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Fig. 8.14
Effect of pH on dissolution from Al-mica-organo matter complexes (Hargrove 1986 )
Fig. 8.15 Typical trends of dissolved Cu (black circle), Pb (black diamond), and Zn (black up-
pointing triangle) concentrations and pH (-) in effluent solutions collected during a flow column
experiment on soil samples from the Bogue site (USA), as a function of the throughput volume of
acidified, 0.01 M CaCl 2 solution (Bang and Hesterberg 2004 )
(XANES). Typical trends for dissolution of Cu, Pb, and Zn, as affected by pH, are
presented in Fig. 8.15 . The maximum dissolved concentration of these compounds
occurred at the lowest pH. Dissolved Cu, Pb, and Zn concentrations increased as
pH declined, compensating for the Na + . This phenomenon occurs below pH
threshold levels of pH *4 for Cu and Pb and pH *5 for Zn. The Cu and Zn
results were consistent with synchrotron (XANES) spectroscopy data, suggesting
that Cu was bound mainly to soil OM, while Zn was associated with Al- and Fe-
oxide-type minerals.
Another key process involves gypsum dissolution; gypsum is found in the
subsurface as a natural constituent or as an added reclamation material. In cases
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