英国圣安德鲁斯大学Barth, Patrick及其课题组提出地球早期生物圈中，同位素限制了作为固定氮来源的闪电。相关论文发表在2023年5月22日出版的《自然—地球科学》杂志上。

课题组人员展示了N₂-CO₂和N₂-O₂气体混合物火花放电实验的结果。结果表明，与现代相比，闪电驱动的固氮作用在太古代大气中同样有效。溶液中放电产生的亚硝酸盐和硝酸盐的同位素比率(δ¹⁵N) 测量显示，在与气相平衡后，显示出非常低的值，为-6‰到-15‰，计算端元成分为-17‰。这些结果远低于沉积记录中记录的大多数的δ¹⁵N值，这支持了早于32亿年前生物固氮的发展的观点。然而，一些古太古代记录(37亿年前)显示，可能与闪电产生的氮输入一致，突出了这一过程对早期生态系统的潜在作用。

据介绍，生物可利用的氮被认为是生命起源和维持生命的必要条件。在生物固氮作用开始之前，非生物途径来固定大气中的N₂占主导地位，为地球最早的生态系统提供生物可利用的氮。以N₂和O₂占主导地位的现代大气中，闪电已经被证明以亚硝酸盐和硝酸盐的形式产生固定氮，类似于太古代地球，N₂和CO₂主导大气。然而，人们需要更好地理解闪电产生的固定氮的同位素指纹，以评估这一过程在早期地球系统中的作用。

附：英文原文

Title: Isotopic constraints on lightning as a source of fixed nitrogen in Earth’s early biosphere

Author: Barth, Patrick, Steken, Eva E., Helling, Christiane, Rossmanith, Lukas, Peng, Yuqian, Walters, Wendell, Claire, Mark

Issue&Volume: 2023-05-22

Abstract: Bioavailable nitrogen is thought to be a requirement for the origin and sustenance of life. Before the onset of biological nitrogen fixation, abiotic pathways to fix atmospheric N₂ must have been prominent to provide bioavailable nitrogen to Earth’s earliest ecosystems. Lightning has been shown to produce fixed nitrogen as nitrite and nitrate in both modern atmospheres dominated by N₂ and O₂ and atmospheres dominated by N₂ and CO₂ analogous to the Archaean Earth. However, a better understanding of the isotopic fingerprints of lightning-generated fixed nitrogen is needed to assess the role of this process on early Earth. Here we present results from spark discharge experiments in N₂-CO₂ and N₂-O₂ gas mixtures. Our experiments suggest that lightning-driven nitrogen fixation may have been similarly efficient in the Archaean atmosphere, compared with modern times. Measurements of the isotopic ratio (δ¹⁵N) of the discharge-produced nitrite and nitrate in solution show very low values of -6‰ to -15‰ after equilibration with the gas phase with a calculated endmember composition of -17‰. These results are much lower than most δ¹⁵N values documented from the sedimentary rock record, which supports the development of biological nitrogen fixation earlier than 3.2 billion years ago. However, some Paleoarchean records (3.7 billion years ago) may be consistent with lightning-derived nitrogen input, highlighting the potential role of this process for the earliest ecosystems.

DOI: 10.1038/s41561-023-01187-2

Source: https://www.nature.com/articles/s41561-023-01187-2