PARTITIONING OF HYDROPHOBIC CONTAMINANTS IN THE VADOSE ZONE IN THE PRESENCE OF A NONAQUEOUS PHASE

Partitioning behavior of organic contaminants in the vadose zone may b e influenced by the presence of a nonaqueous phase liquid (NAPL). The bulk NAPL phase not only serves as a sink for hydrophobic contaminants but may also cover a significant fraction of the soil surface, reduci ng the surface area available for vapor-solid adsorption. Experiments were carried out to examine the applicability of binary partitioning p arameters when applied to a multiphase system. Dodecane was used as th e model NAPL phase, while toluene and benzene were used as the model h ydrophobic contaminants. Several soil types and water contents were ex amined. Results indicated that two-phase equilibrium parameters were s ufficient to predict partitioning among the various phases if fraction al soil surface coverage by each phase was considered. A previously de veloped model was extended to account for the presence of NAPL and was used to describe the multiphase contaminant partitioning presented In this work.