Equilibrium approaches to natural water systems—Part 3 |
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| Authors: | Jan Lidén |
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| Institution: | 1. Department of Inorganic Chemistry, University of Ume?, S-90187, Ume?, Sweden
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| Abstract: | The concentrational control of Fe2+ has been studied in the anoxic hypolimnion of an ice-covered lake with special reference to redox equilibria with the suspended phase. The anoxic bottom water formed during ice conditions differed substantially in terms of vertical distributions from that reported from thermally stratified waters. This was particularly evident for the pH and pe gradients. The main process explaining the Fe2+ concentration profile was a diffusional model in which upwards moving Fe2+ met an opposing O2 flux at the redox cline and precipitated as ferric hydroxide. When the anoxic water column is divided into thin stratums an equilibrium reaction between Fe2+ and amorphous FeOOH explained the Fe2+ concentrations in the upper hypolimnion. Increasing supersaturation was observed at greater depths. Similarly equilibration control of the sulfide concentration by Fe2+ could be shown in the lower hypolimnion. Apparent equilibrium constants for FeS and FeOOH have been calculated together with the eddy diffusion coefficient of Fe2+. |
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