Comprehensive microstructural characterization of saline-alkali soils in the Yellow River Delta, China

Soil salinization in the Yellow River Delta, China, is a matter of concern from agricultural and environmental perspectives. This study characterizes the relationship between the permeability and microstructure of saline-alkali soil. Soil microstructure, including mineral composition, pore distribution, and particle morphology of soils at different depths, was analyzed using X-ray diffraction, mercury intrusion porosimetry, and scanning electron microscopy. Results indicated that the soil mean saturated hydraulic conductivity and porosity, excluding the surface soil, were only 6.0 x 10(-5) cm/s and 33.0%, respectively, and the mean proportion of clay minerals (illite, chlorite and kaolinite) was 6.1%. The pore distribution results showed that small pores (2 <= d< 10 mu m) and micropores (0.1 <= d< 2 mu m) constituted the majority of the soil pores. We attributed the deterioration of the soil permeability to low soil porosity, which, in turn, was associated with soil pore size distribution and a closely inlaid 'brick wall'-type particle arrangement. Quantitative analysis of the scanning electron microscopy images showed that the fractal dimension of pores and roundness of particles increased with depth, whereas the fractal dimension of particles and roundness of pores decreased with depth. However, the azimuth, perimeter, Fred diameter, and orientation of saline-alkali soil did not significantly change with the increase in depth. This study revealed that the microstructure of saline-alkali soil exhibits a good correlation with its permeability.

Automated summary

The study found a correlation between the microstructure of saline-alkali soil and its permeability, with low porosity leading to deterioration in soil permeability. Pore distribution and particle arrangement also play a role in affecting permeability.