Lead Isotopes as Particulate Contaminant Tracers and Chronostratigraphic Markers in Lake Sediments in Northeastern North America

The utility of lead isotopes as particulate contaminant tracers and chronostratigraphic markers was assessed in six lakes from the Great Lakes region. The geographic range of the 19th century Upper Mississippi Valley ore smelting marker was expanded into southern and central Ontario and its northwestern extent was reached within Lake Superior. This marker is useful for dating sediments deposited 100-200 years ago when other dating techniques are problematic. Leaded gasoline was dominant in one lake in the 20th century; its signal was absent elsewhere because the other lakes were affected by regional industrial output or were too remote to receive the leaded gasoline signal. Lead isotopes and trace metals identified a coal combustion marker in the 20th century in southern Ontario, where coal combustion was important enough to outweigh leaded gasoline input. This thesis demonstrates the usefulness of lead isotopes for identifying contamination sources where several pollution sources exist.