The Influence Of Biodegradable Chelants On The Phytoextraction Efficiency Of Amaranthus Hybridus L. In Cd Contaminated Soil

Phytoremediation was largely restricted by the bioavailability of heavy metal. Therefore, adding chelants in soils for assisting phytoextraction has been proposed an alternative to enhance phytoextraction efficiency. In order to investigate the ideal dosage and time for the treatments of biodegradable chelants, Amaranthus hybridus L. Was selected as matching plant for chelant-assisted phytoremediation in Cd contaminated soil to study the tolerance of A.hybridus under chelant treatments and compare the potential of the three kinks of biodegradable chelants to enhance the phytoextraction of A.hybridus. the pot experiments and plot experiments were taken. The main results showed as follows.The results showed that A.hybridus performed some Cd tolerance under the application of EDDS, NTA and APAM. No significant differences were observed for the root and shoot biomass, root morphology and photo synthetic responses of A.hybridus in 10 mg kg-1 Cd contaminated soil (P>0.05), while POD and CAT activities, glutathione (GSH) concentration and soluble protein content in roots and leaves of A.hybridus significantly increased (P<0.05). When EDDS, NTA and APAM were applied to the 100 mg kg-1 Cd contaminated soil, root biomass, shoot biomass, root length, root surface area, root volume and lateral roots of A.hybridus significantly decreased, and net photosynthetic rate (Pn), stomatal conductance (Gs), internal CO2 concentration (C,) and transpirationrate (Tr) significantly decreased (P<0.05). Moreover, EDDS and APAM addition significantly increased the POD and CAT activities in roots and leaves of A.hybridus, while NTA addition significantly decreased the POD and CAT activities in roots and leaves of A.hybridus in 100 mg kg-1 Cd contaminated soil. GSH concentration in roots and leaves significantly increased by 23.59～106.22% and 44.06-125.45%. Moreover, all the chelants addtion significantly increased soluble protein content by 16.00～60.05% in roots of A.hybridus in 100 mg kg-1 Cd contaminated soil, while soluble protein content significantly decreased by 26.82～30.50% after the addition of 2 mmol kg-1 NTA. However, soluble protein content in leaves of A.hybridus significantly increased by 22.68～136.53% after the chelants addtion in 100 mg kg-1 Cd contaminated soil (P<0.05).When the Cd concentrations were 10 mg kg-1 and 100 mg kg-1, the application of chelants significantly enhanced the Cd concentrations in roots and shoots of A.hybridus by 40.78～103.13%,45.00～156.41%,15.02～49.48% and 25.58～67.31%, respectively. The phytoextraction of Cd in roots and shoots reached the maximum of 126.22μg pot-1,758.16 μg pot-1,286.35 μg pot-1 and 1666.20 μg pot-1, respectively. And the RF reached 0.36～0.95% and 0.14～0.21%, respectively.A.hybridus had great phytoextraction potential in Cd polluted sites. In the plot experiment, chelant addition significantly enhanced the phytoextraction potential of A.hybridus. The results showed that under the treatments of EDDS, NTA and APAM, no significant differences were observed for the root and shoot biomass. And the PP reached 1772.20-2119.80 g ha-1. When compared the phytoextraction efficiency of EDDS, NTA and APAM, we can conclude that 2 mmol kg-1 NTA applied on the 65th day was the best choice for phytoextraction of Cd polluted soils in this study. And APAM may be more suitable for the condition of mine remediation because it possesses the certain dissolved ability, moisture holding capacity and has the potential benefits of large-scale application.