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1. Microbial N2O consumption in and above marine N2O production hotspots

   https://doi.org/10.1038/s41396-020-00861-2  

   Sun, Xin; Jayakumar, Amal; Tracey, John C.; Wallace, Elizabeth; Kelly, Colette L.; Casciotti, Karen L.; Ward, Bess B. (May 2021, The ISME Journal)

   null (Ed.)

   Abstract The ocean is a net source of N 2 O, a potent greenhouse gas and ozone-depleting agent. However, the removal of N 2 O via microbial N 2 O consumption is poorly constrained and rate measurements have been restricted to anoxic waters. Here we expand N 2 O consumption measurements from anoxic zones to the sharp oxygen gradient above them, and experimentally determine kinetic parameters in both oxic and anoxic seawater for the first time. We find that the substrate affinity, O 2 tolerance, and community composition of N 2 O-consuming microbes in oxic waters differ from those in the underlying anoxic layers. Kinetic parameters determined here are used to model in situ N 2 O production and consumption rates. Estimated in situ rates differ from measured rates, confirming the necessity to consider kinetics when predicting N 2 O cycling. Microbes from the oxic layer consume N 2 O under anoxic conditions at a much faster rate than microbes from anoxic zones. These experimental results are in keeping with model results which indicate that N 2 O consumption likely takes place above the oxygen deficient zone (ODZ). Thus, the dynamic layer with steep O 2 and N 2 O gradients right above the ODZ is a previously ignored potential gatekeeper of N 2 O and should be accounted for in the marine N 2 O budget. 

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2. Sustained bacterial N2O reduction at acidic pH

   https://doi.org/10.1038/s41467-024-48236-x  

   He, Guang; Chen, Gao; Xie, Yongchao; Swift, Cynthia M.; Ramirez, Diana; Cha, Gyuhyon; Konstantinidis, Konstantinos T.; Radosevich, Mark; Löffler, Frank E. (May 2024, Nature Communications)

   Abstract Nitrous oxide (N₂O) is a climate-active gas with emissions predicted to increase due to agricultural intensification. Microbial reduction of N₂O to dinitrogen (N₂) is the major consumption process but microbial N₂O reduction under acidic conditions is considered negligible, albeit strongly acidic soils harbornosZgenes encoding N₂O reductase. Here, we study a co-culture derived from acidic tropical forest soil that reduces N₂O at pH 4.5. The co-culture exhibits bimodal growth with aSerratiasp. fermenting pyruvate followed by hydrogenotrophic N₂O reduction by aDesulfosporosinussp. Integrated omics and physiological characterization revealed interspecies nutritional interactions, with the pyruvate fermentingSerratiasp. supplying amino acids as essential growth factors to the N₂O-reducingDesulfosporosinussp. Thus, we demonstrate growth-linked N₂O reduction between pH 4.5 and 6, highlighting microbial N₂O reduction potential in acidic soils. 

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3. Nitrous Oxide (N2O) Emissions from Subsurface Soils of Agricultural Ecosystems

   https://doi.org/10.1007/s10021-019-00363-z  

   Shcherbak, Iurii; Robertson, G. Philip (April 2019, Ecosystems)

   Nitrous oxide (N2O) is a major greenhouse gas and cultivated soils are the most important anthropogenic source. N2O production and consumption are known to occur at depths below the A or Ap horizon, but their magnitude in situ is largely unknown. At a site in SW Michigan, USA, we measured N2O concentrations at different soil depths and used diffusivity models to examine the importance of depth-specific production and consumption. We also tested the influence of crop and management practices on subsurface N2O production in (1) till versus no-till, (2) a nitrogen fertilizer gradient, and (3) perennial crops including successional vegetation. N2O concentrations below 20 cm exceeded atmospheric concentrations by up to 900 times, and profile concentrations increased markedly with depth except immediately after fertilization when production was intense in the surface horizon, and in winter, when surface emissions were blocked by ice. Diffusivity analysis showed that N2O production at depth was especially important in annual crops, accounting for over 50% of total N2O production when crops were fertilized at recommended rates. At nitrogen fertilizer rates exceeding crop need, subsurface N2O production contributed 25–35% of total surface emissions. Dry conditions deepened the maximum depth of N2O production. Tillage did not. In systems with perennial vegetation, subsurface N2O production contributed less than 20% to total surface emissions. Results suggest that the fraction of total N2O produced in subsurface horizons can be substantial in annual crops, is low under perennial vegetation, appears to be largely controlled by subsurface nitrogen and moisture, and is insensitive to tillage. 

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4. Non-CO2 greenhouse gases (N2O, CH4, CO) and the ocean

   https://doi.org/10.1016/j.oneear.2022.11.011  

   Bange, Hermann W. (December 2022, One Earth)
5. Shock-tube study of the oxidation of ammonia by N2O

   https://doi.org/10.1016/j.proci.2024.105250  

   Mathieu, Olivier; Grégoire, Claire M; Petersen, Eric L (May 2024, Proceedings of the Combustion Institute)