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Science 6 March 1981:
Vol. 211. no. 4486, pp. 1044 - 1046
DOI: 10.1126/science.7466376
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Articles

Science, Vol 211, Issue 4486, 1044-1046
Copyright © 1981 by American Association for the Advancement of Science

articles

Ruminant methane delta(13C/12C) values: relation to atmospheric methane

F Rust

The delta(13C/12C)--values of methane produced by fistulated steers, dairy cattle, and wethers, and dairy and beef cattle herds show a bimodal distribution that appears to be correlated with the plant type (C3 or C4, that is, producing either a three- or a four-carbon acid in the first step of photosynthesis) consumed by the animals. These results indicate that cattle and sheep, on a global basis, release methane with an average delta(13C/12C) value of -60 and -63 per mil, respectively. Together they are a source of atmospheric methane whose delta(13C/12C) is similar to published values for marsh gas and cannot explain the 20 per mil higher values for atmospheric methane.


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