The evolution of Earth's atmosphere as recorded by continental crust

氮气是当今大气中最丰富的气体，但情况可能并不总是如此。最近对不同岩石类型的调查表明，地幔和大陆地壳中储存了大量的氮(图1)，这表明氮可以在大气层和地圈之间转换。这一点很重要，因为地球大气的质量及其波动对地球深层气候和宜居性的发展产生了巨大的控制作用。地质和大气氮循环的长期演变目前尚不清楚[2](图2)。一些数据表明，太古宙(27亿年前)的大气压力明显较低[3]，这意味着当时岩石中储存了更大比例的氮。另一方面，最近对太古宙地壳岩石的测量显示，氮的丰度很低[4]，这表明氮是从大气转移到地圈的。最可能的转移途径是大气中的氮气以氨的形式吸收到生物体中，其次是生物体埋藏在沉积物中，沉积物吸积到大陆地壳上。然而，这一途径的效率并没有受到很好的约束，也不知道氮在矿物和岩石中的固存随着时间的推移发生了怎样的变化[6]。简而言之，氮过去在哪里，以及它是如何到达那里的，都是未知的。该项目旨在解决这些问题，特别强调重建大陆氮气库的生长和同位素组成及其与地球历史进程中大气氮气丰度的关系。

Nitrogen is the most abundant gas in today's atmosphere, but this may not always have been the case. A recent survey of different rock types suggested that large quantities of nitrogen are stored in the mantle and continental crust (Figure 1), indicating that nitrogen can transition between the atmosphere and geosphere. This is important because the mass of Earth's atmosphere, and fluctuations therein, exert a massive control on Earth's deep-time climate, and the development of habitability. The long-term evolution of the geological and atmospheric nitrogen cycle is currently unknown [2] (Figure 2). Some data suggest that atmospheric pressure was markedly lower in the Archean (2.7 billion years ago) [3], which would imply that a larger fraction of nitrogen was stored in rocks at that time. On the other hand, recent measurements of Archean crustal rocks show low nitrogen abundances [4], suggesting that nitrogen was transferred from the atmosphere into the geosphere. The most likely transfer pathway is uptake of atmospheric N2 into biomass as ammonium [5], followed by biomass burial in sediments and accretion of sediments onto continental crust. However, the efficiency of this pathway is not well constrained, and it is unknown how the sequestration of nitrogen into minerals and rocks has changed, over time [6]. In short, it is unknown where nitrogen was in the past and how it got there. This project aims to address these questions with particular emphasis on reconstructing the growth and isotopic composition of the continental nitrogen reservoir and its relationship with atmospheric N2 abundances over the course of Earth's history.