Radiocarbon (¹⁴C) ages of acetogenic lipid biomarkers such as n-alkanes represent a powerful tool to track carbon-cycle turnover times in a range of environments including soils, fluvially exported sediments, and marine sediments. However, the fidelity of this approach requires that biomarker ¹⁴C ages accurately reflect the time that has passed since biosynthesis and are not complicated by issues such as isotope fractionation. Reported ¹⁴C ages are thus always corrected for mass-dependent fractionation using a ¹⁴C/¹³C mass law, b, of $2.0$. However, anomalous deviations from mass dependence could theoretically lead to biases in measured ¹⁴C ages, particularly for compounds such as acetogenic lipids that undergo large ¹³C fractionations. Here, I test this possibility by estimating kinetic and equilibrium mass laws for various processes involved in acetogenic lipid biosynthesis using simple approximations and more robust computational chemistry methods. I find that kinetic b values range from $1.890$ to $1.995$ and that equilibrium b values for several chain elongation steps range from $1.856$ to $1.880$, consistent with previous results for other chemical and biological processes. In contrast, complex reaction networks may lead to large expressed b values, but only when net $\ln ({}^{13}\alpha )\to 0$. Combined, these results imply maximum ¹⁴C age offsets due to biosynthetic fractionation of ~20 to 40 yr. Biomarker ¹⁴C ages are therefore robust to biosynthetic isotope fractionation and can be confidently interpreted to reflect carbon-cycle turnover times.

正构烷烃等产乙酸脂质生物标志物的放射性碳 ( ¹⁴ C) 年龄代表了一种强大的工具，可以在土壤、河流输出的沉积物和海洋沉积物等一系列环境中跟踪碳循环周转时间。然而，这种方法的保真度要求生物标志物¹⁴ C 年龄准确反映自生物合成以来已经过去的时间，并且不会因同位素分馏等问题而变得复杂。报道^14名Ç年龄因此总是用于校正使用质量依赖性分馏¹⁴ C / ¹³ C质量法，b，的$2.0$. 然而，从理论上讲，质量依赖性的异常偏差可能会导致测量的¹⁴ C 年龄出现偏差，特别是对于化合物，例如经过大量¹³ C 分馏的产乙酸脂质。在这里，我通过使用简单的近似和更强大的计算化学方法估计涉及产乙酸脂质生物合成的各种过程的动力学和平衡质量定律来测试这种可能性。我发现动力学b值范围从$1.890$ 至 $1.995$并且几个链延伸步骤的平衡b值范围从$1.856$ 至 $1.880$，与之前其他化学和生物过程的结果一致。相比之下，复杂的反应网络可能会导致表达的b值很大，但只有当 net$\mathrm{输入}({}^{13}\alpha )\to 0$. 综合起来，这些结果意味着由于生物合成分馏约 20 至 40 年，最大¹⁴ C 年龄补偿。因此，生物标志物¹⁴ C 年龄对生物合成同位素分馏具有稳健性，并且可以自信地解释以反映碳循环周转时间。