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The article discusses the consensus on decommissioning piped nitrous oxide from UK and Ireland operating theatre suites due to its inefficiency and environmental impact as a potent greenhouse gas. The joint statement by various medical associations calls for a shift to more efficient methods of supply and highlights the financial and environmental benefits of decommissioning piped nitrous oxide. The article emphasizes the importance of addressing the environmental impact of medical practices and the need for healthcare institutions to prioritize sustainability without compromising patient care. [Extracted from the article]

Atmospheric trace gas measurements can be used to independently assess national greenhouse gas inventories through inverse modeling. Atmospheric nitrous oxide (N2O) measurements made in the United Kingdom (UK) and Republic of Ireland are used to derive monthly N2O emissions for 2013–2022 using two different inverse methods. We find mean UK emissions of 90.5 ± 23.0 (1σ) and 111.7 ± 32.1 (1σ) Gg N2O yr−1 for 2013–2022, and corresponding trends of −0.68 ± 0.48 (1σ) Gg N2O yr−2 and −2.10 ± 0.72 (1σ) Gg N2O yr−2, respectively, for the two inverse methods. The UK National Atmospheric Emissions Inventory (NAEI) reported mean N2O emissions of 73.9 ± 1.7 (1σ) Gg N2O yr−1 across this period, which is 22%–51% smaller than the emissions derived from atmospheric data. We infer a pronounced seasonal cycle in N2O emissions, with a peak occurring in the spring and a second smaller peak in the late summer for certain years. The springtime peak has a long seasonal decline that contrasts with the sharp rise and fall of N2O emissions estimated from the bottom‐up UK Emissions Model (UKEM). Bayesian inference is used to minimize the seasonal cycle mismatch between the average top‐down (atmospheric data‐based) and bottom‐up (process model and inventory‐based) seasonal emissions at a sub‐sector level. Increasing agricultural manure management and decreasing synthetic fertilizer N2O emissions reduces some of the discrepancy between the average top‐down and bottom‐up seasonal cycles. Other possibilities could also explain these discrepancies, such as missing emissions from NH3 deposition, but these require further investigation. Plain Language Summary: Atmospheric nitrous oxide (N2O) is an important greenhouse gas and ozone depleting substance. Atmospheric N2O measurements made in the United Kingdom (UK) and Republic of Ireland were used to derive UK N2O emissions for 2013–2022 using two inverse methods. UK emissions derived using atmospheric N2O measurements were on average 22%–51% higher than emissions reported in the UK National Atmospheric Emissions Inventory. A pronounced seasonal cycle in N2O emissions is inferred from the atmospheric N2O observations which contrasts the seasonal N2O emissions estimated in the bottom‐up (process model and inventory‐based) UK Emissions Model (UKEM). We find increasing agricultural manure management N2O emissions and decreasing synthetic fertilizer N2O emissions reduces some of the discrepancy between the seasonal cycles. Key Points: Atmospheric N2O measurements from 2013 to 2022 are used to evaluate the UK's reported emissions using two inverse methodsEmissions derived from atmospheric data are on average 22%–51% higher than the UK's national emissions inventory values across 2013–2022Agreement between the average top‐down and bottom‐up seasonal emissions was improved by decreasing bottom‐up synthetic fertilizer emissions [ABSTRACT FROM AUTHOR]

Atmospheric concentrations of nitrous oxide (N2O), a potent greenhouse gas that is also responsible for significant stratospheric ozone depletion, have increased in response to intensified use of agricultural fertilizers and other human activities that have accelerated nitrogen cycling processes. Microbial denitrification in soils and sediments is a major source of N2O, produced as an intermediate during the reduction of oxidized forms of nitrogen to dinitrogen gas (N2). Substrate availability (nitrate and organic matter) and environmental factors such as oxygen levels, temperature, moisture, and pH influence rates of denitrification and N2O production. Here we describe the role of physicochemical perturbation (defined here as a change from the ambient environmental conditions) on denitrification and N2O production. Changes in salinity, temperature, moisture, pH, and zinc in agricultural soils induced a short-term perturbation response characterized by lower rates of total denitrification and higher rates of net N2O production. The N2O to total denitrification ratio (N2O : DNF) increased strongly with physicochemical perturbation. A salinity press experiment on tidal freshwater marsh soils revealed that increased N2O production was likely driven by transcriptional inhibition of the nitrous oxide reductase (nos) gene, and that the microbial community adapted to altered salinity over a relatively short (within one month) timeframe. Perturbation appeared to confer resilience to subsequent disturbance, and denitrifiers from an environment without salinity fluctuations (tidal freshwater estuarine sediments) demonstrated a stronger N2O perturbation response than denitrifiers from environments with more variable salinity (oligohaline and mesohaline estuarine sediments), suggesting that the denitrifying community from physicochemically stable environments may have a stronger perturbation response. These findings provide a framework for improving our understanding of the dynamic nature of N2O production in soils and sediments, in which changes in physical and/or chemical conditions initiate a short-term perturbation response that promotes N2O production that moderates over time and with subsequent physicochemical perturbation. [ABSTRACT FROM AUTHOR]

