The increased mercury content in a Greenland ice sheet over the last several decades suggests the dissemination of this element about the earth's atmosphere through the activities of man. The mercury content in the atmosphere appears to result primarily from the degassing of the earth's crust. Increased flux may come about as a result of the enhancement of this degassing process through the actions of man.

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In the combustion of fossil fuels, selenium is mobilized in the atmosphere to a much lesser extent than is sulfur. This difference is ascribed to the chemical behavior of their respective tetravalent oxides. The ratio of selenium to sulfur in glacial ice is characteristic of terrestrial matter, and these elements may find their way to ice sheets by the formation of volatile compounds in biochemical processes.