Phytoextraction, a remediation strategy for lead (Pb)-contaminated soils th
at removes soil Pb through plant uptake and harvest, may be enhanced by use
of synthetic chelates. We evaluated Pb desorption from four contaminated s
oils (total Ph 1278-14 349 mg kg(-1)) by seven chelates (CDTA, DTPA, EDDHA,
EGTA, HEDTA, HEIDA, and NTA) at three rates (0.2, 2.0, and 20 mmol chelate
ks soil(-1)). The three most effective chelates (CDTA, DTPA, and HEDTA) we
re used in greenhouse studies with an uncontaminated soil and a Pb-contamin
ated soil (total Pb = 3212 mg kg(-1)) to determine the effect of chelate ty
pe and rate on growth, Pb uptake, and plant elemental composition. Lead des
orption varied with chelate and soil and increased with chelate rate, avera
ging 948 mg Pb kg(-1) at the 20 mmol kg(-1) rate vs. 28 mg Pb kg(-1) by the
control. The general ranking of chelate effectiveness, based on total Pb d
esorbed, was HEDTA > CDTA > DTPA > EGTA > HEIDA > EDDHA similar to NTA. Pla
nt uptake of Pb from the contaminated soil was enhanced by CDTA, DTPA, and
HEDTA, but with even the most effective treatment (corn, high CDTA rate), t
he amount of Pb extracted by plants was rather low (0.4 kg Pb ha(-1)). Lead
extractable by the Toxicity Characteristic Leaching Procedure) (TCLP) was
increased from 9 mg L-1 in the control to from 47 to 174 mg L-1 in soils tr
eated with 20 mmol kg(-1) CDTA or DTPA and chelates generally caused a shif
t in Pb from resistant to more soluble chemical fractions.