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1. The Modeled Seasonal Cycles of Surface N ₂ O Fluxes and Atmospheric N ₂ O

   https://doi.org/10.1029/2023GB008010  

   Sun, Qing; Joos, Fortunat; Lienert, Sebastian; Berthet, Sarah; Carroll, Dustin; Gong, Cheng; Ito, Akihiko; Jain, Atul K; Kou‐Giesbrecht, Sian; Landolfi, Angela; et al (July 2024, Global Biogeochemical Cycles)

   Abstract Nitrous oxide (N₂O) is a greenhouse gas and stratospheric ozone‐depleting substance with large and growing anthropogenic emissions. Previous studies identified the influx of N₂O‐depleted air from the stratosphere to partly cause the seasonality in tropospheric N₂O (aN₂O), but other contributions remain unclear. Here, we combine surface fluxes from eight land and four ocean models from phase 2 of the Nitrogen/N₂O Model Intercomparison Project with tropospheric transport modeling to simulate aN₂O at eight remote air sampling sites for modern and pre‐industrial periods. Models show general agreement on the seasonal phasing of zonal‐average N₂O fluxes for most sites, but seasonal peak‐to‐peak amplitudes differ several‐fold across models. The modeled seasonal amplitude of surface aN₂O ranges from 0.25 to 0.80 ppb (interquartile ranges 21%–52% of median) for land, 0.14–0.25 ppb (17%–68%) for ocean, and 0.28–0.77 ppb (23%–52%) for combined flux contributions. The observed seasonal amplitude ranges from 0.34 to 1.08 ppb for these sites. The stratospheric contributions to aN₂O, inferred by the difference between the surface‐troposphere model and observations, show 16%–126% larger amplitudes and minima delayed by ∼1 month compared to Northern Hemisphere site observations. Land fluxes and their seasonal amplitude have increased since the pre‐industrial era and are projected to grow further under anthropogenic activities. Our results demonstrate the increasing importance of land fluxes for aN₂O seasonality. Considering the large model spread, in situ aN₂O observations and atmospheric transport‐chemistry models will provide opportunities for constraining terrestrial and oceanic biosphere models, critical for projecting carbon‐nitrogen cycles under ongoing global warming. 

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2. Rapid photochemical equilibration of isotope bond ordering in O ₂: Photochemical isotope reordering in O2

   https://doi.org/10.1002/2014JD021909  

   Yeung, Laurence Y.; Ash, Jeanine L.; Young, Edward D. (September 2014, Journal of Geophysical Research: Atmospheres)
3. Atmospheric measurements of the terrestrial O ₂  : CO ₂ exchange ratio of a midlatitude forest

   https://doi.org/10.5194/acp-19-8687-2019  

   Battle, Mark O.; Munger, J. William; Conley, Margaret; Sofen, Eric; Perry, Rebecca; Hart, Ryan; Davis, Zane; Scheckman, Jacob; Woogerd, Jayme; Graeter, Karina; et al (January 2019, Atmospheric Chemistry and Physics)

   Abstract. Measurements of atmospheric O2have been used to quantify large-scalefluxes of carbon between the oceans, atmosphere and landsince 1992 (Keeling and Shertz, 1992). With time,datasets have grownand estimates of fluxes have become more precise, buta key uncertainty in these calculations is the exchange ratioof O2and CO2 associated with the net land carbon sink(αB). We present measurements of atmosphericO2 and CO2 collected overa 6-year period from a mixed deciduous forest in centralMassachusetts, USA (42.537∘ N, 72.171∘ W).Using a differential fuel-cell-basedinstrument for O2 and a nondispersive infrared analyzer forCO2, we analyzed airstreams collected within and ∼5 m above the forest canopy. Averaged over the entireperiod of record, we find these two species covary with a slope of -1.081±0.007 mol of O2 per mole ofCO2 (themean and standard error of 6 h periods).If we limit the data to values collected on summer days within thecanopy, the slope is -1.03±0.01. These are the conditions in whichbiotic influences are most likely to dominate.This result is significantlydifferent from the value of −1.1 widely used in O2-basedcalculations of the global carbon budget, suggesting the need for a deeper understanding of the exchange ratios of the various fluxes and pools comprising the net sink. 

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4. Structural changes upon magnetic ordering in magnetocaloric AlFe ₂ B ₂

   https://doi.org/10.1063/5.0007266  

   Oey, Yuzki M.; Bocarsly, Joshua D.; Mann, Dallas; Levin, Emily E.; Shatruk, Michael; Seshadri, Ram (May 2020, Applied Physics Letters)
5. Reactive uptake of N ₂ O ₅ by atmospheric aerosol is dominated by interfacial processes

   https://doi.org/10.1126/science.abd7716  

   Galib, Mirza; Limmer, David T. (February 2021, Science)

   Nitrogen oxides are removed from the troposphere through the reactive uptake of N₂O₅into aqueous aerosol. This process is thought to occur within the bulk of an aerosol, through solvation and subsequent hydrolysis. However, this perspective is difficult to reconcile with field measurements and cannot be verified directly because of the fast reaction kinetics of N₂O₅. Here, we use molecular simulations, including reactive potentials and importance sampling, to study the uptake of N₂O₅into an aqueous aerosol. Rather than being mediated by the bulk, uptake is dominated by interfacial processes due to facile hydrolysis at the liquid-vapor interface and competitive reevaporation. With this molecular information, we propose an alternative interfacial reactive uptake model consistent with existing experimental observations. 

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