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photo historic lake mercury plant

Characteristics of Mercury

Mercury is a naturally occurring metallic element noted for its occurrence as a liquid at room temperature. Elemental mercury is a heavy, silver-white liquid metal that can be found at trace levels in many minerals with greater concentrations in fossil fuels. There are three forms of mercury in the environment: elemental, inorganic, and organic mercury. All forms of mercury are toxic.

Elemental mercury occurs naturally in three valence states: elemental (Hg0), monovalent-mercurous (Hg1+), and the divalent mercuric (Hg2+). Elemental mercury is the most stable form and is only slightly water-soluble. Both mercuric and mercurous mercury are thermally unstable and readily decompose to elemental mercury. Vapors of elemental mercury can occur at room temperature presenting a hazard if spills occur.

Inorganic mercury compounds contain ionic mercury usually in a salt formation (e.g. mercuric chloride). Many inorganic mercury compounds have been banned from use by the EPA in consumer products and agriculture. Inorganic mercury compounds continue to be used globally as disinfectants and pesticides.

Organic mercury compounds can be chemically synthesized or biologically converted from mercury compounds by bacteria (e.g. methyl mercury). Chemically synthesized organic compounds have been used as fungicides. Some organic mercury compounds are water-soluble and cable of transport in the aquatic food chain through the process of bioaccumulation.


Manahan, Stanley E. Environmental Chemistry. Fourth Edition. University of Missouri:
Lewis Publishers, 1990.

USEPA “Mercury & compounds”, Persistent Bioaccumlative Toxins Website,

USEPA “Mercury, Health Issues, Fish Advisories in the NE”, Region One Website

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