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

Novel methods are developed and tested for measuring the octanol-air p artition coefficient (K-OA), which is suggested to be a valuable descr iptor of air-vegetation and air-soil equilibrium. Data are reported fo r six chlorobenzenes (CBs), five polychlorinated biphenyls (PCBs), and DDT over the temperature range -10 to +20 degrees C with values appro aching 10(12). K-OA varies log-linearly with reciprocal absolute tempe rature and increases by a factor of approximately 30 over this tempera ture 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 with in a factor of 4 of values calculated as the ratio of the octanol-wate r and the air-water partition coefficients, with a factor of 7.4 apply ing to DDT. It is suggested that for hydrophobic chemicals it is prefe rable to measure K-OA directly since this avoids handling aqueous solu tions.