Lingering inconsistencies in the global methane (CH) budget and ambiguity in CH sources and sinks triggered efforts to identify new CH formation pathways in natural ecosystems. Herein, we reported a novel mechanism of light-induced generation of hydroxyl radicals (•OH) that drove the production of CH from aquatic dissolved organic matters (DOMs) under ambient conditions. A total of five DOM samples with different origins were applied to examine their potential in photo-methanification production under aerobic conditions, presenting a wide range of CH production rates from 3.57 × 10 to 5.90 × 10 nmol CH mg-C h. Experiments of •OH generator and scavenger indicated that the contribution of •OH to photo-methanificaiton among different DOM samples reached about 4∼42 %. In addition, Fourier transform infrared spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry showed that the carbohydrate- and lipid-like substances containing nitrogen-bonded methyl groups, methyl ester, acetyl groups, and ketones, were the potential precursors for light-induced CH production. Based on the experimental results and simulated calculations, the contribution of photo-methanification of aquatic DOMs to the diffusive CH flux across the water-air interface in a typical eutrophic shallow lake (e.g., Lake Chaohu) ranged from 0.1 % to 18.3 %. This study provides a new perspective on the pathways of CH formation in aquatic ecosystems and a deeper understanding on the sources and sinks of global CH.

中文翻译：

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有氧条件下不同来源水生溶解有机物的光甲烷化：羟基自由基的作用不可忽视

全球甲烷 (CH) 预算中长期存在的不一致以及 CH 源和汇的模糊性引发了人们努力确定自然生态系统中新的 CH 形成途径。在此，我们报道了一种光诱导产生羟基自由基（·OH）的新机制，该机制驱动在环境条件下从水生溶解有机物（DOM）中产生CH。总共使用了五个不同来源的 DOM 样品来检查它们在有氧条件下光甲烷化生产的潜力，呈现出从 3.57 × 10 到 5.90 × 10 nmol CH mg-C h 的广泛 CH 生产率。 •OH发生剂和清除剂的实验表明，不同DOM样品中•OH对光甲烷化的贡献达到4∼42%左右。此外，傅里叶变换红外光谱和傅里叶变换离子回旋共振质谱表明，含有氮键甲基、甲酯、乙酰基和酮的碳水化合物和脂质类物质是光诱导CH的潜在前体。生产。根据实验结果和模拟计算，水生DOMs的光甲烷化对典型富营养化浅湖（如巢湖）水-空气界面扩散CH通量的贡献范围为0.1%至18.3%。该研究为水生生态系统中CH的形成途径提供了新的视角，并为全球CH的源汇提供了更深入的认识。