Ion transport and permeability in an allophanic andisol at low pH

Abstract

Allophanic Andisols have a significant pH-dependent charge. The positive charge increases and the negative charge decreases as pH decreases; therefore, anion movement becomes slower and cation movement becomes faster as pH decreases in the soil. At low pH, soil dispersion occurs easily due to electric repulsive force. The permeability of the soil then decreases because of structural changes that occur when dilute HCl or HNO3 is percolated in the soil. However, soil permeability does not decrease when dilute H2SO 4 is percolated in the soil. This is because SO42- strongly adsorbs on the soil surface at low pH and the soil remains flocculated.