• The nosZ gene of N 2 O reductase determined by paddy soil tillage state. • The clade Ⅱ and Ⅰ nosZ gene was dominated in the tillage and fallow period, respectively. • Heavy-metal pollution inhibited the N 2 O emission while not affecting the genes' switch. • The genus Bradyhizobium most significantly regulated the N 2 O flux. Paddy soils are an important source of atmospheric nitrous oxide (N 2 O). However, numerous studies have focused on N 2 O production during the soil tillage period, neglecting the N 2 O production during the dry fallow period. In this study, we conducted an incubation experiment using the acetylene inhibition technique to investigate N 2 O emission and reduction rates of paddy soil profiles (0-1 m) from Guangdong Province and Jinlin Province in China, with different heavy-metal pollution levels. The abundance and community structures of denitrifying bacteria were determined via quantitative -PCR and Illumina MiSeq sequencing of nosZ, nirK , and nirS genes. Our results showed that the potential N 2 O emission rate, N 2 O production rate, and denitrification rate have decreased with increasing soil vertical depth and heavy-metal pollution. More importantly, we found that the functional gene type of N 2 O reductase switched with the tillage state of paddy soils, which clade Ⅱ nosZ genes were the dominant gene during the tillage period, while clade Ⅰ nosZ genes were the dominant gene during the dry fallow period. The heavy-metal pollution has less effect on the niche differentiation of the nosZ gene. The N 2 O emission rate was significantly regulated by the genus Bradyhizobium , which contains both N 2 O reductase and nitrite reductase genes. Our findings suggests that the nosZ gene of N 2 O reductase can significantly impact the N 2 O emission from paddy soils. [Display omitted] [ABSTRACT FROM AUTHOR]

This study presents atmospheric N2O mole fractions measured from discrete air samples from 2001 to 2018 at Mt. Waliguan (WLG) station (36°17′N, 100°54′E, 3816 m asl) in China, which is a global background station of the World Meteorological Organization/Global Atmosphere Watch Programme (WMO/GAW) in central Eurasia. Observed N2O characteristics of annual means, interannual variability, and seasonal cycles were investigated. Our results show that N2O at WLG possess a distinct increasing trend and a statistically significant seasonal cycle, with an average growth rate of 0.9±0.01 ppb yr−1 (1σ)(1ppb=10−9), which is close to the global mean. The detrended seasonal cycle shows a trough of −0.25±0.04 (1σ) ppb in June and a peak of 0.13±0.07 (1σ) ppb in September, with an amplitude of 0.38 ppb. The pattern is due to combined effects of variation in surface sources, vertical convection within the boundary layer and stratosphere to troposphere transportation (STE). The interannual variability in growth rate was partly driven by quasi-biennial oscillation (QBO) of tropical zonal wind through stratospheric transport into the troposphere. According to a cluster analysis of back trajectories and the corresponding average N2O load, most air masses cover arid and semi-arid areas in inner Asia with low N2O emissions, indicating that the atmospheric N2O at the WLG represents the background N2O level in central Eurasia. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) is an important greenhouse gas which destroys the ozone in the stratosphere. Primary sources of atmospheric N2O are nitrification and denitrification in terrestrial soils and the ocean, and the main sink is photolysis in the stratosphere. Studies have mostly focused on the climate‐related response of N2O during glacial‐interglacial periods. However, its mechanism of variation during the Holocene remains unclear. We present a high‐resolution N2O record from the South Pole Ice (SPICE) core covering the Holocene epoch. The millennial‐scale N2O trend agrees with existing records. We constructed a Holocene composite consisting of the new N2O measurements in SPICE and existing records from other ice core sites. The N2O composite reveals four distinct periods of N2O variation during 11.5–10.0 ka, 10.0–6.2 ka, 6.2–2.2 ka, and 2.2–1.4 ka, including two maxima in 11.0–10.0 ka and 3.0–2.2 ka and minima in 8.8–6.2 ka and approximately 1.4 ka. Apart from these, our new high‐resolution record from SPICE shows a short‐term N2O decrease around 2.8 ka which is not observed in other records possibly due to lower sample resolution and/or higher age smoothing. Comparison of our new Holocene N2O composite with the paleo‐proxy records suggests the plausible linkage of major monsoon (Asian, North African, South and North American, and Australian‐Indonesian monsoon) and upwelling (Arabian Sea and Eastern Tropical South Pacific) regions in regulating the atmospheric N2O during the Holocene. Plain Language Summary: Nitrous oxide (N2O) is an important greenhouse and ozone‐depleting gas. The growing level of N2O in the atmosphere is of global concern, and records of past N2O variations can provide an essential context for understanding the links between N2O and climate change. In this study, we report a new, high‐quality N2O record covering the Holocene epoch using an ice core obtained from the South Pole. Our record shows four important periods of N2O variation during 11.5–10.0 ka, 10.0–6.2 ka, 6.2–2.2 ka, and 2.2–1.4 ka. These include two local N2O maxima in 11.0–10.0 ka and 3.0–2.2 ka and minima in 8.8–6.2 ka and approximately 1.4 ka. Comparison with climate records suggests that the variation in monsoon precipitation and ocean productivity contributed to centennial‐ to millennial‐scale N2O variations during the Holocene. Key Points: High‐resolution N2O record from the South Pole Ice core covering the Holocene epoch is investigated for N2O variationInsight into the key drivers of atmospheric N2O on millennial time scales during the Holocene is providedN2O exhibits two local maxima during 11.0–10.0 ka and 3.0–2.2 ka, and two local minima during 8.8–6.2 ka and at around 1.4 ka [ABSTRACT FROM AUTHOR]

