Schulze E, Lohmeyer S, Giese W
Fachgebiet Medizinische Physik der Tierärztlichen Hochschule Hannover, Deutschland.
Isotopes Environ Health Stud. 1998;34(1-2):75-9.
Naturally produced methane shows different delta 13C-values with respect to its origin, e.g., geological or biological. Methane-production of ruminants is considered to be the dominant source from the animal kingdom. Isotopic values of rumen methane--given in literature--range between -80/1000 and -50/1000 and are related to feed composition and also sampling techniques. Keeping cows, camels and sheep under identical feed conditions and sampling rumen gases via implanted fistuale we compared delta PDB 13C-values of methane and CO2 between the species. Referring to mean values obtained from 4 or 5 samples at different times of 11 animals (n = 47) we calculated delta PDB 13C-medians resulting in small but not significant differences within and significant differences between the species for CO2 and methane. The delta PDB 13C-differences between methane and CO2 were statistically equal within and also between the species. Therefore a linear regression of methane values on CO2 is appropriate and leads to: delta PDB 13C(methane)/1000 = 1.57 * delta PDB 13C(CO2)/1000 - 47/1000 with a correlation coefficient of r = 0.87.
天然产生的甲烷因其来源（如地质或生物来源）不同而具有不同的δ13C值。反刍动物产生的甲烷被认为是动物界的主要来源。文献中给出的瘤胃甲烷的同位素值在-80‰至-50‰之间，并且与饲料组成以及采样技术有关。在相同的饲料条件下饲养奶牛、骆驼和绵羊，并通过植入的瘘管采集瘤胃气体，我们比较了不同物种之间甲烷和二氧化碳的δPDB 13C值。参考从11只动物（n = 47）在不同时间采集的4或5个样本获得的平均值，我们计算了δPDB 13C中位数，结果表明，对于二氧化碳和甲烷，物种内部存在微小但不显著的差异，而物种之间存在显著差异。甲烷和二氧化碳之间的δPDB 13C差异在物种内部和物种之间在统计学上是相等的。因此，甲烷值对二氧化碳的线性回归是合适的，得到：δPDB 13C（甲烷）/‰ = 1.57×δPDB 13C（二氧化碳）/‰ - 47/‰，相关系数r = 0.87。
