ABSTRACT
Many physical and biological processes, both natural and anthropogenic, result in the evolution of selenium compounds into the atmosphere. Mosher and Duce (1987) estimated that one-half to two-thirds of the worldwide selenium emissions come from natural sources. Approximately 90% of all natural emissions are biogenic, with the marine biosphere accounting for about 70%, and the continen tal biosphere about 20%. The biogenic emissions are mainly of dimethyl selenide gas. Nonbiogenic natural sources include volcanoes (8%), sea salt (2%), and crustal weathering ( < 1%). Two-thirds of the anthropogenic selenium emissions come from combustion: 50% from coal, 9% from oil combustion, and 10% from other combustion. Metals production accounts for most of the rest: 20% from copper, 4% from zinc and lead, and 4% from selenium. Other manufacturing accounts for the remaining 4%, primarily from glass and ceramic manufacturing.
