Amy Kluke

This study examines the spatial distribution of dieldrin, a persistent organic pollutant previously used as an agricultural pesticide, in the sediments of the Great Lakes System. Using Environment Canada Sediment Quality data for both historical and contemporary sampling periods, graduated symbol maps were generated for lakes Superior, Huron, St. Clair, Erie, and Ontario. Additionally, ordinary kriging was applied to the Lake Erie and Lake Ontario datasets. The use of ordinary kriging allows for a more in-depth understanding of the spatial trends occurring within the Great Lakes sediments. Cross-validation was performed to ensure that all of the interpolated surfaces were statistically valid. Results indicate low dieldrin levels with no evident point sources in both the historical and contemporary sediments of Lakes Superior, Huron, and St. Clair. This suggests that dieldrin has mainly entered these lakes via atmospheric deposition and some agricultural runoff. Dieldrin concentrations in Lake Erie have increased since the historical sampling period, indicating a shift in the spatial distribution of the contaminant. Historically, levels were higher in the eastern-most depositional basins, but contemporary data show that the western side of the lake exceeds Canadian sediment quality guidelines. The prediction surface generated in this study clearly shows that the Detroit River is a point source of contamination. Alternatively, lakewide dieldrin concentrations in Lake Ontario have appeared to decrease between sampling periods. While historically the Niagara River was a point source of contamination, levels in the Niagara Basin have been reduced. In all cases, the highest levels of dieldrin are seen in the depositional basins of the lakes, and the interpolated surfaces help in data interpretation by providing a better understanding of the spatial distribution of this contaminant.