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The atmospheric helium isotope ratio: Is it changing?
Author(s) -
Lupton John,
Evans Leigh
Publication year - 2004
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2004gl020041
Subject(s) - helium , environmental science , atmospheric sciences , isotopes of helium , geothermal gradient , fossil fuel , isotopic ratio , isotope , geology , chemistry , physics , nuclear physics , geophysics , atomic physics , organic chemistry
We have compared the helium isotope ratio of samples of Pacific marine air collected over the 30‐year period from 1973 to 2003 against a secondary geothermal gas standard and also against a running air standard. The results are consistent with zero rate of change for atmospheric 3 He/ 4 He. When the errors are taken into account, the rate of change in the air 3 He/ 4 He ratio is between −0.0102 and +0.0019 %/year. At the most this corresponds to a 0.3% change in the air 3 He/ 4 He ratio over the past 3 decades, which is at or below the detection limit of most laboratories. While there may be a small decrease in air 3 He/ 4 He due to anthropogenic release of 4 He associated with use of fossil fuels, this decrease is not large enough to prevent the use of air helium as an isotopic standard.