Soils are the largest source of atmospheric nitrous oxide (N2O), a powerful greenhouse gas. Dry soils rarely harbor anoxic conditions to favor denitrification, the predominant N2O-producing process, yet, among the largest N2O emissions have been measured after wetting summer-dry desert soils, raising the question: Can denitrifiers endure extreme drought and produce N2O immediately after rainfall? Using isotopic and molecular approaches in a California desert, we found that denitrifiers produced N2O within 15 minutes of wetting dry soils (site preference = 12.8 ± 3.92 per mil, δ15Nbulk = 18.6 ± 11.1 per mil). Consistent with this finding, we detected nitrate-reducing transcripts in dry soils and found that inhibiting microbial activity decreased N2O emissions by 59%. Our results suggest that despite extreme environmental conditions--months without precipitation, soil temperatures of≥40°C, and gravimetric soilwater content of <1%--bacterial denitrifiers can account for most of the N2O emitted when dry soils are wetted. [ABSTRACT FROM AUTHOR]

This article explores the concept of the Anthropocene, a term used to describe the period in which human activities have significantly impacted the Earth's environment. It discusses the "Great Acceleration," which encompasses processes like climate change, urbanization, and species extinction. The recognition of the Anthropocene as a geological unit is a topic of ongoing debate, and geographers play a crucial role in understanding and defining this concept. The article also highlights the challenges in determining the beginning of the Anthropocene and the importance of using various datasets to study the Great Acceleration. Geographers are encouraged to contribute papers that offer conceptual frameworks and solutions for addressing the challenges of the Anthropocene, with the Covid-19 pandemic serving as a template for studying this phenomenon. [Extracted from the article]

Keywords: addiction; B12 deficiency; Entonox™; greenhouse gas; nitrous oxide; occupational exposure EN addiction B12 deficiency Entonox™ greenhouse gas nitrous oxide occupational exposure 1315 1319 5 10/11/23 20231101 NES 231101 Discovered by Joseph Priestley in 1772, the anaesthetic potential of nitrous oxide was introduced to the world in 1845 by Horace Wells. They also found that nitrous oxide depleted hepatic stores of methyl-cobalamin by 20-60% and produced cobalamin analogues which are excreted preferentially and might not be as active as cobalamin [[2]]. Environmental pollution and greenhouse gas Data from the US Environmental Protection Authority showed that medical use of nitrous oxide contributed to <1% of global nitrous oxide pollution, with the remainder coming from agricultural, aviation, automotive and industrial processes [[20]]. [Extracted from the article]

