Plants are a natural source of nitrous oxide even in field conditions as explained by 15N site preference

Abstract. Nitrous oxide (N2O) is an important and strong greenhouse gas in the atmosphere and part of a feed-back loop with climate. N2O is produced by microbes during nitrification and denitrification in terrestrial and aquatic ecosystems. The main sinks for N2O are turnover by denitrification and photolysis and photo-oxidation in the stratosphere. The position of the isotope 15N in the linear N = N = O molecule can be distinguished between the central or terminal position (isotopomers of N2O). It has been demonstrated that nitrifying and denitrifying microbes have a different relative preference for the terminal and central position. Therefore, measurements of the site preference in N2O can be used to determine the source of N2O i.e. nitrification or denitrification. Recent instrument development allows for continuous (on the order of days) position dependent δ15N measurements at N2O concentrations relevant for studies of atmospheric chemistry. We present results from continuous incubation experiments with denitrifying bacteria, Pseudomonas fluorescens (producing and reducing N2O) and P. chlororaphis (only producing N2O). The continuous position dependent measurements reveal the transient pattern (KNO3 to N2O and N2, respectively), which can be compared to previous reported site preference (SP) values. We find bulk isotope effects of −5.5 ‰ ± 0.9 for P. chlororaphis. For P. fluorescens, the bulk isotope effect during production of N2O is −50.4 ‰ ± 9.3 and 8.5 ‰ ± 3.7 during N2O reduction. The values for P. fluorescens are in line with earlier findings, whereas the values for P. chlororaphis are larger than previously published δ15Nbulk measurements from production. The calculations of the SP isotope effect from the measurements of P. chlororaphis result in values of −6.6 ‰ ± 1.8. For P. fluorescens, the calculations results in SP values of −5.7 ‰ ± 5.6 during production of N2O and 2.3 ‰ ± 3.2 during reduction of N2O. In summary, we implemented continuous measurements of N2O isotopomers during incubation of denitrifying bacteria and believe that similar experiments will lead to a better understanding of denitrifying bacteria and N2O 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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Factors Affecting Nitrous Oxide Emission from a Sandy Grassland Soil under Controlled Field Conditions

Progress in Nitrogen Cycling Studies ◽

10.1007/978-94-011-5450-5_94 ◽

1996 ◽

pp. 575-579

Author(s):

C. A. Langeveld ◽

P. A. Leffelaar ◽

J. Goudriaan

Keyword(s):

Nitrous Oxide ◽

Nitrous Oxide Emission ◽

Field Conditions ◽

Grassland Soil ◽

Factors Affecting ◽

Sandy Grassland

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Biogeochemical controls and isotopic signatures of nitrous oxide production by a marine ammonia-oxidizing bacterium

Biogeosciences ◽

10.5194/bg-7-2695-2010 ◽

2010 ◽

Vol 7 (9) ◽

pp. 2695-2709 ◽

Cited By ~ 136

Author(s):

C. H. Frame ◽

K. L. Casciotti

Keyword(s):

Nitrous Oxide ◽

Stratospheric Ozone ◽

Nitrifying Bacteria ◽

Site Preference ◽

Ammonia Oxidizing Bacteria ◽

N2o Production ◽

O2 Concentration ◽

Cell Densities ◽

Dissolved O2

Abstract. Nitrous oxide (N2O) is a trace gas that contributes to the greenhouse effect and stratospheric ozone depletion. The N2O yield from nitrification (moles N2O-N produced per mole ammonium-N consumed) has been used to estimate marine N2O production rates from measured nitrification rates and global estimates of oceanic export production. However, the N2O yield from nitrification is not constant. Previous culture-based measurements indicate that N2O yield increases as oxygen (O2) concentration decreases and as nitrite (NO2−) concentration increases. Here, we have measured yields of N2O from cultures of the marine β-proteobacterium Nitrosomonas marina C-113a as they grew on low-ammonium (50 μM) media. These yields, which were typically between 4 × 10−4 and 7 × 10−4 for cultures with cell densities between 2 × 102 and 2.1 × 104 cells ml−1, were lower than previous reports for ammonia-oxidizing bacteria. The observed impact of O2 concentration on yield was also smaller than previously reported under all conditions except at high starting cell densities (1.5 × 106 cells ml−1), where 160-fold higher yields were observed at 0.5% O2 (5.1 μM dissolved O2) compared with 20% O2 (203 μM dissolved O2). At lower cell densities (2 × 102 and 2.1 × 104 cells ml−1), cultures grown under 0.5% O2 had yields that were only 1.25- to 1.73-fold higher than cultures grown under 20% O2. Thus, previously reported many-fold increases in N2O yield with dropping O2 could be reproduced only at cell densities that far exceeded those of ammonia oxidizers in the ocean. The presence of excess NO2− (up to 1 mM) in the growth medium also increased N2O yields by an average of 70% to 87% depending on O2 concentration. We made stable isotopic measurements on N2O from these cultures to identify the biochemical mechanisms behind variations in N2O yield. Based on measurements of δ15Nbulk, site preference (SP = δ15Nα−δ15Nβ), and δ18O of N2O (δ18O-N2O), we estimate that nitrifier-denitrification produced between 11% and 26% of N2O from cultures grown under 20% O2 and 43% to 87% under 0.5% O2. We also demonstrate that a positive correlation between SP and δ18O-N2O is expected when nitrifying bacteria produce N2O. A positive relationship between SP and δ18O-N2O has been observed in environmental N2O datasets, but until now, explanations for the observation invoked only denitrification. Such interpretations may overestimate the role of heterotrophic denitrification and underestimate the role of ammonia oxidation in environmental N2O production.

