Induced phytoextraction is an emerging soil remediation technology that makes
use of soil amendments and high biomass crop species to accumulate and
remove heavy metals from soils.
The failure to rehabilitate an uranium trial mine on Rietkuil 307 in the Karoo
Uranium Province of South Africa, has led to above normal concentrations of
uranium (U), molybdenum (Mo) and arsenic (As) in topsoil in the vicinity of U
ore stockpiles. A greenhouse evaluation was executed to assess the potential
of citric acid to induce metal uptake in the shoots of Indian mustard [Brassica
juncea (L.) Czern, cultivars: 211000 and 426308] and sunflower (Helianthus
annuus L.) to decontaminate the low-level U (28 mg U kg-1 soil), Mo (4.1 mg Mo
kg-1 soil) and As (8.9 mg As kg-1 soil) contaminated soil to background
concentrations. A further greenhouse study was performed in a soil with high
levels of metal concentrations; U (165 mg U kg-1 soil), Mo (125 mg Mo kg-1 soil)
and As (49 mg As kg-1 soil), to assess the feasibility of phytoextraction on a
high-level metal contaminated soil.
Citric acid proved to be effective in enhancing shoot-U, -Mo and -As
concentrations and the highest concentrations were observed in B. juncea
211000 (1788 mg U kg-1; 467 mg Mo kg-1; and 24 mg As kg-1) grown in the lowlevel
contaminated soil. With a biomass yield of 5.51 tonnes per year for B.
juncea 211000, it would take 9 to 14 years to decontaminate Mo and U on
Rietkuil 307 soil to background concentrations. As a result of the low As
solubility in soil and subsequent low shoot concentrations of the plant species, it
is suggested that other measures for As remediation be investigated.
Furthermore, plants grown in the high-level contaminated soil achieved
considerably lower biomass yields and shoot-metal concentrations than in the
low-level soil due to metal toxicity. Phytoextraction will, therefore, not be a
feasible remediation technology on high-level U, Mo and As contaminated soils. These results suggest that citric acid induced phytoextraction may provide an
environmentally friendly alternative for the decontamination of low-level U and
Mo contaminated soils.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-09252007-144411 |
| Date | 25 September 2007 |
| Creators | Scholtz, Ockert Fourie |
| Contributors | Mr N Scholtz, Dr GP Potgieter |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-09252007-144411/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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