The increasing atmospheric nitrous oxide (N2O) concentration stems from the development of agriculture. However, N2O emissions from global rice‐based ecosystems have not been explicitly and systematically quantified. Therefore, this study aims to estimate the spatiotemporal magnitudes of the N2O emissions from global rice‐based ecosystems and determine different contribution factors by improving a process‐based biogeochemical model, TRIPLEX‐GHG v2.0. Model validation suggested that the modeled N2O agreed well with field observations under varying management practices at daily, seasonal, and annual steps. Simulated N2O emissions from global rice‐based ecosystems exhibited significant increasing trends from 0.026 ± 0.0013 to 0.18 ± 0.003 TgN yr−1 from 1910 to 2020, with ∼69.5% emissions attributed to the rice‐growing seasons. Irrigated rice ecosystems accounted for a majority of global rice N2O emissions (∼76.9%) because of their higher N2O emission rates than rainfed systems. Regarding spatial analysis, Southern China, Northeast India, and Southeast Asia are hotspots for rice‐based N2O emissions. Experimental scenarios revealed that N fertilizer is the largest global rice‐N2O source, especially since the 1960s (0.047 ± 0.010 TgN yr−1, 35.24%), while the impact of expanded irrigation plays a minor role. Overall, this study provides a better understanding of the rice‐based ecosystem in the global agricultural N2O budget; further, it quantitively demonstrated the central role of N fertilizer in rice‐based N2O emissions by including rice crop calendars, covering non‐rice growing seasons, and differentiating the effects of various water regimes and input N forms. Our findings emphasize the significance of co‐management of N fertilizer and water regimes in reducing the net climate impact of global rice cultivation. Plain Language Summary: Nitrous oxide (N2O) is a greenhouse gas with ∼300 times greater effect on climate warming than carbon dioxide. Global croplands represent the largest source of anthropogenic N2O emissions. However, the contribution of global rice‐based cropping ecosystems to the N2O budget remains largely uncertain because of inconsistent observed results. Inspired by the increasing availability of reliable global data sets, we improved and applied a process‐based biogeochemical model by describing the dynamics of various microbial activities to simulate N2O emissions from rice‐based ecosystems on a global scale. Model simulations showed that 0.18 million tons of N2O‐N were emitted from global rice‐based N2O emissions in the 2010s, which was five times larger than that in the 1910s. In the context of regional contribution, southern China, northern India, and Southeast Asia are responsible for more than 80% of the total emissions during 1910–2020. Results suggest that N fertilizer is the most important rice‐N2O source quantitively and that increasing irrigation exerts a buffering effect. This study confirmed the potential mitigating effect of co‐managing N fertilizer and irrigation on mitigating rice‐based N2O emissions globally. Key Points: N2O emissions from global rice‐based ecosystem increased from 0.026 to 0.18 TgN yr−1 between 1910 and 2020Irrigated rice‐based ecosystems showed larger N2O fluxes than rainfed rice globally due to higher N fertilizer use and frequent aerationsN fertilizer represents the largest N2O source, and co‐management of N fertilizer and flooding regimes is important for mitigation [ABSTRACT FROM AUTHOR]

Oceans are identified as potent sources of atmospheric nitrous oxide (N2O), while the magnitude of its flux and microbial production mechanisms remain uncertain in highly perturbed coastal zones. Here, the first analyses of N2O isotopocule signatures in the East China Sea (ECS) are presented, along with hydroxylamine (NH2OH) and N2O concentrations, to clarify the dominant N2O production processes in coastal water. In the ECS in October 2015, N2O ranged from 6.3 to 33.1 nmol L−1, equivalent to 99%–251% saturation, leading to air‐sea fluxes of 1.6–10.5 μmol m−2 d−1 (4.8 ± 2.5 μmol m−2 d−1) using the W2014 formula. The coexistence of high levels of NH4+, NH2OH, and NO2− indicated the potential for nitrification and/or hybrid N2O formation. In the shallow water (<300 m), the concentration (∼9.3 nmol L−1), δ15Nbulk–N2O (∼6.8‰), δ18O–N2O (∼45.1‰), and 15N site preference (SP, ∼14.8‰) of N2O were close to the isotopic signatures in atmospheric N2O, whereas values in the deep water increased with depth, with N2O reaching maxima of 33.1 nmol L−1, 8.6‰, 54.7‰, and 18.7‰, respectively. From the dual N2O isotopocule mapping approach, almost equal contributions of archaeal N2O production (archaeal nitrification and/or hybrid mechanism, ∼47%) and nitrifier denitrification (or denitrification) (∼53%) to total in situ N2O production were identified for the shallow water, but archaeal nitrification was responsible for ∼83% of the deeper N2O production. Moreover, the far‐field lateral advection from other areas served as a potential physical supply of deeper N2O. Our findings enhance the understanding of N2O dynamics in coastal waters. Plain Language Summary: Nitrous oxide (N2O) is a powerful climatically trace gas, of which the global warming potential per mole is nearly 300 times that of carbon oxide, and it also acts as a significant ozone depletion agent. Coastal seas, which are influenced by anthropogenic perturbations, are identified as potent sources of N2O. Based on the isotopic analysis of dissolved N2O and other environmental parameters in the ECS, a northwestern Pacific marginal sea, we can obtain a further understanding of the N2O biogeochemical dynamics in coastal waters. In the ECS, N2O production in the shallow water was attributed to a mixed pool of archaeal N2O production and nitrifier denitrification (or denitrification) with almost equal contributions, while archaeal nitrification represented the major source of deeper N2O production. The advected supply of N2O‐enriched waters from other regions and air‐sea gas exchange were important physical processes in coastal N2O cycling. Deciphering coastal N2O biogeochemical dynamics would further constrain and predict global climate change. Key Points: Archaeal N2O production (archaeal nitrification and/or hybrid formation) and nitrifier denitrification contributed equally to shallow N2OArchaeal nitrification dominated deep N2O productionAir‐sea gas exchange and water mass mixing are important physical processes influencing coastal N2O cycling [ABSTRACT FROM AUTHOR]

