Monday, November 5, 2007
106-2
Multi-Scale Pedologic Investigation of Highly Manganiferous Soils in the Maryland Piedmont.
Soils in the Mid-Atlantic region typically contain <50 g kg-1 Fe (as Fe oxides) and <1 g kg -1 Mn (as Mn oxides). However, soils have been discovered in the Piedmont of MD that contain as much as 169 g kg-1 dithionite-citrate-bicarbonate (DCB)-extractable Fe and 140 g kg-1 DCB-extractable Mn. The properties of these previously unstudied manganiferous soils are being examined at multiple scales in order to develop a theory of their pedogenesis. The soils occur in an area of complicated metamorphic geology and particularly in association with marble bedrock composed primarily of calcite and dolomite. Electromagnetic Induction (EMI) was employed at the sites as a non-invasive, empirical method to generate maps showing the location of manganiferous soil materials. The soils were studied along several topographic transects to assess their areal extent and range in properties. From these transects, three sites and six pedons were chosen from which morphological, micromorphological, physical, chemical, and mineralogical data have been generated.
The exceptionally high levels of Fe(III)(hydr)oxides and Mn(III, IV)(hydr)oxides impart an extremely dark color to the soil material (moist Munsell value and chroma commonly <2/1). Concentrations of total organic C, however, were found to be typical for well drained soils of the region (<20 g kg-1 at the surface and <3 g kg-1 in subsoil horizons). Manganiferous soil materials have unusual physical properties such as high particle density (up to 3.25 on bulk soil), low bulk density (commonly around 1.0 and as low as 0.39), and extremely high porosity (maximum calculated 88%). Mineralogical examinations via Fourier Transform Infrared (FTIR) spectra and Differential X-Ray Diffraction (DXRD) show that the dominant Fe oxide and Mn oxide minerals in the soils are hematite and lithiophorite, respectively.
Ongoing work includes micromorphological analysis, mineralogical and chemical analysis of non-carbonate residues from marble bedrock, and particle size analysis.
The exceptionally high levels of Fe(III)(hydr)oxides and Mn(III, IV)(hydr)oxides impart an extremely dark color to the soil material (moist Munsell value and chroma commonly <2/1). Concentrations of total organic C, however, were found to be typical for well drained soils of the region (<20 g kg-1 at the surface and <3 g kg-1 in subsoil horizons). Manganiferous soil materials have unusual physical properties such as high particle density (up to 3.25 on bulk soil), low bulk density (commonly around 1.0 and as low as 0.39), and extremely high porosity (maximum calculated 88%). Mineralogical examinations via Fourier Transform Infrared (FTIR) spectra and Differential X-Ray Diffraction (DXRD) show that the dominant Fe oxide and Mn oxide minerals in the soils are hematite and lithiophorite, respectively.
Ongoing work includes micromorphological analysis, mineralogical and chemical analysis of non-carbonate residues from marble bedrock, and particle size analysis.
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