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Is site preference of N2O a tool to identify benthic denitrifier N2O?

Environmental Chemistry ◽

10.1071/en13021 ◽

2013 ◽

Vol 10 (4) ◽

pp. 281 ◽

Cited By ~ 11

Author(s):

Aurélie Mothet ◽

Mathieu Sebilo ◽

Anniet M. Laverman ◽

Véronique Vaury ◽

André Mariotti

Keyword(s):

Nitrous Oxide ◽

Greenhouse Gas ◽

Nitrate Reduction ◽

Reduction Rate ◽

Aquatic Environments ◽

Site Preference ◽

Reduction Step ◽

Oxide Reduction ◽

Nitrous Oxide Reduction ◽

Highly Correlated

Environmental context The greenhouse gas nitrous oxide is produced by bacteria and emitted from terrestrial and aquatic environments; the origin of this compound can be determined by its 15N intramolecular distribution (site preference). The site preference of nitrous oxide was characterised experimentally in bacterial denitrifying communities under controlled conditions. This study shows the importance of the last step of denitrification on the site preference values, and that complementary methods are necessary to identify the sources of nitrous oxide. Abstract Site preference values of nitrous oxide emitted during different steps of benthic denitrification were determined. Compared to that of nitrous oxide as end product, the site preference during complete denitrification presents a large variation, due to the final step, and is highly correlated with nitrate reduction rate. The nitrous oxide reduction step appears decisive on the site preference values.

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Nitrous oxide distribution and its origin in the central and eastern South Pacific Subtropical Gyre

Biogeosciences ◽

10.5194/bg-4-729-2007 ◽

2007 ◽

Vol 4 (5) ◽

pp. 729-741 ◽

Cited By ~ 28

Author(s):

J. Charpentier ◽

L. Farias ◽

N. Yoshida ◽

N. Boontanon ◽

P. Raimbault

Keyword(s):

Nitrous Oxide ◽

Coastal Upwelling ◽

South Pacific ◽

Site Preference ◽

Natural Environments ◽

Intermediate Water ◽

N2o Production ◽

South Pacific Ocean ◽

Nitrifier Denitrification ◽

Organic Particles

Abstract. The mechanisms of microbial nitrous oxide (N2O) production in the ocean have been the subject of many discussions in recent years. New isotopomeric tools can further refine our knowledge of N2O sources in natural environments. This study compares hydrographic, N2O concentration, and N2O isotopic and isotopomeric data from three stations along a coast-perpendicular transect in the South Pacific Ocean, extending from the center (Sts. GYR and EGY) of the subtropical oligotrophic gyre (~26° S; 114° W) to the upwelling zone (St. UPX) off the central Chilean coast (~34° S). Although AOU/N2O and NO3− trends support the idea that most of the N2O (mainly from intermediate water (200–600 m)) comes from nitrification, N2O isotopomeric composition (intramolecular distribution of 15N isotopes) expressed as SP (site preference of 15N) shows low values (10 to 12\\permil) that could be attributed to the production through of microbial nitrifier denitrification (reduction of nitrite to N2O mediated by ammonium oxidizers). The coincidence of this SP signal with high – stability layer, where sinking organic particles can accumulate, suggests that N2O could be produced by nitrifier denitrification inside particles. It is postulated that deceleration of particles in the pycnocline can modify the advection - diffusion balance inside particles, allowing the accumulation of nitrite and O2 depletion suitable for nitrifier denitrication. As lateral advection seems to be relatively insignificant in the gyre, in situ nitrifier denitrification could account for 40–50% of the N2O produced in this layer. In contrast, coastal upwelling system is characterized by O2 deficient condition and some N deficit in a eutrophic system. Here, N2O accumulates up to 480% saturation, and isotopic and isotopomer signals show highly complex N2O production processes, which presumably reflect both the effect of nitrification and denitrification at low O2 levels on N2O production, but net N2O consumption by denitrification was not observed.

