Gentle remediation options (GROs) are risk management strategies or technologies involving plant (phyto-), fungi (myco-), and/or bacteria-based methods that result in a net gain (or at least no gross ...reduction) in soil function as well as effective risk management. GRO strategies can be customised along contaminant linkages, and can generate a range of wider economic, environmental and societal benefits in contaminated land management (and in brownfields management more widely). The application of GROs as practical on-site remedial solutions is still limited however, particularly in Europe and at trace element (typically metal and metalloid) contaminated sites. This paper discusses challenges to the practical adoption of GROs in contaminated land management, and outlines the decision support tools and best practice guidance developed in the European Commission FP7-funded GREENLAND project aimed at overcoming these challenges. The GREENLAND guidance promotes a refocus from phytoremediation to wider GROs- or phyto-management based approaches which place realisation of wider benefits at the core of site design, and where gentle remediation technologies can be applied as part of integrated, mixed, site risk management solutions or as part of “holding strategies” for vacant sites. The combination of GROs with renewables, both in terms of biomass generation but also with green technologies such as wind and solar power, can provide a range of economic and other benefits and can potentially support the return of low-level contaminated sites to productive usage, while combining GROs with urban design and landscape architecture, and integrating GRO strategies with sustainable urban drainage systems and community gardens/parkland (particularly for health and leisure benefits), has large potential for triggering GRO application and in realising wider benefits in urban and suburban systems. Quantifying these wider benefits and value (above standard economic returns) will be important in leveraging funding for GRO application and soft site end-use more widely at vacant or underutilized sites.
•Gentle Remediation Options (GROs) are evaluated as practical risk management methods.•Outputs and case studies are presented from the GREENLAND EC FP7 project.•Data are drawn from long-term (>5 years duration) GRO field trials across Europe.•GROs can effectively manage site contaminant risk while delivering wider benefits.
(Aided) phytostabilisation has been proposed as a suitable technique to decrease the environmental risks associated with metal(loid)-enriched mine tailings. Field scale evaluations are needed for ...demonstrating their effectiveness in the medium- to long-term. A field trial was implemented in spring 2011 in Cu-rich mine tailings in the NW of Spain. The tailings were amended with composted municipal solid wastes and planted with Salix spp., Populus nigra L. or Agrostis capillaris L. cv. Highland. Plant growth, nutritive status and metal accumulation, and soil physico- and bio-chemical properties, were monitored over three years (four years for plant growth). The total bacterial community, α- and β-Proteobacteria, Actinobacteria and Streptomycetaceae were studied by DGGE of 16s rDNA fragments. Compost amendment improved soil properties such as pH, CEC and fertility, and decreased soil Cu availability, leading to the establishment of a healthy vegetation cover. Both compost-amendment and plant root activity stimulated soil enzyme activities and induced important shifts in the bacterial community structure over time. The woody plant, S. viminalis, and the grassy species, A. capillaris, showed the best results in terms of plant growth and biomass production. The beneficial effects of the phytostabilisation process were maintained at least three years after treatment.
•Compost amendment reduced soil acidity, improved fertility and decreased available Cu.•Reduced phytotoxicity enabled the establishment of a grass cover and short rotation coppice system.•Soil enzyme activities increased after compost addition and were highest under Salix viminalis.•Shifts in bacterial community structure were associated with amendments and plant species.•Organic wastes can be effectively incorporated into phytostabilisation techniques.
