Phosphorus sorption and desorption in soils treated by thermal desorption

Authors: CROAT, SAMANTHA - North Dakota State University; DESUTTER, THOMAS - North Dakota State University; CASEY, FRANCIS - North Dakota State University; O'Brien, Peter

Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2020
Publication Date: 7/27/2020
Citation: Croat, S.J., DeSutter, T.M., Casey, F.X.M., O'Brien, P.L. 2020. Phosphorus sorption and desorption in soils treated by thermal desorption. Water, Air, and Soil Pollution. 231:216. https://doi.org/10.1007/s11270-020-04579-x.
DOI: https://doi.org/10.1007/s11270-020-04579-x

Interpretive Summary: Crude oil spills on agricultural land decrease crop yields, so many resources are often devoted to removing the oil from soil (i.e., remediation). One technique, called thermal desorption, removes oil from the soil by heating it up to 500 °C, but this heating can affect soil characteristics that make it less suitable for crop production, such as chemical characteristics like soil phosphorus (P) dynamics. The soil P dynamics are critical to successfully managing agricultural land, while mismanaging soil P can have negative environmental impacts. The objective of this research is to determine if thermal desorption is suitable for remediating oil spills on agricultural land by investigating soil P dynamics. A series of laboratory experiments were conducted on uncontaminated topsoil and thermal desorption-treated soils to determine changes in soil P availability for plant uptake and risk for run-off. This study showed that soil P was bound more tightly to the soil following thermal desorption treatment, which suggests that less soil P will be available to plants and that risk of soil P run-off is low. This research is useful to guide land managers in nutrient management plans for soils treated by thermal desorption, which will help return the land to successful agricultural production as quickly as possible.

Technical Abstract: Thermal desorption (TD) is an effective way to remove hydrocarbons from soil. Soil exposure to temperatures between 200 and 500 °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 run-off. The average relative increase in P sorption after TD-treatment was 19.5% as shown by Smax values. This increase is likely due to the potential creation of biochar materials and mineral transformations of Fe- and Al-oxides during TD treatment causing increase in the soil’s P sorption capacity. 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 were 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, there is no apparent threat to nearby surface waters (k values) when using TD-treated soils for agricultural use.