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 concen trations 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 co ncentrations have been decreasing since 1991 at all sites, particle-phase c oncentrations have been decreasing only at Sleeping Bear Dunes. To determin e whether these results represent trends in background levels or regional e missions, 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 fo und that that PAH concentrations at Eagle Harbor and Sleeping Bear Dunes re present regional background levels but that PAH from the Buffalo region int rude on the background levels measured at the Sturgeon Point site. At this site, wind from over Lake Erie reduces local PAH concentrations.