Themercury cycle is abiogeochemical cycle influenced by natural andanthropogenic processes that transformmercury through multiple chemical forms and environments.

Mercury is present in theEarth's crust and in various forms on the Earth's surface. It can be elemental, inorganic, or organic.^[1] Mercury exists in threeoxidation states: 0 (elemental mercury), I (mercurous mercury), and II (mercuric mercury).

Mercury emissions to the atmosphere can be primary sources, which release mercury from thelithosphere, or secondary sources, which exchange mercury between surface reservoirs.^[2] Annually, over 5000 metric tons of mercury is released to the atmosphere by primary emissions and secondary re-emissions.^[3]

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Related topics Biogeochemistry geochemical cycle chemical cycling environmental chemistry Biosequestration Deep biosphere Ocean acidification acid rain Biogeochemical planetary boundaries
Research groups DAAC GEOTRACES IMBER NOBM SOLAS
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Primary sources of mercury emissions can be natural oranthropogenic.^[4] Most natural mercury occurs as themercury sulfide mineral,cinnabar, which is one of the only significant ores of mercury.^[5][6] Organic-richsedimentary rocks can also contain elevated mercury.Weathering of minerals and geothermal activity release mercury to the environment.^[7][8] Active volcanoes are another significant primary source of natural mercury.^[9] Anthropogenic primary sources of mercury include gold mining, burning coal, and production of non-iron metals, such ascopper orlead.^[8][10]

Secondary natural sources, which re-emit previously deposited mercury, include vegetation, evasion from oceans and lakes, andbiomass burning, includingforest fires.^[3] Primary anthropogenic emissions are leading to increased sizes of mercury in surface reservoirs.^[11]

Mercury is transported and distributed byatmospheric circulation, which moves elemental mercury from the land to the ocean.^[12] Elemental mercury in the atmosphere is returned to the Earth's surface by several routes. A major sink of elemental mercury (Hg(0)) in the atmosphere is throughdry deposition.^[13] Some of elemental mercury, on the other hand, is photooxidized to gaseous mercury(II), and is returned to the Earth's surface by both dry andwet deposition.^[14] Because photooxidation is very slow, elemental mercury can circulate over the entire globe before being oxidized and deposited.^[14] Wet and dry deposition is responsible for 90% of the mercury of surface waters, including open ocean.^[15][16]

A fraction of deposited mercury instantaneously re-volatilize back to the atmosphere.^[17]

Inorganic mercury can be converted bybacteria andarchaea intomethylmercury ([CH₃Hg]⁺),^[18] whichbioaccumulates in marine species such astuna andswordfish andbiomagnifies further up the food chain.^[19][20]

Certainxenophyophores have been found to have abnormally high concentrations of mercury within their bodies.^[21]

• Mercury (element)
• Mercury in fish
• Minamata Convention on Mercury
• Mercury poisoning
• COLEX process (isotopic separation)

• Biogeochemical cycle
• Mercury (element)

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• Use mdy dates from March 2014
• Use mdy dates from March 2012