SURFACE-CHARGE CHARACTERISTICS OF PODZOLIZED SOIL

Recently developed methods for the accurate measurement of surface charge components and the points of zero charge in soils containing both permanent- and variable-charge constituents were applied to a Haplorthod that is typical of podzolized soils in North America, Scandinavia, and Russia. Independently measured values of the density of structural surface charge, net proton charge, and net adsorbed ion charge were obtained for soil samples from the E2 and Bhs horizons suspended in LiCl or Li2SO4 solutions of ionic strength 1 or 10 mmol kg(-1). Data taken across the pH range 2 to 6 tested successfully for conformity to the law of surface charge balance. Relationships between the point of zero net proton charge and the point of zero net charge were consistent with the fact that, at any pH, increasing ionic strength favored an increase in the net adsorbed ion charge, whereas changing from Cl- to SO42- favored a decrease in the net adsorbed ion charge. The methodology and charge balance analysis are applicable to any podzolized soil.