Effects of Solution and Soil Chemistry on the Distribution of Oil Residual in Patagonian Soil

The distribution coefficient of oil residuals between water and the soil under equilibrium conditions is, in the case of Patagonian soils, strongly dependent on the clay contents and humidity of the soil. Other variables such as, the soil salinity and the environmental exposure conditions, also affect the interactions between the phases. The oil residuals are generally accompanied by water spills, that are extracted together with the oil and which, frequently, have high salinity. These salts stay on soils during long times and finally they became part of the soil. The resulting oil aqueous concentrations and the soil-water distribution ratio (Kd) may be strongly influenced by these factors. Based on experimental data of several parameters determined in different regional field samplings, a semi-empiric model was developed that allows prediction of the Kd dependence with the exposure time, the salinity of the equilibrium aqueous concentration and the clay contents of the soil. The Monte Carlo simulation was used in this work. Distribution values of soil conductivity, clays content, and assumed fixed values of the age of the oil spill were used in the model. A set of calculated values of Kd was obtained and the results show a distribution that was probabilistically analyzed. The Kd values increase with increasing age of spill and soil salinity and decrease when the salinity of the initial aqueous concentration is greater than the soil salinity. The determined parameters are useful for modeling of the environmental impact on polluted soils and for the design of remediation techniques.