Source receptor modeling of airborne particles collected over the Great Lakes.

摘要

High-volume air samplers were used to collect aerosol samples on Whatman 41 air filters at the Canadian air sampling stations Burnt Island, Egbert and Point Petre. Once collected, the samples were analyzed for trace elements by neutron activation analysis. Air concentrations of over thirty trace elements were determined. A special focus was made to utilize Compton suppression gamma-ray spectroscopy and epithermal irradiations to enhance the detection limits of neutron activation analysis. These vanguard techniques allowed for the determination of trace elements at very low levels. Advancements were also made for the determination of Br through short-lived irradiations.; After the air concentrations were determined for trace elements from the neutron activation analysis data, the trends, sources and origin of the atmospheric aerosols were investigated. Exploration of the seasonal trends revealed that elements from a salt source like Na, Cl and Br were highest in the winter while elements originating from crustal weathering like Al, Ca and Si were highest in the summer. Many elements of anthropogenic origin demonstrated no seasonal trend. Enrichment factor analysis revealed elements from non-crustal sources including the elements Ag, As, Br, Cl, I, In, Sb, Se, Sn and Zn. Factor analysis exhibited trends that indicate oil and coal combustion, mining, incineration, and smelting as anthropogenic sources to aerosols of the rural Great Lakes. Potential source contribution function analysis indicated that many of the anthropogenic atmospheric pollutants in the Great Lakes originate from industrial centers in the eastern and southeastern United States. Study of the trace metal dry deposition into Lakes Huron and Ontario indicated that the majority of the total deposition resulted from crustal materials. However, dry deposition is a significant pathway for many toxic anthropogenic trace metals into the Great Lakes.