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Fig. 8. Predicted vs. measured (Pt combination redox electrode) Eh based on soluble concentrations of Fe2+ (measured) and Fe3+ (estimated, in equilibrium with amorphous (am-)Fe(OH)3 or 
-FeOOH solid phase) for Hanford soil–water suspensions. The EH comparisons based on the SO42––HS– (measured) redox couple are also shown. Measured Fe2+ concentrations for highlighted (square-enclosed) samples were less than the detection limit (9.0 x 10–6 M) and were estimated at 1.0 x 10–6 M. Straight line indicates 1:1 correlation between measured and predicted EH values.
