Chapter 5. Contaminant Partition and Bioconcentration

Summary

The partition coefficients of a wide range of nonpolar and polar organic solutes in octanol-water (K_ow), heptane-water (K_hw), butanol-water (K_bw), and lipid-water (K_tw) mixtures are analyzed with Raoult's law and Flory-Huggins model. The analysis elucidates the effects of solute water solubility, solvent polarity, solvent-water mutual solubility, and solvent-solute size disparity on the solute partition behavior. The similar and dissimilar aspects of solute partition behaviors with ordinary solvents and biological lipids are illustrated. The analysis sheds light on the correlation, or the lack of it, between solute partition coefficients from different solvent-water mixtures. The physical basis is revealed for the effect of a functional group on the partition coefficient of a substituted compound (i.e., the so-called π constant). The mechanism for organic contaminant uptake by fish and the utility of the lipid-water partition coefficient to estimate fish bioconcentration factors (BCFs) of contaminants are presented with both laboratory and field BCF data.