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Are PCBs in the Canadian Arctic atmosphere declining? : evidence from 5 years of monitoring.

Hung, Hayley H. and Halsall, Crispin J. and Blanchard, P. and Li, H. H. and Fellin, P. and Stern, G. and Rosenberg, B. (2001) Are PCBs in the Canadian Arctic atmosphere declining? : evidence from 5 years of monitoring. Environmental Science & Technology, 35 (7). pp. 1303-1311. ISSN 0013-936X

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Abstract

A long-term database of weekly air concentrations was examined to establish temporal trends of PCBs in the Arctic atmosphere. Several methods were employed to reduce the intra-annual variability allowing the elucidation of long-term trends for a selection of congeners at Alert located in the Canadian Arctic. These methods included temperature normalization (TN), multiple linear regression (MLR), and digital filtration (DF). Estimation of the slope (m) resulting from the linear regression between the natural logarithm of the partial pressure in air versus reciprocal temperature (ln P = m/T + b), required for TN and MLR, proved difficult due to the poor correlation with temperature experienced for the majority of congeners. Values of m were considerably lower than those obtained from temperate studies, implying that regional air−surface exchange plays a minor role in supporting the observed air concentrations in the Arctic. The lighter congeners generally showed very low slopes, and some even showed positive correlation with 1/T. This might be a result of their relatively fast reaction rates with OH radicals following the onset of 24-h sunlight in spring. Use of DF (in combination with TN and MLR) revealed declining trends for several of the lower chlorinated congeners in the high Arctic atmosphere, with estimated first-order half-lives, t1/2, ranging from 3 to 20 yr. Declining trends of the lower congeners probably reflect falling levels in source regions, as a result of long-range transport to this Arctic site. There were no apparent trends for the higher chlorinated congeners (penta-substituted and above), except for PCB 180, in marked contrast to temperate studies, indicating a lag time for decline between the Arctic and source regions.

Item Type: Article
Journal or Publication Title: Environmental Science & Technology
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Departments: Faculty of Science and Technology > Lancaster Environment Centre
Faculty of Science and Technology > School of Computing & Communications
ID Code: 21547
Deposited By: ep_ss_importer
Deposited On: 21 Jan 2009 13:26
Refereed?: Yes
Published?: Published
Last Modified: 26 Jul 2012 15:48
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/21547

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