美国爱荷华州立大学Sajjad A. Akam课题组的最新研究，揭示了含铁半对流湖的甲烷-碳收支及其对早期地球海洋甲烷动力学的启示。2024年1月5日，国际知名学术期刊《地质学》发表了这一成果。

研究证明了甲烷生成是明尼苏达州布朗尼湖(美国中西部)的主要有机碳再矿化过程，这是一个含铁(富铁，缺乏硫酸盐)和部分混成(分成与永久缺氧的底层水)系统。研究报告：在水体和沉积物中甲烷生成分别占厌氧有机碳再矿化的≥90%和>9%±7%，布朗尼胡缺氧区总颗粒有机碳负载对CH₄的转化效率≥18%±7%。

研究结果连同先前关于含铁系统的报告表明，即使在前寒武纪海洋初级生产力较低的情况下，有机碳的有效转化也会使海洋CH₄在早期地球生物地球化学演化中发挥重要作用。

据了解，前寒武纪时期较年轻的太阳很微弱，但温室气体甲烷(CH₄)仍促成了温暖的气候，并维持了液态水的存在和地球的宜居性。然而，在含铁环境中甲烷生成(ME)的可行性是存在争议的，因为作为有机碳再矿化(OCR)的途径，铁还原可能胜过产甲烷的可行性。

附：英文原文

Title: Methane-carbon budget of a ferruginous meromictic lake and implications for marine methane dynamics on early Earth

Author: Sajjad A. Akam, Pei-Chuan Chuang, Sergei Katsev, Chad Wittkop, Michelle Chamberlain, Andrew W. Dale, Klaus Wallmann, Adam J. Heathcote, Elizabeth D. Swanner

Issue&Volume: 2024-01-05

Abstract: The greenhouse gas methane (CH4) contributed to a warm climate that maintained liquid water and sustained Earth’s habitability in the Precambrian despite the faint young sun. The viability of methanogenesis (ME) in ferruginous environments, however, is debated, as iron reduction can potentially outcompete ME as a pathway of organic carbon remineralization (OCR). Here, we document that ME is a dominant OCR process in Brownie Lake, Minnesota (midwestern United States), which is a ferruginous (iron-rich, sulfate-poor) and meromictic (stratified with permanent anoxic bottom waters) system. We report ME accounting for ≥90% and >9% ± 7% of the anaerobic OCR in the water column and sediments, respectively, and an overall particulate organic carbon loading to CH4 conversion efficiency of ≥18% ± 7% in the anoxic zone of Brownie Lake. Our results, along with previous reports from ferruginous systems, suggest that even under low primary productivity in Precambrian oceans, the efficient conversion of organic carbon would have enabled marine CH4 to play a major role in early Earth’s biogeochemical evolution.

DOI: 10.1130/G51713.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G51713.1/632104/Methane-carbon-budget-of-a-ferruginous-meromictic