Manganese-Containing Nodules in two Calcareous Rice Soils of Pakistan
Elsevier, 1990
Online
unknown
Zugriff:
Manganese (Mn) and Fe are reduced in anaerobic conditions and their concentrations increase in soil solution. These elements when moved downward to an oxidized zone accumulate as Fe and Mn nodules and coatings. Mineral precipitates have been predicted by solubility product relationships, yet data on such phases in seasonally submerged soils are not available. Nodules from the of Gujranwala (Udic Haplustalf) Btc2 (96- 130 cm) and Satghara (Typic Natrargid) 2Btcknb2 (80–108 cm) soil horizons were sectioned or ground and fractionated. Fractionated samples were analyzed by elemental and mineralogical methods. Thin sections for both nodule samples showed some black Mn oxide accumulation. Scanning electron microscope (SEM) microprobe analysis showed Mn present in a cavity in a Gujranwala nodule and Mn and Fe were associated with a carbonate particle in the Satghara sample. Hydroxylamine hydrochloride dissolved 0.8 to 1.8% Mn and dithionite-citrate-bicarbonate (DCB) dissolved 7 to 12% Fe from the Gujranwala nodule fractions. Gujranwala nodules contained birnessite and lithiophorite. The Mn-oxide phase in Satghara nodules was not determined but Mn-containing calcite was suggested. The Fe oxide in Satghara nodules appears to be goethite. The Gujranwala nodules contained mica, chlorite, quartz, goethite and some feldspars. The Satghara nodules contained mainly calcite with some dolomite, quartz, mica, chlorite and vermiculite. Selectively dissolved Mn was more concentrated in the coarse clay (2-0.2 μm) than fine clay (
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Manganese-Containing Nodules in two Calcareous Rice Soils of Pakistan
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Autor/in / Beteiligte Person: | Golden, D. C. ; Ullah, Rahmat ; Dixon, Joe B. |
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Veröffentlichung: | Elsevier, 1990 |
Medientyp: | unknown |
DOI: | 10.1016/s0166-2481(08)70352-0 |
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