Iron‐manganese Concretions in Hydrosequences of Soils in Loess in Bavaria
Iron‐manganese Concretions in Hydrosequences of Soils in Loess in Bavaria
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DOI：
10.2136/sssaj1976.03615995004000050034x
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发表时间：
1976-09
影响因子：
2.9
通讯作者：
U. Schwertmann;D. Fanning
中科院分区：
文献类型：
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作者：
U. Schwertmann;D. Fanning
为了扩大对土壤中铁锰结核的性质和分布的了解，特别是它们与水态程度的关系，确定了德国巴伐利亚黄土上两个水文层序剖面中结核的数量和成分（0.2-0.63、0.63-2.0 和 >2.0 毫米直径）。通过湿筛风干土壤样品分离结核。随着湿度的增加，最大的结核形成（高达 7.5 重量％）发生在接近地表的上层 B 层（约 50 厘米深）。最大结核形成（高达 40 kg/m²）也发生在中等湿度下，而不是在最潮湿的剖面上。 Mn、Fe 和 P（除最湿部分中的 P 除外）集中在结核中，Fe 主要以针铁矿形式存在，Mn 可能以水钠锰矿形式存在，P（根据相关性得出的结论）吸附在 Fe 氧化物上，但不吸附在 Mn 氧化物上。选定的结核和微探针研究表明，在结核形成过程中，Mn 和一些 Fe 首先富集，随后 Mn 基本耗尽，几乎只有 Fe 积累。由于 2000 年前骨头中的磷在结核中积累，它们的形成似乎一直持续到近代。
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.