Despite the key role of the Arctic in the global Earth system, year-round in-situ atmospheric composition observations within the Arctic are sparse and mostly rely on measurements at ground-based coastal stations. Measurements of a suite of in-situ trace gases were performed in the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. These observations give a comprehensive picture of year-round near-surface atmospheric abundances of key greenhouse and trace gases, i.e., carbon dioxide, methane, nitrous oxide, ozone, carbon monoxide, dimethylsulfide, sulfur dioxide, elemental mercury, and selected volatile organic compounds (VOCs). Redundancy in certain measurements supported continuity and permitted cross-evaluation and validation of the data. This paper gives an overview of the trace gas measurements conducted during MOSAiC and highlights the high quality of the monitoring activities. In addition, in the case of redundant measurements, merged datasets are provided and recommended for further use by the scientific community. Measurement(s) atmospheric ozone • atmospheric carbon dioxide • atmospheric methane • atmospheric carbon monoxide • atmospheric nitrous oxide • atmospheric dimethylsulfide • atmospheric sulfur dioxide • atmospheric gaseous elemental mercury • volatile organic compounds Technology Type(s) ozone analyzer • carbon dioxide analyzer • methane analyzer • carbon monoxide analyzer • nitrous oxide analyzer • dimethylsulfide analyzer • sulfur dioxide analyzer • gaseous elemental mercury analyzer • gas chromatography-mass spectrometry Sample Characteristic - Environment Atmosphere Sample Characteristic - Location central Arctic [ABSTRACT FROM AUTHOR]

Nitrous oxide is a potent greenhouse gas (GHG) and ozone-depleting substance, whose atmospheric abundance has risen throughout the contemporary record. In this work, we carry out the first global hierarchical Bayesian inversion to solve for nitrous oxide emissions, which includes prior emissions with truncated Gaussian distributions and Gaussian model errors, in order to examine the drivers of the atmospheric surface growth rate. We show that both emissions and climatic variability are key drivers of variations in the surface nitrous oxide growth rate between 2011 and 2020. We derive increasing global nitrous oxide emissions, which are mainly driven by emissions between 0 and 30 ∘ N, with the highest emissions recorded in 2020. Our mean global total emissions for 2011–2020 of 17.2 (16.7–17.7 at the 95 % credible intervals) Tg N yr -1 , comprising of 12.0 (11.2–12.8) Tg N yr -1 from land and 5.2 (4.5–5.9) Tg N yr -1 from ocean, agrees well with previous studies, but we find that emissions are poorly constrained for some regions of the world, particularly for the oceans. The prior emissions used in this and other previous work exhibit a seasonal cycle in the extra-tropical Northern Hemisphere that is out of phase with the posterior solution, and there is a substantial zonal redistribution of emissions from the prior to the posterior. Correctly characterizing the uncertainties in the system, for example in the prior emission fields, is crucial for deriving posterior fluxes that are consistent with observations. In this hierarchical inversion, the model-measurement discrepancy and the prior flux uncertainty are informed by the data, rather than solely through "expert judgement". We show cases where this framework provides different plausible adjustments to the prior fluxes compared to inversions using widely adopted, fixed uncertainty constraints. [ABSTRACT FROM AUTHOR]

Estuaries at the global scale are significant but highly uncertain sources of atmospheric nitrous oxide (N2O), which is an intense greenhouse gas and ozone depletion agent. As the largest estuary in the United States, the Chesapeake Bay is suggested to be a spatially and temporally variable source and sink of N2O. However, limited observations of N2O cycling preclude us from estimating and predicting its net N2O flux. To improve our mechanistic understanding of the processes that control the N2O flux at the point of production, we applied multiple 15N tracers (NH4+15, 15N‐urea, NO2−15, and NO3−15) to separately track N2O production from nitrification and denitrification under in situ and manipulated O2 concentrations in the Chesapeake Bay. Nitrification was the major N2O production pathway in oxic waters (up to 7.5 nmol N2O L−1 d−1). In contrast, denitrification dominated N2O production from hypoxic/anoxic waters (up to 20 nmol N2O L−1 d−1). N2O production from urea was observed for the first time in estuarine waters. The contribution from urea was small, but interestingly, showed a depth pattern distinct from other N2O precursors. Experimentally lowering the O2 concentration substantially enhanced N2O production. Therefore, the expansion of hypoxic and anoxic zones in the Chesapeake Bay under climate change as suggested by some climate models may favor the production of N2O, potentially providing positive feedback on warming. Overall, our study provides mechanistic constraints on N2O dynamics that could benefit modeling studies to better estimate the N2O flux in the Chesapeake Bay and other coastal environments. [ABSTRACT FROM AUTHOR]

