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  • 1
    Electronic Resource
    Electronic Resource
    Organo-mineral associations in sandy acid forest soils: importance of specific surface area, iron oxides and micropores (2005)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    European journal of soil science 56 (2005), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Organo-mineral associations stabilize soil organic matter, though the mechanisms by which they do so are unclear. We used particle-size fractions 〈 6.3 μm of two soils to examine the importance of Fe oxides, short-range order Al silicates and the surface areas of minerals and micropores on the formation of organo-mineral associations. In the subsoil Fe oxides were most strongly statistically correlated with the mineral-bound organic carbon. We therefore assume that they are the most important substrates for the formation of organo-mineral associations. There is no indication that this is caused by physical protection of organic matter in their micropores (〈 2 nm). In the Haplic Podzol, dithionite–citrate–bicarbonate-soluble short-range order Al silicates may also play a role. Fe oxide particles were calculated to offer specific surface areas of ∼ 200 m2 g−1 (goethite) and ∼ 800 m2 g−1 (ferrihydrite), corresponding to crystal diameters of only a few nm. We assume that the resulting large amount of oxide-specific reactive surface sites (conditionally charged hydroxyl groups) is responsible for their dominant role as sorbents. With maximum C loadings of 1.3 mg C per m2 Fe oxide for the Dystric Cambisol and 1.1 mg C per m2 Fe oxide + short-range order Al silicates for the Haplic Podzol the subsoils of both soils seem to have reached saturation with respect to organic matter sorption. In contrast to subsoil horizons, organo-mineral associations from topsoils contain much larger amounts of organic matter. Here a larger C loading on Fe oxides or a greater importance of other sorbents in addition to the oxides must be assumed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.2005.00710.x
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  • 2
    Electronic Resource
    Electronic Resource
    The concentrations of fatty acids in organo-mineral particle-size fractions of a Chernozem (2004)
    Oxford, UK; Malden, USA : Blackwell Publishing Ltd/Inc.
    European journal of soil science 55 (2004), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Fatty acids, the most abundant class of soil lipids, indicate pedogenetic processes and soil management. However, their quantitative distribution in organo-mineral particle-size fractions is unknown. The concentrations of n-C10:0 to n-C34:0 fatty acids both in whole soil samples and in the organo-mineral particle-size fractions of the Ap horizon of a Chernozem were determined (i) to evaluate the effects of long-term fertilization and (ii) to investigate their influence on the aggregation of organo-mineral primary particles. Quantification by gas chromatography/mass spectrometry (GC/MS) showed that long-term fertilization with nitrogen, phosphorus and potassium (NPK) and farmyard manure (FYM) led to larger concentrations (25.8 µg g−1) of fatty acids than in the unfertilized sample (22.0 µg g−1). For particle-size fractions of the unfertilized soil, the fatty acid concentrations increased from the coarse silt to the clay fractions (except for fine silt). Fertilization with NPK and FYM resulted in absolute enrichments of n-C21:0 to n-C34:0 fatty acids with a maximum at n-C28:0 in clay (×2.2), medium silt (×2.0), coarse silt (×1.8) and sand (×2.9) compared with the unfertilized treatment (the factors of enrichment are given in parentheses). New evidence for the aggregate stabilizing function of n-C21:0 to n-C34:0 fatty acids was shown by the characteristic pattern in size-fractionated, disaggregated and aggregated samples. Highly significant correlations of fatty acid concentrations with organic C concentrations and specific surface areas are interpreted as indicators of (i) trapping of fatty acids in organic matter macromolecules and (ii) direct bonding to mineral surfaces. This interpretation was supported by the thermal volatilization and determination of fatty acids by pyrolysis-field ionization mass spectrometry (Py-FIMS).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.2004.00623.x
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    Paper (German National Licenses)
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