| Concentration data from the Integrated Atmospheric Deposition Network (IADN) has been used to model the sources of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides to the atmosphere of the Great Lakes. Many of these compounds have well defined sources ranging in distance from local to continental. The effect of these sources on measured concentrations varies from small effects for the PCBs to large effects for the PAH, whose deviations in atmospheric concentration are best explained by atmospheric transport.; We have investigated the role of atmospheric transport using both qualitative and quantitative models. Qualitatively, we have mapped the sources of PCBs, PAHs, and pesticides on a 0.5° x 0.5° latitude/longitude grid. With these maps as a visual reference, we were able to state that PCBs and PAHs are influenced by urban sources, often near the sampling site. The banned organochlorine pesticides, such as chlordane, are transported from the southern United States to the Great Lakes. Currently used pesticides, such as endosulfan, are transported from within the Great Lakes region to IADN sites.; Quantitatively, we used regression models incorporating wind direction and average back-trajectory direction to determine the optimal direction of the source relative to the sampling site and the influence this source direction has on measured partial pressures. The back-trajectory model has slightly more explanatory power than local wind direction for the pesticides dieldrin and chlordane, but overall the source direction only explains a maximum of 15% of the variability in the data. The wind direction model accounts for the most variability in the PAH data reinforcing the idea that these compounds come from local sources.; Expanding on the idea of local sources for PAH, we calculated the correlation between local human populations and PAH concentrations for sampling studies throughout the world. Although deviations from this correlation exist for coastal and industrial site, the overall trend indicates that the same processes driving concentrations of PAH in the Great Lakes atmosphere are applicable to the industrialized world. |
