| Abstract
| - Data are presented for PCBs and HCB measured bypassive air samplers (SPMDs) along a latitudinal transectfrom the south of the UK to the north of Norway during 1998−2000. This work is part of an ongoing air sampling campaignin which data were previously gathered for 1994−1996.Comparisons of the masses of chemicals sequestered bythe SPMDs during these different time intervals are used toinvestigate spatial and temporal trends. Results arediscussed in the context of sources, long-range atmospherictransport, fractionation/cold condensation, and globalclearance processes controlling ambient levels of POPs.Spatial trends show a decrease in absolute sequesteredamounts of PCBs with increasing latitude i.e., with increasingdistance from the source area. However, relativesequestered amounts of the homologue groups (expressedas a ratio to penta-PCB) show a clear latitudinal trend,with the relative contribution of the lighter congenersincreasing with increasing latitude, providing evidence oflatitudinal fractionation. Absolute amounts of HCBincrease with latitude, suggesting this compound isundergoing cold condensation. Sequestered amounts ofPCBs generally decreased between the two sampling periodsby a factor 2−5 over 4 years, suggesting half-lives onthe order of 1.7−4 years. The relative rates of decline (1998−2000 data as a percentage of the 1994−1996 data) werecompared for different congeners and latitudes. No clearlatitudinal trends were found, with all sites/congenersshowing a similar marked decline over time to ca. 30% ofthe former value. We discuss the interpretation of theseobservations and conclude they imply that the underlyingtrends of current ambient levels of PCBs in Europeanbackground air are still largely controlled by primary emissions,rather than recycling/secondary emissions from themajor environmental repositories such as soils or waterbodies.
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