| Abstract
| - A long-term database of weekly air concentrations wasexamined to establish temporal trends of PCBs in the Arcticatmosphere. Several methods were employed to reducethe intra-annual variability allowing the elucidation of long-term trends for a selection of congeners at Alert locatedin the Canadian Arctic. These methods included temperaturenormalization (TN), multiple linear regression (MLR), anddigital filtration (DF). Estimation of the slope (m) resultingfrom the linear regression between the natural logarithm ofthe partial pressure in air versus reciprocal temperature(ln P = m/T + b), required for TN and MLR, proved difficultdue to the poor correlation with temperature experiencedfor the majority of congeners. Values of m were considerablylower than those obtained from temperate studies, implyingthat regional air−surface exchange plays a minor role insupporting the observed air concentrations in the Arctic. Thelighter congeners generally showed very low slopes,and some even showed positive correlation with 1/T. Thismight be a result of their relatively fast reaction rateswith OH radicals following the onset of 24-h sunlight inspring. Use of DF (in combination with TN and MLR) revealeddeclining trends for several of the lower chlorinatedcongeners in the high Arctic atmosphere, with estimated first-order half-lives, t1/2, ranging from ∼3 to 20 yr. Decliningtrends of the lower congeners probably reflect falling levelsin source regions, as a result of long-range transport tothis Arctic site. There were no apparent trends for the higherchlorinated congeners (penta-substituted and above),except for PCB 180, in marked contrast to temperate studies,indicating a lag time for decline between the Arctic andsource regions.
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