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This article in SSSAJ

  1. Vol. 59 No. 4, p. 1012-1018
     
    Received: July 28, 1994


    * Corresponding author(s): kurt_pennell@um.cc.umich.edu
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doi:10.2136/sssaj1995.03615995005900040008x

Surface Area of Soil Organic Matter Reexamined

  1. K. D. Pennell ,
  2. L. M. Abriola and
  3. S. A. Boyd
  1. Dep. of Civil and Environmental Engineering, 116 ERWE Bldg., Univ. of Michigan, Ann Arbor, MI 48109-2125
    Dep. of Crop and Soil Sciences, Michigan State Univ., East Lansing, MI 48824-1325

Abstract

Abstract

The specific surface area of soil organic matter has traditionally been considered to range from 550 × 103 to 800 × 103 m2 kg−1, based on the change in ethylene glycol (EG) retention before and after treatment of soils with H2O2. Recent studies, however, indicate that when N2 is used as the adsorbate, the surface area of soil organic matter is approximately 1 × 103 m2 kg−1. To investigate this large discrepancy, the surface areas of four H2O2-treated soils were determined by EG retention and the N2-Brunauer, Emmett, and Teller (BET) method. After exposure of the soils to H2O2, retention of EG decreased, while N2 adsorption increased. The surface area of soil organic matter calculated from the reduction in EG retention ranged from 65 × 103 to 481 × 103 m2 kg−1 and was dependent on the initial organic C content of the soil. In contrast, the N2-BET data yielded negative estimates of soil organic matter surface area that varied from −13 × 103 to −410 × 103 m2 kg−1. These results demonstrate that techniques based on the removal of organic C fail to provide consistent and reliable values for the surface area of soil organic matter. Due to the complex nature of interactions between soil organic matter and EG, including cation solvation, partitioning, and surface adsorption, it is recommended that EG retention be regarded as an estimate of the total uptake capacity of soils for polar liquids, rather than a measure of surface area.

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