Inland ships are an important source of NO x , especially for cities along busy waterways. The amount and effect of these emissions depends on the traffic density and the NO x emission rates of the individual vessels. Monitoring of ship emissions is usually carried out using in situ instruments on land and often relative NO x emission factors, e.g. the amount of emitted pollutants per amount of burnt fuel is reported, but in this study, NO x emission rates in g s-1 are investigated. Within the EU Life project Clean Inland Shipping (CLINSH), a new approach to calculate NO x emission rates from data of in situ measurement stations has been developed and is presented in this study. Peaks (i.e. elevated concentrations) of NO x were assigned to the corresponding source ships and each ship passage was simulated using a Gaussian-puff-model in order to derive the emission rate. In total over 32900 ship passages have been monitored over the course of 4 years. The emission rates of NO x were investigated with respect to ship speed, ship size and direction of travel. Individual comparisons of the on-shore emission rates and those made on-board of selected CLINSH ships show good agreement. Also the emission rates are of similar magnitude as emission factors from previous studies. In contrast to relative emission factors (in grams per kilogram fuel), the emission rates (in grams per second) do not need further knowledge about the fuel consumption of the ship and can therefore be used directly to investigate the effect of ship traffic on air quality. [ABSTRACT FROM AUTHOR]

Heavy grassland degradation is evident across the Tibetan Plateau. However, atmospheric nitrous oxide (N2O) emission rates and their underlying driving mechanisms in the southeast regions and across the Tibetan Plateau remain unclear. We analyzed the N2O emission rates of heavily degraded and undegraded alpine meadow soil incubation using gas chromatography in three river sources and meta-analysis methods across the Tibetan Plateau. The N2O emission rates of the heavily degraded and control meadows were respectively 4.29 ± 0.64 and 3.27 ± 0.53 g kg−1 h−1 in the southeast Tibetan Plateau (p < 0.01), indicating an increase of 31.16% on the N2O flux of heavy degradation. Heavy degradation increased N2O emission rates by 0.55 ± 0.14 (95% confidence interval: 0.27–0.83) through meta-analysis. High degradation increased by approximately 71.6% compared with that of the control. The water-filled pore space (WFPS) significantly influenced the N2O emission rate based on the moderator test (p < 0.05). The mixed-effect model results revealed that WFPS, soil nitrate, and bulk soil could explain 59.90%, 16.56%, and 15.19% of the variation in the N2O emission rates between the control and heavily degraded meadows, respectively. In addition, the N2O emission rates of heavily degraded meadows can be reduced by increasing WFPS and bulk density, and by reducing the soil nitrate content. [ABSTRACT FROM AUTHOR]

Atmospheric nitrous oxide (N2O) increase contributes substantially to global climate change due to its large global warming potential. Soil N2O emissions have been widely studied, but plants have so far been ignored, even though they are known as an important source of N2O. The specific objectives of this study are to (1) reveal the effects of nitrogen and biochar addition on plant functional traits and N2O emission of Cinnamomum camphora seedlings; (2) find out the possible leaf traits affecting plant N2O emissions. The effects of nitrogen and biochar on plant functional traits and N2O emissions from plants using C. camphora seedlings were investigated. Plant N2O emissions, growth, each organ biomass, each organ nutrient allocation, gas exchange parameters, and chlorophyll fluorescence parameters of C. camphora seedlings were measured. Further investigation of the relationships between plant N2O emission and leaf traits was performed by simple linear regression analysis, principal component analysis (PCA), and structural equation model (SEM). It was found that nitrogen addition profoundly increased cumulative plant N2O emissions (+109.25%), which contributed substantially to the atmosphere's N2O budget in forest ecosystems. Plant N2O emissions had a strong correlation to leaf traits (leaf TN, P n , G s , C i , T r, WUE L , α, ETR max, I k , Fv/Fm , Y (II), and SPAD). Structural equation modelling revealed that leaf TN, leaf TP, P n , C i , T r, WUE L , α, ETR max, and I k were key traits regulating the effects of plants on N2O emissions. These results provide a direction for understanding the mechanism of N2O emission from plants and provide a theoretical basis for formulating corresponding emission reduction schemes. [ABSTRACT FROM AUTHOR]

This paper presents an algorithm for the retrieval of nitrous oxide profiles from the Atmospheric InfraRed Sounder (AIRS) on the Earth Observing System (EOS)/Aqua using a nonlinear optimal estimation method. First, an improved Optimal Sensitivity Profile (OSP) algorithm for channel selection is proposed based on the weighting functions and the transmissions of the target gas and interfering gases, with 13 channels selected for inversion in this algorithm. Next, the data of the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) aircraft and the Earth System Research Laboratory (ESRL) are used to verify the retrieval results, including the atmospheric nitrous oxide profile and the column concentration. The results show that using AIRS satellite data, the atmospheric nitrous oxide profile between 300–900 hPa can be well retrieved with an accuracy of ~0.1%, which agrees with the corresponding Jacobian peak interval of selected channels. Analysis of the AIRS retrievals demonstrates that the AIRS measurements provide useful information to capture the spatial and temporal variations in nitrous oxide between 300–900 hPa. [ABSTRACT FROM AUTHOR]

