Phytosiderophore effects on subsurface actinide contaminants: potential for phytostabilization and phytoextraction. Page: 3 of 4
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Table 1: Stability consta nts (log K) of Phytosiderophores and other chelators with various metal ions.
Chelator Nn(II Fe(d) Co(11) Zn(1) Ni(II) Cu(II) Fe(111) Pu(IV) U(VI)
Nicotianamine 8.8 12.4 14.8 -15 16.1 18.6
Mugincic acid 8.C 8.3 10.7 14.9 -18.4 18.1
Desfcerrioxamine [3 7.2 103 10.1 10.9 14.1 30.6 30.8 18
Citrate 3.A 4.6 5.0 5.0 5.4 5.9 11.4 -12 7.4
FDTA 13. 14.3 16.3 18.6 16.5 18.8 25.1 25.6 7.4
Phytosiderophore-producing plants are known to uptake uranium and translocate it into above ground parts3
and may have higher Pu uptake than other plant species.4 Plutonium uptake and transport in plants seems to
mimic nutrient transport, with similarities found to Fe transport.5 Plutonium and uranium most likely track 'hard'
metal nutrient transport systems in plant, such as Fe uptake by phytosiderophores. Phytosiderophores will
predictably strongly chelate Pu, L and Th, and increase their solubility and mobility in soils, similar to EDTA
and bacterial siderophores. Phytusiderophores-mediated uptake could explain many of the observations made
on Pu uptake into plants.
Some phytosiderophores are up to 100 times more efficient than anthropogenic or bacterial Fe chelators
for Fe uptake into graminaceous plants.' They may be able to enhance Pu uptake by similar amounts. It is likely
that applying additional phytosiderophores to these plants would show even greater increases in Pu uptake than
seen with applied synthetic chelators. This is due to the fact that phytosiderophores would increase solubility of
Pu and increase root translocation rates, whereas synthetic chelators can only increase solubility of Pu. At least
for grasses, metal uptake rates will depend on the amount of phytosiderophore available that can outcompete
EDTA for the metal; i.e. when solubility of the metal is no longer limiting, root translocation rates are
ultimately limited by available transport ligands and the uptake rate of these metal-ligand complexes. This has
been directly demonstrated with barley, where application of EDTA to Fe-deficient plants actually decreased
xylem concentration of Cu, Fe, Mn, and Zn.' Using phytosiderophores directly eliminates this
competition/exchange step and nsures solubilized metal is balanced with metal uptake ability, eliminating a
problem of chelate induced phytoextraction.
Here, we will present our initial research findings on the ability of applied phytosiderophores
(synthesized) to chelate, solubilize, and mobilize plutonium from amorphous solids and soil samples, compared
to synthetic chelators (such as EDTA) and bacterial siderophores. We will also demonstrate the effect of
phytosiderophores on the uptake rate of plutonium in plants by comparing plutonium uptake amounts in a
phytosiderophore producing plant (barley) grown hydroponically in Fe-replete and Fe-depleted conditions and
in a non-phytosiderophore producing plant uysed commonly in phytoremediation technologies (Indian
Mustard), also grown in Fe-replete and Fe-depleted conditions.
S e :+t lll
1 \@ Z
Pu removed from soil
Pu Pu Pu
P u Pu P
Pu concentrated - Puuptake
- _ __& stabilized Phytostabilization:
& i d Pu association
plants deg1a de cheIawr's n Iplutonium
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Ruggiero, C. E. (Christy E.); Twary, S. N. (Scott N.) & Deladurantaye, E. (Elise). Phytosiderophore effects on subsurface actinide contaminants: potential for phytostabilization and phytoextraction., article, January 1, 2003; United States. (digital.library.unt.edu/ark:/67531/metadc930925/m1/3/: accessed November 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.