Zonation of Contaminated Bottom Sediments in Hamilton Harbour as Defined by Statistical Classification Techniques

Abstract Hamilton Harbour, a 2,150-ha embayment at the western end of Lake Ontario, is the receiving water for a number of industrial and municipal effluents. Their accumulation over the past decades has resulted in a seriously degraded aquatic environment that is now being subjected to remedial actions. Chemical determinations of total and weak acid-extractable metals were carried out on 40 sediment samples from the harbour. These data were subjected to two multivariate statistical techniques to assess their ability to discriminate samples that could be associated with common sources or transport processes. The techniques used were ratio matching followed by cluster analysis and principal component analysis. The cluster analysis technique resolved six groups related to contaminant sources, sandy, relatively clean nearshore areas and a large contaminated central area. The principal components technique supported this by showing factors related to the large central area as a result of sediment focusing, plus a factor related to contaminant source input and one related to input of silt-sized particles rich in Ca and Sr. Two “outlier” samples were noted, one related to a heavily contaminated area near the steel industries and one consisting of virtually pure sand at the northeastern corner of the harbour.