The role of soil properties in pyrene sorption and desorption

Soil type will greatly affect the sorption and subsequent desorption of hydrophobic contaminants. To gain a better understanding of the impact 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 with 3.54% soil organic matter (SOM) and 18% clay materials (< 2 microns). The New Mexico soil is a sandy lean clay comprised of 8.4% SOM and 10% clay. The last soil originated from Ohio 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 followed by the New Mexico and Ohio soils. The Freundlich model could fit both the Colombia and New Mexico soils. For the Ohio soil, a two-stage Freundlich model was required. For all three soils, PYR desorption was slow and resistant, and depicted 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.