Fig. 3. Pore water ion activity products (IAP) with respect to end-member metal monosulfides for Fe (a), Co (b), and Ni (c). IAP is defined as {Me2+} {HS−}/{H+} and values are calculated using visual MINTEQ with pore water data from late-summer (□) and spring (△). Vertical lines represent correspondingmetal sulfide solubilities (LogKso) for the reactionMeS(s)+H +=Me2++HS−. Values for FeS (s) determined by Davison et al. (1999; −3.0, solid line), Benning et al. (2000;−3.9, dotted line), andWolthers (Wolthers et al., 2005;−2.1, dash-dot line). The LogKso values for CoS (s) andNiS (s) are obtained from Dyrssen and Kremling (1990; CoS=−7.4; NiS=−5.6). Solutions are super-saturated when the Log IAP value is greater than the Log Kso.
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