Portal de Periódicos da CAPES

Surface area and size distributions of soil particles

1993; Elsevier BV; Volume: 73; Linguagem: Inglês

10.1016/0927-7757(93)80007-2

1873-4359

Michal Borkovec, Qing Wu, G. Degovics, P. Laggner, H. Sticher,

Groundwater flow and contamination studies

Small-angle X-ray scattering was employed to show that the surface of soil particles is rough and scales as A ∝ rDs where A is the surface area of a given size fraction of radius r and Ds is the surface fractal dimension (Ds = 2.4 ± 0.1). This relation has been confirmed by independent surface-area measurements on fractionated soil samples using nitrogen-gas adsorption and Methylene Blue adsorption from solution. These results bear an interesting relationship to recent size-distribution measurements of soil particles. The number of particles per unit volume with a radius larger than r has been shown to follow a power law N(r) ∝ r−D where the exponent D is the fragmentation fractal dimension (D = 2.8 ± 0.1). The power law is typically valid between two cut-off radii r1⪡r⪡r2 with values around r1 ≈ 10–100 nm and r2 ≈ 10–5000 μm. The specific surface area of the unfractionated soil sample depends critically upon the position of the lower cut-off r1 and can be accurately estimated from size-distribution data and the knowledge of Ds. These features can be related to a class of fragmented fractals which are characterized by the two fractal dimensions D and Ds. These fractal dimensions obey the inequalities 2<Ds<D<3 and 2Ds–D⩽2 which are also satisfied by the present experimental estimates.