Mercury cycle

The mercury cycle is a biogeochemical cycle influenced by natural and anthropogenic processes that transform mercury through multiple chemical forms and environments.

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

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

Sources of mercury

Primary sources
Sample of the mercury sulfide ore, cinnabar

Primary sources of mercury emissions can be natural or anthropogenic.[4] Most natural mercury occurs as the mercury sulfide mineral, cinnabar, which is one of the only significant ores of mercury.[5][6] Organic-rich sedimentary 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. Anthropogenic primary sources of mercury include gold mining, burning coal, and production of non-iron metals, such as copper or lead.[8][9]

Secondary sources

Secondary natural sources, which re-emit previously deposited mercury, include vegetation, evasion from oceans and lakes, and biomass burning, including forest fires.[3] Primary anthropogenic emissions are leading to increased sizes of mercury in surface reservoirs.[10]

Processes

Mercury is transported and distributed by atmospheric circulation, which moves elemental mercury from the land to the ocean.[11] 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 through dry deposition.[12] 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 and wet deposition.[13] Because photooxidation is very slow, elemental mercury can circulate over the entire globe before being oxidized and deposited.[13] Wet and dry deposition is responsible for 90% of the mercury of surface waters, including open ocean.[14][15]

A fraction of deposited mercury instantaneously re-volatilize back to the atmosphere.[16]

Inorganic mercury can be converted by bacteria and archaea into methylmercury ([CH3Hg]+),[17] which bioaccumulates in marine species such as tuna and swordfish and biomagnifies further up the food chain.[18][19]

Certain xenophyophores have been found to have abnormally high concentrations of mercury within their bodies.[20]

See also

References
  1. "Mercury and health". www.who.int. Retrieved April 10, 2019.
  2. Beckers F, Rinklebe J (May 3, 2017). "dycling of mercury in the environment: Sources, fate, and human health implications: A review". Critical Reviews in Environmental Science and Technology. 47 (9): 693–794. doi:10.1080/10643389.2017.1326277. ISSN 1064-3389. S2CID 99877193.
  3. Pirrone N, Cinnirella S, Feng X, Finkelman RB, Friedli HR, Leaner J, Mason R, Mukherjee AB, Stracher GB, Streets DG, Telmer K (July 2, 2010). "Global mercury emissions to the atmosphere from anthropogenic and natural sources". Atmospheric Chemistry and Physics. 10 (13): 5951–5964. doi:10.5194/acp-10-5951-2010. ISSN 1680-7324.
  4. US EPA, OITA (February 27, 2014). "Mercury Emissions: The Global Context". US EPA. Retrieved October 20, 2020.
  5. "Cinnabar: A toxic ore of mercury, once used as a pigment". geology.com. Retrieved April 12, 2019.
  6. Rytuba JJ (August 2, 2002). "Mercury from mineral deposits and potential environmental impact". Environmental Geology. 43 (3): 326–338. doi:10.1007/s00254-002-0629-5. S2CID 127179672.
  7. Bagnato E, Aiuppa A, Parello F, Allard P, Shinohara H, Liuzzo M, Giudice G (2011). "New clues on the contribution of Earth's volcanism to the global mercury cycle". Bulletin of Volcanology. 73 (5): 497–510. Bibcode:2011BVol...73..497B. doi:10.1007/s00445-010-0419-y. ISSN 0258-8900. S2CID 129282620.
  8. Xu J, Bravo AG, Lagerkvist A, Bertilsson S, Sjöblom R, Kumpiene J (January 2015). "Sources and remediation techniques for mercury contaminated soil". Environment International. 74: 42–53. doi:10.1016/j.envint.2014.09.007. PMID 25454219.
  9. Horowitz HM, Jacob DJ, Amos HM, Streets DG, Sunderland EM (September 2014). "Historical Mercury releases from commercial products: global environmental implications". Environmental Science & Technology. 48 (17): 10242–50. Bibcode:2014EnST...4810242H. doi:10.1021/es501337j. PMID 25127072.
  10. United Nations Environment Programme (2013). "Global Mercury Assessment 2013: Sources, Emissions, Releases and Environmental Transport". hdl:20.500.11822/7984. Cite journal requires |journal= (help)
  11. Boening DW (2000). "Ecological effects, transport, and fate of mercury: a general review". Chemosphere. 40 (12): 1335–1351. Bibcode:2000Chmsp..40.1335B. doi:10.1016/S0045-6535(99)00283-0. PMID 10789973.
  12. Driscoll CT, Mason RP, Chan HM, Jacob DJ, Pirrone N (May 2013). "Mercury as a global pollutant: sources, pathways, and effects". Environmental Science & Technology. 47 (10): 4967–83. Bibcode:2013EnST...47.4967D. doi:10.1021/es305071v. PMC 3701261. PMID 23590191.
  13. Morel FM, Kraepiel AM, Amyot M (1998). "The chemical cycle and bioaccumulation of mercury". Annual Review of Ecology and Systematics. 29 (1): 543–566. doi:10.1146/annurev.ecolsys.29.1.543. ISSN 0066-4162. S2CID 86336987.
  14. Mason RP, Fitzgerald WF, Morel FM (1994). "The biogeochemical cycling of elemental mercury: Anthropogenic influences". Geochimica et Cosmochimica Acta. 58 (15): 3191–3198. Bibcode:1994GeCoA..58.3191M. doi:10.1016/0016-7037(94)90046-9.
  15. Leopold K, Foulkes M, Worsfold P (March 2010). "Methods for the determination and speciation of mercury in natural waters--a review". Analytica Chimica Acta. 663 (2): 127–38. doi:10.1016/j.aca.2010.01.048. PMID 20206001.
  16. Selin NE (2009). "Global Biogeochemical Cycling of Mercury: A Review". Annual Review of Environment and Resources. 34 (1): 43–63. doi:10.1146/annurev.environ.051308.084314. ISSN 1543-5938.
  17. Gilmour CC, Podar M, Bullock AL, Graham AM, Brown SD, Somenahally AC, Johs A, Hurt RA, Bailey KL, Elias DA (October 2013). "Mercury methylation by novel microorganisms from new environments". Environmental Science & Technology. 47 (20): 11810–20. Bibcode:2013EnST...4711810G. doi:10.1021/es403075t. PMID 24024607.
  18. "Mercury: Overview". Oceana. Oceana: Protecting the World's Oceans. 2012. Retrieved February 28, 2012.
  19. Schartup AT, Balcom PH, Mason RP (January 2014). "Sediment-porewater partitioning, total sulfur, and methylmercury production in estuaries". Environmental Science & Technology. 48 (2): 954–60. Bibcode:2014EnST...48..954S. doi:10.1021/es403030d. PMC 4074365. PMID 24344684.
  20. Gooday AJ, Sykes D, Góral T, Zubkov MV, Glover AG (August 2018). "Micro-CT 3D imaging reveals the internal structure of three abyssal xenophyophore species (Protista, Foraminifera) from the eastern equatorial Pacific Ocean". Scientific Reports. 8 (1): 12103. doi:10.1038/s41598-018-30186-2. PMC 6092355. PMID 30108286.
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