How the particle interaction forces determine soil water infiltration: Specific ion effects

Journal of Hydrology

Wuquan Ding

Many studies have shown that K+ has more favourable effects on soil water infiltration than Na+ , which is a result of specific ion effects or Hofmeister effects. In this study, we employed four alkali metal cation species (Li+ , Na+ , K+ , and Cs+ ) to determine how the particle interactions influence the water infiltration in a soil with permanent surface charges. Moreover, the defined Hofmeister energy was employed to characterize the specific ion effects. The DLVO force plus the hydration force between two adjacent soil particles mainly determines water infiltration rate through affecting the soil pore-size distribution, which exhibits strong specific ion effects. The hydration force may originate from the surface hydration of soil particles and the hydration of cations in the double layer. The hydration pressure between adjacent soil particles was complexly influenced by electrolyte concentration, Debye length, cationic distribution in the double layer through the Hofmeister energy of cation.