Pedosphere 14(2): 223--228, 2004
ISSN 1002-0160/CN 32-1315/P
©2004 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Cadmium release in contaminated soils due to organic acids
LIAO Min and XIE Xiao-Mei
Department of Resources Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310029 (China). E-mail: liaomin@zju.edu.cn
ABSTRACT
      There is limited information on the release behavior of heavy metals from natural soils by organic acids. Thus, cadmium release, due to two organic acids (tartrate and citrate) that are common in the rhizosphere, from soils polluted by metal smelters or tailings and soils artificially contaminated by adding Cd were analyzed. The presence of tartrate or citrate at a low concentration (≤ 6 mmol L-1 for tartrate and ≤ 0.5 mmol L-1 for citrate) inhibited Cd release, whereas the presence of organic acids in high concentrations (≥ 2 mmol L-1 for citrate and ≥ 15 mmol L-1 for tartrate) apparently promoted Cd release. Under the same conditions, the Cd release in naturally polluted soils was less than that of artificially contaminated soils. Additionally, as the initial pH rose from 2 to 8 in the presence of citrate, a sequential valley and then peak appeared in the Cd release curve, while in the presence of tartrate the Cd release steadily decreased. In addition, Cd release was clearly enhanced as the electrolyte concentration of KNO3 or KCl increased in the presence of 2 mmol L-1 tartrate. Moreover, a higher desorption of Cd was shown with the KCl electrolyte compared to KNO3 for the same concentration levels. This implied that the bioavailability of heavy metals could be promoted with the addition of suitable types and concentrations of organic acids as well as reasonable field conditions.
Key Words:  artificially contaminated soil, cadmium, organic acid, polluted soil, release
Citation: Liao, M. and Xie, X. M. 2004. Cadmium release in contaminated soils due to organic acids. Pedosphere. 14(2): 223-228.
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