The Nitrogen Budget of Earth
| dc.contributor.author | Johnson, Ben | |
| dc.contributor.author | Goldblatt, Colin | |
| dc.date.accessioned | 2015-08-31T21:13:28Z | |
| dc.date.available | 2016-05-15T11:22:07Z | |
| dc.date.copyright | 2015 | en_US |
| dc.date.issued | 2015-05-15 | |
| dc.description | Pre-print | en_US |
| dc.description.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 {\delta}15N 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. | en_US |
| dc.description.reviewstatus | Reviewed | en_US |
| dc.description.scholarlevel | Faculty | en_US |
| dc.description.sponsorship | NSERC | en_US |
| dc.identifier.citation | Johnson, B. & Goldblatt, C. 2015, "The nitrogen budget of Earth", Earth-Science Reviews, vol. 148, pp. 150-173. | en_US |
| dc.identifier.uri | http://dx.doi.org/10.1016/j.earscirev.2015.05.006 | |
| dc.identifier.uri | arXiv:1505.03813v1 | |
| dc.identifier.uri | http://hdl.handle.net/1828/6623 | |
| dc.language.iso | en | en_US |
| dc.publisher | Elsevier | en_US |
| dc.subject | Nitrogen | |
| dc.subject | Earth | |
| dc.subject | geochemistry | |
| dc.subject | isotopes | |
| dc.subject | chondrite | |
| dc.subject | core | |
| dc.subject.department | Department of Earth and Ocean Sciences | |
| dc.subject.department | School of Earth and Ocean Sciences | |
| dc.title | The Nitrogen Budget of Earth | en_US |
| dc.type | Article | en_US |