Pedosphere 8(3): 245--250, 1998
ISSN 1002-0160/CN 32-1315/P
©1998 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Effect of sulfate on adsorption of zinc and cadmium by variable charge soils
ZHANG Gang-Ya1, G. W. BRMMER2 and ZHANG Xiao-Nian1
1 Institute of Soil Science, the Chinese Academy of Sciences, P. O. Box 821, Nanjing 210008 (China)
2 Department of Soil Science, University of Bonn, Nussalle 13, D 53115 Bonn (Germany)
      SO42- and Zn2+ or Cd2+ were added to three variable charge soils in different sequences. In one sequence sulfate was added first, and in the other, Zn2+ or Cd2+ first. The addition of sulfate to the system invariably caused an increase in adsorption of the heavy metal added, with the effect more remarkable when the soil reacted with the sulfate prior to the metal. The shift in pH50 for both Zn and Cd adsorption was also comparatively larger in the first sequence of reactions. It was suggested that the increase in negative charge density and the resultant negative potential of the soil were the primary cause of the pronounced effect of sulfate on adsorption of Zn or Cd, and the formation of the ternary surface complex-S-SO4-M might also play a role in the effect.
Key Words:  adsorption, cadmium, sulfate, variable charge soil, zinc
Citation: Zhang, G. Y., Brmmer, G. W. and Zhang, X. N. 1998. Effect of sulfate on adsorption of zinc and cadmium by variable charge soils. Pedosphere. 8(3): 245-250.
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