Editing Californium (section)

== Occurrence ==
Traces of californium can be found near facilities that use the element in mineral prospecting and in medical treatments.{{sfn|Emsley|2001|p=90}} The element is fairly insoluble in water, but it adheres well to ordinary soil; and concentrations of it in the soil can be 500 times higher than in the water surrounding the soil particles.<ref name="ANL2005">{{cite web|url=http://www.evs.anl.gov/pub/doc/Californium.pdf |title=Human Health Fact Sheet: Californium |date=August 2005 |publisher=Argonne National Laboratory |url-status=dead |archive-url=https://web.archive.org/web/20110721032736/http://www.evs.anl.gov/pub/doc/Californium.pdf |archive-date=July 21, 2011 }}</ref>

[[Nuclear fallout]] from atmospheric [[nuclear weapons testing]] prior to 1980 contributed a small amount of californium to the environment.<ref name="ANL2005" /> Californium-249, -252, -253, and -254 have been observed in the radioactive dust collected from the air after a nuclear explosion.<ref>{{cite journal|title = Transplutonium Elements in Thermonuclear Test Debris|journal = Physical Review|date = 1956|volume = 102|issue = 1|pages = 180–182|doi = 10.1103/PhysRev.102.180|bibcode = 1956PhRv..102..180F|last1=Fields|first1=P. R.|last2 = Studier|first2 = M.|last3 = Diamond|first3 = H.|last4 = Mech|first4 = J.|last5 = Inghram|first5 = M.|last6 = Pyle|first6 = G.|last7 = Stevens|first7 = C.|last8 = Fried|first8 = S.|last9 = Manning|first9 = W.|display-authors=8}}</ref> Californium is not a major radionuclide at [[United States Department of Energy]] legacy sites since it was not produced in large quantities.<ref name="ANL2005" />

Californium was once believed to be produced in [[supernova]]s, as their decay matches the 60-day half-life of {{sup|254}}Cf.<ref name="super1">{{cite journal|last=Baade|first=W.|author2=Burbidge, G. R.|author3=Hoyle, F.|author4=Burbidge, E. M.|author5=Christy, R. F.|author6=Fowler, W. A.|title=Supernovae and Californium 254|journal=Publications of the Astronomical Society of the Pacific|date=August 1956|volume=68|issue=403|pages=296–300|doi=10.1086/126941|url=http://authors.library.caltech.edu/6553/1/BURpr56.pdf |archive-url=https://ghostarchive.org/archive/20221010/http://authors.library.caltech.edu/6553/1/BURpr56.pdf |archive-date=2022-10-10 |url-status=live|access-date=September 26, 2012|bibcode = 1956PASP...68..296B |doi-access=free}}</ref> However, subsequent studies failed to demonstrate any californium spectra,<ref name="super2">{{cite journal|last=Conway|first=J. G.|author2=Hulet, E.K. |author3=Morrow, R.J. |title=Emission Spectrum of Californium|journal=Journal of the Optical Society of America|date=February 1, 1962|volume=52|issue=2|pages=222|doi=10.1364/josa.52.000222 |pmid=13881026|bibcode=1962JOSA...52..222C |osti=4806792|url=http://www.escholarship.org/uc/item/9c3297wf}}</ref> and supernova light curves are now thought to follow the decay of [[Isotopes of nickel|nickel-56]].{{sfn|Ruiz-Lapuente1996|p=274}}

The [[transuranic element]]s [[americium]] to [[fermium]], including californium, occurred naturally in the [[natural nuclear fission reactor]] at [[Oklo]], but no longer do so.<ref name="emsley">{{cite book|last=Emsley|first=John|title=Nature's Building Blocks: An A-Z Guide to the Elements|edition=New|date=2011|publisher=Oxford University Press|location=New York, NY|isbn=978-0-19-960563-7}}</ref>

[[Spectral line]]s of californium, along with those of several other non-primordial elements, were detected in [[Przybylski's Star]] in 2008.<ref name=gopka08>{{cite journal |last1=Gopka |first1=V. F. |last2=Yushchenko |first2=A. V. |last3=Yushchenko |first3=V. A. |last4=Panov |first4=I. V. |last5=Kim |first5=Ch. |title=Identification of absorption lines of short half-life actinides in the spectrum of Przybylski's star (HD 101065) |journal=Kinematics and Physics of Celestial Bodies |date=15 May 2008 |volume=24 |issue=2 |pages=89–98 |doi=10.3103/S0884591308020049 |bibcode = 2008KPCB...24...89G |s2cid=120526363 }}</ref>