Analyzing the Global Fractionation of Persistent Organic Pollutants (Pops)

Persistent organic pollutants (POPs) such as PCBs, but also substances still on the market such as PBDEs are transported over long distances and are present in many environmental media. In principle, differences in the physicochemical properties and environmental half-lives of different POPs would lead to a “fractionation” process, i.e., more volatile substances would be transported more rapidly and over larger distances than less volatile compounds. However, the fractionation pattern to be expected on the basis of chemical properties is often confounded by spatial and temporal variability of the emissions of the chemicals and by the conditions under which samples are taken in the field. Here, modeling results are presented that support the identification of fractionation patterns, and key questions in the area of global fractionation requiring further investigation are identified. Research needs concern the degradation processes of POPs in the gas phase, the interaction of POPs with atmospheric aerosols (aerosol—air partitioning; reactivity of the aerosol-bound fraction; deposition and transport with aerosols), and the characterization of various surface media (soil, vegetation, ice/snow, and water) with respect to their sorptive capacity for POPs (importance of secondary sources).