Isotopic variability of N2O emissions from tropical forest soils

Pérez, Tibisay; Trumbore, Susan E.; Tyler, S. C.; Davidson, Eric A.; Keller, Michael; Camargo, Plínio Barbosa de

doi:10.1029/1999gb001181

Cited by 134 publications

(149 citation statements)

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“…However, the latest IPCC Assessment Report (Ciais et al, 2013) for the first time separated oceanic emissions into a natural component and an anthropogenic component, e.g., due to atmospheric N deposition to rivers (Syakila and Kroeze, 2011;Duce et al, 2008;Kroeze et al, 2005). The oceanic fraction of the anthropogenic source was estimated as 1 Tg year −1 N. N 2 O emitted from agricultural soils and biomass burning is more depleted in δ 15 N av and δ 18 O than the tropospheric background (Park et al, 2011;Goldberg et al, 2010;Ostrom et al, 2010;Tilsner et al, 2003;Pérez et al, 2001Pérez et al, , 2000, while N 2 O emitted from other minor sources, such as automobiles, coal combustion, and industry, has values closer to tropospheric N 2 O values (Syakila and Kroeze, 2011;Toyoda et al, 2008;Ogawa and Yoshida, 2005a, b). An increase in strongly depleted agricultural emissions in the first part of our reconstruction, followed by a decreasing relative contribution from agriculture and increasing contributions from more enriched sources like industry, automobiles, and coal combustion, could qualitatively explain the reconstructed changes in isotope signatures of both the total source and the anthropogenic component.…”

Section: Discussionmentioning

confidence: 99%

Constraining N2O emissions since 1940 using firn air isotope measurements in both hemispheres

et al. 2017

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Abstract. N 2 O is currently the third most important anthropogenic greenhouse gas in terms of radiative forcing and its atmospheric mole fraction is rising steadily. To quantify the growth rate and its causes over the past decades, we performed a multi-site reconstruction of the atmospheric N 2 O mole fraction and isotopic composition using new and previously published firn air data collected from Greenland and Antarctica in combination with a firn diffusion and densification model. The multi-site reconstruction showed that while the global mean N 2 O mole fraction increased from (290 ± 1) nmol mol −1 in 1940 to (322 ± 1) nmol mol −1 in 2008, the isotopic composition of atmospheric N 2 O decreased by (−2.2 ± 0.2) ‰ for δ 15 N av , (−1.0 ± 0.3) ‰ for δ 18 O, (−1.3 ± 0.6) ‰ for δ 15 N α , and (−2.8 ± 0.6) ‰ for δ 15 N β over the same period. The detailed temporal evolution of the mole fraction and isotopic composition derived from the firn air model was then used in a two-box atmospheric model (comprising a stratospheric box and a tropospheric box) to infer changes in the isotopic source signature over time. The precise value of the source strength depends on the choice of the N 2 O lifetime, which we choose to fix at 123 years. The average isotopic composition over the investigated period is δ 15 N av = (−7.6 ± 0.8) ‰ (vs. air-N 2 ), δ 18 O = (32.2 ± 0.2) ‰ (vs. Vienna Standard Mean Ocean Water -VSMOW) for δ 18 O, δ 15 N α = (−3.0 ± 1.9) ‰ and δ 15 N β = (−11.7 ± 2.3) ‰. δ 15 N av , and δ 15 N β show some temporal variability, while for the other signatures the error bars of the reconstruction are too large to retrieve reliable temporal changes. Possible processes that may explain trends in 15 N are discussed. The 15 N site preference (= δ 15 N α − δ 15 N β ) provides evidence of a shift in emissions from denitrification to nitrification, although the uncertainty envelopes are large.

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Section: Discussionmentioning

confidence: 99%

Constraining N2O emissions since 1940 using firn air isotope measurements in both hemispheres

et al. 2017

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“…However, occasionally (e.g., D-O event 15 and 17) the N 2 O concentration increases long before the onset of the dramatic temperature change (Schilt et al, 2010), providing a potential early warning for rapid climate change. Isotopomers of N 2 O provide information on the sources (Pérez et al, 2000(Pérez et al, , 2001Park et al, 2011), i.e., whether N 2 O originates predominately from nitrification or denitrification processes. As the conditions/circumstances leading to emissions from the two processes differ both for the marine and terrestrial sources, measuring isotopomers potentially improves our understanding of the climate conditions leading to the release of N 2 O over rapid climatic changes.…”

