THE MEASUREMENT AND MECHANISM OF ION DIFFUSION IN SOILS

The diffusive flux of soil cations and anions to an absorbing surface may be measured by a simple, quick, and accurate method using ion exchange resin paper as a sink maintaining, initially, zero concentration of the diffusate at the soil surface. The quantity of ions diffusing from the soil of semi-infinite thickness is directly proportional to the square root of the diffusion time until about half the counter-ions originally on the resin have been exchanged. Values of average effective diffusion coefficients are calculated using this proportionality constant and the concentration of total exchangeable ions. The effect of the counter-ions of the resin on soil-ion flux is small but measurable.