The aim of this study was to assess how the solubility and the speciation of Cd in soil solution were affected over time by the soil temperature for three metal-contaminated soils. The changes of solution Cd concentration (either total or free ionic) and other physico-chemical parameters (e.g. pH, ionic strength, the concentrations of NO3-, SO42- Ca, Mg and dissolved organic carbon) were monitored over a 28-day culture of lettuce (Lactuca sativa L.) in soils incubatedat 10 degrees C, 20 degrees C or 30 degrees C. The major result of this study was that Cd2+ concentration greatly varied over time in soil solution. The Cd2+ concentration declined over time in soil solution as did the concentration of cations that may compete for adsorption (Ca2+, mg(2+)). The rise in soil temperature primarily impacted on the concentration of Cd2+ via promoting the microbial C-degradation and, thus, the complexation of Cd in soil solution. The integration of the temporal variations in Cd2+ concentration through the calculation of the root exposure to solution Cd (E-Cd) provided a fairly close and robust prediction of Cd concentration in lettuce roots. The present work thus provided new insights on the fate of Cd in contaminated soils that may be relevant for predicting the root uptake of Cd.