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Interaction of copper and zinc with allophane and organic matter in the B horizon of an Andosol
Author(s) -
Latrille C.,
Denaix L.,
Lamy I.
Publication year - 2003
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1046/j.1365-2389.2003.00530.x
Subject(s) - allophane , andosol , chemistry , organic matter , zinc , imogolite , humus , inorganic chemistry , soil organic matter , copper , environmental chemistry , soil water , mineralogy , clay minerals , geology , organic chemistry , soil science
Summary Andosols developed on basaltic material are naturally rich in metals. Organic matter and allophane, the key colloids of these soils, have a strong affinity for trace metals, but are intimately mixed so that speciation of trace metal is difficult to determine. We used three complementary approaches, namely physical fractionation, chemical extraction and potentiometric measurement, to distinguish them. Physical particle‐size separations and chemical selective dissolution of allophanes and organic matter were combined to demonstrate relations between the occurrence of colloids and contents of Cu and Zn in an andic B horizon. About 22% of total soil Cu and 7% of total soil Zn were present in the < 5‐μm fraction, associated with organic or amorphous mineral constituents. To support this association further, the affinity of soil colloids for Cu and Zn in a mimicked system was demonstrated. An Al‐rich allophane was synthesized, and a portion of the organic matter was extracted from the clay fraction, and their reactivities towards Cu 2+ or Zn 2+ were studied by potentiometry. The two metallic cations displayed specific affinity towards allophane or soluble organic matter. Furthermore, the behaviour of copper and zinc in the ternary system, allophane + soluble organic matter + trace element, revealed a synergy in the surface complexation. The use of these three speciation approaches highlighted the linkage between metals and constituents, and showed how important the colloidal constituents are in the behaviour of Cu and Zn in Andosols.