The Role of Soil Properties in Pyrene Sorption and Desorption

Soil type will greatly affect the sorption and subsequent desorptionof hydrophobic contaminants. To gain a better understanding of theimpact of soil type on sorptive behavior, the sorption-desorption of pyrene (PYR) with three different soils was studied. The first soil originated from Colombia and is classified as silty sand with3.54% soil organic matter (SOM) and 18% clay materials (<2 microns). The New Mexico soil is a sandy lean clay comprisedof 8.4% SOM and 10% clay. The last soil originated fromOhio and is a silty sand with 1.84% SOM and 9.6% clay. Based on soil mineralogy and sorption-desorption isotherms,the Colombia soil had the greatest binding potential followedby the New Mexico and Ohio soils. The Freundlich model couldfit both the Colombia and New Mexico soils. For the Ohiosoil, a two-stage Freundlich model was required. For allthree soils, PYR desorption was slow and resistant, anddepicted an apparent hysteresis. The extent of sorption-desorption for each soil was attributed to its individual classification.For instance, the SOM present in the New Mexico soil (8.4%) enabled a relatively easy desorption in comparison to the other two soils. For the Ohio and Colombia soils, the interaction with the clay fractions rendered a stronger sorptive bond.