EQUILIBRIUM PARTITIONING OF PCB CONGENERS IN THE WATER COLUMN - FIELD-MEASUREMENTS FROM THE HUDSON-RIVER

The environmental behavior of hydrophobic organic compounds in water i s driven by partitioning between dissolved and sorbed phases. Partitio ning behavior of a compound is often based on empirical relationships to other properties of the chemical, such as water solubility and octa nol-water partition coefficients, but actual partitioning in the envir onment may differ significantly from such predictions. We conducted in tensive studies of the distribution of PCBs in the fresh water portion of the Hudson River, using sensitive capillary-column gas chromatogra phy methods to calibrate and resolve quantitations for 90 PCB congener s in 48 samples at 10 locations. A linear equilibrium model of PCB con gener partitioning, when corrected for temperature and suspended-matte r organic carbon content, provides a good representation of phase dist ribution. When particulate-phase concentrations are predicted from dis solved` concentrations with a two-phase model, the predictions are unb iased for the majority of samples and the average percent difference b etween observed and predicted particulate concentrations is +/-43 perc ent. Estimated in situ partition coefficients show systematic differen ces from partition coefficients predicted from octanol-water partition ing. Partitioning to colloids appears to be a significant component of total concentration for mono-and dichloro biphenyls, but not for more highly chlorinated congeners. The colloidal fraction may still cause significant overestimation of the bioavailable fraction for more hydro phobic congeners when a two-component model is used. (C) 1998 Elsevier Science Ltd. All rights reserved.