The Global Cycle of Mercury

Mercury is emitted to the atmosphere from both natural and anthropogenic sources in the form of elemental vapor (Hg·). It is converted to a soluble form assumed to be Hg++. The letter is returned to the surface of the earth in rain water and may be reduced to Hg· and re-emitted to the atmosphere. Ocean sediment is believed to be the final sink where mercury is deposited in the form of HgS (WHO, 1990).