Using EDDS and NTA for enhanced phytoextraction of Cd by water spinach

A greenhouse experiment was used to test the applicability of [S,S]-Ethylenediaminedisuccinic acid (EDDS) and nitrilotriacetic acid (NTA) at rates of 2.5 mmol kg−1 and 5.0 mmol kg−1, respectively, to increase the uptake of Cd by water spinach (Ipomoea aquatic Forsk) in soils with 2.5–30 mg Cd kg−1. The addition of EDDS and NTA significantly increased water soluble Cd in soils. However, the Cd concentration in the root and shoot was higher in the NTA treatment than in the EDDS treatment. No instance of Cd hyperaccumulation was observed; however, the 5.0 mmol kg−1 NTA treatment for soil with 30 mg Cd kg−1 caused the Cd concentration to increase to 86 mg kg−1, which is close to the critical concentration (100 mg kg−1) of a hyperaccumulator. The total Cd uptake in the treatments of EDDS and NTA for soils with 2.5, 5.0, and 10 mg Cd kg−1 was acceptable, and was higher than the control. The level of 5.0 mmol kg−1 EDDS was excessively high for enhanced phytoextraction in soils with 20 and 30 mg Cd kg−1. Water spinach for Cd phytoextraction is a viable alternative to using herbaceous hyperaccumulators.

► This is the first study on water spinach for Cd phytoextraction in soil.
► Cd tolerance of water spinach was acceptable in this study.
► Cd concentration in the shoot increased 1.5–2.1-fold compared to the control.
► NTA was more effective in the enhanced phytoextraction of water spinach than EDDS.