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Fig. 6. (A) Plots of aqueous Fe(II) concentrations for equilibrium with ferric hydroxide versus p
. Lines are for pH 7.5 (characteristic of the experiment), and range bars indicate shifts in Fe(II) concentrations for pH 7 and 8. (B) Effective first-order rate constants for Cr(VI) reduction by Fe2+ as functions of the negative logarithm of the electron activity (p), for equilibrium with ferric hydroxide. Lines are for pH 7.5, and range bars indicate shifts in rate constants for pH 7 and 8. Also shown are ranges of measured k and estimated p from the nonsterile soils.
