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Lead (Pb) is one of the ubiquitous soil contaminants. The strategy to increase Pb phytoremediation is of highly critical considering the difficulty in phytoextraction of Pb due to its low solubility and high retention on soil particles. The effects of application nano hydroxyapatite (NHAP) on Pb phytoextraction by ryegrass ( Lolium Perenne L.) were evaluated. Ninety pots of Pb-contaminated soil with different Pb concentrations (0–800 mg/kg) were seeded with ryegrass. The effects of NHAP on biomass and Pb uptake were examined. The results indicated that the application of 5 g/kg NHAP to Pb-contaminated soils significantly increased the ryegrass biomass. The removal rates of Pb from the soil by ryegrass were enhanced obviously after NHAP addition. These results suggested that NHAP was suitable for application to in-situ Pb-contaminated soils for remediation. The observation in this study provides useful information about the effects of NHAP on lead removal, which plays an important role in the phytoremediation. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a novel experimental setup (one pot placed above another) was used to investigate the residual effects of EDDS application on plant growth and metal uptake. Two plant species, garland chrysanthemum and ryegrass, were grown in the upper pots (mimicking the upper soil layers) and were harvested 7days after EDDS application. During this period the upper pots were watered twice. The lower pots (mimicking the subsoil under the upper soil layers) served as leachate collectors. Thereafter, the two pots were separated, and the same plants were grown in the upper and lower pots in two continuous croppings. Results showed that EDDS application restrained the growth of the first crop and resulted in a dramatic enhancement of Cu accumulation in plants grown in the upper pots. However, no negative growth effects were identified for the second and third crops, which were harvested 81 and 204days after the EDDS application, respectively. In the lower pots, the leachate from the upper pots after EDDS application exhibited the increased total and CaCl2-extractable Cu concentrations in the soil. However, the growth of garland chrysanthemum and ryegrass, and their shoot Cu concentrations were unaffected. These data suggest that the residual risk associated with EDDS application was limited, and that subsoil to which EDDS leachate was applied may exhibit reduced Cu bioavailability for plants due to the biodegradation of EDDS. [Copyright &y& Elsevier]