Slow release chelate enhancement of lead phytoextraction by corn (Zea mays L.) from contaminated soil—a preliminary study

Abstract

(2005). Slow release chelate enhancement of lead phytoextraction by corn (Zea mays L.) from contaminated soil: A preliminary study. Science of The Total Environment, 339(1-3), 179-187. DOI: 10.1016179-187. DOI: 10. /j.scitotenv.2004 Published in: Science of The Total Environment Queen's University Belfast -Research Portal: Link to publication record in Queen's University Belfast Research Portal General rights Copyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Abstract Short-term enhancement of lead (Pb) and zinc (Zn) uptake by corn (Zea mays L.) seedlings from a contaminated soil was compared using slow-release coated EDTA granules-a coated chelating agent (CCA), uncoated EDTA granules, and EDTA solution in a greenhouse experiment. Soil Pb and Zn fractions were determined using a sequential extraction scheme. Release of the metals in the soil was examined in a column leaching study. After only 7 days of seedling growth, shoot biomass was decreased by all EDTA treatments compared with the zero-EDTA control. The amount of shoot biomass produced was highest with uncoated EDTA, intermediate with CCA, and lowest with the EDTA solution. Shoot Pb contents were highest with solid EDTA, intermediate with CCA, and lowest with EDTA solution, and they were always higher with EDTA treatments than in controls. In contrast, shoot Zn contents following EDTA treatments were lower than in the control. Levels of soil dissolved organic carbon (DOC) in aqueous soil extracts were much lower after CCA application than following treatments with solid EDTA and EDTA solution. After 17 days of plant growth, when most of the chelating agent had been released from the CCA, soil organic carbon levels remained relatively constant and similar to those in the control, indicating that a relatively low chelating agent concentration can be maintained for the plants to take up the metals. The distribution of Pb in the sequential extraction procedure showed that the Pb level in the exchangeable+carbonate-bound fraction with CCA was significantly lower than that with solid EDTA or EDTA solution, further indicating that slow release of CCA improves the bioavailability of metals in the soil to match plant uptake of those metals. The results suggest that CCA can enhance shoot content of Pb but not of Zn from the contaminated soil in the short term, and may also reduce the risk of metal leaching from the soil. D

Use of non-hyperaccumulator plant species for the phytoextraction of heavy metals using chelating agents

“…Heavy metal contamination of soils is an important environmental issue because of its impact on soil preservation and human health (Li et al, 2005). In São Paulo State, Brazil, 4,131 contaminated sites have been identified, and 543 of them are contaminated with a variety of metals (CETESB, 2011).…”

Phytoextraction of Pb and Cu Contaminated Soil With Maize and Microencapsulated EDTA

“…To lower the speed of release of Pb by EDTA, Shen et al (2002) tested split applications of EDTA and found that Pb was leached much more slowly with split application than single application. Li et al (2005) developed a controlled-release EDTA by coating the EDTA with a layer of silicate. Unfortunately, the silicate-coated EDTA was released within a short period, probably due to the properties of the coating materials.…”

Phytoextraction: a review on enhanced metal availability and plant accumulation

“…Therefore, even if suitable irrigation strategies are implemented as proposed (Blaylock et al, 1997;Madrid et al, 2003), the potential of metals leaching in synthetic chelator-treated soil is still high during seasons of intense rainfall. In a preliminary study that used 1 week-old seedlings, Li et al (2005) registered that turning EDTA into a slow-release compound through coating of the EDTA granules with silicates could reduce the risk of metal leaching. More studies with older plants on a field scale are needed to assess the usefulness of this technique for overcoming the leaching risks while maintaining a high metal uptake rate by plants.…”

“…For instance, coating natural organic acids to maintain a stead concentration of metal-organic acids complexes in soil solution, as done to EDTA by Li et al (2005), could be an alternative. Apparently fast biodegradation rather than the low organic acid ability to solubilize metals is the main reason for unsuccessful phytoextraction (Krishnamurti et al, 1997;Nascimento et al, 2006).…”