Long-range transport of organic chemicals in the environment

The long-range transport (LRT) of organic chemicals in the environment is reviewed, with particular focus on the role of environmental fate and transport models and the relationship between model results and field data. Results from generic multimedia box models, spatially resolved multimedia box models, and atmospheric transport models are highlighted, including conceptual investigations of cold-trap effect and global fractionation as well as results for particular chemicals, such as hexachlorocyclohexanes, DDT, polychlorinated biphenyls, perfluoroocctanoic acid, and polybrominated diphenyl ethers. Comparison of model results to field data shows that in many cases environmental fate models provide a good description of the distribution dynamics observed in the field, with deviations between measured and modeled concentrations around a factor of five. Sorption to atmospheric aerosols as a key process influencing the LRT of semivolatile organic chemicals (SOCs) is discussed, and the need for more measurements of the aerosol-air partitioning of SOCs and of the reactivity of particle-bound chemicals is pointed out. Key findings from field campaigns measuring legacy persistent organic pollutants (POPs) as well as new POPs are summarized. Finally, the relationship between science and politics in the field of POPs is addressed. Research into the LRT of organic chemicals has always occurred in interaction with political activities aiming to reduce the emissions of POPs. Since the late 1990s, the Stockholm Convention and the Aarhus Protocol on POPs have formed an important political context for research concerning POPs; the implementation of these international treaties creates a demand for ongoing research into the LRT of organic chemicals.