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1K - Tropospheric Fate (MO13/3) Seasonality and temporal trends of atmospheric PAH concentrations. Sweetman, Andrew1, Prevedouros, Konstantinos1, Halsall, Crispin1, Jones, Kevin1, Lee, Robert1, 1 Lancaster University, Lancaster, Lancashire, United Kingdom ABSTRACT- Long-term atmospheric monitoring data for selected polynuclear aromatic hydrocarbons (PAHs) have been compiled for remote, rural and urban locations in the UK, Sweden, Finland and Arctic Canada. The objective was to examine the seasonal and temporal trends within the datasets and to investigate which factors may exert a dominating influence over ambient PAH levels. The evidence suggests that proximity to primary sources 'drives' tropospheric PAH concentrations. Urban centres within the UK have concentrations 1-2 orders of magnitude higher than for rural locations in Europe and up to 3 orders of magnitude higher than Arctic Canada. Seasonality, with winter (W) higher than summer (S), was apparent for most compounds at most sites; high molecular weight compounds (e.g. benzo[a]pyrene) showed this most clearly and consistently. Some low molecular weight compounds (e.g. phenanthrene) displayed S levels higher than W with some evidence of seasonality at rural locations. Strong W to S seasonality has been shown to be linked to seasonally-dependent sources which are greater in winter. This suggests that inefficient combustion processes, notably the diffusive domestic burning of wood and coal, may be important. However, sometimes seasonality can also be strongly influenced by broad changes in meteorology and air mass origin (e.g. in the Canadian Arctic). Only a few long-term (e.g. >10 years) datasets of air concentrations are available internationally. The datasets under examination suggested a downward trend for many PAHs at some sites, but this is by no means apparent for all sites and compounds. The inherent noise in ambient air monitoring data makes it difficult to derive clear, unambiguous evidence for long-term change. Key words: Atmospheric concentrations , Polynuclear Aromatic Hydrocarbons, Seasonality and temporal trends , Multi-year datasets |
