[Effects of solid-to-solution ratio on sorption of dissolved petroleum hydrocarbons to soils]

The influence of solid-to-solution ratio (SSR) on the sorption and desorption of dissolved petroleum hydrocarbons (DPH) to two surface soils (agricultural and black) was evaluated by batch reactor experiments. Previous characterization suggested that the organic carbon content (OC) of black soil was higher. The sorption and desorption isotherms at different SSRs fit well to a linear equation. Desorption hysteresis due to sorption irreversibility was observed and hysteresis index (HI) used to quantify the desorption hysteresis increased from 1.43 to 2.21 with increasing SSR from 10.00 g x L(-1) to 75.00 g x L(-1) for agricultural soil (OC = 1.54%) and increased from 1.18 to 1.37 with increasing SSR from 2.50 g x L(-1) to 5.00 g x L(-1) for black soil (OC = 15.91%), indicating that an increase of SSR and decrease of OC of soils caused a simultaneous increase in sorption irreversibility of DPH. The organic-carbon-normalized sorption coefficients (K(OC)) derived from sorption isotherms, were dependent on SSR. A SSR-effect isotherm equation for a given system, which could be applied in the extrapolation of batch-measured sorption parameters to field conditions, was established.