Further studies on the latitudinal and temporal trends of persistent organic pollutants in Norwegian and U.K. background air.

Data are presented for PBDEs, PCBs, and selected organochlorine compounds, measured at background locations by passive air samplers (semipermeable membrane devices, SPMDs) along a latitudinal transect from the south of the U.K. to the north of Norway during 2000-2002. This work is part of an ongoing air sampling campaign in which PCB data were previously obtained in 1994-1996 and 1998-2000. Comparisons of the masses of chemicals sequestered by the SPMDs during these different time intervals are used to investigate spatial and temporal trends. The study yielded examples of compounds that increase, decrease, or remain uniform with latitude, suggestive of differences in the relative importance of deposition versus atmospheric reaction in controlling their long-range atmospheric transport potential. The main constituents of the penta-BDE product were detected at amounts equivalent to 2.0 (range 1.1-2.5) and 1.1 (0.8-1.6) pg m(-3) for the U.K. and Norway background sites, respectively. Fractionation of PBDEs was observed, because the amounts of lighter BDEs decreased with latitude, while the heavier molecular weight congeners were quite uniformly distributed. In contrast, the sequestered amounts of the lighter PCBs were uniformly distributed with latitude, with heavier PCBs decreasing. Sequestered amounts of hexachlorobenzene increased with latitude. Preliminary PCB atmospheric clearance rates were derived using the 1994-1996, 1998-2000, and 2000-2002 data. They averaged ca. 3.5 years for all congeners/locations. No systematic differences in congeners or locations were noted, supporting the hypothesis that the underlying trends in European background air are still controlled by primary, rather than secondary, sources.