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Quantifying Pacific Ocean Nitrous Oxide Cycling Using Intramolecular Isotope Measurements and Modeling
Quantifying Pacific Ocean Nitrous Oxide Cycling Using Intramolecular Isotope Measurements and Modeling
상세정보
- 자료유형
- 학위논문 서양
- 최종처리일시
- 20260202104746
- ISBN
- 9798290652696
- DDC
- 363
- 서명/저자
- Quantifying Pacific Ocean Nitrous Oxide Cycling Using Intramolecular Isotope Measurements and Modeling
- 발행사항
- [Sl] : Stanford University, 2023
- 발행사항
- Ann Arbor : ProQuest Dissertations & Theses, 2023
- 형태사항
- 295 p
- 주기사항
- Source: Dissertations Abstracts International, Volume: 87-01, Section: B.
- 주기사항
- Advisor: Casciotti, Karen Lynn.
- 학위논문주기
- Thesis (Ph.D.)--Stanford University, 2023.
- 초록/해제
- 요약Nitrous oxide (N2O) is a potent greenhouse gas, with a greenhouse gas potential almost 300 times that of carbon dioxide, as well as the most significant ozone depletion agent of the 21stcentury. Broadly, the major natural sources of nitrous oxide flux to the atmosphere are microbial processes in soils and in the ocean. Marine nitrous oxide production is concentrated in oxygen deficient zones, where dissolved oxygen remains below detection for hundreds of meters of the water column, and whose steep redox gradients allow for multiple overlapping processes that produce N2O. But the rates of these processes, and their relative importance in contributing to these hotspots of nitrous oxide production, remain a matter of debate. Using the largest oxygen deficient zone - the eastern tropical North Pacific - as a study site, this dissertation brings together geochemical measurements, field experimentation, and modeling to understand the rates and processes of nitrous oxide production in oxygen deficient zones and thus contribute to our understanding of potential feedbacks between ocean biogeochemistry and climate change.The stable isotopes of nitrogen (15N and 14N) and oxygen (18O and 16O) can act as tracers of microbial N2O cycling. The nitrous oxide molecule contains an oxygen atom as well as two chemically unique nitrogen atoms, the stable isotopes of which provide different kinds of information about the cycling of the molecule. This work centers on leveraging these site-specific nitrogen isotopes, or isotopomers, as well as the oxygen isotopes of nitrous oxide to constrain its cycling in oxygen deficient zones. First, in Chapter 1, I measured the natural abundance isotopomers and oxygen isotopes of nitrous oxide along a transect through the eastern tropical North Pacific and developed a forward-running model to explain these isotopic measurements. I find that the high accumulations of N2O found near the surface result mainly from denitrification, with a smaller contribution from nitrification. I also show that in the core anoxic depths at several stations, nitrous oxide cycling is not in steady state, while nitrous oxide isotope signatures in other parts of the region can be explained with denitrification with a positive site preference. Second, in Chapter 2, I present a software package for isotopomer data processing and discuss the assumptions and performance of this software.Of all the microbial processes that produce nitrous oxide, the least well understood is that mediated by ammonia-oxidizing archaea via a hybrid mechanism, socalled because it combines nitrogen derived from ammonium and nitrite to form N2O. In Chapter 3, I present the first combination of 15N tracer experiments with isotopomer measurements to identify the rates of this hybrid mechanism in the eastern tropical North Pacific. I show that hybrid nitrous oxide production is inhibited by oxygen and reaches high yields at oxic-anoxic interfaces where ammonia oxidation is active. Hybrid nitrous oxide production also has the potential for a variable site preference signature. Integrating the information learned from these biogeochemical measurements, Chapter 4 presents a 1D advection-diffusion-reaction model of nitrogen cycling constrained with N2O isotopomers to understand the dynamic nature of N2O cycling in the eastern tropical North Pacific and test the sensitivity of that cycling to ocean deoxygenation and changes in organic matter export. I show that N2O production from denitrification, nitrification, and hybrid N2O production are all important to near surface N2O accumulations, and that these processes are highly sensitive to low oxygen conditions and organic matter source, conditions that are subject to change with ocean deoxygenation, warming, and stratification.
- 일반주제명
- Climate change
- 기타저자
- Stanford University.
- 기본자료저록
- Dissertations Abstracts International. 87-01B.
