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  • 1995-1999  (2)
  • 1975-1979
  • 1995  (2)
Materialart
Erscheinungszeitraum
  • 1995-1999  (2)
  • 1975-1979
Jahr
  • 1
    ISSN: 1432-0789
    Schlagwort(e): Phospholipids ; Microbial biomass ; Phosphatase ; Cropping systems ; Long-term experiments Prairie
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In agricultural ecosystems that have had consistent cropping histories, standard microbial methods may be used to evaluate past and present practices. Our objective was to evaluate several microbial methods that best indicate cropping histories and soil quality on long-term plots. We selected soil microbial carbon (C), phospholipid analyses, direct counts of total fungal and bacterial biomass, and soil enzymes (phosphatases) to measure direct and indirect microbial activity on the Sanborn Field and Tucker Prairie. The Sanborn Field has been under various cropping and management practices since 1888 and the Tucker Prairie is an uncultivated site. Seven different plots were chosen on the Sanborn Field and random samples were taken in the summit area on the Tucker Prairie, which represented a reference site. Soil microbial biomass C, phospholipids, and enzyme activity were reflective of the cropping and management histories observed on the Sanborn Field. Enzymatic activity was highly correlated to soil organic matter. The direct counts of fungal and bacterial biomass showed that fungal populations dominated these soils, which may be attributed to soil pH. Soil microbial biomass C and enzyme assays seemed to be better potential indicators of cropping histories than the other methods tested in the long-term plots.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of radioanalytical and nuclear chemistry 193 (1995), S. 113-117 
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract A new method for the determination of Tc-99 in different environmental samples has been developed. The sample is carefully ashed in a muffle furnace and then fused with Na2CO3 and K2CO3. The first step is an enrichment and purification of TcO 4 − on an anion exchange resin. The Tc is desorbed as a cationic thiourea complex, which is held on a cation exchange resin. The complex is destroyed by oxidation to TcO 4 − with (NH4)2S2O8 in sulfuric acid. From this solution TcO 4 − is extracted into TBP/toluene and the organic phase is mixed with a scintillation cocktail and counted in an anticoincidence shielded LSC. Tc-99m is used as a chemical yield tracer. The decontamination factors for all important fission and activation products and naturally occurring radionuclides are in the range between 〉 105 and 〉 108. The detection limit is about 5 mBq per sample at a counting time of 1000 minutes. The maximum sample amount of plants is 500 g dry weight and therefore the lowest detection limit achievable is 10 mBq/kg. Ashing and dissolution of the samples takes 24 h and 4 analyses are performed by one technician in 8 hours. The chemical yield ranges from 50 to 80%.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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