Pedosphere 16(6): 718--725, 2006
ISSN 1002-0160/CN 32-1315/P
©2006 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Interactions of heavy metal ions with paddy soils as inferred from wien effect measurements in dilute suspensions |
JIANG Jun1 , LI Cheng-Bao1, ZHAO An-Zhen1, XU Ren-Kou1, WANG Yu-Jun1 and S. P. FRIEDMAN2 |
1 Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China). E-mail: jjiang@issas.ac.cn;
2 Institute of Soil, Water, and Environmental Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250 (Israel) |
| ABSTRACT |
| Interactions of three heavy metal ions, Cu2+, Cd2+, and Pb2+, and, for comparison, Na+ with electrodialytic clay fractions (less than 2μm in diameter) of four paddy soils as well as a yellow-brown soil as a control soil were evaluated based on measurements of the Wien effect in dilute suspensions with a clay concentration of 10 g kg-1 in four nitrate solutions of 2 × 10-4/z mol L-1, where z is the cation valence, and a nitric acid solution of 3 × 10-5 mol L-1.Field strengths ranging from 15 to 230 kV cm-1 were applied for measuring the electrical conductivities (ECs) of the suspensions. The mean free binding energies between the various cations and all of the soils determined from exchange equilibrium increased in the order: Na+ < Cd2+ < Cu2+ < Pb2+. In general, the ECs of the suspensions in the sodium nitrate solution were smaller than those of the suspensions in the heavy metal solutions because of the lower electrophoretic mobility of sodium compared to the divalent cations. In terms of relative electrical conductivity-field strength relationships, relative electrical conductivity (REC) of suspensions containing various cations at field strengths larger than about 50 kV cm-1 were in the descending order: Na+ > Cu2+ > Cd2+ > Pb2+ for all tested soils. A characteristic parameter of the REC-field strength curves, △REC200, REG at a field strength of 200 kV cm-1 minus that at the local minimum of the concave segment of the REC-field strength curves, characterized the strength of adsorption of the cations stripped off by the applied strong electrical field, and for all soils the values of △REC200 were generally in the order: Na+ < Cu2+ ≤ Cd2+ ≤ Pb2+. |
| Key Words: binding energy, electrical conductivity, field strength, heavy metal ions, paddy soils |
| Citation: Jiang, J., Li, C. B., Zhao, A. Z., Xu, R. K., Wang, Y. J. and Friedman, S. P. 2006. Interactions of heavy metal ions with paddy soils as inferred from wien effect measurements in dilute suspensions. Pedosphere. 16(6): 718-725. |
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