The influence of nitrilotriacetate on heavy metal uptake of lettuce and ryegrass

Metal uptake and removal from the soil. by plants may be a useful measure t o remediate contaminated soils. These processes can be enhanced by adding m etal chelators to soil. We investigated the effect of nitrilotriacetate (NT A) and urea on the uptake of Cd, Cn, and Zn by lettuce (Lactuca sativa L. c v. Orion) and Italian ryegrass (Lolium perenne L. cv. Bastion) in pot exper iments. Nitric acid-extractable heavy metal concentrations in the contamina ted soil were 2 mg Cd, 530 mg Cu, and 700 mg Zn kg(-1). Three NTA treatment s (0.5, 1.8, and 5.3 mol m(-2)) were compared with two urea treatments (0.2 5 and 0.9 mol m(-2)), and a control. Nitrilotriacetate and urea increased t he NaNO3-extraftable soil concentrations of the three metals. At the highes t NTA dose, metal concentrations in the aboveground plant biomass was 4 to 24 times greater than in the control plants. While NTA increased plant meta l concentrations, it reduced plant matter production. At lower doses, this effect was small. At the highest NTA dose, plant growth was almost complete ly inhibited. Severe visual symptoms indicated metal toxicity as the likely cause. The urea treatments generally increased the plant matter production . Total metal uptake was in general larger at the lowest or at the intermed iate NTA dose than at the highest doses. Little additional total metal upta ke was achieved with NTA treatments than with urea. Compared with the contr ols, neither NTA nor urea enhanced total uptake under the given conditons b y more than threefold.