Octanol-Air Partition Coefficient Koa

This, then, gives the relationship between pL and the octanol-air partitioning coefficient, KOA. Rearranging Eq. (NNN) to obtain an expression for pL and substitution into Eq. (JJJ) give (Finizio et al.,... 

Hamer T. 2001. Measurements on octanol-air partition coefficients (KOA) for polybrominated diphenyl ethers (PBDEs) Predicting partitioning in the environment. BFR 55-58. 

The exchange of chemical compounds from the gas phase to a surface, e.g. atmospheric particles, soil, water, vegetation or other surfaces, is controlled by the affinity of the compound to this surface. The ratio of vapour pressure to water solubility can be used as indicator between levels in the atmosphere and water surface (Henry s law H constant). In many model calculations, the ratio between POP levels in octanol and water, the octanol-water partitioning coefficient (Kow), is used as reference for the distribution of POP in organic material [14]. Consequently, the expression ///RT (Cair/Cwalcr) and Kow (Coctanoi/Cwater) provide the octanol-air partitioning coefficient (Koa) ... 

The octanol-air partition coefficient (KOA) has played an important role in the study of plant-air partitioning. At the end of the 1980s, when interest in this subject started to grow, octanol was already well established as a model for the partitioning properties of organic carbon and lipids in aquatic systems. Several researchers borrowed from this experience and postulated that the partitioning properties of the hydrophobic or lipid-like portions of plants also could be modelled using octanol (Schramm et al., 1987 Paterson and Mackay, 1989 McLachlan et al., 1989). Since the partner phase was air, the octanol-water partition coefficient could not be used and it became necessary to define an octanol-air partition coefficient. 

Top Octanol-air partition coefficient (Koa) vs. liquid-phase vapor pressure (PSL) for PCB congeners (indicated by IUPAC numbers). Black squares = mono- and non-ortho substituted congeners, white squares = multi-ortho congeners (Harner and Bidleman, 1996). Bottom PAHs compared to PCBs (Harner and Bidleman, 1998a). 

Log-log plots of the particle/gas partition coefficient (Kp) for PAHs (top) and organochlorine compounds (PCBs, pesticides) (bottom) vs. the octanol-air partition coefficient (Koa). Points denote individual field studies. Figures and data from Finizio et al. (1997). 

Replacing P with the octanol-air partition coefficient (Koa) improves the absorption model. Advantages of the Koa - based model are twofold Koa is directly measureable as a function of temperature, and the model depends on the ratio of activity coefficients of the solute in octanol and the organic film on the particle (yoct/ yom). This ratio is more likely to be constant among classes of compounds than yom alone. 

Harner, T. and T.F. Bidleman. 1998a Octanol-air partition coefficient (Koa) for describing particle-gas partitioning of aromatic compounds in urban air. Environ. Sci. Technol, 32 1494-1502. 

Pankow, J.F. 1998. Further discussion of the octanol-air partition coefficient, Koa, as a correlating parameter for gas/partide partitioning coeffidents. Atmos. Environ. 32 1493-1497. 

Su, Y., Lei, Y.D., Daly, G.L., Wania, F. (2002) Determination of octanol-air partition coefficient (KOA) values for chlorobenzenes and polychlorinated naphthalenes form gas chromatographic retention times. J. Chem. Eng. Data 47, 449 155. 

Finizio, A., Mackay, D., Bidleman, T.F., Hamer, T. (1997) Octanol-air partition coefficient KOA as a correlating parameter of semivolatile chemicals to aerosols. Atoms. Environ. 31, 2289-2296. 

The gas-particle partitioning refers to the propensity for a typical molecule of the chemical to exist between the two phases, and is characterized by the partition coefficient Kp. The value of Kp is dependent of not only the physicochemical properties of the chemical such as vapor pressure (P°) and octanol-air partition coefficient (Koa), but also the concentration, size distribution, and chemical... 

The octanol/air partition coefficient, Koa, is the ratio of the solute concentration in n-octanol to that in air when the octanol-air system is at equilibrium. It is a key descriptor of the absorptive partitioning of SVOCs between the atmosphere and organic phases found in soil, in vegetation, and on aerosols. The application of Koa is based on the assumption that the interaction between the SVOCs and the environmental organic phases sufficiently resembles the interaction between the SVOCs and n-octanol. 

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