美国麻省理工学院Benjamin T. Uveges团队研究了永久大气充氧前1亿年的有氧氮循环。相关论文于2025年5月12日发表在《美国科学院院刊》杂志上。
大氧化事件（GOE）代表了地球表面氧化还原平衡的重大转变。通过表征氮等氧化还原敏感元素的循环，可以帮助描绘GOE的驱动因素和节奏及其对微生物进化和生物地球化学的影响。虽然之前的研究表明，向广泛有氧海洋氮循环的过渡与23.3亿年前（Ga）GOE的最后阶段是同步的，但对GOE作为动态振荡过程的不断发展的理解以及现有研究的狭窄空间分布突显了海洋氮循环在导致永久大气氧化过程中的模糊性。
研究组展示了从相距数百公里的四个钻孔岩芯中的~2.43 Ga Duitschland和~2.33 Ga Rooihoogte地层中获得的稳定碳（δ13C）和氮（δ15N）同位素比值。Duitschland组中显著的负碳同位素偏移（6至8‰）表明，有机碳的大量氧化与假定的雪球地球事件和2.43 Ga的早期大气氧脉冲密切相关。此外，Duitschlan组中持续的正δ15N值（≤+20.3‰），加上全球δ15N记录的广泛时间变化，与现代海洋沉积物的分布相当，表明有氧氮循环比以前接受的要早约100 My。该研究结果更新了海洋氮循环演变和GOE周围地球表面氧化的关键时间点。
附：英文原文
Title: Aerobic nitrogen cycle 100 My before permanent atmospheric oxygenation
Author: Uveges, Benjamin T., Izon, Gareth, Junium, Christopher K., Ono, Shuhei, Summons, Roger E.
Issue&Volume: 2025-5-12
Abstract: The Great Oxidation Event (GOE) represents a major shift in Earth’s surficial redox balance. Delineating the driver(s) and tempo of the GOE and its impact on microbial evolution and biogeochemistry can be aided by characterizing the cycling of redox-sensitive elements such as nitrogen. While previous studies have shown that the transition to a broadly aerobic marine nitrogen cycle occurred in step with the final phase of the GOE ~2.33 billion years ago (Ga), an evolving understanding of the GOE as a dynamic oscillatory process and the narrow spatial distribution of existing studies highlight ambiguity in the marine nitrogen cycle in the lead up to permanent atmospheric oxygenation. Here, we present stable carbon (δ13C) and nitrogen (δ15N) isotope ratios derived from the ~2.43 Ga Duitschland and ~2.33 Ga Rooihoogte formations in four drill cores separated by hundreds of kilometers. A significant negative carbon isotope excursion (6 to 8‰) in the Duitschland Formation indicates massive oxidation of organic carbon in close association with a putative snowball Earth event and an earlier pulse of atmospheric oxygen at 2.43 Ga. Further, consistently positive δ15N values (≤ +20.3‰) within the Duitschland Formation, combined with a broad temporal shift across global δ15N records to a distribution comparable to modern marine sediments, signify an aerobic nitrogen cycle ~100 My earlier than previously accepted. Our results update a key timepoint in the evolution of the marine nitrogen cycle and the oxidation of the Earth’s surface surrounding the GOE.
DOI: 10.1073/pnas.2423481122
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2423481122