A series of miscible displacement experiments was conducted to investigate the significance of intraorganic matter diffusion as the rate-limiting step in sorption of organic and inorganic solutes during steady water flow in soil columns. Displacement studies were performed using Eustis surface soil and the same soil treated with hydrogen peroxide to reduce soil organic carbon content from 0.2% to <0.01%. Two herbicides (diuron and atrazine) were also displaced with binary solvent mixtures containing varying fractions of methanol and water (0-50% methanol). A bi-continuum nonequilibrium sorption model was used to simulate the measured effluent breakthrough curves obtained by simultaneous displacement of a nonadsorbed tracer (tritiated water), an organic solute (herbicide), and a metal cation ((45)Ca). (Copyright (c) 1989 American Chemical Society.)