Iron-manganese Concretions in Hydrosequences of Soils in Loess in Bavaria1
- U. Schwertmann and
- D. S. Fanning2
To expand knowledge about the nature and distribution of Fe-Mn concretions in soils, and in particular about their relation to degree of hydromorphism, the amounts and composition of concretions (0.2–0.63, 0.63–2.0, and >2.0-mm diam) in profiles of two hydrosequences on loess in Bavaria, Germany were determined. Concretions were separated by wet sieving air-dried soil samples. Maximum concretion formation (up to 7.5 weight percent) occurred in the upper B horizons (∼50-cm depth) approaching the surface with increasing wetness. Maximum concretion formation (up to 40 kg/m2) also occurred under medium wetness and not in the wettest profile. Mn, Fe, and P (except not P in the wettest members) were concentrated in the concretions, Fe predominantly as goethite, Mn presumably as birnessite and P (as concluded from correlations) adsorbed to Fe-oxides, but not to Mn-oxides. Selected concretion and microprobe studies showed that during concretion formation Mn with Some Fe is concentrated first with Mn being essentially exhausted at a later stage where nearly only Fe accumulates. Inasmuch as P from 2,000-year-old bones accumulated in concretions, their formation appears to have been continuing through recent time.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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