INVESTIGATING THE INFLUENCE OF INCOMPLETE SEPARATION OF SEDIMENT AND WATER ON EXPERIMENTAL SORPTION COEFFICIENTS OF CHLORINATED BENZENES

The influence of incomplete separation of water and sediment in batch sorption experiments was investigated with five chlorinated benzenes ( sediment/water ratios between 0.25 and 50 g/L). Only the sorption coef ficients of the most hydrophobic chemical, hexachlorobenzene, decrease d with increasing sediment/water ratios. This decrease is assumed to b e caused by an increasing amount of sediment that was not separated fr om the aqueous phase. To quantify this incomplete water/sediment separ ation, the unseparated sediment fraction, called the third phase, was analyzed in suspension water. For this purpose the apparent enhanced s olubilities of hexachlorobenzene and two polychlorinated biphenyls wer e determined in the suspension water. Solubilities of these compounds were found to be considerably enhanced (up to about 8 times). In addit ion, turbidity, dry weight, and dissolved organic carbon (DOC) measure ments were used to quantify the third phase. On the basis of these thi rd-phase analyses, experimental sorption coefficients of hexachloroben zene were corrected for third-phase influence, where the apparent solu bility measurements were the most successful.