| Phytoremediation has been increasingly proposed as a green, high-effective and environment-friendly technology for remediation of soils contaminated by heavy metals in recent years, Chelate-induced phytoremediation is considered as an effective tool for the extraction of heavy metals from soils by plants. A soil site contaminated by Cu, Zn, Pb, Cd near the Cu smeltering mill was investigated in Fu-Yang city, Zhejiang province. Accumulation and distribution of Cu, Zn, Pb, Cd in the soil-rice plant system within the contaminated site was characterised. A pot experiment was conducted using 16 different metals contaminated soils from contaminated site to study phytoavailability of heavy metals for Zebrine pendula, Chemical extraction methods (0.005mol L-1 DTPA and 1mol L-1 NH4NO3) were used for evaluating the phytoavailability of heavy metals in the soil, The potential use of Zebrine pendula for revegetation of the contaminated soils was explored. Because of the environmental risk of not-readily biodegradable chelate agent such as EDTA in chelate-induced phytoremediation. EDDS, a structural isomer of EDTA was report as a readily- biodegradable replacement for EDTA, EDDS and metal-EDDS complexes were much readily biodegradable. EDDS exhibited lower toxicity and lower environmental risk. A pot experiment was performed to compare the effects of different doses of EDDS and EDTA on Brassica juncea extraction of Cu, Zn, Pb and Cd. The soil moisture sampler was employed to examine the changes of heavy metals and total organic carbon in the soil solutions and their relationships. The effect of EDDS and EDTA on soil pH, NH4NO3-extractable heavy metals was also investigated. In order to futher understand the soil mechanism and environmental risk of chelate-induced phytoremediaton, Then three-step sequential extraction procedure was performed to study the speciation of heavy metals following addition of EDDS and EDTA.The results indicates that the total concentrations (mg kg-1) of the four heavy metals in the contaminated soil ranged from: 59-683 for Cu, 237-2117 for Zn, 80-473 for Pb, and 1.4-12.1 for Cd, with average concentrations of 193, 820, 182, 3.5, respectively; the percentages of exceeding the national soil environmental quality standards (GB15618-1995) were 92%, 100%, 16%, 100% for Cu, Zn, Pb, Cd, respectively, demonstrating that the agricultural field site was polluted severely with Cu, Zn and Cd.The total metal concentrations (mg kg"1) in the rice ranged from: 2.93-8.23 for Cu, 4.40-45.83 for Zn, 0.05-2.15 for Pb, and 0.07-2.92 for Cd. The rice concentrations of Cu, Zn was under the national food quality standards while the rates of exceeding the standards of Pb and Cd were 28% and 92%, indicating a high risk of safety and health resulting from Pb and Cd pollution.The increase sequence of heavy metal concentration in different tissues of rice plant was: root>shoot, leaf >polished rice, and the sequence of metal enrichment coefficient in polished rice was Cd>Zn>Cu>Pb. The different metal elements had different transfer abilities, showing easier transfer for Cd from soil to rice plant, and easier transport for Zn from root to shoot and leaf.The results from the pot experiment in which Zebrine pendula was grown in the metal mixed polluted agricultural soils showed that the mixed metal pollution had no adverse effects on growth of the plants, and indicated that power or exponential functions could be used to describe the relationships between the DTPA-extractable metal (Cu, Zn, Cd) concentration and total metal concentration in soil and also the relationships between the NH4NO3-extractable metal (Cu, Zn, Cd , Pb) concentration and the total in soil. The exponential function also fitted into describing the relationships between the aboveground metal concentration of Zebrine pendula and soil total metal (Zn, Pb, Cd) or soil NH4NO3-extractable metal (Zn and Pb) . However, No such relationships were found for Cu. Although.Zebrine pendula had no potential for hyperaccumulation, the plant did show a h...
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