title: Immobilization of lead in anthropogenic contaminated soils using phosphates with/without oxalic acid.
abstract: 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 CaCl2, 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 after 120 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.
authors: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: sl_505@126.com.
authors: Xiaojuan
authors: X
authors: Su
authors: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors: Jun
authors: J
authors: Zhu
authors: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors: Qingling
authors: Q
authors: Fu
authors: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors: Jichao
authors: J
authors: Zuo
authors: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
authors: Yonghong
authors: Y
authors: Liu
authors: Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: hqhu@mail.hzau.edu.cn.
authors: Hongqing
authors: H
authors: Hu
mesh_terms: D004787:Environmental Pollution / Q000517:prevention & control*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D007854:Lead / Q000378:metabolism*; D019815:Oxalic Acid / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D012989:Soil Pollutants / Q000378:metabolism*; D013054:Spectrophotometry, Atomic
chemical_list: D010710:Phosphates; D012989:Soil Pollutants; D007854:Lead; D019815:Oxalic Acid
keywords: Lead fraction; Oxalic acid; Phosphorous materials; Soil lead remediation; Toxicity characteristics leaching procedure (TCLP)