Temporal trends in and influence of wind on PAH concentrations measured near the Great Lakes

This paper reports on temporal trends in gas- and particle-phase PAH concentrations measured at three sites in the Great Lakes' Integrated Atmospheric Deposition Network: Eagle Harbor, near Lake Superior, Sleeping Bear Dunes, near Lake Michigan, and Sturgeon Point, near Lake Erie. While gas-phase concentrations have been decreasing since 1991 at all sites, particle-phase concentrations have been decreasing only at Sleeping Bear Dunes. To determine whether these results represent trends in background levels or regional emissions, the average concentrations are compared to those found in "urban" and "rural" studies. In addition, the influence of local wind direction on PAH concentrations is investigated, with the assumption that dependence on wind direction implies regional sources. Using these two methods, it is found that that PAH concentrations at Eagle Harbor and Sleeping Bear Dunes represent regional background levels but that PAH from the Buffalo region intrude on the background levels measured at the Sturgeon Point site. At this site, wind from over Lake Erie reduces local PAH concentrations.