Ni phytomining is a promising technology for Ni recovery from low-grade ores such as ultramafic soils. Metal-hyperaccumulators are good candidates for phytomining due to their extraordinary capacity ...for Ni accumulation. However, many of these plants produce a low biomass, which makes the use of agronomic techniques for improving their growth necessary.
In this study, the Ni hyperaccumulators Alyssum serpyllifolium ssp. lusitanicum, A. serpyllifolium ssp. malacitanum, Alyssum bertolonii and Noccaea goesingense were evaluated for their Ni phytoextraction efficiency from a Ni-rich serpentine soil. Effects of soil inorganic fertilisation (100:100:125kgNPKha−1) and soil organic amendment addition (2.5, 5 or 10% compost) on plant growth and Ni accumulation were determined. All soil treatments greatly improved plant growth, but the highest biomass production was generally found after addition of 2.5 or 5% compost (w/w). The most pronounced beneficial effects were observed for N. goesingense. Total Ni phytoextracted from soils was significantly improved using both soil treatments (inorganic and organic), despite the decrease observed in soil Ni availability and shoot Ni concentrations in compost-amended soils. The most promising results were found using intermediate amount of compost, indicating that these types of organic wastes can be incorporated into phytomining systems.
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•The low biomass of most Ni-hyperaccumulator plants can limit the applicability of phytomining techniques at field scale•The use of traditional agronomic practises such as fertilisation can improve plant establishment and biomass production of these plant species•Changes in soil Ni availability, shoot biomass production and Ni accumulation by four Ni-hyperaccumulator species were evaluated after soil inorganic fertilisation (NPK) or compost amendment•Intermediate doses of compost amendment had a stronger effect on Ni yield, mainly due to the enhanced shoot biomass•The use of organic wastes as amendments in phytomining permits the recycling of these residues
A novel balanced differential bandpass filter implemented in coplanar waveguide (CPW) technology is presented. The filter is based on the use of two magnetically coupled CPW folded-stepped impedance ...resonators. The use of magnetic coupling, instead of the more common electric coupling, provides inherent common-mode rejection. Measured and simulated results demonstrate the benefits of the proposed balanced filter.
AIM: Rhizobacteria can influence plant growth and metal accumulation. The aim of this study was to evaluate the effect of rhizobacterial inoculants on the Ni phytoextraction efficiency of the ...Ni-hyperaccumulator Alyssum pintodasilvae. METHOD: In a preliminary screening 15 metal-tolerant bacterial strains were tested for their plant growth promoting (PGP) capacity or effect on Ni bioaccumulation. Strains were selected for their Ni tolerance, plant growth promoting traits and Ni solubilizing capacity. In a re-inoculation experiment five of the previously screened bacterial isolates were used to inoculate A. pintodasilvae in two contrasting Ni-rich soils (a serpentine (SP) soil and a sewage sludge-affected agricultural (LF) soil). RESULTS: Plant growth was greater in serpentine soil (where it grows naturally) than in the LF soil, probably due to Cd phytotoxicity. Rhizobacterial inoculants influenced plant growth and Ni uptake and accumulation, but the effect of the strains was dependent upon soil type. The increase in plant biomass and/or Ni accumulation significantly promoted shoot Ni removal. CONCLUSION: One strain (Arthrobacter nicotinovorans SA40) was able to promote plant growth and phytoextraction of Ni in both soil types and could be a useful candidate for future field-based trials.
Purpose
Rhizosphere processes are known to modify uptake of elements from soil, but limited information is available for hyperaccumulators. We investigated labile Ni fractions and their kinetics of ...replenishment in the rhizospheres of the Ni-hyperaccumulator
Odontarrhena serpyliffolia
, the Ni-excluder
Holcus lanatus
and in bulk soils collected at the same serpentine outcrop.
Methods
Labile Ni fractions in rhizosphere and bulk soil were evaluated using conventional extractions and also by the Diffusive Gradients in Thin Films (DGT) technique. DGT data were used to predict the kinetics of Ni resupply using DIFS modelling. Chemical imaging of Ni distribution along roots using DGT coupled with laser-ablation was conducted.
Results
Labile Ni forms were higher in both rhizosphere than in bulk soils, together with an increase in dissolved organic C, cation exchange capacity and the Ca/Mg ratio. Ni fractionation indicated a shift towards less stable Ni fractions in the rhizosphere, particularly in the hyperaccumulator.