Section: Introductionmentioning

confidence: 99%

Continuous measurements of nitrous oxide isotopomers during incubation experiments

et al. 2018

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Abstract. Nitrous oxide (N 2 O) is an important and strong greenhouse gas in the atmosphere. It is produced by microbes during nitrification and denitrification in terrestrial and aquatic ecosystems. The main sinks for N 2 O are turnover by denitrification and photolysis and photo-oxidation in the stratosphere. In the linear N=N=O molecule 15 N substitution is possible in two distinct positions: central and terminal. The respective molecules, 14 N 15 N 16 O and 15 N 14 N 16 O, are called isotopomers. It has been demonstrated that N 2 O produced by nitrifying or denitrifying microbes exhibits a different relative abundance of the isotopomers. Therefore, measurements of the site preference (difference in the abundance of the two isotopomers) in N 2 O can be used to determine the source of N 2 O, i.e., nitrification or denitrification. Recent instrument development allows for continuous positiondependent δ 15 N measurements at N 2 O concentrations relevant for studies of atmospheric chemistry. We present results from continuous incubation experiments with denitrifying bacteria, Pseudomonas fluorescens (producing and reducing N 2 O) and Pseudomonas chlororaphis (only producing N 2 O). The continuous measurements of N 2 O isotopomers reveals the transient isotope exchange among KNO 3 , N 2 O, and N 2 . We find bulk isotopic fractionation of −5.01 ‰ ± 1.20 for P. chlororaphis, in line with previous results for production from denitrification. For P. fluorescens, the bulk isotopic fractionation during production of N 2 O is −52.21 ‰ ± 9.28 and 8.77 ‰ ± 4.49 during N 2 O reduction.The site preference (SP) isotopic fractionation for P. chlororaphis is −3.42 ‰ ± 1.69. For P. fluorescens, the calculations result in SP isotopic fractionation values of 5.73 ‰ ± 5.26 during production of N 2 O and 2.41 ‰ ± 3.04 during reduction of N 2 O. In summary, we implemented continuous measurements of N 2 O isotopomers during incubation of denitrifying bacteria and believe that similar experiments will lead to a better understanding of denitrifying bacteria and N 2 O turnover in soils and sediments and ultimately hands-on knowledge on the biotic mechanisms behind greenhouse gas exchange of the globe.

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“…Proximally, whether originating from denitrification or nitrifier-denitrification, bacterial pathways of gaseous N removal would be expected to elevate the 15 N/ 14 N of nitrate relative to any upstream isotope effects (23,24). Indeed, the average isotope effect of denitrification on nitrate is substantial in both pure culture (Ϫ20 Ϯ1.0‰) and in natural soil communities (Ϫ16 Ϯ1.6‰) ( Table S6).…”

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confidence: 99%

Imprint of denitrifying bacteria on the global terrestrial biosphere

Houlton

Bai

2009

Proc. Natl. Acad. Sci. U.S.A.

188

234

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Loss of nitrogen (N) from land limits the uptake and storage of atmospheric CO2 by the biosphere, influencing Earth's climate system and myriads of the global ecological functions and services on which humans rely. Nitrogen can be lost in both dissolved and gaseous phases; however, the partitioning of these vectors remains controversial. Particularly uncertain is whether the bacterial conversion of plant available N to gaseous forms (denitrification) plays a major role in structuring global N supplies in the nonagrarian centers of Earth. Here, we use the isotope composition of N ( 15 N/ 14 N) to constrain the transfer of this nutrient from the land to the water and atmosphere. We report that the integrated 15 N/ 14 N of the natural terrestrial biosphere is elevated with respect to that of atmospheric N inputs. This cannot be explained by preferential loss of 14 N to waterways; rather, it reflects a history of low 15 N/ 14 N gaseous N emissions to the atmosphere owing to denitrifying bacteria in the soil. Parameterizing a simple model with global N isotope data, we estimate that soil denitrification (including N2) accounts for Ϸ1/3 of the total N lost from the unmanaged terrestrial biosphere. Applying this fraction to estimates of N inputs, N2O and NOx fluxes, we calculate that Ϸ28 Tg of N are lost annually via N2 efflux from the natural soil. These results place isotopic constraints on the widely held belief that denitrifying bacteria account for a significant fraction of the missing N in the global N cycle.denitrification ͉ isotope ͉ nitrogen ͉ ecosystem ͉ microbe

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Isotopic variability of N₂O emissions from tropical forest soils

Cited by 134 publications

References 45 publications

Constraining N<sub>2</sub>O emissions since 1940 using firn air isotope measurements in both hemispheres

Constraining N<sub>2</sub>O emissions since 1940 using firn air isotope measurements in both hemispheres

Continuous measurements of nitrous oxide isotopomers during incubation experiments

Imprint of denitrifying bacteria on the global terrestrial biosphere

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Isotopic variability of N2O emissions from tropical forest soils

Cited by 134 publications

References 45 publications

Constraining N&lt;sub&gt;2&lt;/sub&gt;O emissions since 1940 using firn air isotope measurements in both hemispheres

Constraining N&lt;sub&gt;2&lt;/sub&gt;O emissions since 1940 using firn air isotope measurements in both hemispheres

Continuous measurements of nitrous oxide isotopomers during incubation experiments

Imprint of denitrifying bacteria on the global terrestrial biosphere

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Isotopic variability of N₂O emissions from tropical forest soils

Constraining N<sub>2</sub>O emissions since 1940 using firn air isotope measurements in both hemispheres

Constraining N<sub>2</sub>O emissions since 1940 using firn air isotope measurements in both hemispheres