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The isotopic composition of atmospheric nitrous oxide observed at the high-altitude research station Jungfraujoch, Switzerland

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-6495-2020 ◽

2020 ◽

Vol 20 (11) ◽

pp. 6495-6519 ◽

Cited By ~ 2

Author(s):

Longfei Yu ◽

Eliza Harris ◽

Stephan Henne ◽

Sarah Eggleston ◽

Martin Steinbacher ◽

...

Keyword(s):

Nitrous Oxide ◽

Isotopic Composition ◽

High Altitude ◽

High Precision ◽

Large Scale ◽

Late Summer ◽

Site Preference ◽

Research Station ◽

N2o Production ◽

Mixing Ratios

Abstract. Atmospheric nitrous oxide (N2O) levels have been continuously growing since preindustrial times. Mitigation requires information about sources and sinks on the regional and global scales. Isotopic composition of N2O in the atmosphere could contribute valuable constraints. However, isotopic records of N2O in the unpolluted atmosphere remain too scarce for large-scale N2O models. Here, we report the results of discrete air samples collected weekly to biweekly over a 5-year period at the high-altitude research station Jungfraujoch, located in central Switzerland. High-precision N2O isotopic measurements were made using a recently developed preconcentration and laser spectroscopy technique. The measurements of discrete samples were accompanied by in situ continuous measurements of N2O mixing ratios. Our results indicate a pronounced seasonal pattern with minimum N2O mixing ratios in late summer, associated with a maximum in δ15Nbulk and a minimum in intramolecular 15N site preference (δ15NSP). This pattern is most likely due to stratosphere–troposphere exchange (STE), which delivers N2O-depleted but 15N-enriched air from the stratosphere into the troposphere. Variability in δ15NSP induced by changes in STE may be masked by biogeochemical N2O production processes in late summer, which are possibly dominated by a low-δ15NSP pathway of N2O production (denitrification), providing an explanation for the observed seasonality of δ15NSP. Footprint analyses and atmospheric transport simulations of N2O for Jungfraujoch suggest that regional emissions from the planetary boundary layer contribute to seasonal variations of atmospheric N2O isotopic composition at Jungfraujoch, albeit more clearly for δ15NSP and δ18O than for δ15Nbulk. With the time series of 5 years, we obtained a significant interannual trend for δ15Nbulk after deseasonalization (-0.052±0.012 ‰ a−1), indicating that the atmospheric N2O increase is due to isotopically depleted N2O sources. We estimated the average isotopic signature of anthropogenic N2O sources with a two-box model to be -8.6±0.6 ‰ for δ15Nbulk, 34.8±3 ‰ for δ18O and 10.7±4 ‰ for δ15NSP. Our study demonstrates that seasonal variation of N2O isotopic composition in the background atmosphere is important when determining interannual trends. More frequent, high-precision and interlaboratory-compatible measurements of atmospheric N2O isotopocules, especially for δ15NSP, are needed to better constrain anthropogenic N2O sources and thus the contribution of biogeochemical processes to N2O growth on the global scale.

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Intercomparison of fast response commercial gas analysers for nitrous oxide flux measurements under field conditions

Biogeosciences ◽

10.5194/bg-12-415-2015 ◽

2015 ◽

Vol 12 (2) ◽

pp. 415-432 ◽

Cited By ~ 23

Author(s):

Ü. Rannik ◽

S. Haapanala ◽

N. J. Shurpali ◽

I. Mammarella ◽

S. Lind ◽

...

Keyword(s):

