Comparison of the octanol-air partition coefficient and liquid-phase vapor pressure as descriptors for particle/gas partitioning using laboratory and field data for PCBs and PCNs

The conventional Junge-Pankow adsorption model uses the sub-cooled liquid vapor pressure (p(L)(O)) as a correlation parameter for gas/particle interactions. An alternative is the octanol-air partition coefficient (K-oa) absorption model. Log-log plots of the particle-gas partition coefficient versus p(L)(O) were previously made for partitioning data from controlled laboratory studies, resulting in separate trend lines for different ortho-substituted PCB classes. The same plots applied to field data for PCBs and PCNs resulted in separate regression lines with slopes that were statistically different at the 99% confidence level. When K-oa is used as the correlation parameter, these differences are resolved showing the ability of the model to reduce variability both within a compound class and between compound classes, The K-oa model is also preferred because it uses parameters that can be measured directly (K-oa and f(om)), unlike the parameters of the Junge-Pankow model which must be estimated. Published by Elsevier Science Ltd.