Distribution of nitrous oxide dissolved in water masses in the eastern subtropical North Pacific and its origin inferred from isotopomer analysis

Fujii, Ayako; Toyoda, Sakae; Yoshida, Osamu; Watanabe, Shuichi; Sasaki, Ken‐ichi; Yoshida, Naohiro

doi:10.1007/s10872-012-0162-4

Cited by 30 publications

(38 citation statements)

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“…The ranges of δ values measured for the studied region are comparable to those measured for the East China Sea (Zhang et al, unpublished data) and the Station ALOHA in the subtropical North Pacific gyre (Ostrom et al, ; Popp et al, ); however, SP and δ 18 O spanned a narrower range than the subtropical and subarctic western North Pacific (Breider et al, ; Toyoda et al, ), especially the eastern tropical North Pacific (Yamagishi et al, ) and the Peruvian coastal upwelling (Bourbonnais et al, ). Previous research shows that N 2 O production mechanisms are different at various water depth and locations in the ocean (Breider et al, ; Frame et al, ; Fujii et al, ). To elucidate the relative importance of the roles of nitrification and nitrifier‐denitrification in forming N 2 O at different depths, we divided the water column into the shallow water (0–120 m), the intermediate water (120–1,000 m), and deep water (>1,000 m).…”

Section: Discussionmentioning

confidence: 99%

“…However, the deep water in the study region originates partly from the western North Pacific waters (Kuroshio; Liu & Gan, ), which may carry an isotopic signal from a remote region with water column denitrification, that is, the ETNP. In these waters, N 2 O may be produced predominantly by denitrification with partial reduction in the oxygen deficient zone (Fujii et al, ; Yamagishi et al, ). Hence, N 2 O in the deep water of the SCS might come from the accumulation of N 2 O produced by nitrification, nitrifier denitrification in the intermediate water and N 2 O produced by denitrification with partial reduction in the deep waters transported from other regions.…”

Section: Discussionmentioning

confidence: 99%

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Distribution of Concentration and Stable Isotopic Composition of N₂O in the Shelf and Slope of the Northern South China Sea: Implications for Production and Emission

et al. 2019

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Oceans are an important natural source of the greenhouse gas nitrous oxide (N2O). The isotopomer signature of N2O provides a useful tool to differentiate the production processes of N2O in the oceans. Here we present the distribution of the concentration and stable isotopic composition of dissolved N2O in the water column of the shelf and slope region of the northern South China Sea (SCS) in June 2015. Dissolved N2O concentrations in surface waters ranged from 6.9 to 9.1 nM with an average of 7.7 ± 0.6 nM (136 ± 10% saturation). Higher N2O was found at the region influenced by coastal water entrained by eddies. Vertical profiles of dissolved N2O showed a general increase with depth below the mixed layer and reached a broad peak (23–29 nM) at around 700 m coinciding with the nitrate maximum and oxygen minimum. The SP values measured for N2O ranged between 10.2‰ and 18.8‰, suggesting that dissolved N2O in the water column had been produced from both nitrification (ammonium oxidation) and nitrifier denitrification (nitrite reduction). Nitrification dominated in the intermediate water (120–1,000 m) while nitrifier denitrification dominated in the euphotic zone. The sea‐to‐air fluxes of N2O were estimated to be 7.0 ± 6.1 and 6.9 ± 6.5 μmol m−2 day−1 using two different gas transfer relationships. N2O emissions from the shelf and slope regions of the northern SCS were estimated to be 0.25 Tg N2O year−1, suggesting that coastal areas like the SCS are net sources of N2O to the atmosphere.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Distribution of Concentration and Stable Isotopic Composition of N₂O in the Shelf and Slope of the Northern South China Sea: Implications for Production and Emission

et al. 2019

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“…Actually, δ 15 N bulk shows a small fluctuation from the equilibrium value (approximately 6.5‰) in the subsurface water, and increases slightly to about 8‰ until the N 2 O concentration maximum. It is almost constant below that depth (Popp et al, ; Toyoda et al, ; Fujii et al, ) (Fig. b).…”

