METAL POLLUTION IN THE GREAT LAKES IN RELATION TO THEIR CARRYING CAPACITY Jerome O. Nriagu National Water Research Institute Department of the Environment P.O. Box 5050 Burlington, Ontario, Canada L7R 4A6 ABSTRACT. Although the Great Lakes may be resilient to moderate inputs of nutrients and some biodegradable organics, they are seriously vulnerable to the persistent tQxic metals. This report makes the point that the assimilative capacity of the Great Lakes for toxic metals has already been exceeded in Lakes Michigan, Erie and Ontario, and in the problem areas of Lakes Huron and Superior. Any added use of these lakes as waste space for the disposal of metal contaminated refuse will only further depreciate the health of the Great Lakes ecosystems. 1. INTRODUCTION The five Great Lakes represent the largest reservoir of freshwater in the world. The Great Lakes basin itself covers about 785,450 km 2 (about 300,000 square miles) and extends for more than 1000 km inland from the Atlantic Ocean to the heart of the North American continent (Figure 1). Because of their enormous size, it is not surprising that these "sweetwater seas" have often evoked comparisons with the oceans as the following analogy by Herman Melville aptly illustrates: "Those grand fresh-water seas of ours -- Erie, and Ontario, and Huron, and Superior, and Michigan -- possess an ocean-like expansiveness with many of the ocean's noblest traits; with many of its rimmed varieties of races and of climes. They contain round archipelagoes of romantic isles, even as the Polynesian waters do; in large part, are shored by two great contrasting nations, as the Atlantic is" (from Twine Line, vol. 8, no. 6, p. 3, Dec. 1984). This unique water with extensive mineral wealth in its basin and the agricultural opportunities afforded by the fertile land and an agreeable climate supports one of the largest and most rapidly growing industrial and urban complexes in the world. Today, over 37 million people (which include 40% and 15% respectively of the populations of Canada and the United States) dump their wastes into and drink the water from these lakes. And the population is expected to rise to over 50 million by the year 2020, with attendant sharp increases in industrial and urban development in the lake basin. 441 G. Kullenberg (ed.), The Role of the Oceans as a Waste Disposal Option, 441-468. © 1986 by D. Reidel Publishing Company.