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United States Department of Agriculture

Agricultural Research Service

Title: Hg (Ii) and Pb (Ii) Retention Capacity of the Model Associations of Soil Colloids

Authors
item Cruz-Guzman, M - CSIC-IRNAS SEVILLA SPAIN
item Celis, R - CSIC-IRNAS SEVILLA SPAIN
item Hermosin, M - CSIC-IRNAS SEVILLA SPAIN
item Cornejo, J - CSIS-IRNAS SEVILLA SPAIN
item Koskinen, William

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 4, 2002
Publication Date: October 4, 2002
Citation: Cruz-Guzman, M., Celis, R., Hermosin, M.C., Cornejo, J., Koskinen, W.C. 2002. Hg (II) and pb (II) retention capacity of the model associations of soil colloids. Midwest Environmental Chemistry Workshop Abstract. p. 10.

Technical Abstract: Heavy metal movement in the environment is controlled by sorption on soil colloids. There is increasing attention in determining the metal sorption on multicomponent model sorbents in order to achieve a more realistic interpretation of the sorption process in soil as compared to interpretations based on the sum of the sorption capacity of individual soil constituents. Model associations of soil colloids were characterized by elemental analysis, FT-IR Spectroscopy and X-Ray Diffraction. Sorption of Pb(II) and Hg(II) by binary and ternary model sorbents containing montmorillonite (SW), ferrihydrite and humic acid (HA) were compared to sorption behavior of individual constituents. For single sorbents, Pb(II) sorption was high on HA, moderate on SW, and zero on ferrihydrite, whereas Hg(II) sorption decreased in the order: HA >> ferrihydrite > SW. Ferrihydrite coatings on SW had little effect on Pb(II) and Hg(II) sorption, whereas HA significantly enhanced sorption of both metals on SW. HA coatings on ferrihydrite did not enhance metal sorption as a results of blockage of the functional groups of HA responsible for metal sorption as a result of their interaction with the ferrihydrite surface. Similar behavior was observed for Pb(II) in ternary particles containing HA. Sorption by the model associations was reversible. The three main active soil colloidal constituents, clay minerals, iron oxides, and humic acids are important sorbents for heavy metals, but the results of this study confirmed that mutual interactions between these constituents can greatly alter their sorptive behavior when associated in organomineral soil colloids. Consequently, sorption predictions from soil composition would be greatly improved with a better understanding of how interactions between individual soil constituents affect the sorption behavior of naturally-occurring soil colloids.

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