SURFACTANT SOLUBILIZATION OF HYDROPHOBIC COMPOUNDS IN SOIL AND WATER .2. THE ROLE OF DODECYL-SULFATE-SOIL INTERACTIONS FOR HEXACHLOROBENZENE

The soil/water partition coefficient (K-d) of hexachlorobenzene (HCB) ranged from 220 l/kg to 1800 l/kg for eight soils having a wide range of physico-chemical properties. K-d normalised to soil organic carbon (K-oc) was found to be 28000 +/- 4800 l/kg. Anionic surfactant dodecyl sulphate (DS) present at concentrations above the critical micellar co ncentration (CMC) caused reductions in the apparent soil/water partiti on coefficient (K-d) in the range of 3-26 times for most soils and up to 36-91 times for sandy soils. Below CMC, at environmentally relevan t surfactant concentrations, K-d was reduced by a factor of 1-13. For clay and calcareous soils significant adsorption/complexation/precipi tation of DS occurred. At the lowest DS concentration this produced a two-fold increase in K-d. At increasing DS concentrations this effect was shielded by the solubilizing effect from DS. Monomer (K-mn) and m icellar (K-mc) surfactant/water partition coefficients for HCB were de termined to be, 980 +/- 190 l/kg and 21000 +/- 1600 l/kg, respectively .