Biosurfactant- and biodegradation-enhanced partitioning of polycyclic aromatic hydrocarbons from nonaqueous-phase liquids

A study was conducted on the effect of two different biological factors, microbial surfactants and biodegradation, on the kinetics of partitioning of polycyclic aromatic hydrocarbons (PAHs) from nonaqueous-phase liquids (NAPLs). The effect of rhamnolipid biosurfactants on partitioning into the aqueous phase of naphthalene, fluorene, phenanthrene, and pyrene, initially dissolved in di-2-ethylhexyl phthalate (DEHP) or 2,2,4,4,6,8,8-heptamethylnonane (HMN), was determined in multiple-solute experiments. Biosurfactants at a concentration above the CMC enhanced the partitioning rate of fluorene, phenanthrene, and pyrene but were ineffective with naphthalene. Enhancement of partitioning was also observed in the presence of suspended humic acid−clay complexes, which simulated the solids often present in the subsurface. Biosurfactants sorbed to the complexes modified PAH partitioning between the NAPL and these solids, increasing the fraction of solid-phase PAH. Biodegradation-driven partitioning was estimated in ...