Gentle Remediation Options (GRO) are risk management strategies or techniques for contaminated sites that result in no gross reduction in soil functionality (or a net gain) as well as risk ...management. Intelligently applied GROs can provide: (a) rapid risk management via pathway control, through containment and stabilisation, coupled with a longer term removal or immobilisation/isolation of the contaminant source term; and (b) a range of additional economic (e.g. biomass generation), social (e.g. leisure and recreation) and environmental (e.g. CO2 sequestration) benefits. In order for these benefits to be optimised or indeed realised, effective stakeholder engagement is required. This paper reviews current sector practice in stakeholder engagement and its importance when implementing GRO and other remediation options. From this, knowledge gaps are identified, and strategies to promote more effective stakeholder engagement during GRO application are outlined. Further work is required on integrating stakeholder engagement strategies into decision support systems and tools for GRO (to raise the profile of the benefits of effective stakeholder engagement and participation, particularly with sector professionals), and developing criteria for the identification of different stakeholder profiles/categories. Demonstrator sites can make a significant contribution to stakeholder engagement via providing evidence on the effectiveness of GRO under varying site contexts and conditions. Effective and sustained engagement strategies however will be required to ensure that site risk is effectively managed over the longer-term, and that full potential benefits of GRO (e.g. CO2 sequestration, economic returns from biomass generation and “leverage” of marginal land, amenity and educational value, ecosystem services) are realised and communicated to stakeholders.
•Stakeholder engagement when applying gentle remediation options (GRO) is reviewed.•A context for GRO application within sustainable remediation strategies is outlined.•Key principles of stakeholder engagement are described for GRO.•Effective long-term engagement is required to optimise potential benefits from GRO.
To characterize bacteria associated with Zn/Cd-accumulating Salix caprea regarding their potential to support heavy metal phytoextraction. Three different media allowed the isolation of 44 ...rhizosphere strains and 44 endophytes, resistant to Zn/Cd and mostly affiliated with Proteobacteria, Actinobacteria and Bacteroidetes/Chlorobi. 1-Aminocyclopropane-1-carboxylic acid deaminase (ACCD), indole acetic acid and siderophore production were detected in 41, 23 and 50% of the rhizosphere isolates and in 9, 55 and 2% of the endophytes, respectively. Fifteen rhizosphere bacteria and five endophytes were further tested for the production of metal-mobilizing metabolites by extracting contaminated soil with filtrates from liquid cultures. Four Actinobacteria mobilized Zn and/or Cd. The other strains immobilized Cd or both metals. An ACCD- and siderophore-producing, Zn/Cd-immobilizing rhizosphere isolate (Burkholderia sp.) and a Zn/Cd-mobilizing Actinobacterium endophyte were inoculated onto S. caprea. The rhizosphere isolate reduced metal uptake in roots, whereas the endophyte enhanced metal accumulation in leaves. Plant growth was not promoted. Metal mobilization experiments predicted bacterial effects on S. caprea more reliably than standard tests for plant growth-promoting activities. Bacteria, particularly Actinobacteria, associated with heavy metal-accumulating Salix have the potential to increase metal uptake, which can be predicted by mobilization experiments and may be applicable in phytoremediation.
BACKGROUND AND AIMS: Graminaceous plants exude phytosiderophores (PS) for acquiring Fe. Adsorption of PS and its metal complexes to the soil solid phase reduces the FePS solution concentration and ...hence Fe uptake. In this study we aimed to quantify adsorption, and to determine to what extent adsorption depends on the complexed metal and on soil properties. Furthermore, we examined if adsorption is a reversible process. METHODS: Adsorption and desorption of PS and metal-PS complexes were examined in batch experiments in which the PS 2â²-deoxymugineic acid (DMA) and its metal-complexes (FeDMA, CuDMA, NiDMA and ZnDMA) interacted with several calcareous soils. RESULTS: Adsorption of DMA ligand (0â1000 μM) and metal-DMA complexes (0â100 μM) was linear in the concentration range examined. Adsorption varied by a factor â2 depending on the complexed metal and by up to a factor 3.5 depending on the soil. Under field-like conditions (50 % water holding capacity), 50â84 % of the DMA was predicted to be retained to the soil solid phase. Alike adsorption, desorption of metal-DMA complexes is fast (approximate equilibrium within 1 hour). However, only a small fraction of the adsorbed FeDMA (28â35 %) could be desorbed. CONCLUSIONS: Despite this small fraction, the desorbed FeDMA still exceeded the amount in solution, indicating that desorption of FeDMA from soil reactive compounds can be an important process buffering the solution concentration.
