A differential availability enhancement factor for the evaluation of pollutant availability in soil treatments

An availability enhancement factor (AEF) is proposed and its usefulness for determining the effectiveness of desorption treatments of pollutants from soils is discussed. In addition, its relationship to a new Coefficient of Hysteresis (CH) is derived. The AEF was defined as the ratio of the slope of the desorption curve of a given pollutant with a surfactant or solvent treatment to the slope of the corresponding desorption curve of a reference treatment. This factor is shown to be useful for the quantification of the effect of a given soil treatment (with surfactants, biosurfactants, solvents) on the eventual improvement of the pollutant desorption and availability for biodegradation or further physicochemical removal. Several easy algebraic equations are developed for finding the values of the AEF in the most common desorption cases (linear, FREUNDLICH, and LANGMUIR isotherms). Data from the refereed literature were used to show how the AEF concept works when a biosurfactant is applied to increase the desorption of polynuclear aromatic hydrocarbons from soils. The AEF concept allows for more objective decisions regarding the selection of desorption treatments of pollutants from soils and sediments to be made.