EDTA / EGTA
Ethylene diamine tetraacetic
acid is a synthetic chelator that has been shown to substantially lower
soil CEC. It has been used since the 1950s to alleviate iron deficiency,
and has been used frequently to improve phytoextraction of metal contaminants,
such as lead, from soil (Jorgenson, 1993). Oftentimes, a sudden increase
in bioavailable metals resulting in EDTA application will be fatal to plants.
This is overcome by growing plants up to a large biomass, then adding EDTA.
The metal will become highly bioavailable, and will be taken up in large
quantities by the plant for a short time before the plant dies (Salt, et
al. 1998). In this way, large amounts of metal can be extracted from soil.
This strategy is referred to as chelator-assisted phytoextraction (Salt,
et al. 1998). A similar compound called ethylene glycol tetra acetic acid
(EGTA) has been shown to be very effective at increasing Cd bioavailability
(Blaylock, et al. 1997).
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