Kurzbeschreibung
(Englisch)
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In previous projects of the EC and Switzerland a non-GMO approach of conventional in-vitro breeding and mutagenesis was used to obtain promising new genotype of crop plants with significantly enhanced properties for metal accumulation, extraction and exclusion, for improving the efficiency of phytoextraction technique to clean up contaminated soil. Whereas theoretical extrapolations from free-land phytoextraction experiments show difficulties for a fast decontamination of the “total metal” concentrations in soil, very promising prognosis of a short decontamination time of a few years only, can be made for the fast and economically feasible phytoextraction of the “soluble metal” contamination in soil. The proposed project is therefore directly based on successful attempts in that field. Within two work-packages we will specially focus on the decontamination-efficiency of the improved phytoextraction technique for soluble metal concentrations in soil, as follow: Workpackage 1: Field-based assessment of the decontamination-efficiency for bioavailable fraction of heavy metals in topsoil by improved phytoextraction, using improved plant cultivars and agronomical techniques. Workpackage 2: Field-based assessement of the stability of sunflower M5-mutant lines, useful for practical phytoextraction, including seed production of M6-generation. The expected deliverables of our work will allow both, to quantify the decontamination-efficiency of the improved phytoextraction technique for soluble metal concentrations in soil, and to better establish a promising set of well assessed, new genotypes of sunflower and tobacco with improved characteristics of metal accumulation and extraction from contaminated soil. These results are of great interest for at least 3 of 4 Working Groups of the COST Action 859.
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Partner und Internationale Organisationen
(Englisch)
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AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GR, HU, IE, IL, IT, LT, LU, NL, NO, PL, PT, RO, SE, SI, SK, TR, UK
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Abstract
(Englisch)
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In previous projects of the EC and Switzerland a non-GMO approach of conventional in-vitro breeding and mutagenesis was used to obtain promising new genotype of crop plants with significantly enhanced properties for metal accumulation, extraction and exclusion, for improving the efficiency of phytoextraction technique to clean up contaminated soil. Whereas theoretical extrapolations from free-land phytoextraction experiments show difficulties for a fast decontamination of the 'total metal' concentrations in soil, very promising prognosis of a short decontamination time of a few years only, can be made for the fast and economically feasible phytoextraction of the 'soluble metal' contamination in soil. The successfully maintanied pilot field experient was therefore directly based on previous attempts in that field. Within two work-packages we specially focussed on the decontamination-efficiency of the improved phytoextraction technique for soluble metal concentrations in soil, as follow: - Field-based assessment of the decontamination-efficiency for bioavailable fraction of heavy metals in topsoil by enhanced phytoextraction, using improved plant cultivars and agronomical techniques (Work-package 1), and assessement of the stability of sunflower M5-mutant lines, useful for practical phytoextraction, including seed production of M6-generation (Work-package 2). The expected deliverables of our work allowed both, to better quantify the decontamination-efficiency of the enhanced phytoextraction technique for soluble metal concentrations in soil, and to better establish a promising set of well assessed, new genotypes of sunflower and tobacco with improved characteristics of metal accumulation and extraction from contaminated soil. These results were of great interest for at least 3 of 4 Working Groups of the COST Action 859. Whereas theoretical extrapolations of field data from comparative phytoextraction experiments show difficulties for an efficient decontamination of the 'total metal' soil concentration, especially for Zn, Cu and Pb, very promising prognosis for a fast and efficient decontamination within a few years only, can be made for the phytoextraction of the 'soluble metal' contamination of topsoil. Field experiments were thus focused on the fast reduction of soluble metal concentration that is available to plants and thereby, save the food chain and reduce the risk of a possible groundwater contamination. Our experimental phytoremediation field was located on a zinc contaminated site in eastern Switzerland. The pseudo-total soil concentration varied from Zn 471-54'000 mg kg-1, the soluble Zn concentrations from 0.10-40 mg kg-1. Other metals present were: Cd 0.25-15.4, Cr 32-189, Ni 28-48, Cu 28-115, and Pb 30-1924 mg kg-1, pH values 6.0-7.1. Based on promising results obtained in 2006, a larger phytoextraction experiment started in 2007 on a new site with a much higher spread zinc contamination. The aim was to bring the sustainable phytoextraction to a practical use and to reduce the future destructive soil decontamination by excavation. The on-going experiment started in May 2007 with most promising mutants of tobacco, sunflower and energy maize, cultivated for 5 months, using the most appropriate fertilization treatment, to guarantee best zinc extraction. Representative samples of topsoil and plants were taken at regular times during the vegetation period and several weeks after harvest in wintertime in the direct plant rhizosphere and on soil plots without plant, to assess the effect of phytoextraction. The experiment was continued in 2008 by a crop rotation. The results of the promising two year time series experiment can be summarized as follow: - While we observed no visual symptoms of phytotoxicity and a very good biomass production for tobacco clones at the highest Zn-contamination level, the best sunflower mutants showed a significant lower tolerance. For medium to high Zn contamination, tobacco and sun-flower mutants showed a clearly enhanced tolerance and Zn extraction, compared to controls. - A strong positive correlation between Zn concentration and extraction by the tobacco and sunflower mutants and the soluble Zn in soil was found. Moreover a negative correlation was found between the soluble Zn concentration and pH in soil. While the soluble zinc concentration strongly decreased in the soil plots with tobacco, sunflower and energy maize (between 33-52% within two harvests), the soil pH increased up to 0.85 unit. The findings showed a positive two-way effect of phytoextraction: a fast reduction of the soluble metal soil concentration, combined with an enhanced pH and immobilization of metals, using efficient cultivars of tobacco and sunflower. - The second year trial revealed a more pronounced Zn extraction or stability of the first year the extraction, and no clear signs, that the soluble Zn extraction is simply recharged from the pool of 'total' contamination over wintertime could be found. This paper will show and critically comment the latest results and progress of the on-going time series phytoremediation experiment following the new approach of a risk based, fast decontamination of the soluble (plant available) metal contamination from contaminated soil. More detailed metal extraction tests with the sunflower and tobacco mutants showed in the 2008 field experiment at the landfill site of Bettwiesen 'Grüenau-Buech-Alpenblick', that our most efficient mutant lines of tobacco NBCu10-4F1 and sunflower B1/67-35-190-04-M4 can take up until 2000mg Zn/kg DW, combined with a excellent metal tolerance and biomass production, even on the most with zinc contaminated soil. This leads to a stongly enhanced zinc extraction of up to 30kg Zn/ha*a. In comparison, non improved, commercial cultivars of tobacco and sunflowers reach at the maximum 4-13kgZn/ha*a. In cooperation with our commercial client GALVASWISS our time series phytoextraction experiment could be contiuned in 2009. The results of that third year trial are expected until spring 2010.
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