Section: N2o Isotopocules In Various Environmentsmentioning

confidence: 93%

“…N 2 O concentration increases with depth and exhibits a maximum value of about 45 nmol kg −1 at 500–800 m depth, where dissolved oxygen is minimal. The concentration gradually decreases with depth (Dore et al, ; Toyoda et al, ; Fujii et al, ). The maximum concentration of N 2 O is found at deeper depths in the subtropical North Pacific than in the western North Pacific (Fig.…”

Section: N2o Isotopocules In Various Environmentsmentioning

confidence: 99%

Isotopocule analysis of biologically produced nitrous oxide in various environments

Toyoda

Yoshida

Koba

2015

Mass Spectrometry Reviews

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157

166

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Natural abundance ratios of isotopocules, molecules that have the same chemical constitution and configuration, but that only differ in isotope substitution, retain a record of a compound's origin and reactions. A method to measure isotopocule ratios of nitrous oxide (N O) has been established by using mass analysis of molecular ions and fragment ions. The method has been applied widely to environmental samples from the atmosphere, ocean, fresh water, soils, and laboratory-simulation experiments. Results show that isotopocule ratios, particularly the N-site preference (difference between isotopocule ratios N N O/ N N O and N N O/ N N O), have a wide range that depends on their production and consumption processes. Observational and laboratory studies of N O related to biological processes are reviewed and discussed to elucidate complex material cycles of this trace gas, which causes global warming and stratospheric ozone depletion. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:135-160, 2017.

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“…Very limited information is available regarding N 2 O production in intermediate waters, approximately between 500 and 1200 m depth, (Suntharalingam and Sarmiento, 2000;Nevison et al, 2003;Freing et al, 2012), with several of these studies carried out in the eastern tropical North Pacific and the Arabian Sea (Naqvi and Noronha, 1991;Bange et al, 2005;Yamagishi et al, 2007;Fujii et al, 2013). The intermediate depths of the eastern South Pacific (ESP) are occupied by two water masses that move in opposite directions and mix as they converge, i.e., Equatorial Subsurface Water (ESSW) and Antarctic Intermediate Water (AAIW).…”

Section: Introductionmentioning

confidence: 99%

On the Nitrous Oxide Accumulation in Intermediate Waters of the Eastern South Pacific Ocean

Carrasco

Karstensen

2017

Front. Mar. Sci.

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because N 2 O and AOU do not follow a linear trend, we suspect that, in addition to nitrification, denitrification also takes place in N 2 O cycling. By making use of water mass mixing analyses, we show that an increase in N 2 O occurs in the region where high oxygen from AAIW merges with low oxygen from Equatorial Subsurface Water (ESSW), creating favorable conditions for local N 2 O production. We conclude that the non-linearity in the relationship between N 2 O and O 2 is a result of mixing between two water masses with very different source characteristics, paired with the different time frames of nitrification and denitrification processes that impact water masses en route before they finally meet and mix in the ESP region.

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Distribution of nitrous oxide dissolved in water masses in the eastern subtropical North Pacific and its origin inferred from isotopomer analysis

Cited by 30 publications

References 28 publications

Distribution of Concentration and Stable Isotopic Composition of N₂O in the Shelf and Slope of the Northern South China Sea: Implications for Production and Emission

Distribution of Concentration and Stable Isotopic Composition of N₂O in the Shelf and Slope of the Northern South China Sea: Implications for Production and Emission

Isotopocule analysis of biologically produced nitrous oxide in various environments

On the Nitrous Oxide Accumulation in Intermediate Waters of the Eastern South Pacific Ocean

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Distribution of nitrous oxide dissolved in water masses in the eastern subtropical North Pacific and its origin inferred from isotopomer analysis

Cited by 30 publications

References 28 publications

Distribution of Concentration and Stable Isotopic Composition of N2O in the Shelf and Slope of the Northern South China Sea: Implications for Production and Emission

Distribution of Concentration and Stable Isotopic Composition of N2O in the Shelf and Slope of the Northern South China Sea: Implications for Production and Emission

Isotopocule analysis of biologically produced nitrous oxide in various environments

On the Nitrous Oxide Accumulation in Intermediate Waters of the Eastern South Pacific Ocean

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Product

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Distribution of Concentration and Stable Isotopic Composition of N₂O in the Shelf and Slope of the Northern South China Sea: Implications for Production and Emission

Distribution of Concentration and Stable Isotopic Composition of N₂O in the Shelf and Slope of the Northern South China Sea: Implications for Production and Emission