Atmospheric nitrous oxide (N2O) contributes to global warming and stratospheric ozone depletion, so reducing uncertainty in estimates of emissions from different sources is important for climate policy. In this study, we simulate atmospheric N2O using an atmospheric chemistry-transport model (ACTM), and the results are first compared with the in situ measurements. Five combinations of known (a priori) N2O emissions due to natural soil, agricultural land, other human activities, and sea-air exchange are used. The N2O lifetime is 127.6 ± 4.0 yr in the control ACTM simulation (range indicates interannual variability). Regional N2O emissions are optimized using Bayesian inverse modeling for 84 partitions of the globe at monthly intervals, using measurements at 42 sites around the world covering 1997 - 2019. The best estimated global land and ocean emissions are 12.99 ± 0.22 TgN yr-1 and 2.74 ± 0.27 TgN yr-1, respectively, for 2000 - 2009, and 14.30 ± 0.20 TgN yr-1 and 2.91 ± 0.27 TgN yr-1, respectively, for 2010 - 2019. On regional scales, we find that the most recent ocean emission estimation, with lower emissions in the Southern Ocean regions, fits better with that predicted by the inversions. Marginally higher (lower) emissions than the inventory/model for the tropical (extratropical) land regions are estimated and validated using independent aircraft observations. Global land and ocean emission variabilities show a statistically significant correlation with El Niño Southern Oscillation (ENSO). Analysis of regional land emissions shows increases over America (Temperate North, Central, and Tropical), Central Africa, and Asia (South, East, and Southeast) between the 2000s and 2010s. Only Europe as a whole recorded a slight decrease in N2O emissions due to the chemical industry. Our inversions suggest revisions to seasonal emission variations for three of the 15 land regions (East Asia, Temperate North America, and Central Africa), and the Southern Ocean region. The terrestrial ecosystem model (Vegetation Integrative SImulator for Trace Gases) can simulate annual total emissions in agreement with the observed N2O growth rate since 1978, but the lag-time scales of N2O emissions from nitrogen fertilizer application may need to be revised. [ABSTRACT FROM AUTHOR]

The atmospheric concentration of nitrous oxide (N2O) has increased by 23% since the pre‐industrial era, which substantially destructed the stratospheric ozone layer and changed the global climate. However, it remains uncertain about the reasons behind the increase and the spatiotemporal patterns of soil N2O emissions, a primary biogenic source. Here, we used an integrative land ecosystem model, Dynamic Land Ecosystem Model (DLEM), to quantify direct (i.e., emitted from local soil) and indirect (i.e., emissions related to local practices but occurring elsewhere) N2O emissions in the contiguous United States during 1900–2019. Newly developed geospatial data of land‐use history and crop‐specific agricultural management practices were used to force DLEM at a spatial resolution of 5 arc‐min by 5 arc‐min. The model simulation indicates that the U.S. soil N2O emissions totaled 0.97 ± 0.06 Tg N year−1 during the 2010s, with 94% and 6% from direct and indirect emissions, respectively. Hot spots of soil N2O emission are found in the US Corn Belt and Rice Belt. We find a threefold increase in total soil N2O emission in the United States since 1900, 74% of which is from agricultural soil emissions, increasing by 12 times from 0.04 Tg N year−1 in the 1900s to 0.51 Tg N year−1 in the 2010s. More than 90% of soil N2O emission increase in agricultural soils is attributed to human land‐use change and agricultural management practices, while increases in N deposition and climate warming are the dominant drivers for N2O emission increase from natural soils. Across the cropped acres, corn production stands out with a large amount of fertilizer consumption and high‐emission factors, responsible for nearly two‐thirds of direct agricultural soil N2O emission increase since 1900. Our study suggests a large N2O mitigation potential in cropland and the importance of exploring crop‐specific mitigation strategies and prioritizing management alternatives for targeted crop types. [ABSTRACT FROM AUTHOR]

The presence of biogenic gases such as oxygen, methane, and nitrous oxide (N2O) in the atmospheres of extraterrestrial bodies has been postulated as a biosignature of life. Abiotic N2O production was documented recently in Don Juan Pond (DJP), Antarctica, a cold, hypersaline Mars analog environment. Here we quantify the temperature‐driven kinetics of abiotic N2O production and combine this with stable isotope labeling to demonstrate that N2O is produced from DJP sediment and brine at Mars‐analog temperatures down to at least −40°C. Further, we show that at any given temperature, N2O production is controlled by the availability of reduced Fe‐bearing minerals rather than nitrate. We conclude that abiotic N2O production is possible on Mars and on other extraterrestrial bodies and exoplanets. Thus, the presence of atmospheric N2O on these bodies should not be taken by itself as an indicator of microbial life. Plain Language Summary: The search for extraterrestrial life has long captured our collective imagination, but it is hindered by the difficulty of actually visiting extraterrestrial planets, moons, asteroids, etc. to search for life. An alternative strategy is to remotely analyze the atmospheres of these planets to look for trace gases that exist in Earth's atmosphere because they are produced by living organisms across the biosphere. One such gas is nitrous oxide. We visited a remote, extremely cold, and salty desert pond in the Dry Valleys of Antarctica, an environment that is considered to be among the most similar to Mars that can be found on Earth. There, we studied the production of nitrous oxide in the absence of microbial life. We show that this gas is produced through the interaction between rock and chemical precursors in water at extremely cold temperatures (−40°C) that are similar to those observed on Mars. Because nitrous oxide can be produced in the absence of life, we conclude that its presence in the atmosphere of another planet or planetary moon does not necessarily indicate the presence of life on that object. Key Points: Abiotic nitrous oxide production occurs at temperatures down to −40°C in Mars‐analog environment (DJP), AntarcticaAcross temperatures, abiotic nitrous oxide production is controlled by the availability of reduced iron rather than nitrate availabilityThe presence of atmospheric nitrous oxide on an extraterrestrial body should not by itself be considered evidence of life [ABSTRACT FROM AUTHOR]

