Surfactant solubilization of hydrophobic compounds in soil and water : II. The role of dodecylsulphate-soil interactions for hexachlorobenzene.

The soil/water partition coefficient (Kd) of hexachlorobenzene (HCB) ranged from 220 1/kg to 1800 1/kg for eight soils having a wide range of physico-chemical properties. Kd normalised to soil organic carbon (Koc) was found to be 28000 ± 4800 1/kg. Anionic surfactant dodecylsulphate (DS) present at concentrations above the critical micellar concentration (CMC) caused reductions in the apparent soil/water partition coefficient (Kd ()) in the range of 3-26 times for most soils and up to 36-91 times for sandy soils. Below CMC, at environmentally relevant surfactant concentrations, Kd () was reduced by a factor of 1-13. For clay and calcareous soils significant adsorption/complexation/precipitation of DS occurred. At the lowest DS concentration this produced a two-fold increase in Kd (*). At increasing DS concentrations this effect was shielded by the solubihzing effect from DS. Monomer (Kmn) and micellar (Kmc) surfactant/water partition coefficients for HCB were determined to be, 980 ± 190 1/kg and 21000 ± 1600 1/kg, respectively.