How do geometric factors influence soil water retention? A study using computerized microtomography

Relating porous media morphological parameters to their water retention characteristics is fundamental to develop predictive water retention models. The main objective of this study was to verify how connectivity, tortuosity, accessible porosity, and pore size distribution affect the porous media water retention characteristic. The study employed three-dimensional (3D) image analysis, obtained using X-ray computerized microtomography (mu CT). The evaluation of these parameters was accomplished associating the morphological opening method to an approach proposed in this study, which we called the filling method-fiLMe. The fiLMe allows the separation of the pore system into pore diameter intervals, which is not possible with the opening method. Our results indicated that within the tension region associated with greater variation in the water retention (ranging from 2.5 to 52.5 cmH(2)O-considering all porous media studied), a higher number of connected and sinuous pores was found. This means that the primary characteristic of these pores is drainage. The connectivity and tortuosity results obtained by the two methods (morphological opening and fiLMe) showed that the samples analyzed presented bottleneck characteristics in the pore space. However, the fiLMe method was faster and more versatile when compared to the morphological opening method. The 3D reconstructions of the porous medium allowed a quantitative analysis of the water retention properties of the samples investigated, enabling the observation of the regions of saturation, highest moisture content variation, and residual moisture content in the retention curves.

Automated summary

Relating the morphological parameters of porous media to their water retention characteristics is crucial for developing predictive water retention models. This study utilized three-dimensional image analysis to evaluate the effects of connectivity, tortuosity, accessible porosity, and pore size distribution on water retention. The results showed that pores with higher connectivity and sinuosity were associated with greater variation in water retention within the tension region. Additionally, the fiLMe method proved to be faster and more versatile than the morphological opening method in assessing the porous media characteristics. The 3D reconstructions allowed for a quantitative analysis of water retention properties.