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| Immobilization and Its Mechanisms of Heavy Metal Contaminated Soils by Phosphate-containing Amendment and Biochar |
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| KeyWord:heavy metals； biochar；phosphorus material； immobilization；mechanism |
| Author Name | Affiliation | | LIANG Yuan | School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215011, China | | LI Fei-yue | School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
College of Urban Construction and Environment Science, Anhui Science and Technology University, Fengyang 233100, China | | YANG Fan | School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China | | SHI Wei-lin | School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215011, China |
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| Abstract: |
| Biochar has been used to remediate soils contaminated by heavy metals. In this study we compared the immobilization of Pb, Zn and Cd in soils by phosphorus-containing material（PT）, dairy manure-derived biochar（DM） and rice straw-derived biochar（RS） . Factors influencing the immobilization and underlying mechanisms were explored. Applications of three amendments dramatically decreased leachability of Pb, Zn and Cd after 56 days of incubation, with order of Pb ＞ Zn ＞ Cd. Of three amendments, PT was the most effective in retaining Pb, and Cd, followed by DM and RS, but they did not show difference in Zn immobilization. Compared with CK, percent reduction of Pb, Zn, and Cd concentrations in TCLP extraction was 77.6%, 31.5%, and 27.9% for PT treatment, 56.0%, 26.1% and 10.0% for DM treatment, and 35.8%, 25.0%, and 4.4% for RS treatment, respectively. These amendments could transform Pb and Cd from soluble to stable forms. The precipitation would contribute to Pb immobilization by PT amendment, as presence of Ca2Pb8（PO4）6（OH）2 and Pb10（PO4 ）6（OH）2 was evidenced by XRD analysis. The Pb immobilization by DM biochar was resulted from precipitation, adsorption and cation exchange, with Ca2Pb8（PO4）6（OH）2 presence as shown by XRD. However, RS biochar stabilized heavy metals only via adsorption and cation exchange. In conclusion, phosphate amendment and dairy manure-derived biochar could effectively immobilize Pb, Zn, and Cd in soil. |
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