MEASUREMENT OF OCTANOL - AIR PARTITION-COEFFICIENTS FOR CHLOROBENZENES, PCBS, AND DDT

Novel methods are developed and tested for measuring the octanol-air partition coefficient (K-OA), which is suggested to be a valuable descriptor of air-vegetation and air-soil equilibrium. Data are reported for six chlorobenzenes (CBs), five polychlorinated biphenyls (PCBs), and DDT over the temperature range -10 to +20 degrees C with values approaching 10(12). K-OA varies log-linearly with reciprocal absolute temperature and increases by a factor of approximately 30 over this temperature range, the temperature coefficient being approximately 62 kJ/mol for CBs and 70 kJ/ mot for PCBs. For PCBs, the values of K-OA are within a factor of 4 of values calculated as the ratio of the octanol-water and the air-water partition coefficients, with a factor of 7.4 applying to DDT. It is suggested that for hydrophobic chemicals it is preferable to measure K-OA directly since this avoids handling aqueous solutions.