Nitrous Oxide ◽

Continuous Wave ◽

Sampling Rate ◽

Fast Response ◽

Systematic Difference ◽

Field Conditions ◽

Coefficient Of Determination ◽

Stochastic Error ◽

Flux Measurements ◽

N2o Fluxes

Abstract. Four gas analysers capable of measuring nitrous oxide (N2O) concentration at a response time necessary for eddy covariance flux measurements were operated from spring until winter 2011 over a field cultivated with reed canary grass (RCG, Phalaris arundinacea, L.), a perennial bioenergy crop in eastern Finland. The instruments were TGA100A (Campbell Scientific Inc.), CW-TILDAS-CS (Aerodyne Research Inc.), N2O / CO-23d (Los Gatos Research Inc.) and QC-TILDAS-76-CS (Aerodyne Research Inc.). The period with high emissions, lasting for about 2 weeks after fertilization in late May, was characterized by an up to 2 orders of magnitude higher emission, whereas during the rest of the campaign the N2O fluxes were small, from 0.01 to 1 nmol m−2 s−1. Two instruments, CW-TILDAS-CS and N2O / CO-23d, determined the N2O exchange with minor systematic difference throughout the campaign, when operated simultaneously. TGA100A produced the cumulatively highest N2O estimates (with 29% higher values during the period when all instruments were operational). QC-TILDAS-76-CS obtained 36% lower fluxes than CW-TILDAS-CS during the first period, including the emission episode, whereas the correspondence with other instruments during the rest of the campaign was good. The reasons for systematic differences were not identified, suggesting further need for detailed evaluation of instrument performance under field conditions with emphasis on stability, calibration and any other factors that can systematically affect the accuracy of flux measurements. The instrument CW-TILDAS-CS was characterized by the lowest noise level (with a standard deviation of around 0.12 ppb at 10 Hz sampling rate) as compared to N2O / CO-23d and QC-TILDAS-76-CS (around 0.50 ppb) and TGA100A (around 2 ppb). We identified that for all instruments except CW-TILDAS-CS the random error due to instrumental noise was an important source of uncertainty at the 30 min averaging level and the total stochastic error was frequently of the same magnitude as the fluxes when N2O exchange was small at the measurement site. Both instruments based on continuous-wave quantum cascade laser, CW-TILDAS-CS and N2O / CO-23d, were able to determine the same sample of low N2O fluxes with a high mutual coefficient of determination at the 30 min averaging level and with minor systematic difference over the observation period of several months. This enables us to conclude that the new-generation instrumentation is capable of measuring small N2O exchange with high precision and accuracy at sites with low fluxes.

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Isotopomeric characterization of nitrous oxide produced by reaction of enzymes extracted from nitrifying and denitrifying bacteria

Biogeosciences ◽

10.5194/bg-11-2679-2014 ◽

2014 ◽

Vol 11 (10) ◽

pp. 2679-2689 ◽

Cited By ~ 26

Author(s):

T. Yamazaki ◽

T. Hozuki ◽

K. Arai ◽

S. Toyoda ◽

K. Koba ◽

...

Keyword(s):

Nitrous Oxide ◽

Pure Culture ◽

Paracoccus Denitrificans ◽

In Vivo Studies ◽

Site Preference ◽

Ammonia Oxidizing Bacteria ◽

Small Contribution ◽

N2o Production ◽

No2 Reduction

Abstract. Nitrous oxide (N2O) is a potent greenhouse gas and produced in denitrification and nitrification by various microorganisms. Site preference (SP) of 15N in N2O, which is defined as the difference in the natural abundance of isotopomers 14N15NO and 15N14NO relative to 14N14NO, has been reported to be a useful tool to quantitatively distinguish N2O production pathways. To determine representative SP values for each microbial process, we firstly measured SP of N2O produced in the enzyme reaction of hydroxylamine oxidoreductase (HAO) purified from two species of ammonia oxidizing bacteria (AOB), Nitrosomonas europaea and Nitrosococcus oceani, and that of nitric oxide reductase (NOR) from Paracoccus denitrificans. The SP value for NOR reaction (−5.9 ± 2.1‰) showed nearly the same value as that reported for N2O produced by P. denitrificans in pure culture. In contrast, SP value for HAO reaction (36.3 ± 2.3‰) was a little higher than the values reported for N2O produced by AOB in aerobic pure culture. Using the SP values obtained by HAO and NOR reactions, we calculated relative contribution of the nitrite (NO2–) reduction (which is followed by NO reduction) to N2O production by N. oceani incubated under different O2 availability. Our calculations revealed that previous in vivo studies might have underestimated the SP value for the NH2OH oxidation pathway possibly due to a small contribution of NO2– reduction pathway. Further evaluation of isotopomer signatures of N2O using common enzymes of other processes related to N2O would improve the isotopomer analysis of N2O in various environments.

