Pedosphere 25(1): 37--45, 2015
ISSN 1002-0160/CN 32-1315/P
©2015 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Kinetics of specific and non-specific copper sorption on aggregates of an acidic paddy soil from the Taihu Lake Region in East China |
LIU Pei-Ya1, WEN Qin-Liang1, LI Yu-Jiao1, DONG Chang-Xun1 and PAN Gen-Xing2 |
1College of Sciences, Nanjing Agricultural University, Nanjing 210095 (China)
2Institute of Resource, Ecosystem and Environment of Agriculture, Nanjing Agricultural University, Nanjing 210095 (China) |
| ABSTRACT |
| The Taihu Lake region in East China has become prone to soil acidification, which changes heavy metals such as copper (Cu) in soil into water-soluble species and increases the mobility and contamination risks of heavy metals in the biological environment. In this study, the kinetics of Cu2+ sorption by the bulk soil and the aggregate size fractions of an acidic paddy soil collected from the Taihu Lake region, the effects of temperature on Cu2+ sorption, and the pH changes of the solution were investigated by static sorption and magnetic stirring. The aggregate size fractions were prepared by low-energy ultrasonic dispersing and freeze-drying. The total sorption amounts of the bulk soil and the aggregate size fractions for Cu2+ followed a descending order of clay > coarse sand > bulk soil > silt > sand, corresponding to those of organic matter content, free iron oxide content, free aluminum oxide content, and cation exchange capacity. The kinetic sorption curves of Cu2+ by the bulk soil and the aggregates, which were divided into two stages (rapid and slow sequentially), were well fitted by the first-order equation, the diffusion equation, and the Elovich equation, showing significant correlations (P < 0.05). Specific and non-specific sorption dominated in the fast and slow stages, respectively, and the former was predominant throughout the sorption process. The specific sorption accelerated and the non-specific sorption decelerated with rising temperature. The pH of the solution decreased significantly during the specific sorption and remained unchanged or increased slightly during the non-specific sorption. When the specific sorption terminated, the pH of the solution was minimized nearly simultaneously. The sorption progress of Cu2+ by the bulk soil significantly preceded that by the aggregates. Therefore, heavy metal contamination may be another factor reducing soil pH and metal sorption forms should be taken into consideration in studies of mitigating soil heavy metal pollution or determining environmental capacity of heavy metal in soil. |
| Key Words: bulk soil, contamination, heavy metal, kinetic equation, pH, soil acidification, temperature |
| Citation: Liu, P. Y., Wen, Q. L., Li, Y. J., Dong, C. X. and Pan, G. X. 2015. Kinetics of specific and non-specific copper sorption on aggregates of an acidic paddy soil from the Taihu Lake Region in East China. Pedosphere. 25(1): 37-45. |
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