Parametric assessment of soil retention at presence of petroleum in three-phase system

Reclamation of oil-contaminated soils is essential for optimal conservation of soil and water resources. Any decontamination of such soils from hydrocarbons contamination requires quantitative evaluation of soil hydraulic properties at presence of such contaminants. The objective of this study was to investigate the soil retention in NAPL-water-air three-phase systems. Consequently, soil retention curves were obtained using hanging column method with three primary NAPL-water ratios 25-75, 50-50 and 75-25. The parameters of soil retention curves were then obtained based on van Genuchten, Brooks-Corey and Campbell models. The model performance was also evaluated based on ME, RMSE, EF, CD and CRM. The results indicated that by decreasing the amount of NAPLs, the pore size distribution parameters of the hydraulic models (n, λ and 1/b) and their bubbling pressure parameters were both reduced. Therefore, bubbling pressure and slope of soil retention curves were increased. The results also showed that in a given amount of soil liquid phase, more suction is needed to drain out fluids in three-phase (NAPL-water-air) systems compares to two-phase (water-air) system. Thus, in a given quantity of NAPL, the porous media provide more retention for three-phase systems. Also, the calculated statistics indicated that van Genuchten model provides more reasonable predictions for NAPLs retention in three-fluid phase systems for monotonic drainage paths.