Measurement of geologic nitrogen using mass spectrometry, colorimetry, and a newly adapted fluorometry technique
| dc.contributor.author | Johnson, Benjamin W. | |
| dc.contributor.author | Drage, Natashia | |
| dc.contributor.author | Spence, Jody | |
| dc.contributor.author | Hanson, Nova | |
| dc.contributor.author | El-Sabaawi, Rana | |
| dc.contributor.author | Goldblatt, Colin | |
| dc.date.accessioned | 2018-08-07T20:00:24Z | |
| dc.date.available | 2018-08-07T20:00:24Z | |
| dc.date.copyright | 2017 | en_US |
| dc.date.issued | 2017 | |
| dc.description.abstract | Long viewed as a mostly noble, atmospheric species, recent work demonstrates that nitrogen in fact cycles throughout the Earth system, including the atmosphere, biosphere, oceans, and solid Earth. Despite this new-found behaviour, more thorough investigation of N in geologic materials is limited due to its low concentration (one to tens of parts per million) and difficulty in analysis. In addition, N can exist in multiple species (NO3-, NH4+, N-2, organic N), and determining which species is actually quantified can be difficult. In rocks and minerals, NH4+ is the most stable form of N over geologic timescales. As such, techniques designed to measure NII4+ can be particularly useful. We measured a number of geochemical rock standards using three different techniques: elemental analyzer (EA) mass spectrometry, colorimetry, and fluorometry. The fluorometry approach is a novel adaptation of a technique commonly used in biologic science, applied herein to geologic NH4+. Briefly, NH4+ can be quantified by HF dissolution, neutralization, addition of a fluorescing reagent, and analysis on a standard fluorometer. We reproduce published values for several rock standards (BCR-2, BHVO-2, and G-2), especially if an additional distillation step is performed. While it is difficult to assess the quality of each method, due to lack of international geologic N standards, fluorometry appears better suited to analyzing mineral- bound NH4+ than EA mass spectrometry and is a simpler, quicker alternative to colorimetry. To demonstrate a potential application of fluorometry, we calculated a continental crust N budget based on new measurements. We used glacial tills as a proxy for upper crust and analyzed several poorly constrained rock types (volcanics, mid- crustal xenoliths) to determine that the continental crust contains similar to 2 x 10(18) kg N. This estimate is consistent with recent budget estimates and shows that fluorometry is appropriate for large-scale questions where high sample throughput is helpful. Lastly, we report the first f N-15 values of six rock standards: BCR-2 (1 : 05 +/- 0 : 4%), BHVO-2 (0 : 3 +/- 0 : 2%), G2 (1 : 23 +/- 1 : 32%), LKSD-4 (3 : 59 +/- 0 : 1%), Till-4 (6 : 33 +/- 0 : 1%), and SY-4 (2 : 13 +/- 0 : 5%). The need for international geologic N standards is crucial for further investigation of the Earth system N cycle, and we suggest that existing rock standards may be suited to this need. | en_US |
| dc.description.reviewstatus | Reviewed | en_US |
| dc.description.scholarlevel | Faculty | en_US |
| dc.description.sponsorship | The authors thank P. Barry and one anonymous reviewer for their constructive feedback and the editors at Solid Earth (A. Di Muro and J. Gottsmann). The authors acknowledge an NSERC Discovery grant to Colin Goldblatt for funding Colin Goldblatt and Benjamin W. Johnson, a University of Victoria NSERC Undergraduate Student Research Award to Natashia Drage, and NSERC awards to Rana El- Sabaawi for funding support. Nitrogen isotope measurements were done at the University of Washington and were funded by the Virtual Planetary Laboratory. | en_US |
| dc.identifier.citation | Johnson, B.W.; Drage, N.; Spence, J.; Hanson, N.; El-Sabaawi, R.; & Goldblatt, C. (2017). Measurement of geologic nitrogen using mass spectrometry, colorimetry, and a newly adapted fluorometry technique. Solid Earth, 8, 307-318. https://doi.org/10.5194/se-8-307-2017 | en_US |
| dc.identifier.uri | https://doi.org/10.5194/se-8-307-2017 | |
| dc.identifier.uri | http://hdl.handle.net/1828/9874 | |
| dc.language.iso | en | en_US |
| dc.publisher | Solid Earth | en_US |
| dc.subject.department | School of Earth and Ocean Sciences | |
| dc.subject.department | Department of Biology | |
| dc.title | Measurement of geologic nitrogen using mass spectrometry, colorimetry, and a newly adapted fluorometry technique | en_US |
| dc.type | Article | en_US |