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| Effects of water management and phosphate application on the transformation of Cd in paddy soil |
| Received:November 14, 2016 |
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| KeyWord:water management;phosphate;Cd;bioavailability;heavy metal speciation |
| Author Name | Affiliation | E-mail | | LONG Ling-zhi | College of Environment Science and Engineering, Hunan University, Changsha 410082, China
Key Laboratory of Environment Biology and Pollution Control, Ministry of Education, Hunan University, Changsha 410082, China | | | LI Zhong-wu | College of Environment Science and Engineering, Hunan University, Changsha 410082, China
Key Laboratory of Environment Biology and Pollution Control, Ministry of Education, Hunan University, Changsha 410082, China | lizw@hnu.edu.cn | | LUO Ning-lin | College of Environment Science and Engineering, Hunan University, Changsha 410082, China
Key Laboratory of Environment Biology and Pollution Control, Ministry of Education, Hunan University, Changsha 410082, China | | | ZHANG Qiu | College of Environment Science and Engineering, Hunan University, Changsha 410082, China
Key Laboratory of Environment Biology and Pollution Control, Ministry of Education, Hunan University, Changsha 410082, China | | | HUANG Mei | College of Environment Science and Engineering, Hunan University, Changsha 410082, China
Key Laboratory of Environment Biology and Pollution Control, Ministry of Education, Hunan University, Changsha 410082, China | |
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| Abstract: |
| In order to investigate the effect of water management and phosphate application on the transformation of Cd in paddy soil, incubation experiments were carried out under four water managements, namely 75% field capacity (75%FC), field capacity (FC), continuous flooding (CF) and flooding-drying (FD). KH2PO4 was added into the soil with the molar ratio of KH2PO4/Cd at 2:1. The pH values and concentrations of CaCl2-extractable Cd in soil samples were determined, and the European Community Bureau of Reference (BCR) sequential extraction procedure was conducted to analyze the fraction distribution of Cd. The results showed that, compared to the control groups, the application of KH2PO4 reduced CaCl2-extractable Cd by 10.0% and 37.3% for FC and CF treatments, respectively, whereas increased its concentration by 12.5% and 9.5% in 75%FC and FD treatments, respectively. The fraction distribution results of Cd revealed that phosphate application slightly promoted the transform of Cd from acid-soluble fraction to reducible and oxidizable fractions. The proportions of acid-soluble Cd decreased significantly in the 75%FC treatment which was benefit for the stabilization of Cd, in contrast, higher acid-soluble Cd concentrations were observed in FD treatments, suggesting a higher-risk of leaching and migrating of Cd in soil. It was observed that pH varied remarkably during the incubation period, and there was a significant negative correlation (r=-0.861 8) between CaCl2-extractable Cd content and soil pH in 75%FC treatment. As for CF and FD treatments, the reduction process of flooding had a complicated impact on the availability of Cd. In summary, water management and phosphate application had an interaction on CaCl2-extractable Cd, and the stabilization effect of phosphate application on Cd was better in the case of 75%FC, furthermore, water management was the main influential factor controlling the transformation of Cd in paddy soil. |
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