Immobilization of lead in anthropogenic contaminated soils using phosphates with/without oxalic acid  

作　　者：Xiaojuan Su Jun Zhu Qingling Fu Jichao Zuo Yonghong Liu Hongqing Hu 

机构地区：[1]Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University

出　　处：《Journal of Environmental Sciences》2015年第2期64-73,共10页环境科学学报（英文版）

基　　金：supported by the National High Technology Research and Development Program (863) of China (No. 2012AA101402);the National Natural Science Foundation of China (No. 41071165)

摘　　要：Understanding the effects of oxalic acid（OA） on the immobilization of Pb（Ⅱ） in contaminated soils by phosphate materials, has considerable benefits for risk assessment and remediation strategies for the soil. A series of phosphate amendments with/without oxalic acid were applied to two anthropogenic contaminated soils. We investigated the immobilization of Pb（Ⅱ） by KH2PO4, phosphate rock（PR）, activated phosphate rock（APR） and synthetic hydroxyapatite（HAP） at different phosphate：Pb（P：Pb） molar ratios（0, 0.6, 2.0 and 4.0） in the presence/absence of 50 mmol oxalic acid/kg soil, respectively. The effects of treatments were evaluated using single extraction with deionized water or Ca Cl2, Community Bureau of Reference（BCR） sequential extraction and toxicity characteristic leaching procedure（TCLP）methods. Our results showed that the concentration of water extractable, exchangeable and TCLP-Pb all decreased with incubation time. The concentration of water-extractable Pb after120 days was reduced by 100% when soils were amended with APR, HAP and HAP ＋ OA, and the TCLP-Pb was 〈5 mg/L for the red soil at P：Pb molar ratio 4.0. Water-soluble Pb could not be detected and the TCLP-Pb was 〈5 mg/L at all treatments applied to the yellow-brown soil. BCR results indicated that APR was most effective, although a slight enhancement of water-soluble phosphate was detected at the P：Pb molar ratio 4.0 at the beginning of incubation. Oxalic acid activated phosphates, and so mixing insoluble phosphates with oxalic acid may be a useful strategy to improve their effectiveness in reducing Pb bioavailability.Understanding the effects of oxalic acid（OA） on the immobilization of Pb（Ⅱ） in contaminated soils by phosphate materials, has considerable benefits for risk assessment and remediation strategies for the soil. A series of phosphate amendments with/without oxalic acid were applied to two anthropogenic contaminated soils. We investigated the immobilization of Pb（Ⅱ） by KH2PO4, phosphate rock（PR）, activated phosphate rock（APR） and synthetic hydroxyapatite（HAP） at different phosphate：Pb（P：Pb） molar ratios（0, 0.6, 2.0 and 4.0） in the presence/absence of 50 mmol oxalic acid/kg soil, respectively. The effects of treatments were evaluated using single extraction with deionized water or Ca Cl2, Community Bureau of Reference（BCR） sequential extraction and toxicity characteristic leaching procedure（TCLP）methods. Our results showed that the concentration of water extractable, exchangeable and TCLP-Pb all decreased with incubation time. The concentration of water-extractable Pb after120 days was reduced by 100% when soils were amended with APR, HAP and HAP ＋ OA, and the TCLP-Pb was 〈5 mg/L for the red soil at P：Pb molar ratio 4.0. Water-soluble Pb could not be detected and the TCLP-Pb was 〈5 mg/L at all treatments applied to the yellow-brown soil. BCR results indicated that APR was most effective, although a slight enhancement of water-soluble phosphate was detected at the P：Pb molar ratio 4.0 at the beginning of incubation. Oxalic acid activated phosphates, and so mixing insoluble phosphates with oxalic acid may be a useful strategy to improve their effectiveness in reducing Pb bioavailability.

关 键 词：Soil lead remediation Toxicity characteristics leaching procedure（TCLP） Phosphorous materials Oxalic acid Lead fraction 

分 类 号：X53[环境科学与工程—环境工程]