FURTHER DISCUSSION OF THE OCTANOL AIR PARTITION-COEFFICIENT K-OA AS ACORRELATING PARAMETER FOR GAS/PARTICLE PARTITIONING COEFFICIENTS/

The pure-compound liquid vapor pressure (p(L)(o)) has been used extens ively as a log-log correlating parameter for gas/particle partitioning constants. When the partitioning to the aerosol particle phase involv es partitioning into an organic material (om) phase, the success of p( L)(o) in this context relies on compound-to-compound constancy of the molecular activity coefficient zeta(om) in the om phase. While zeta(om ) for a particular type of aerosol may indeed tend to remain constant within a given compound class, significant class-to-class variations i n zeta(om) are certain. This paper discusses the theory underlying the advantages of using the octanol/air partition coefficient K-oa as a c orrelating parameter for gas/particle partitioning constants. In parti cular, it is far more likely that different compounds will exhibit sim ilar values of the ratio zeta(oct)/zeta(om) than it is that they will exhibit similar values of zeta(om). The conclusion that the octanol-ba sed partition coefficient K-oa has significant advantages over the pur e-compound partition coefficient p(L)(o) when parameterizing gas/parti cle partitioning has a direct analog in the selection of the octanol/w ater partition coefficient K-ow as a correlating parameter for soil/wa ter partition coefficients like the organic carbon/water partition coe fficient K-oc. The nature of this analogy is discussed in detail. The acknowledged success of log K-ow in this regard presages wide applicat ion of log K-oa as a correlating parameter for gas/particle partition coefficients. (C) 1998 Elsevier Science Ltd. All rights reserved.