Multimedia Models of Global Transport and Fate of Persistent Organic Pollutants

Abstract

Persistent organic pollutants (POPs) are long-lived multimedia chemicals that cycle between the different environmental compartments and are capable of traveling long distances, thus becoming ubiquitous global pollutants. With the help of multimedia fate and transport models, the interplay of release, phase partitioning, degradation and transport of these pollutants on the global scale can be systematically described and analyzed. Currently, multimedia box models and models based on atmospheric dispersion models are used to investigate the global behavior of POPs. Box models are simpler to construct and use, yet have only low spatial and temporal resolution. Dispersion models have high resolution but also require high computational effort. In this chapter, both types of models are described and results from their application to selected POPs (α-HCH, polychlorinated biphenyls, DDT) are summarized. The model results show, e.g., that only small fractions of the total global inventory of a POP are sufficient to cause contamination of polar regions and that long-range transport may occur via both air and ocean water. Due to incomplete or uncertain data on POP emissions, physical-chemical properties and degradation rate constants, as well as a lack of process understanding in regions other than the temperate North, there is significant uncertainty associated with the model results. Since also data from field studies are scarce, quantitative comparison of model results with measured data is difficult. Sensitivity and uncertainty analyses as well as model comparison studies are important means for the evaluation of global POPs models.