Metal-accumulating woody species have been considered for phytoextraction of metal-contaminated sites. We investigated Zn and Cd accumulation in tissues of adult trees and associated herbaceous ...species collected from contaminated areas in Central Europe. We found considerable Cd and Zn accumulation in various willow, poplar and birch species with up to 116
mg
Cd
kg
−1 and 4680
mg
Zn
kg
−1 in leaves of
Salix caprea. Annual variation of Cd and Zn concentrations in leaves of
Salix caprea were small, indicating that data obtained in different years can be compared. Metal concentrations in leaves were not related to total (
aqua regia) or labile (1
M NH
4NO
3 extract) concentrations in soil but the accumulation factors (leaf concentration: soil concentration) for Cd and Zn followed an inverse log type function. Metal partitioning between tissues showed a minimum in the wood, with increasing concentrations of Cd and Zn towards the leaves and fine roots.
Adult field-grown Salix caprea, Populus tremula and other tree species accumulate up to 4680
mg
Zn
kg
−1 and 116
mg
Cd
kg
−1 in their leaves.
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.
Aims Phytomanagement of metal-polluted soils requires information on plant responses to metal availability in soil, but the predictability of metal accumulation in plant shoots and/or roots may be ...limited by metal toxicity and inherent shortfalls of the bioavailability assays. Methods We measured the uptake of Cd and Zn in a Salix smithiana clone grown in a pot experiment on soils with different characteristics and metal availabilities, determined by conventional soil single extractions (0.05 M Na₂-EDTA and 1 M NH₄NO₃), soil solution obtained by centrifugation, and diffusive gradients in thin films (DGT). The Cd and Zn phytoavailability after a 2-year phytoextraction by willow was assessed by metal accumulation in the straw of the following barley culture.
Results The phytoextraction efficiency was largest on a moderately polluted acid soil. Biomass and shoot Zn concentrations of S. smithiana were better predicted by DGT-measured Zn concentrations in soil solution (C
DGT
) than by Zn concentrations in the soil solution and extractable soil fractions. The weaker correlation for Cd in shoots may be related to relative Cd enrichment in the plant tissues. The metal accumulation in barley straw was unaffected or increased after a 2-year phytoextraction.
Conclusions The shoot Zn and Cd removal of the tested Salix clone can be predicted by C
DGT
concentrations and is highest on either calcareous or moderately polluted acid soils. Single extraction with NH₄NO₃ and the C
DGT
value of Cd were not able to predict shoot Cd removal on the tested soils. Only shoot removal of Zn was predicted fairly well by the C
DGT
value.
Cadmium accumulation and physiological response of sunflower plants to Cd during the vegetative growing cycle De Maria, S., University of Basilicata, Potenza (Italy). School of Agricultural, Forest, Food and Environmental Sciences; Puschenreiter, M., University of Natural Resources and Life Sciences, Vienna (Austria). Dept. of Forest and Soil Science; Rivelli, A.R., University of Basilicata, Potenza (Italy). School of Agricultural, Forest, Food and Environmental Sciences
Plant, soil and environment,
(Jun 2013), Letnik:
59, Številka:
6
Journal Article
Recenzirano
Odprti dostop
The effects of soil cadmium (Cd) contamination on Cd accumulation and distribution, growth and physiological responses of sunflower plants were investigated. Plants were subject to six levels of soil ...contamination (from 2.5 to 15 mg Cd kg/soil) with an untreated control, from the emergence of the cotyledon leaves until the harvest, when plants were at the flower bud stage. An overall increase of Cd concentration was found in all tissues of the plants (roots, stem, young, mature and old leaves) by increasing the Cd contamination in the soil. Regardless of treatments, Cd concentration in roots always exceeded those in the aboveground dry matter with a low translocation from roots to shoots. At early stage of growth, Cd concentration in plants was higher than at the flower bud stage. Soil Cd contamination did not affect plant growth, relative water content and gas exchange parameters. Negative and significant correlation was only found between Cd concentration in the young leaves and chlorophyll concentration at the end of vegetative growing stage. Roots and old leaves are the main metal sinks suggesting a defense or tolerance mechanism of the plants to avoid toxic levels in physiologically most active apical tissues. These results should be tested in open field to verify the suitability of sunflower in the area of phytotechnologies.
PDF
