基于总量和同位素质量平衡法对沉积有机碳埋藏通量的估算存在分歧。研究人员使用对海洋-大气系统输入的修正评估，对同位素质量平衡的新计算解决了这一明显的差异。输入包括碳酸盐和老干酪根风化作用、地质成因甲烷氧化作用、火山和变质脱气作用。火山和变质岩脱气约占总碳输入的23%。来自同位素轻OCpetro和CH4-geo的输入使得输入的平均δ13C值为=-8.0±1.9‰，明显低于通常假设的火山脱气值。
同位素质量平衡模型得出现代埋藏通量为15.9±6.6Tmol y-1。中新世中期气候最适同位素异常的影响是18和11Ma期间的综合过量沉积约4.3 × 106 Tmol，比哥伦比亚河玄武岩喷发总脱气的估计时间更长且更大，暗示了对大型喷发事件的复杂碳系统响应。蒙特卡洛评估发现，晚新生代碳酸盐岩储层极有可能净增长，而Corg储层净增长不太确定，但可能性较大。目前，俯冲作用似乎没有跟上净沉积的速度，沉积碳酸盐和有机碳的总体质量可能在增加。沉积Corg储层的生长表明地表环境氧化，大气pO2可能增加。
附：英文原文
Title: Closing the geologic carbon cycle
Author: Derry, Louis A.
Issue&Volume: 2024-10-7
Abstract: Estimates of sedimentary organic carbon burial fluxes based on inventory and isotope mass balance methods have been divergent. A new calculation of the isotope mass balance using a revised assessment of the inputs to the ocean-atmosphere system resolves the apparent discrepancy. Inputs include weathering of carbonate and old kerogen, geogenic methane oxidation, and volcanic and metamorphic degassing. Volcanic and metamorphic degassing comprise ≈23% of the total C input. Inputs from isotopically light OCpetro and CH4-geo drive the mean δ13C of the input to =-8.0 ± 1.9‰, notably lower than the commonly assumed volcanic degassing value. The isotope mass balance model yields a modern burial flux =15.9 ± 6.6 Tmol y-1. The impact of the mid-Miocene Climatic Optimum isotope anomaly is an integrated excess deposition ≈ 4.3 × 106 Tmol between 18 and 11 Ma, which is both longer and larger than estimates for the total degassing by the Columbia River Basalt eruptions, implying a complex carbon system response to large eruptive events. Monte Carlo evaluation finds that late Cenozoic net growth of the carbonate reservoir is very likely while net growth of the Corg reservoir is less certain but more likely than not. At present, subduction does not appear to keep up with net sedimentation and the overall masses of sedimentary carbonate and organic carbon are likely increasing. Growth in the sedimentary Corg reservoir implies oxidation of the surface environment and likely increases in atmospheric pO2.
DOI: 10.1073/pnas.2409333121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2409333121