Disparity of cadmium transport behavior in soils at different temperatures

The influence of temperature on sorption and transport behavior of cadmium in three soils (sandy loam, loam, and clay loam) was studied with column and batch experiments. In the column experiments, nonequilibrium transport behavior was observed in breakthrough curves at 10 and 21°C, whereas the transport behavior at 35°C was in general agreement with the prediction of the equilibrium transport model. The durations of tailing were also reduced with increasing temperatures, indicating a lesser extent of nonequilibrium. The shift from nonequilibrium to equilibrium transport behavior with increasing temperature was probably promoted by the corresponding increase of sorption rate coefficient. The extent of increase in the sorption rate coefficient advocates intraparticle diffusion being the rate-limiting process. The retardation was found to increase with increasing temperature. This was likely because of the change of transport behavior and variation of surface chemical properties with temperature. Similar positive temperature dependence of sorption was revealed in the batch experiments. The recognition of nonequilibrium transport behavior at low temperature provides a better solute transport prediction and soil treatment design in cold regions.