Partition coefficients particle-water

The base set of partition coefficients needed for most multimedia models include the Henry s law constant (JCh) to describe partitioning between air and water, partition coefficients between water and various solid phases in soils, sediments, and particulate matter in the water coliunn (fCa), and a coefficient describing partitioning between air-borne particles and air (Kp). If not available from direct experimental measurements, soUd phase-water partition coefficients are often derived from the organic carbon-water partition coefficient, Kqc (Eq. 4), the underlying assumption being that sorption into organic matter dominates the overall sorption to bulk solid material. 

Concentrations in Water and Particles. In order to obtain the rates of reaction, the concentrations of the two monomers and the chain transfer agent in the water and polymer phases were calculated using equilibrium partition coefficients (H). ... 

Winters and Lee134 describe a physically based model for adsorption kinetics for hydrophobic organic chemicals to and from suspended sediment and soil particles. The model requires determination of a single effective dififusivity parameter, which is predictable from compound solution diffusivity, the octanol-water partition coefficient, and the adsorbent organic content, density, and porosity. 

Watarai, H., Tanaka, M., Suzaki, N. (1982) Determination of partition coefficient of halobenzenes in heptane/water and 1-octanol/water systems and comparison with the scaled particle calculation. Anal. Chem. 54, 702-705. 

A series of experiments was also conducted by Bowman et al. [34] to ascertain the effects of differing environmental factors on the sediment-water interactions of natural estrogens (estradiol and estrone) under estuarine conditions. Sorption onto sediment particles was in this case relatively slow, with sorption equilibrium being reached in about 10 and 170 h for estrone and estradiol, respectively. On the other hand, true partition coefficients calculated on colloids were found to be around two orders of magnitude greater that those on sediment particles. Hence, it was concluded that under estuarine conditions, and in comparison to other more hydrophobic compounds, both estrone and estradiol... 

Kd is difficult to define when dealing with actual field conditions. Laboratory studies have demonstrated that an approximation of Kd can be made based on the more easily determined factors such as organic carbon content of the soil and the octanol-water partitioning coefficient of the compound. For sediment particles <50 pm ... 

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) ... 

PAHs have been found all over the globe in all compartments of the environment. They are ubiquitous because the are persistent. Recalcitrance in PAHs may stem, in part, from the delocalized electrons in the planar pi orbitals of the aromatic structure. Their relatively high octanol-water partition coefficients, Kows, make them rather lipophilic. The lipophilicity of PAHs forces them from the dissolved phase to particles and also into lipid rich organisms, but they can be metabolized in higher organisms. However, these metabolites are often more toxic than their parent PAHs. When combined with other stressors, particularly ultraviolet radiation, PAHs can exert enhanced toxicity. 

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