The forms of occurrence of manganese in some acidic soils

Abstract

The forms of occurrence of Mn were examined in some acidic surface and sub-soils from areas of permanent grassland using chemical extractants. Despite high total contents of Mn in some of the soils and low pH, only minor proportions occurred as exchangeable Mn2+. Much larger proportions were present as reducible hydrous oxides, e.g. up to 38% and 54% of the total contents in surface and subsoils, respectively, were present as hydroquinone extractable, or easily reducible, Mn. Reducible forms ofMn were poorly correlated with other more mobile forms. Large proportions of the total Mn contents were accounted for when estimates of different fractions were calculated from differences in amounts extracted by different individual extractants, i.e. M NH,OAc, 0.2% hydroquinone, 0.1 M pyrophosphate, and ammonium oxalate. The distribution of Mn amongst the different fractions as determined by a sequential fractionation scheme differed markedly from the distribution calculated by differences. In particular, there was a marked change in form after extraction with pyrophosphate.

The association of cobalt with easily reducible manganese in some acidic permanent grassland soils

“…McKenzie (1970McKenzie ( , 1972 has demonstrated the specific nature of the reaction of Co with Mn oxide minerals and suggested that CoL+ is first oxidized to Co3+, which then replaces Mn3+ where this has substituted for Mn4+ in the lattice. If this is the case, the reaction of hydroquinone with the most reactive forms of MnO, would release only limited amounts of the Co. On average, over 70% of the total Mn oxides in the present soils was not extracted with hydroquinone and was presumably present in unreactive forms, or in an occluded, inaccessible state (Jarvis, 1984). Furthermore, the data from the concretions, although from only two soils, indicate that high proportions of the total soil Co will be held within discrete Mn particles, and released only by the action of prolonged or strong reduction.…”

“…There is therefore a need for a simple, rapid technique to determine the extent to which Co is associated with Mn in British soils. Chemical extractants have been used for many years to estimate specific forms of soil Mn (Leeper, 1947;Jones & Leeper, 195 1;Heintze & Mann, 1951;Chao, 1972;Jarvis, 1984). In the present study, the relationship between Co and the most reactive form of oxidized Mn (i.e.…”

Extractability of manganese and iron oxides in typical Japanese soils by 0.5 mol L−1hydroxylamine hydrochloride (pH 1.5)

“…We used Mn extracted by acid ammonium oxalate (Mn o ) as described above to approximate total Mn oxides (Jarvis 1984). Oxalate, however, is also likely to extract Mn bound to organic matter.…”

Chemical and physical fractions of manganese in soil during intensive ryegrass cropping

“…In soil M, Mn content was similar in the Fe oxide and organically bound fractions. In both soils the exchangeable Mn fraction was the lowest; our values for exchangeable Mn were also lower than those found in acid soils (Jarvis, 1984). The exchangeable Mn fraction has been shown to fall markedly with rising pH (Sims, 1986), suggesting that the alkaline reaction of our soils may have been responsible for the low levels of exchangeable Mn recorded.…”