of microbial indicators of soil health (microbial biomass, activity, and diversity parameters) were determined. The rhizosphere bacterial and fungal microbiomes were assessed by measuring the structural diversity and composition via amplicon sequencing. Establishment of spontaneous vegetation led to greater plant and soil microbial diversity. Intercropping enhanced the activity of soil enzymes involved in nutrient cycling. The mycorrhizal treatment was a key contributor to the establishment of intercropping with poplar and alfalfa. Inoculated and poplar-alfalfa intercropped soils had a higher microbial abundance than soils colonized by spontaneous vegetation. Our study provided evidence of the potential of mycorrhizal-assisted phytoremediation and intercropping strategies to improve soil health in degraded peri-urban areas. [ABSTRACT FROM AUTHOR]

Contaminated soils are frequently characterized by the simultaneous presence of organic and inorganic contaminants, as well as a poor biological and nutritional status. Rhizoremediation, the combined use of phytoremediation and bioremediation, has been proposed as a Gentle Remediation Option to rehabilitate multi-contaminated soils. Recently, newer techniques, such as the application of metallic nanoparticles, are being deployed in an attempt to improve traditional remediation options. In order to implement a phytomanagement strategy on calcareous alkaline peri-urban soils simultaneously contaminated with several metals and diesel, we evaluated the effectiveness of Brassica napus L., a profitable crop species, assisted with organic amendment and zero-valent iron nanoparticles (nZVI). A two-month phytotron experiment was carried out using two soils, i.e. amended and unamended with organic matter. Soils were artificially contaminated with Zn, Cu and Cd (1500, 500 and 50 mg kg − 1 , respectively) and diesel (6000 mg kg − 1 ). After one month of stabilization, soils were treated with nZVI and/or planted with B . napus . The experiment was conducted with 16 treatments resulting from the combination of the following factors: amended/unamended, contaminated/non-contaminated, planted/unplanted and nZVI/no-nZVI. Soil physicochemical characteristics and biological indicators (plant performance and soil microbial properties) were determined at several time points along the experiment. Carbonate content of soils was the crucial factor for metal immobilization and, concomitantly, reduction of metal toxicity. Organic amendment was essential to promote diesel degradation and to improve the health and biomass of B . napus . Soil microorganisms degraded preferably diesel hydrocarbons of biological origin (biodiesel). Plants had a remarkable positive impact on the activity and functional diversity of soil microbial communities. The nZVI were ineffective as soil remediation tools, but did not cause any toxicity. We concluded that rhizoremediation with B . napus combined with an organic amendment is promising for the phytomanagement of calcareous soils with mixed (metals and diesel) contamination. [ABSTRACT FROM AUTHOR]

Soils contaminated by organic and inorganic pollutants like Cr(VI) and lindane, is currently a main environmental challenge. Biological strategies, such as biostimulation, bioaugmentation, phytoremediation and vermiremediation, and nanoremediation with nanoscale zero-valent iron (nZVI) are promising approaches for polluted soil health recovery. The combination of different remediation strategies might be key to address this problem. For this reason, a greenhouse experiment was performed using soil without or with an organic amendment. Both soils were contaminated with lindane (15 mg kg−1) and Cr(VI) (100 or 300 mg kg−1). After one month of aging, the following treatments were applied: (i) combination of bioaugmentation (actinobacteria), phytoremediation (Brassica napus), and vermiremediation (Eisenia fetida), or (ii) nanoremediation with nZVI, or (iii) combination of biological treatments and nanoremediation. After 60 days, the wellness of plants and earthworms was assessed, also, soil health was evaluated through physico-chemical parameters and biological indicators. Cr(VI) was more toxic and decreased soil health, however, it was reduced to Cr(III) by the amendment and nZVI and, to a lesser extent, by the biological treatment. Lindane was more effectively degraded through bioremediation. In non-polluted soils, nZVI had strong deleterious effects on soil biota when combined with the organic matter, but this effect was reverted in soils with a high concentration of Cr(VI). Therefore, under our experimental conditions bioremediation might be the best for soils with a moderate concentration of Cr(VI) and organic matter. The application of nZVI in soils with a high content of organic matter should be avoided except for soils with very high concentrations of Cr(VI). According to our study, among the treatments tested, the combination of an organic amendment, biological treatment, and nZVI was shown to be the strategy of choice in soils with high concentrations of Cr(VI) and lindane, while for moderate levels of chromium, the organic amendment plus biological treatment is the most profitable treatment. • Biostimulation, bioaugmentation, phyto-, vermi-, and nanoremediation were combined. • The remediation success was demonstrated physico-chemically and biologically. • The combination of nZVI and organic matter had deleterious effects on soil biota. • Organic matter and nZVI were the most effective treatments reducing Cr(VI). • Lindane was successfully degraded by combination of biological treatments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A field trial was carried out to assess the effectiveness of organic amendments (COW: cow slurry; POULTRY: poultry manure; PAPER: paper mill sludge mixed with poultry manure) for the aided phytostabilization of vegetated and non-vegetated sites of an abandoned Pb/Zn contaminated mine. A native ecotype of Festuca rubra L. was used for colonizing the initially non-vegetated sites. Two and six months after amendment application, soil Pb and Zn availability (CaCl2-extractability) decreased. COW and POULTRY treatments resulted in highest reduction in Pb extractability in non-vegetated sites. In vegetated sites, COW-treated plots showed the highest decrease in metal extractability at 6 months. All amendments, especially POULTRY, led to higher F. rubra biomass and vegetation cover in vegetated and initially non-vegetated sites, respectively. Two months after soil treatment, soil basal and substrate-induced respiration peaked in vegetated sites. Based on a root elongation bioassay with Lactuca sativa L., beneficial effects of soil amendments were also observed in terms of soil phytotoxicity. The problem of high variability (spatial, temporal and environmental) of vegetated and non-vegetated mine soils for an effective aided phytostabilization is discussed. [ABSTRACT FROM AUTHOR]