DIFS modelling showed that the rhizosphere of the excluder was able to sustain the initially lower soluble Ni concentration through replenishment from the solid phase, while Ni resupply in the rhizosphere of the hyperaccumulator was not sufficient to maintain the initially high concentrations of soluble Ni. However, the amount of DGT-labile Ni was higher in the rhizosphere of the hyperaccumulator compared to the excluder in all deployment times.
Conclusion
Our data suggest that compounds derived from root activity, in particular DOC, are important controls of Ni availability to plants growing on serpentine soil.
The application of plant growth regulators (PGRs) or phytohormones could be an interesting option for stimulating biomass production of hyperaccumulating plants and, consequently, their metal ...phytoextraction capacity. The effect of exogenous applications of phytohormones (PGR) on the Ni phytoextraction capacity of four Ni hyperaccumulating species (Alyssum corsicum, Alyssum malacitanum, Alyssum murale and Noccaea goesingense) was evaluated. Four different commercially available phytohormones (B, C, K and P) based on gibberellins, cytokinins and auxins were applied to the plant aerial tissues. Each product was applied at three different concentrations (B1-3, C1-3, K1-3 and P1-3). The effect on biomass production was dependent on the species, the PGR type and the concentration at which it was applied. Two of the four products (K and P) consistently increased biomass production compared to untreated control plants in all four plant species. On the other hand, all four products led to a significant increase in the number of branches (and leaves in the case of N. goesingense) of all four species compared to control plants. Application of phytohormones generally led to a reduction in shoot Ni concentration. Nonetheless, in some cases as a consequence of the increase observed in biomass after the application of phytohormones a significant increase in the Ni phytoextraction efficiency was also observed (but this was species- and PGR type-dependent). The results show that PGRs can be successfully used to improve the growth and biomass production of hyperaccumulating species such as Alyssum and Noccaea. However, an increase in biomass did not always lead to a higher Ni removal, and the most effective PGR for increasing Ni removal was the IAA-based product.
•Ni hyperaccumulating plants were treated with gibberellins, cytokinins and auxins.•Two commercial products increased biomass in four hyperaccumulating plant species.•Phytohormones application generally reduced plant Ni accumulation.•IAA treatments increased phytoextraction efficiency in hyperaccumulator species.
► The plant-microorganism-soil system of three pseudometallophytes was described. ► An efficient metal excluding population of Festuca rubra was identified. ► Metal-tolerant bacteria with potential ...use in phytoremediation were isolated. ► Five rhizobacterial strains enhanced the growth of two contrasting plant species. ► Biomass enhancement by PGP bacteria could improve phytoremediation efficiency.
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 20,000mgkg−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.
Aims Compare bacterial communities in non-vegetated soils and in the rhizosphere of Ni-hyperaccumulating or Ni-excluding plants from four serpentine sites of the Iberian Peninsula. Methods Bacterial ...communities in non-vegetated soil and in rhizosphere of Alyssum serpyllifolium, and Dactylis glomerata, were analysed using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments of the total bacterial community and of Alphaproteobacteria, Actinobacteria and Streptomycetaceae. Results Rhizosphere bacterial communities of, either the hyperaccumulators or the excluder plants, were significantly different from communities in non-vegetated soils, especially for Alphaproteobacteria and Actinobacteria. The main differences between the rhizobacterial communities of the hyperaccumulator and of the excluder corresponded to Alphaproteobacteria profiles. Communities in non-vegetated soil were significantly influenced by intrinsic soil properties while in rhizosphere soil these factors were replaced by parameters related to nutrient availability. Members of the genera Blastococcus, Geodermatophilus, Modestobacter, Rhodococcus, Pseudonocardia, Devosia and Hyphomicrobium were detected in the rhizosphere of the Ni-hyperaccumulating plants. Conclusions Bacterial communities significantly differed between hyperaccumulator and excluder rhizosphere and non-vegetated soil. Actinobacteria of the Geodermatophilaceae family and Alphaproteobacteria of the Hyphomicrobiaceae family predominated in the rhizosphere profiles of the Ni-hyperaccumulators. Alphaproteobacteria could participate in the tolerance of Poaceae to trace elements in ultramafic soils.
