Daniela MacLeod

The problem of estimating sediment contamination values at locations where no measurements are available is addressed in this research. Historical data from a 1973 survey conducted by Environment Canada were used to produce prediction maps, which display, for the first time, the spatial distribution of 34 major elements and trace elements in the surficial sediments of Lake Superior. Cross-validation statistics were used to assess the accuracy of the resulting surfaces produced with the ordinary kriging geostatistical method. Canadian sediment quality guidelines were utilized to identify areas where sediment quality was frequently threatened or impaired. In general, the concentration of contaminants was lower in sediment collected along the southern shore of Lake Superior and higher in depositional basins. Thunder Bay, Silver Bay, and Duluth were found to be influential point sources of contamination and nickel and chromium were found to be at concentrations above which adverse biological effects frequently occur. Reasons are brought forth to explain the distributions and patterns observed by incorporating: the location of known point pollution sources that existed in the basin in L973, current locations of designated areas of concern, and knowledge of lake circulation patterns and bathymetry. The lake-wide prediction surfaces more comprehensively represent overall pollution levels when compared with point measurements. In addition, they provide a better understanding of sediment contamination and supply benchmark data concerning Lake Superior as it was over thirty years ago.