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Influence of pore size distribution and soil water content on nitrous oxide emissions

Soil Research ◽

10.1071/sr11112 ◽

2012 ◽

Vol 50 (2) ◽

pp. 125 ◽

Cited By ~ 61

Author(s):

Tony J. van der Weerden ◽

Francis M. Kelliher ◽

Cecile A. M. de Klein

Keyword(s):

Nitrous Oxide ◽

Pore Size Distribution ◽

Pore Size ◽

Water Content ◽

Size Distribution ◽

Soil Water ◽

Gas Diffusion ◽

Field Conditions ◽

Nitrous Oxide Emissions ◽

N2o Emissions

Nitrous oxide (N2O) emissions from agricultural soils have been estimated to comprise about two-thirds of the biosphere’s contribution of this potent greenhouse gas. In pasture systems grazed by farmed animals, where substrate is generally available, spatial variation in emissions, in addition to that cause by the patchiness of urine deposition, has been attributed to soil aeration, as governed by gas diffusion. However, this parameter is not readily measured, and the soil’s water-filled pore space (WFPS) has often been used as a proxy, despite gas diffusion in soils depending on the volumetric fractions of water and air. With changing water content, these fractions will reflect the soil’s pore size distribution. The aims of this study were: (i) to determine if the pore size distribution of two pastoral soils explains previously observed differences in N2O emissions under field conditions, and (ii) to assess the most appropriate soil water/gas diffusion metric for estimating N2O emissions. The N2O emissions were measured from intact cores of two soils (one classified as well drained and one as poorly drained) that had been sampled to a depth of 50 mm beneath grazed pasture. Nitrogen (N, 500 kg N/ha) was applied to soil cores as aqueous nitrate solution, and the cores were drained under controlled conditions at a constant temperature. The poorly drained soil had a larger proportion of macropores (23.5 v. 18.7% in the well-drained soil), resulting in more rapid drainage and increased pore continuity, thereby reducing the duration of anaerobicity, and leading to lower N2O emissions. Emissions were related to three soil water proxies including WFPS, volumetric water content (VWC), and matric potential (MP), and to relative diffusion (RD). All parameters showed highly significant relationships with N2O emissions (P < 0.001), with RD, WFPS, VWC, and MP accounting for 59, 72, 88, and 93% of the variability, respectively. As VWC is more readily determined than MP, the former is potentially more suitable for estimating N2O emission from different soils across a range of time and space scales under field conditions.

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The influence of tillage and fertilizer on the flux and source of nitrous oxide with reference to atmospheric variation using laser spectroscopy

Biogeochemistry ◽

10.1007/s10533-020-00742-y ◽

2021 ◽

Author(s):

Peggy H. Ostrom ◽

Samuel DeCamp ◽

Hasand Gandhi ◽

Joshua Haslun ◽

Nathaniel E. Ostrom

Keyword(s):

Nitrous Oxide ◽

Panicum Virgatum ◽

Fertilizer Treatment ◽

Site Preference ◽

Soil Microbial ◽

The Third ◽

No Till ◽

Wide Range ◽

Atmospheric Variation ◽

Fertilization Experiments

AbstractNitrous oxide (N2O) is the third most important long-lived greenhouse gas and agriculture is the largest source of N2O emissions. Curbing N2O emissions requires understanding influences on the flux and sources of N2O. We measured flux and evaluated microbial sources of N2O using site preference (SP; the intramolecular distribution of 15N in N2O) in flux chambers from a grassland tilling and agricultural fertilization experiments and atmosphere. We identified values greater than that of the average atmosphere to reflect nitrification and/or fungal denitrification and those lower than atmosphere as increased denitrification. Our spectroscopic approach was based on an extensive calibration with 18 standards that yielded SP accuracy and reproducibility of 0.7 ‰ and 1.0 ‰, respectively, without preconcentration. Chamber samples from the tilling experiment taken ~ monthly over a year showed a wide range in N2O flux (0–1.9 g N2O-N ha−1 d−1) and SP (− 1.8 to 25.1 ‰). Flux and SP were not influenced by tilling but responded to sampling date. Large fluxes occurred in October and May in no-till when soils were warm and moist and during a spring thaw, an event likely representing release of N2O accumulated under snow cover. These high fluxes could not be ascribed to a single microbial process as SP differed among chambers. However, the year-long SP and flux data for no-till showed a slight direct relationship suggesting that nitrification increased with flux. The comparative data in till showed an inverse relationship indicating that high flux events are driven by denitrification. Corn (Zea mays) showed high fluxes and SP values indicative of nitrification ~ 4 wk after fertilization with subsequent declines in SP indicating denitrification. Although there was no effect of fertilizer treatment on flux or SP in switchgrass (Panicum virgatum), high fluxes occurred ~ 1 month after fertilization. In both treatments, SP was indicative of denitrification in many instances, but evidence of nitrification/fungal denitrification also prevailed. At 2 m atmospheric N2O SP had a range of 31.1 ‰ and 14.6 ‰ in the grassland tilling and agricultural fertilization experiments, respectively. These data suggest the influence of soil microbial processes on atmospheric N2O and argue against the use of the global average atmospheric SP in isotopic modeling approaches.

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