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B.; Mabey, W.; Holt, B.; Gould, C. "Water Related Environmental Fate of 129 Priority Pollutants"; US. Environmental Protection Agency: Washington, DC, 1979; EPA 440/4-79-029a, Vol. 1 and 2. (21) Ahlberg, M.; Bergheim, L.; Nordberg, G.; Persson, S.; Rudling, L.; Steen, B.H The distribution ratio of hydrophobic ionizable organic compounds (HIOC's) between aqueous and nonaqueous phases is shown to depend on the pH and ionic strength of the aqueous phase. Four models are presented to describe the association of the HIOC with the nonaqueous phase: (i) transfer of the neutral organic species from the bulk of the aqueous phase to the bulk of the nonaqueous phase; (ii) transfer of the ionic organic species with inorganic counterions to the bulk of the nonaqueous phase; (iii)transfer of the ionic organic species to the aqueous-nonaqueous interface with inorganic counterions in the aqueous phase; (iv) association of the organic species with specific functional groups of the nonaqueous phase. The distribution of 2,3,4,5-tetrachlorophenol and pentachlorophenol in the two-phase system composed of KOH, KC1, H20, octanol, and the chlorophenol was determined as a function of ionic strength and interpreted quantitatively in terms of models i and ii. For aqueous phases with high pH values and ionic strengths, the dominant species of the chlorophenols in the octanol phase were the chlorophenolate ions in association with K+ counterions. IntroductionThe distribution ratios of nonpolar organic compounds between water and natural sorbents have been estimated with satisfactory accuracy from their relationships to the organic carbon content of the sorbent and the octanolwater partition constant of the solute. These correlations have been of great value in the estimation of the degree of sorption of a wide variety of compounds on a wide variety of sorbents. However, it has been noted in some of the correlation studies that polar and especially ionizable organic compounds do not fit to the same pattern as the nonpolar compounds.In a recent study on the sorption of chlorinated phenols by sediments and aquifer materials, Schellenberg et al. (1) demonstrated that sorption of not only the neutral phenol but also the anionc phenolate occur. In certain cases the phenolate species contributes significantly to the overall distribution ratio of the compounds. Kaiser and Vald-

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