作者：Wang, J., Wu, B., Yao, Y., Chen, B., Peng, S. & Chu, C.

Methane (CH₄) production is commonly associated with anaerobic microbial respiration, yet substantial CH₄ production has been observed in aerobic surface waters, presenting the "aerobic methane paradox". Clarifying the mechanism behind aerobic CH₄ production is essential for refining the global CH₄ budget. Here, we demonstrate that sunlight-driven photochemical processes can effectively produce CH₄ across various surface waters, including river, lake, and seawater. The CH₄ formation rates ranged from 0.4 +/- 0.1 to 0.7 +/- 0.1 mu mol/m2/h in the daytime, which were 2.3- to 3.9-fold higher as compared to those driven by the decomposition of organic matter by methanogenic archaea in the nighttime. Such aerobic CH₄ production stems from the rapid oxidation of naturally abundant methyl donors (e.g., dimethyl sulfoxide) by a photochemically produced hydroxyl radical (center dot OH), which yields a methyl radical (center dot CH₃) and subsequently leads to CH₄ production. Simulations on CH₄ productions across varying seasons, latitudes, altitudes, and regions at the global scale suggest that the photochemical processes contribute to 35.3-70.7% of marine CH₄ emissions. Our study highlights a ubiquitous yet previously overlooked photochemical source of CH₄ production in surface waters, shedding light on the "aerobic methane paradox", which has implications on the global CH₄ budget.

甲烷（CH₄）生成通常与厌氧微生物呼吸相关联，然而在好氧表层水体中已观测到可观的CH₄生成，即所谓“好氧甲烷悖论”（aerobic methane paradox）。阐明好氧CH₄生成的机制对于精化全球CH₄收支至关重要。研究证明，太阳光驱动的光化学过程可在河流、湖泊、海水等多种表层水体中有效生成CH₄。白天光化学CH₄生成速率为0.4 ± 0.1 至 0.7 ± 0.1 μmol·m⁻²·h⁻¹，比夜间由产甲烷古菌分解有机物驱动的生成速率高2.3-3.9倍。这种好氧CH₄生成源于天然丰度较高的甲基供体（如二甲基亚砜，DMSO）被光化学产生的羟基自由基（·OH）快速氧化：该反应先生成甲基自由基（·CH₃），进而生成CH₄。对全球不同季节、纬度、海拔与区域CH₄生成的模拟表明，光化学过程贡献了海洋CH₄排放的35.3%-70.7%。研究揭示了一个普遍存在却长期被忽视的表层水体CH₄生成的光化学来源，为“好氧甲烷悖论”提供了解释，并对全球CH₄收支具有重要意义。

（来源：Environmental Science & Technology 2026 Issue 22  DOI: 10.1021/acs.est.6c02525）