Measuring Specific Surface of Soil with the WP4C (13389-00 AN)
The specific surface area of a soil sample is the total surface area contained in a unit mass of soil. Soils with high specific surface areas have high water holding capacities, more adsorption of contaminants, and greater swell potentials.
Specific surface is therefore an important parameter. Specific surface is closely tied to particle size distribution. This can be seen with a simple thought experiment. A cube, 1 cm on a side, with a density of 1 g/cm3 has a surface area of 6 cm2/g. If the cube were divided into smaller cubes 1 mm on a side, the resulting 1000 cubes would have the same mass of material, but a surface area ten times that of the single cube, or 60 cm2/g. If the cube were divided into 1012 cubes 1 um on a side, the surface area would be 6 x 104 cm2/g. Thus, the smaller the particles, the greater the surface area per unitmass of soil.
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