Micronutrient Cation Complexes in Soil Solution: IV. The Chemical State of Manganese in Soil Solution

Geering, H. R.; Hodgson, J. F.; Sdano, Caroline

Micronutrient Cation Complexes in Soil Solution: IV. The Chemical State of Manganese in Soil Solution

1969

Geering, H. R. | Hodgson, J. F. | Sdano, Caroline

Soil solutions from several areas of the US were analyzed by atomic absorption for total Mn and by resin exchange for percent Mn complexed. Values for the latter (84%–99%) in soil solution from the A horizon were intermediate to those previously reported for Zn and Cu. Soil solution from a New York forest soil at pH 7 contained 13 ppm Mn, of which 93% was complexed. Spectrophotometric and polarographic methods were developed to determine the oxidation state of Mn in this soil solution. Both methods indicated the Mn in solution was present in the +2 oxidation state. The presence of such large concentrations of Mn²⁺ in a soil solution of a neutral soil was still less than that predicted from measured values of the Eh of the soil solution and the Mn²⁺/MnO₂ half-cell potential. Soil microorganisms oxidized and precipitated Mn²⁺, presumably as MnO₂, but the presence of the neutral soil solution that contained 13 ppm Mn partially inhibited this precipitation.

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