Implications of the minor element content of some major streams of the world

Of 15 or more minor elements in the world's principal river waters only aluminum, iron, manganese, barium and strontium range much over 100 μgl">100 μgl. (parts per billion). Most minor elements range at or below 100 μg1">100 μg1. and have median (or middle) values of 10 micrograms per liter or less. Significant areal differences in minor element content are found in the river waters. For example, Atlantic Coastal river waters in the aggregate are slightly more enriched in concentrations of silver, chromium, manganese, molybdenum, nickel, strontium and titanium, and slightly deficient in barium and lithium when compared with median values for North America. Median values of ratios BaSr">BaSr, NiCr">NiCr and NiCu">NiCu are reasonably consistent (within a factor of two) in principal drainage from North America. Noteworthy are consistent median ratios of NiCu">NiCu for large rivers of United States, but the ratio tends to be slightly greater in global northern latitudes than in southern latitudes. Median values for aluminum, barium, copper, lead, molybdenum and silver in North American runoff are of the same order as published world averages for ocean water.

Hydrologic and geochemical aspects of continental runoff are strongly implied in observations of minor element content of large rivers. Evidence to date is that median values of BaSr ratios">BaSr ratios are relatively uniform in global river waters. There is real danger in oversimplifying chemical systems in broad assessments of lower reaches of large drainage basins because individual hydrologic and chemical events upstream are largely obscured.