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Chelator complexes enhanced Amaranthus hypochondriacus L. phytoremediation efficiency in Cd-contaminated soils

Wang, Kai, Liu, Yonghong, Song, Zhengguo, Wang, Di, Qiu, Weiwen
Chemosphere 2019 pp. 124480
Amaranthus hypochondriacus, agricultural soils, cadmium, chelating agents, citric acid, enzyme activity, ethylenediamines, glutamic acid, nitrilotriacetic acid, phytoaccumulation, phytomass, plant growth, polluted soils, pollution, soil enzymes, China
The use of degradable chelating agent to enhance phytoextraction is a promising and low-cost method for remediation of heavy metals-polluted soil. However, very limited information is available regarding the effect of chelating agent combinations on plant growth and its capacity to extract metals. In this study, a pot experiment was conducted to evaluate the applicability of [N, N]-bis glutamic acid (GLDA), nitrilotriacetic acid (NTA), [S, S]- ethylenediamine disuccinic acid (EDDS), and citric acid (CA) alone and in combination to enhance the phytoextraction efficiency of amaranth (Amaranthus hypochondriacus L.) in two Cd-contaminated agricultural soils (S1 soil 2.12 mg/kg and S2 soil 2.89 mg/kg, the environmental standard value of Cd in agricultural soils in China is lower than 0.8 mg/kg). The results showed that, except for EDDS, other treatments had no obvious effect on plant biomass, and even promoted biomass increase to reach 1.06 (S1), 2.07 (S2) g/pot. The increase in total Cd extraction amount by 5 mM of single chelators GLDA and NTA reached 3.87 and 2.81 (S1), and 3.28 and 2.50 (S2) times that of the control group, respectively. For complexed chelating agents, G-N (GLDA + NTA) combinations (GLDA = 3 mM, NTA = 2 mM) extracted the highest amount of Cd compared with other treatments, reaching 0.36 and 0.52 mg/pot (4.50 and 3.71 times that of the control group), respectively. The order of extraction amount was G-N > GLDA > NTA > G-E (GLDA + EDDS) > G-C (GLDA + CA) > CA (5 mM total Cd concentration). Moreover, soil enzyme activity of G-N treatment increased significantly compared to that of the control group, indicating the great application potential of a composite chelating agent relative to a single chelating agent. Therefore, degradable chelators, especially the G-N combination, can effectively increase the available Cd content and greatly enhance the ability of plants to absorb and transport Cd in soils.