3 - International Joint Commission

the Great Lakes show sediment concentration trends. Summaries of
geographic patterns of contaminant distribution and concentration changes
over time are given in the conclusion. There is a glossary in Appendix 3.
There is more information available on the contamination of the Great
Lakes than for any other set of freshwater lakes in the world (Allan, 1988).
This report is the most comprehensive document prepared to date on the
concentrations of toxic contaminants in the water and sediments of all of the
Great Lakes and their connecting channels. The sources used to prepare this
literature review included journal articles, journal issues, reports, conference
papers and proceedings, dissertations, monographs, and chapters. When
possible, only primary published sources were used.
1.1 TOXIC CHEMICAL SOURCES, PATHWAYS AND FATE
The Great Lakes system flows from Lake Superior and Lake Michigan
through the other Great Lakes and the St. Lawrence River to the Atlantic
Ocean (Figure 1). The lakes are one unit and are connected by short narrows
at Mackinac and by the short connecting channels of the St. Clair, Detroit
and Niagara Rivers. These channels have extremely high discharges of
approximately 6,000 m3/sec, putting them a on scale with the world’s largest
rivers. The massive transfers of water into and out of Lakes Erie and Ontario
are important for the fate of toxic chemicals in the lower Great Lakes. Less
than 1% of the total volume of water in the system flows out annually
through the St. Lawrence River. The residence times of the lower Great Lakes
are strongly influenced by the flows of the connecting channels (Table 1).
The connecting channels, other tributaries and the atmosphere are
major sources of many toxic chemicals to the lower Great Lakes (Strachan
and Eisenreich, 1988). Canadian industry is concentrated along the shore
of the St. Clair River. Detroit and Windsor are located on the shores of the
Detroit River. Buffalo is located immediately upstream of the Niagara River.
There has been major industrial development on the side of the Niagara
River. Effluents from these cities and industries have introduced toxic
chemicals into the connecting channels and thus to the downstream lakes
(NRTC, 1984; UGLCCS, 1989). The connecting channels rapidly transfer
chemicals discharged into them the to downstream lakes. For example, there
is little or no long term removal of chemicals by burial in the bottom
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