Measurement of particle-bound polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) in Arctic air at Alert, Nunavut, Canada

Abstract

Weekly filter samples, representing air-borne particles, at Alert, Nunavut, (82°30′N, 62°20′W) collected during the winter of 2000/2001 have been analysed for polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs). The sampling period coincided with the occurrence of the Arctic Haze (December–April) when air-borne particulate concentrations are generally high at Alert. Atmospheric phase distribution at average ambient temperature (−28.2°C) estimated using the Junge–Pankow adsorption model and the adsorption model based on octanol–air partition coefficients have shown that most PCDD/F congeners would be particle-bound under such conditions; with particle fractions >90%. The concentrations of both ΣPCDDs and ΣPCDFs observed were lower than those found at Ny-Ålesund (78°55′N, 11°56′E) and other locations worldwide. This is attributable to the remoteness of the site and the absence of anthropogenic activities nearby. An apparent peak in concentrations occurred during the third week of 2001 (15–22/1/2001). Weekly averaged 5-day Lagrangian back trajectories have shown that Alert was mainly affected by air originated from North Atlantic and North America during the first week of 2001. The origin of the airmass shifted eastwards further into Russia and Eurasia during the second and third weeks when the air concentrations of PCDD/Fs peaked at Alert. Then, the influence from Eurasia decreased while the North Atlantic sector regained dominance when the concentrations tapered off during the fourth and fifth weeks. In spite of the remoteness of Alert, congener profiles in most samples were enriched with PCDFs, corresponding to “source” profiles as suggested by Wagrowski and Hites (Environ. Sci. Technol. 34 (2000) 2952). Similar profiles were observed in air and tree bark at other Arctic locations. These profiles were probably the result of PCDD/F physical–chemical properties, which influence their transport behaviour between sources and receptors, as well as the unique Arctic environmental conditions. Therefore, the “source” and “sink” homologue profiles generally applicable to sample collected at temperate sites cannot be applied to those collected in the high Arctic.