Initial results from high-volume air sampling of industrial organic contaminants at Cape Verde, Africa

Polychlorinated biphenyls (PCBs) and some halogenated flame retardants (HFRs), notably selected polybrominated diphenyl ethers (PBDEs) are industrial organic chemicals identified as toxic, bio-accumulative, persistent and subject to long-range atmospheric transport. After bans on production and use, reductions in atmospheric burdens of these chemicals are now typically observed in some industrialized countries in the northern hemisphere. However, elevated air concentrations of PCBs and HFRs have recently been reported off the coast of West Africa, with some of the measured air concentrations of PCBs simply being far too high to be rationalized by historical usage of these chemicals in this area. It has been hypothesized that the sources could be releases of PCBs and HFRs from contaminated wastes exported to African countries from former production and use regions like Europe and USA. The primary objective of this study is to track atmospheric sources and source regions of selected industrial organic contaminants in tropical regions implicated as recipient of relevant wastes, using West Africa as a case study. For this purpose, an active high-volume air sampler was recently installed on The Cape Verde Atmospheric Observatory (CVAO: 16.848°N, 24.871°W), a World Meteorological Organization (WMO) global station at Cape Verde outside the coast of West Africa. Weekly 24 hour sampling commenced in May, 2012 and data from the first 12 months will be used to establish a baseline without any a priori consideration of the origin of air masses. Here, we present initial results from the first samples which have been collected, and compare these with data from other background monitoring sites. Potential source regions affecting these measurements are next evaluated using the Lagrangian particle dispersion model FLEXPART. The FLEXPART model is additionally used to forecast episodes with transport from the West African continent to allow for a more rational, targeted sampling strategy towards suspected source regions. Finally, the model will be used to retrospectively evaluate the principal source regions leading to elevated observed concentrations of PCBs and HFRs in air at Cape Verde.