Editing Cadmium (section)

==Occurrence==
[[File:CadmiumMetalUSGOV.jpg|thumb|left|Cadmium metal]]
{{see also|Category:Cadmium minerals}}
Cadmium makes up about 0.1&nbsp;[[Parts per million|ppm]] of [[Earth's crust]] and is the 65th most abundant element.<ref>{{Cite book |last=Emsley |first=John |url=https://books.google.com/books?id=j-Xu07p3cKwC&dq=%E2%80%9C65th+most+abundant+element%E2%80%9D&pg=PA78 |title=Nature's Building Blocks: An A-Z Guide to the Elements |date=2003 |publisher=Oxford University Press |isbn=978-0-19-850340-8 |language=en}}</ref> It is much rarer than zinc, which makes up about 65&nbsp;ppm.<ref>
{{cite journal
 |last1=Wedepohl |first1=K. H.
 |date=1995
 |title=The composition of the continental crust
 |journal=[[Geochimica et Cosmochimica Acta]]
 |volume=59 |issue=7 |pages=1217–1232
 |bibcode=1995GeCoA..59.1217W
 |doi=10.1016/0016-7037(95)00038-2
}}</ref> No significant deposits of cadmium-containing ores are known. The only cadmium [[mineral]] of importance, [[greenockite]] (Cd[[sulfur|S]]), is nearly always associated with [[sphalerite]] (ZnS). This association is caused by geochemical similarity between zinc and cadmium, with no geological process likely to separate them. Thus, cadmium is produced mainly as a byproduct of mining, smelting, and refining sulfidic ores of zinc, and, to a lesser degree, [[lead]] and [[copper]]. Small amounts of cadmium, about 10% of consumption, are produced from secondary sources, mainly from dust generated by recycling iron and steel scrap. Production in the United States began in 1907,<ref name="Cadold" /> but wide use began after World War I.<ref name="price">
{{cite web
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 |date=1998
 |url=http://minerals.usgs.gov/minerals/pubs/commodity/cadmium/140798.pdf |archive-url=https://web.archive.org/web/20000816225332/http://minerals.usgs.gov/minerals/pubs/commodity/cadmium/140798.pdf |archive-date=2000-08-16 |url-status=live
 |title=Annual Average Cadmium Price
 |pages=17–19
 |publisher=[[U.S. Geological Survey]]
 |access-date=16 June 2010
}}</ref><ref name="lifecycle">
{{cite journal
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 |title=Life cycle impact analysis of cadmium in CdTe PV production
 |journal=[[Renewable and Sustainable Energy Reviews]]
 |volume=8 |issue=4 |pages=303–334
 |doi=10.1016/j.rser.2003.12.001
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 }}</ref>

Metallic cadmium can be found in the [[Vilyuy River]] basin in [[Siberia]].<ref>{{cite journal
 |last1=Fleischer |first1=M.
 |last2=Cabri |first2=L. J.
 |last3=Chao |first3=G. Y.
 |last4=Pabst |first4=A.
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 |title=New Mineral Names
 |url=http://www.minsocam.org/ammin/AM65/AM65_1065.pdf |archive-url=https://ghostarchive.org/archive/20221010/http://www.minsocam.org/ammin/AM65/AM65_1065.pdf |archive-date=2022-10-10 |url-status=live
 |journal=[[American Mineralogist]]
 |volume=65 |pages=1065–1070
}}</ref>

Rocks mined for phosphate fertilizers contain varying amounts of cadmium, resulting in a cadmium concentration of as much as 300&nbsp;mg/kg in the fertilizers and a high cadmium content in agricultural soils.<ref>{{cite journal
 |last1=Grant |first1=C. A.
 |last2=Sheppard |first2=S. C.
 |date=2008
 |title=Fertilizer impacts on cadmium availability in agricultural soils and crops
 |journal=[[Human and Ecological Risk Assessment]]
 |volume=14 |issue=2 |pages=210–228
 |doi=10.1080/10807030801934895
|bibcode=2008HERA...14..210G
 |s2cid=84548398
 }}</ref><ref>{{cite journal
 |last1=Jiao |first1=Y.
 |last2=Grant |first2=C. A.
 |last3=Bailey |first3=L. D.
 |date=2004
 |title=Effects of phosphorus and zinc fertilizer on cadmium uptake and distribution in flax and durum wheat
 |journal=[[Journal of the Science of Food and Agriculture]]
 |volume=84 |issue=8 |pages=777–785
 |doi=10.1002/jsfa.1648
|bibcode=2004JSFA...84..777J
 }}</ref> Coal can contain significant amounts of cadmium, which ends up mostly in [[coal fly ash]].<ref>{{cite journal
 |last1=Bettinelli |first1=M.
 |last2=Baroni |first2=U.
 |last3=Pastorelli |first3=N.
 |date=1988
 |title=Determination of arsenic, cadmium, lead, antimony, selenium and thallium in coal fly ash using the stabilised temperature platform furnace and Zeeman-effect background correction
 |journal=[[Journal of Analytical Atomic Spectrometry]]
 |volume=3 |issue=7 |pages=1005–1011
 |doi=10.1039/JA9880301005
}}</ref>

Cadmium in soil can be absorbed by crops such as rice and cocoa. In 2002, the [[Ministry of Agriculture of the People's Republic of China|Chinese ministry of agriculture]] measured that 28% of rice it sampled had excess lead and 10% had excess cadmium above limits defined by law. ''[[Consumer Reports]]'' tested 28 brands of [[dark chocolate]] sold in the United States in 2022, and found cadmium in all of them, with 13 exceeding the California Maximum Allowable Dose level.<ref>[https://www.wbur.org/hereandnow/2023/02/01/dark-chocolate-lead-cadmium Dark chocolate is high in cadmium and lead. How much is safe to eat?]</ref>

Some plants such as [[Willow|willow trees]] and [[Populus|poplars]] have been found to clean both lead and cadmium from soil.<ref>{{Cite news|url=https://www.economist.com/news/briefing/21723128-and-fixing-it-will-be-hard-and-costly-most-neglected-threat-public-health-china|title=The most neglected threat to public health in China is toxic soil|newspaper=The Economist|access-date=2017-06-13|date=2017-06-08}}</ref>

Typical background concentrations of cadmium do not exceed 5&nbsp;ng/m<sup>3</sup> in the atmosphere; 2&nbsp;mg/kg in soil; 1&nbsp;μg/L in freshwater and 50&nbsp;ng/L in seawater.<ref>
{{cite book
 |last1=Rieuwerts|first1=J.
 |date=2015
 |title=The Elements of Environmental Pollution
 |page=166
 |publisher=Routledge
 |isbn=978-0-415-85920-2
}}</ref> Concentrations of cadmium above 10 μg/L may be stable in water having low total solute concentrations and ''p'' H and can be difficult to remove by conventional water treatment processes.<ref>{{Cite journal|last=Hem|first=John D.|date=1972|title=Chemistry and occurrence of cadmium and zinc in surface water and groundwater|journal=Water Resources Research|language=en|volume=8|issue=3|pages=661–679|doi=10.1029/WR008i003p00661|bibcode=1972WRR.....8..661H|issn=1944-7973}}</ref>