Phosphorus Sorption and Desorption in Soils Treated by Thermal Desorption

Abstract

Thermal desorption (TD) is an effective way to remove hydrocarbons from soil. Soil exposure to temperatures between 100 and 400 °C to volatilize hydrocarbons can alter soil chemical properties that have potential to change phosphorus (P) dynamics. A series of laboratory soil sorption and desorption experiments were conducted on native and thermal desorption (TD)-treated soils to determine behavior of P with respect to availability for plant uptake and risk for runoff. The average relative increase in P sorption after TD treatment was between 14 and 26% as shown by Smax values. This increase in soil P sorption capacity is likely due to the potential creation of biochar materials and mineral transformations of Fe and Al oxides during TD treatment. Dissolved organic carbon association with P did not influence sorption. Desorption of P was least in TD-treated soils, indicating that the interaction between P and binding sites was strong. The amount of P retained by these soils (Smax values) may be of agronomic concern and should be considered when developing fertility plans. Based on these results, TD-treated soils pose no apparent threat to nearby surface waters.