Manganese partition coefficients

Figure 4 Metal/magnesiowUstite partition coefficients for nickel, cobalt, manganese, chromium, and vanadium at 9 GPa, and the effect of temperature (pressure 9 GPa). Partition coefficients are calculated relative to iron, according to the exchange equihhrium, M - - FeO = Fe + MO. Horizontal lines at right side of the diagram indicate the values of ATd that would he required for an equihhrium explanation for these hve elements in the terrestrial mantle (source Gessmann and Ruhie (1998) these authors favor a high-temperature scenario to attain these concentrations in the mantle).

Finally, finely divided hydrous oxides of iron, aluminum, manganese, and silicon are the dominant sorbents in nature because they are common in soils and rivers, where they tend to coat other particles. This is the reason why numerous laboratory researchers have been studying the uptake of trace elements by adsorption on hydrous oxides (Dzomback and Morel, 1990). Partition coefficients (concentration in solid/concentration in the solution) for a number of trace elements and a great variety of surfaces have been determined. The comparison of these experimental with natural values should give information on the nature of the material on which trace elements adsorb in namral systems and allow quantitative modeling. 

Under wet soil (anaerobic) conditions, accumulation of reduced cations such as iron (II) and manganese (II) in mineral soils can potentially occupy much of the cation exchange sites (Figure 8.28). This can result in displacement of ammonium from the exchange complex. The partition coefficients for ammonium are generally lower in anaerobic soils than in drained or aerobic soils. 

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