Rust F
Science. 1981 Mar 6;211(4486):1044-6. doi: 10.1126/science.7466376.
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.
通过瘘管饲养的公牛、奶牛和阉羊以及奶牛和肉牛群所产生的甲烷的δ(13C/12C)值呈现双峰分布，这似乎与动物所消耗的植物类型（C3或C4，即在光合作用第一步产生三碳或四碳酸的植物）相关。这些结果表明，从全球范围来看，牛和羊排放的甲烷的平均δ(13C/12C)值分别为-60‰和-63‰。它们共同构成了大气甲烷的一个来源，其δ(13C/12C)与已公布的沼气值相似，无法解释大气甲烷高出20‰的值。
