Fig. 3.

Interaction of dissolved gaseous Hg(0) with reduced soil HA. (A) Hg retained by HA (5 mg/L) at pH 7 and purgeable Hg(0) at varying initial Hg(0) concentrations. (B) Determination of binding capacity and affinity between Hg and reduced HA. The estimated binding affinity from the initial slope (dashed line) was >10⁶ mL/g. Estimate strong binding sites are ~3.5 μmol/g HA at pH 7 and ~1.6 μmol/g HA at pH 3.5, respectively, assuming the formation of 1:1 Hg:thiol complexes. Controls were performed under the same conditions in water (asterisks) and in the culture solution (▽) prepared identically to that of the reduced HA solution.