The Nitrogen Budget of Earth
arXiv:1505.03813 · doi:10.1016/j.earscirev.2015.05.006
Abstract
We comprehensively compile and review N content in geologic materials to calculate a new N budget for Earth. Using analyses of rocks and minerals in conjunction with N-Ar geochemistry demonstrates that the Bulk Silicate Earth (BSE) contains \sim7\pm4 times present atmospheric N (4\times10^18 kg N, PAN), with 27\pm16\times10^18 kg N. Comparison to chondritic composition, after subtracting N sequestered into the core, yields a consistent result, with BSE N between 17\pm13\times10^18 kg to 31\pm24\times10^18 kg N. In the chondritic comparison we calculate a N mass in Earth's core (180\pm110 to 300\pm180\times10^18 kg) and discuss the Moon as a proxy for the early mantle. Significantly, we find the majority of the planetary budget of N is in the solid Earth. The N estimate herein precludes the need for a "missing N" reservoir. Nitrogen-Ar systematics in mantle rocks and basalts identify two mantle reservoirs: MORB-source like (MSL) and high-N. High-N mantle is composed of young, N-rich material subducted from the surface and is identified in OIB and some xenoliths. In contrast, MSL appears to be made of old material, though a component of subducted material is evident in this reservoir as well. Using our new budget, we calculate a δ15N value for BSE plus atmosphere of \sim2\permil. This value should be used when discussing bulk Earth N isotope evolution. Additionally, our work indicates that all surface N could pass through the mantle over Earth history, and the mantle may act as a long-term sink for N. Since N acts as a tracer of exchange between the atmosphere, oceans, and mantle over time, clarifying its distribution in the Earth is critical for evolutionary models concerned with Earth system evolution. We suggest that N be viewed in the same vein as carbon: it has a fast, biologically mediated cycle which connects it to a slow, tectonically-controlled geologic cycle.
Manuscript accepted in Earth Science Reviews
References in corpus (3)
Cited by in corpus (23)
- Exoplanet Biosignatures: Understanding Oxygen as a Biosignature in the Context of Its Environment
- Venusian Habitable Climate Scenarios: Modeling Venus through time and applications to slowly rotating Venus-Like Exoplanets
- Detecting and Constraining N Abundances in Planetary Atmospheres Using Collisional Pairs
- Nitrogen Oxide Concentrations in Natural Waters on Early Earth
- Atmospheric nitrogen evolution on Earth and Venus
- Modeling pN2 through Geological Time: Implications for Planetary Climates and Atmospheric Biosignatures
- The long-term evolution of the atmosphere of Venus: processes and feedback mechanisms
- EarthN: A new Earth System Nitrogen Model
- Dry Late Accretion inferred from Venus' coupled atmosphere and internal evolution
- Reduced atmospheres of post-impact worlds: The early Earth
- Assessment of Ammonia as a Biosignature Gas in Exoplanet Atmospheres
- Possible Atmospheric Diversity of Low Mass Exoplanets, some Central Aspects
- Impact Induced Atmosphere-Mantle Exchange Sets the Volatile Elemental Ratios on Primitive Earths
- How does Background Air Pressure Influence the Inner Edge of the Habitable Zone for Tidally Locked Planets in a 3D View?
- Climate Diversity in the Solar-Like Habitable Zone due to Varying Background Gas Pressure
- Measuring Changes in the Atmospheric Neutrino Rate Over Gigayear Timescales
- Smaller Sensitivity of Precipitation to Surface Temperature under Massive Atmospheres
- Earth: Atmospheric Evolution of a Habitable Planet
- The origin of Earth's mantle nitrogen: primordial or early biogeochemical cycling?
- Late Delivery of Nitrogen to Earth
- A Disintegrating Rocky World Shrouded in Dust and Gas: Mid-IR Observations of K2-22b using JWST
- The inhabitance paradox: how habitability and inhabitancy are inseparable
- Multiverse Predictions for Habitability: Stellar and Atmospheric Habitability