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| Remediation of Multiple Heavy Metal Polluted Soil Using Different Immobilizing Agents |
| Received:October 30, 2014 |
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| KeyWord:immobilizing agents;heavy metal;soil remediation;bioavailability |
| Author Name | Affiliation | E-mail | | YIN Fei | Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China | | | WANG Hai-juan | Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China | | | LI Yan-yan | Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China | | | LI Qin-chun | Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China | | | HE Shu-juan | Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China | | | WANG Hong-bin | Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China | whb1974@126.com |
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| Abstract: |
| Four immobilizing agents, namely phosphate rock, charcoal, palygorskite and steel slag, were separately added to a soil polluted combinedly by five heavy metals to evaluate their effectiveness of immobilizing heavy metals. Soil pH and bioavailable fraction(single extraction) and chemical fractionations(sequential extraction) of heavy metals were measured. The phase composition, specific surface area and pore characteristics of four immobilizing agents were also analyzed by X-ray diffraction(XRD) and specific surface area-pore size distribution analyzer. Results showed that bioavailable fraction of five metals decreased significantly after additions of palygorskite, steel slag or phosphate rock at a ratio of 20%. The treatment with palygorskite resulted in the greatest reduction of bioavailable Pb, Cd, Cu and As, which was 54.3%, 48.8%, 50.0% and 35.0%, respectively. Applying steel slag also decreased bioavailable Zn by 43.7%. Exchangeable Pb decreased, while residual Pb increased significantly by addition of 20% palygorskite. Exchangeable Cd was decreased by applying 20% palygorskite, steel slag or phosphate rock. Exchangeable Zn was also decreased by additions of 20% steel slag or 20% phosphate rock. Carbonate-bound Zn(a fraction easily taken up by plants) was decreased by 20% phosphate rock or 20% steel slag additions. Residual Zn significantly increased by application of palygorskite. Similar result was also observed in residual Cu when steel slag(5% and 20%) or 20% phosphate rock were added. The Ca-As fractions, an inert fraction for plant uptake, increased significantly with applying 20% phosphate rock. The main immobilizing mechanism of charcoal and palygorskite was adsorption and surface complexation due to their large specific surface areas and pore volumes, while chemical precipitation was dominant immobilizing mechanism for steel slag and phosphate rock because of their high pH values. |
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