Assessment of the effects of soil organic matter and iron oxides on the individual sorption of two polycyclic aromatic hydrocarbons

Soils are the ultimate sink for environmental pollutants like polycyclic aromatic hydrocarbons (PAHs), but the roles of major soil constituents in this process are still unclear. The fate of PAHs is governed by sorption processes which in turn affect transport, chemical and biological reactivity of these PAHs. Thus, the effects and contributions of two major soil constituents (organic matter-OM and iron oxides-IOs) on pyrene and fluorene sorption on soils were assessed by removal of both constituents. The whole soils had higher sorption than the treated OM/IOs soils. Pyrene sorption on OM-rich soils was high and nearly instantaneous, while on the IOs-rich soils, it was lower with delayed equilibrium. The IOs contributed<25% to the sorption process while OM contributed<greater than or equal to>50%. The extent of PAHs desorption was dependent on the main constituent(s) on each soil; soils with high OM content exhibited lower desorption and high hysteresis. Hysteresis was higher for pyrene, and this was far obvious in the presence of OM; the hysteresis trend is whole>IOR>OMR soils. Though, removal of any of these soil constituents usually reduced sorption and enhanced sorbed PAHs desorption, the presence of IOs masked some PAHs sorption sites, thus its removal resulted in higher sorption. In general, this study highlights the contributions of soil OM and IOs on the sorption of pyrene and fluorene.