Chelating Agent And Surfactant Reinforced Pennisetum Spp. Repair Of Lead And Cadmium Pollution Soil Research

Great achievement has been obtained on the remediation of heavy metal contaminated soil by adding chelant and surfactant. Nemerow index was used to evaluate the soil pollution situation by heavy metals which were resulted from the domestic waste fertilizer, and selected the target heavy metal as our studying object. The optimal activation time and adding doses were obtained though static activation experiments. It indicated that TX^-100 and tea saponin could enhance adsorption of Pennisetum spp. on soil Pb and Cd in a pot experiment, EDTA and citric acid to could enhance the adsorption ability of Pennisetum spp. on soil Pb and Cd in the field experiment. It could be concluded that:（1） The Nemero index （NI） was selected as a parameter to estimate the pollution situation of soil heavy metals of the studying area. It indicated that soil showed no obvious contamination from As, slightly pollution from Hg, moderate from Pb and serious pollution from Cd, where the NI of soil Pb and Cd were 2.69 and 9.17, respectively.（2） The pH value of soil solution decreased 0.15-0.99 unit after a 7-day static experimental activation treated by EDTA and citric acid. While the pH value of soil solution decreased 0.11-0.83 unit after a 14-day static experimental activation treated by TX^-100 and tea saponin. After that the soil pH increased gradually and tended to be constant after a 28-day static experimental activation. Except for TX^-100, when treated by the static experimental activation, the bioavailable state of Pb and Cd increased significantly at the 7th day, and peaked at the 28th day.（3） After a 28-days’static experimental activation, the acid soluble state of soil Pb and Cd increased with the dose increasing of chelating agent and surfactant. While the soil labile reduction Pb and Cd decreased significantly with the dose increasing of chelating agent and surfactant.（4） The pot experiment showed that TX^-100 and tea saponin could strengthen the remediation effect of Pennisetum spp. to soil Pb and Cd contamination. It indicated that the acid soluble state, liable reductant state and oxidation state of soil Pb and Cd decreased when adding TX^-100 and tea saponin to the imitated soil after 28 days, and the remedation effect of tea saponin was much better than TX^-100.（5） TX^-100 could promote the Pb and Cd absorption by Pennisetum spp., and oppotimum addition dose was 5.0 g·L^-1. Compared with the controlled, the Pb and Cd accumulation had increased 73.52% and 35.77%, respectively. The Cd and Pb accumulation in Pennisetum spp. reached peak when treated by tea saponin with an addition of 1.0 g·L^-1 and 5.0 g·L^-1, individually. In addition, the tea saponin had expressed a better accumulation effect in helping Pennisetum spp. to remedy Pb and Cd contaminated soil.（6） A filed experiment in a certain vegetation area was carried out to investigate the uptake and accumulation characteristics of Pb and Cd by Pennisetum spp. in response to the addition of EDTA and citric acid at the level of 10 mmol·L^-1. It indicated that the soil Pb concentration decreased 6.31% and 5.72% in rhizospherezone aided by EDTA and citric acid, while soil Cd in rhizosphere had showed an increase of 23.58% and 11.03%, respectively. The concentrations of Cd and Pb in Pennisetum spp. increased 26.8% and 92.9% aided by EDTA, and 12.6%and 72.2% increasing aided by citric acid.