The approach discussed thus far for assessing bioaccumulation of environmental pollutants is actually based on some statistical constructs and the basic equilibrium theory. There is still one other assessment approach in which either a simple or a complex kinetics model can be used to relate the uptake and release of a contaminant in an ecosystem.

Physiologically-based pharmacokinetic (PB-PK) simulation represents the more complex of the two forms of kinetics models. Models of this form allow the incorporation of detailed inputs on biological mechanisms into the bioaccumulation process. These PB-PK models follow closely the one described and used by Anderson (1991) for human exposure. The principles and application of PB-PK modeling also have been introduced briefly in another series of online lectures (Dong, 2001). The following are a few examples for their practical use in assessing the bioaccumulation of organic contaminants, particularly PCBs, in an ecosystem: Lien et al. (1994); McKim (1994); and Nichols et al. (1991).

Unlike the PB-PK models, bioaccumulation kinetics models of the simple form each typically involve a single compartment for the uptake by a test organism and a single compartment for the loss from an ecosystem. Some examples for their practical use are: Barber et al. (1991); Endicott and Cook (1994); Gobas (1993); Lee (1991); and Thomann and Connolly (1984).

An extensive discussion on the use of kinetics models for bioaccumulation is provided by Landrum et al. (1992). It is worth mentioning, however, that due to the complex biological processes involved, PB-PK models require far more input data than typically available.