The Influence of Nitrilotriacetate on Heavy Metal Uptake of Lettuce and Ryegrass

Abstract Metal uptake and removal from the soil by plants may be a useful measure to remediate contaminated soils. These processes can be enhanced by adding metal chelators to soil. We investigated the effect of nitrilotriacetate (NTA) and urea on the uptake of Cd, Cu, and Zn by lettuce ( Lactuca sativa L. cv. Orion) and Italian ryegrass ( Lolium perenne L. cv. Bastion) in pot experiments. Nitric acid‐extractable heavy metal concentrations in the contaminated soil were 2 mg Cd, 530 mg Cu, and 700 mg Zn kg −1 . Three NTA treatments (0.5, 1.8, and 5.3 mol m −2 ) were compared with two urea treatments (0.25 and 0.9 mol m −2 ), and a control. Nitrilotriacetate and urea increased the NaNO 3 ‐extractable soil concentrations of the three metals. At the highest NTA dose, metal concentrations in the aboveground plant biomass was 4 to 24 times greater than in the control plants. While NTA increased plant metal concentrations, it reduced plant matter production. At lower doses, this effect was small. At the highest NTA dose, plant growth was almost completely 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 intermediate NTA dose than at the highest doses. Little additional total metal uptake was achieved with NTA treatments than with urea. Compared with the controls, neither NTA nor urea enhanced total uptake under the given conditions by more than threefold.