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A Non‐Empirical Method for Computing Pore Radii and Soil Water Characteristics from Particle‐Size Distribution
Author(s) -
Arya Lalit M.,
Heitman Joshua L.
Publication year - 2015
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2015.04.0145
Subject(s) - loam , soil water , radius , porosity , soil science , particle (ecology) , range (aeronautics) , mass fraction , mathematics , particle size distribution , empirical modelling , materials science , mineralogy , particle size , geotechnical engineering , environmental science , geology , composite material , engineering , simulation , paleontology , oceanography , computer security , computer science
Soil water characteristics (SWC) is a common requirement in studies of soil physics and hydrology, and modeling this property is preferred because experimental measurements are error‐prone, time‐consuming, and costly. However, unknown empirical parameters in SWC models remain a source of uncertainty. This study proposes a formulation for computing pore radii and SWCs from routinely available particle‐size distribution (PSD), bulk density, and particle density data, without the need for incorporating unknown empirical parameters. The proposed model emerged from combining attributes of natural‐packed soil structure with those of a counterpart hypothetical structure consisting of spherical particles, and has the formr in =0.0717 Φ ( w i / ρ b )n i 4 / 3R iwhere r in is the pore radius for a given fraction of particles on the PSD curve, Φ is the porosity, w i is the fraction solid mass, ρ b is the bulk density, n i is the number of spherical particles that can be formed using the fraction solid mass, and R i is the mean particle radius for the fraction. The model was applied to calculate SWC for 41 soils consisting of loam, clay, sandy loam, and sand textures. Root mean square residuals (RMSRs) of log‐transformed pressure heads were calculated to assess goodness of agreement between experimental pressure heads and those predicted by the non‐empirical model of this study and the empirical model of Arya et al. The distribution of RMSR values (log 10 |h|, cm) showed a range from 0.021 to 1.309. When viewed in conjunction with plotted SWC curves, results showed reasonable to excellent agreement with experimental data in about 75% of the cases. Barring a few exceptions, predictions of the proposed model also agreed well with predictions of the empirical model of Arya et al.