Laboratory kinetic batch and column miscible displacement experiments were carried out to discern the mechanisms controlling the retention and release of mercury on soils. Adsorption of mercury was rapid initially and highly nonlinear by all soils. The sorption capacity of mercury followed the sequence: Sharkey clay>Olivier loam>Windsor sand. The removal of organic matter resulted in a decrease in the adsorption of capacity for mercury on all three soils. Desorption of mercury was strongly irreversible where less than 1% was released based on successive desorptions. A sequential extraction procedure provided evidence that a significant amount of mercury was OM/sulfide mercury and irreversibly adsorbed on all soils. Breakthrough curves (BTC) of mercury were highly retardant in all soils. Mercury is best described as strongly retained and highly "immobile" in porous media.