Toward an understanding of the global atmospheric distribution of persistent organic pollutants: The use of semipermeable membrane devices as time-integrated passive samplers

Triolein-containing semipermeable membrane devices (SPMDs) were deployed as passive air samplers alongside conventional air samplers at two sites, and derived atmospheric concentrations from each were compared. Excellent comparability was noted between sampling systems. SPMDs were also deployed for 2 years at 10 sites across a latitudinal transect from the south of the U.K. (ca. 50 degrees N) to the north of Norway (ca. 70 degrees N) to passively sample air. Time-integrated, simultaneous data were obtained, which were used to test the global fractionation hypothesis in the Northern Hemisphere. Extracts were analyzed for a suite of PCB congeners and alpha- and gamma-HCH. A latitudinal change in PCB profiles was seen. The absolute atmospheric concentration of the tetra-chlorinated PCBs was relatively uniform over the study area (ca. 1.9 pg m(-3)), but their relative concentration increased with increasing latitude or decreasing temperature (12% of total PCB concentrations in the south of the U.K. as compared with 35% at the northern-most station). The concentration of the penta-chlorinated PCBs decreased from 6 pg m(-3) at the southern U.K. site to 1.5 pg m(-3) in the north of Norway, but their relative concentration was uniform (33% total PCB) over the transect. Absolute and relative concentrations of heavier PCBs decreased with increasing latitude and decreasing temperature. These data indicate that a temperature-controlled fractionation of PCBs is occurring in the atmosphere. Data were available for soil PCB concentrations at or near seven of the air sampling sites. Fugacity quotients suggested that across the study area the air/soil system is at or near to equilibrium for PCBs. Concentrations of the alpha-HCH isomer sequestered by the SPMDs increased from south to north while the sequestered gamma-HCH concentrations decreased. The ratio of alpha/gamma-HCH increased by a factor of approximately 20 from the south to the north of the study area, These data are consistent with the selective weathering of these compounds during their long-range atmospheric transport from southerly source regions to remote northern locations.