Stable isotopes of nitrite as a tool for understanding nitrogen cycling and loss in oxygen deficient zones
Abstract/Contents
- Abstract
- Nitrogen (N), a key nutrient in the global ocean, has a complicated biogeochemical cycle. In the ocean, nitrogen is mainly found as nitrate (NO3-), but it also accumulates as nitrite (NO2-) within oxygen deficient zones (ODZs). Nitrite is a key intermediate in several processes that produce nitrous oxide (N2O), a potent greenhouse gas. Using natural abundance stable isotope measurements of NO3- and NO2- help to capture an integrated signal of the N cycle processes. My doctoral work aims to use stable isotopes of N and oxygen (O) in order to further our understanding of the pathways that produce and consume NO2-, which will help us better predict the global impacts of nitrogen cycling both at present and in the future. Many N cycle processes are microbially mediated and impart one or more unique isotope effects on its N substrates and products, and it is important to quantify these isotope effects in order to use numerical models to elucidate relative contributions of different N cycle processes. In Chapter 1, I use pure culture experiments to better constrain estimates of the N and O isotope effects of microbial nitrite reduction, a key step in the process of denitrification, which leads to loss of bioavailable N. I then use the values from this experiment, in conjunction with previous estimates of other N cycle process isotope effects, to model observed NO3- and NO2- data from the Arabian Sea (Chapter 2) and explore the necessity for oxygen-requiring processes within the ODZ. In Chapter 3, I expand upon the results from previous chapters by applying the results to a global 3D inverse model of the N cycle, which includes isotopic fractionation, in order to examine the NO2- production and consumption processes within marine ODZs. I also examine the sensitivity of NO3- and NO2- concentration and isotope profiles to controlling parameters of N cycle processes, such as oxygen thresholds and isotope effects, in order to examine the roles of individual processes in N loss, and their potential for future change.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2018; ©2018 |
| Publication date | 2018; 2018 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Martin, Taylor |
|---|---|
| Degree supervisor | Casciotti, Karen Lynn, 1974- |
| Thesis advisor | Casciotti, Karen Lynn, 1974- |
| Thesis advisor | Arrigo, Kevin R |
| Thesis advisor | Thomas, Leif N |
| Degree committee member | Arrigo, Kevin R |
| Degree committee member | Thomas, Leif N |
| Associated with | Stanford University, Department of Earth System Science. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Taylor Martin. |
|---|---|
| Note | Submitted to the Department of Earth System Science. |
| Thesis | Thesis Ph.D. Stanford University 2018. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2018 by Taylor Sparks Martin
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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