The desorption of contaminants from soils/sediments is one of the most important processes controlling contaminant transport and environmental risks. None of the currently adopted desorption models can accurately quantify desorption at relatively low concentrations; these models often overestimate the desorption and thus the risks of hydrophobic organic chemicals, such as benzene and chlorinated solvents. A newly developed dual-equilibrium desorption (DED) model can more accurately describe desorption; it has been tested using a wide range of laboratory and field data and has been used to explain key observations related to underground storage tank (UST) plumes. The DED model relates the amount of a sorbed chemical to the aqueous concentration using readily available parameters including octanol-water partition coefficient, solubility and fractional organic carbon. The DED model can be easily incorporated into standard risk and transport models. According to this model, many regulatory standards of soils and sediments could be increased without increasing the risks.