Measurement of octanol-air partition coefficients for polycyclic aromatic hydrocarbons and polychlorinated naphthalenes

Measurements of the octanol-air partition coefficient, K-OA, are reported for 4 polycyclic aromatic hydrocarbons (PAHs) and 24 polychlorinated naphthalenes (PCNs) as a function of temperature over the range (0 to 50) degrees C. Results for PAHs are within a factor of 1.5 to 2 of values calculated as the ratio of the octanol-water and air-water partition coefficients. The enthalpies of transfer from octanol to air, Delta(O)(A)H, for fluorene, phananthrene and pyrene are (82.9, 75.5, and 76.3) kJ/mol, respectively. Except for fluorene, these are within the range of reported values of the enthalpy of vaporization, Delta(vap)H. There is also good agreement between Delta(O)(A)H and the temperature coefficient for vegetation-atmosphere partitioning (Q(D)). Correlations of log K-OA against log vapor pressure (p(O)) are compared with previous results for polychlorinated biphenyls (PCBs). Values of log K-OA for PCNs show a stepwise change and increase by more than 3 orders of magnitude from the 2-Cl to 6-Cl homologue groups.