Pore size distribution patterns in tropical soils obtained by mercury intrusion porosimetry: the multifractal approach

We characterized pore size distributions of 54 horizons from 19 soil profiles sampled in Minas Gerais, Brazil, by mercury intrusion porosimetry (MIP). Patterns of PSDs were examined regarding soil groups, texture, and sesquioxides. The MIP curves fit multifractal models, which were compared with models from N adsorption isotherms. Mercury intrusion porosimetry (MIP) is commonly used to determine soil pore size distributions (PSDs) in a wide, but incomplete, range of equivalent pore diameters. Mono- and multifractal analyses of soil PSDs are useful for analyzing the soil porous system. The main objective of this work was to characterize PSDs from tropical soils using the multifractal approach. Duplicate PSDs were measured by MIP for 54 horizons collected from 19 soil profiles in Minas Gerais, Brazil. Although 10 of the studied soils were Ferralsols (Oxisols or Latosols), other soil groups such as Nitisols, Acrisols, Alisols, Luvisols, Planosols, Cambisols, Andisols, and Leptosols also were sampled. Different patterns of PSDs were observed, depending on soil type, texture, and weathering intensity. Textural porosity (0.005-0.2 μm) was positively and significantly correlated to clay and Al2O3 contents and soil specific surface area. Comparison of multifractal analysis from Hg intrusion curves and N2 adsorption isotherms (NAIs) showed entropy dimension values and width of the singularity spectra smaller for the former than for the latter. Multifractal analysis of MIPs and NAIs allowed a thorough characterization of the complexity and heterogeneity of the soil pore space at different scales and was useful to provide new insights for portraying the soil pore system.