Polychlorinated Biphenyls in Arctic Air. 1. Temporal and Spatial Trends:  1992−1994

In 1992, a long term program was established to measure the airborne concentrations of persistent organic pollutants (POPs) in the Arctic. To maximize spatial variation over a wide geographical area, three Arctic locations were selected; two sites in Canada, Alert on Ellesmere Island and Tagish in the western Yukon, and one in Russia at Dunai Island in eastern Siberia. PCB data is presented here for the years 1992−1994. Mean ∑PCB concentrations for 1993, the year when all three sites were running simultaneously, were 27.4, 17.0, and 34.0 pg/m3 at the Alert, Tagish, and Dunai sites, respectively. With the exception of the Tagish site in 1993, where ∑PCB concentrations were found to be weakly correlated with mean monthly tem peratures, no correlation with temperature was observed. However, changes in the homolog group profile with temperature were apparent. On an annual basis, the trichlorinated congeners made the largest single contribution to the atmospheric concentrations of ∑PCB, however, this contribution declined with the onset of warmer months. This temperature-dependent homolog pattern was most clearly evident at Dunai, where the contribution of the pentachlorinated congeners matched or exceeded that of the trichlorinated congeners during May, June, and July of 1993. It was also evident at Alert and Tagish, but not to the same degree. Spatial and year-to-year differences at these Arctic sites were attributed to both the site's proximity to source areas (where different PCB mixtures and quantities have been used) and to the influence of air mass movement from these source regions.