Retinoblastoma represents 3% of cancers in children under fifteen years of age. The standard paediatric treatment for saving the affected eye is supraselective intra-arterial chemotherapy performed ...in interventional rooms. In order to address the radiation toxicity due to the angiography, the aim of this study was to determine the typical dose value corresponding to the procedure, estimate the paediatric patients' eye lens dose and study the relationship between dose indicators and dose to the lens. An automatic dose management software was installed in two interventional rooms to obtain the distribution of the dose indicators kerma-area product and reference-point air kerma, getting a typical value 16 Gy·cm
and 130 mGy, respectively (n = 35). The eye lens dose estimates were obtained with photoluminescent dosimeters placed on the patient's eyelids. In the left eye, the entrance surface air kerma was 44.23 ± 2.66 mGy, and 12.72 ± 0.89 mGy in the right eye (n = 10). There was a positive correlation between dose to the lens per procedure and dose indicators, with R
> 0.65 for both eyes. Based on this information, the threshold for the onset of radiation-induce cataracts (500 mGy) will be exceeded if the treatment is performed for more than 8 sessions.
The organochlorine 1,2,3,4,5,6 hexachlorocyclohexane (HCH) is a broad-spectrum insecticide that was used on a large-scale worldwide. The soil-plant-microbe system and its influence on HCH ...biodegradation are evaluated. A greenhouse experiment was designed to evaluate HCH dissipation and several microbial parameters among rhizosphere and bulk soil of two contrasting plants, Cytisus striatus (Hill) Rothm and Holcus lanatus L. Plants were grown for 180 days in three treatments: uncontaminated soil (control), uncontaminated soil inoculated with soil (3% w/w) from a HCH-contaminated site (INOC), and uncontaminated soil inoculated with soil (3% w/w) from the HCH-contaminated site and artificially contaminated to obtain 100 mg HCH kg-¹ dry soil (100HCH-INOC). At harvest, plant biomass, soil water-extractable organic C, pH and Cl concentration, rhizosphere microbial densities (total heterotrophs, ammonifiers, amylolytics) and C substrate utilization patterns, and degradation of α-, β-, δ- and γ-HCH isomers were determined in bulk and rhizosphere soils. Soil solution Cl concentration was determined every 30 days throughout the entire growth period. Results demonstrate that both Cytisus striatus and Holcus lanatus can grow in soils with up to 100 mg HCH kg-¹. An enhanced degradation of α-HCH, but not β- or δ-HCH, was observed in the rhizosphere. Significant changes in the microbial densities were observed between bulk and rhizosphere soils of Cytisus, and an increase in C source utilization indicated changes in community level physiological profiles (CLPP) in the rhizosphere of this species when grown in contaminated soils. HCH dissipation was also greater in soils planted with this species. In accordance, increases in soil extractable C, Cl concentration and acidity were greater at the rhizosphere of Cytisus. Concentration of Cl in soil solutions also indicates greater HCH dechlorination in soils planted with Cytisus than Holcus. Results suggest that phytostimulation of bacteria present or added to soil is a promising approach to cleaning HCH-contaminated sites, and especially for biodegradation of α-HCH.
In this study different bacterial inoculation methods were tested for tobacco plants growing in a mine-soil contaminated with Pb, Zn, and Cd. The inoculation methods evaluated were: seed inoculation, ...soil inoculation, dual soil inoculation event, and seed+soil inoculation. Each inoculum was added at two bacterial densities (10 ⁶ CFUs mL ⁻¹ and 10 ⁸ CFUs mL ⁻¹). The objectives were to evaluate whether or not the mode of inoculation or the number of applied microorganisms influences plant response. The most pronounced bacterial-induced effect was found for biomass production, and the soil inoculation treatment (using 10 ⁶ CFUs mL ⁻¹) led to the highest increase in shoot dry weight yield (up to 45%). Bacterial-induced effects on shoot metal concentrations were less pronounced; although a positive effect was found on shoot Pb concentration when using 10 ⁸ CFUs mL ⁻¹ in the soil inoculation (29% increase) and in the seed+soil inoculation (34% increase). Also shoot Zn concentration increased by 24% after seed inoculation with 10 ⁶ CFUs mL ⁻¹. The best effects on the total metal yield were not correlated with an increasing number of inoculated bacteria. In fact the best results were found after a single soil inoculation using the lower cellular density of 10 ⁶ CFUs mL ⁻¹.
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Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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