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
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■020 ▼a9798290652696
■035 ▼a(MiAaPQ)AAI32149756
■035 ▼a(MiAaPQ)Stanfordyq704bd0082
■040 ▼aMiAaPQ▼cMiAaPQ
■0820 ▼a363
■1001 ▼aKelly, Colette LaMonica.
■24510▼aQuantifying Pacific Ocean Nitrous Oxide Cycling Using Intramolecular Isotope Measurements and Modeling
■260 ▼a[Sl]▼bStanford University▼c2023
■260 1▼aAnn Arbor▼bProQuest Dissertations & Theses▼c2023
■300 ▼a295 p
■500 ▼aSource: Dissertations Abstracts International, Volume: 87-01, Section: B.
■500 ▼aAdvisor: Casciotti, Karen Lynn.
■5021 ▼aThesis (Ph.D.)--Stanford University, 2023.
■520 ▼aNitrous oxide (N2O) is a potent greenhouse gas, with a greenhouse gas potential almost 300 times that of carbon dioxide, as well as the most significant ozone depletion agent of the 21stcentury. Broadly, the major natural sources of nitrous oxide flux to the atmosphere are microbial processes in soils and in the ocean. Marine nitrous oxide production is concentrated in oxygen deficient zones, where dissolved oxygen remains below detection for hundreds of meters of the water column, and whose steep redox gradients allow for multiple overlapping processes that produce N2O. But the rates of these processes, and their relative importance in contributing to these hotspots of nitrous oxide production, remain a matter of debate. Using the largest oxygen deficient zone - the eastern tropical North Pacific - as a study site, this dissertation brings together geochemical measurements, field experimentation, and modeling to understand the rates and processes of nitrous oxide production in oxygen deficient zones and thus contribute to our understanding of potential feedbacks between ocean biogeochemistry and climate change.The stable isotopes of nitrogen (15N and 14N) and oxygen (18O and 16O) can act as tracers of microbial N2O cycling. The nitrous oxide molecule contains an oxygen atom as well as two chemically unique nitrogen atoms, the stable isotopes of which provide different kinds of information about the cycling of the molecule. This work centers on leveraging these site-specific nitrogen isotopes, or isotopomers, as well as the oxygen isotopes of nitrous oxide to constrain its cycling in oxygen deficient zones. First, in Chapter 1, I measured the natural abundance isotopomers and oxygen isotopes of nitrous oxide along a transect through the eastern tropical North Pacific and developed a forward-running model to explain these isotopic measurements. I find that the high accumulations of N2O found near the surface result mainly from denitrification, with a smaller contribution from nitrification. I also show that in the core anoxic depths at several stations, nitrous oxide cycling is not in steady state, while nitrous oxide isotope signatures in other parts of the region can be explained with denitrification with a positive site preference. Second, in Chapter 2, I present a software package for isotopomer data processing and discuss the assumptions and performance of this software.Of all the microbial processes that produce nitrous oxide, the least well understood is that mediated by ammonia-oxidizing archaea via a hybrid mechanism, socalled because it combines nitrogen derived from ammonium and nitrite to form N2O. In Chapter 3, I present the first combination of 15N tracer experiments with isotopomer measurements to identify the rates of this hybrid mechanism in the eastern tropical North Pacific. I show that hybrid nitrous oxide production is inhibited by oxygen and reaches high yields at oxic-anoxic interfaces where ammonia oxidation is active. Hybrid nitrous oxide production also has the potential for a variable site preference signature. Integrating the information learned from these biogeochemical measurements, Chapter 4 presents a 1D advection-diffusion-reaction model of nitrogen cycling constrained with N2O isotopomers to understand the dynamic nature of N2O cycling in the eastern tropical North Pacific and test the sensitivity of that cycling to ocean deoxygenation and changes in organic matter export. I show that N2O production from denitrification, nitrification, and hybrid N2O production are all important to near surface N2O accumulations, and that these processes are highly sensitive to low oxygen conditions and organic matter source, conditions that are subject to change with ocean deoxygenation, warming, and stratification.
■590 ▼aSchool code: 0212.
■650 4▼aClimate change
■690 ▼a0404
■71020▼aStanford University.
■7730 ▼tDissertations Abstracts International▼g87-01B.
■790 ▼a0212
■791 ▼aPh.D.
■792 ▼a2023
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T17358749▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