Globally, tropical forests are assumed to be an important source of atmospheric nitrous oxide (N2O) and sink for methane (CH4). Yet, although the Congo Basin comprises the second largest tropical forest and is considered the most pristine large basin left on Earth, in situ N2O and CH4 flux measurements are scarce. Here, we provide multi-year data derived from on-ground soil flux (n = 1558) and riverine dissolved gas concentration (n = 332) measurements spanning montane, swamp, and lowland forests. Each forest type core monitoring site was sampled at least for one hydrological year between 2016 - 2020 at a frequency of 7-14 days. We estimate a terrestrial CH4 uptake (in kg CH4-C ha−1 yr−1) for montane (−4.28) and lowland forests (−3.52) and a massive CH4 release from swamp forests (non-inundated 2.68; inundated 341). All investigated forest types were a N2O source (except for inundated swamp forest) with 0.93, 1.56, 3.5, and −0.19 kg N2O-N ha−1 yr−1 for montane, lowland, non-inundated swamp, and inundated swamp forests, respectively. The Congo Basin is home to the second largest stretch of continuous tropical forest, but the magnitude of greenhouse fluxes are poorly understood. Here the authors analyze gas samples and find the region is not actually a hotspot of N2O emissions. [ABSTRACT FROM AUTHOR]

The causes of methane's renewed rise since 2007, accelerated growth from 2014 and record rise in 2020, concurrent with an isotopic shift to values more depleted in 13C, remain poorly understood. This rise is the dominant departure from greenhouse gas scenarios that limit global heating to less than 2°C. Thus a comprehensive understanding of methane sources and sinks, their trends and inter-annual variations are becoming more urgent. Efforts to quantify both sources and sinks and understand latitudinal and seasonal variations will improve our understanding of the methane cycle and its anthropogenic component. Nationally declared emissions inventories under the UN Framework Convention on Climate Change (UNFCCC) and promised contributions to emissions reductions under the UNFCCC Paris Agreement need to be verified independently by top-down observation. Furthermore, indirect effects on natural emissions, such as changes in aquatic ecosystems, also need to be quantified. Nitrous oxide is even more poorly understood. Despite this, options for mitigating methane and nitrous oxide emissions are improving rapidly, both in cutting emissions from gas, oil and coal extraction and use, and also from agricultural and waste sources. Reductions in methane and nitrous oxide emission are arguably among the most attractive immediate options for climate action. This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 1)'. [ABSTRACT FROM AUTHOR]

Increased concentration of atmospheric nitrous oxide (N2O), a potent greenhouse gas (GHG), is of great concern due to its impact on ozone layer depletion leading to climate change. Ozone layer depletion allows penetration of ultraviolet radiations, which are hazardous to human health. Climate change culminates in reduced food productivity. Limited empirical studies have been conducted in Sub-Saharan Africa (SSA) to quantify and understand the dynamics of soil N2O fluxes from smallholder cropping systems. The available literature on soil N2O fluxes in SSA is limited; hence, there is a pressing need to consolidate it to ease mitigation targeting and policy formulation initiatives. We reviewed the state of N2O emissions from selected cropping systems, drivers that significantly influence N2O emissions, and probable soil N2O emissions mitigation options from 30 studies in SSA cropping systems have been elucidated here. The review outcome indicates that coffee, tea, maize, and vegetables emit N2O ranging from 1 to 1.9, 0.4 to 3.9, 0.1 to 4.26, and 48 to 113.4 kg N2O-N ha-1 yr−1, respectively. The yield-scaled and N2O emissions factors ranged between 0.08 and 67 g N2O-N kg−1 and 0.01 and 4.1%, respectively, across cropping systems. Soil characteristics, farm management practices, and climatic and environmental conditions were significant drivers influencing N2O emissions across SSA cropping systems. We found that site-specific soil N2O emissions mitigation measures are required due to high variations in N2O drivers across SSA. We conclude that appropriate fertilizer and organic input management combined with improved soil management practices are potential approaches in N2O emissions mitigation in SSA. We recommend that (i) while formulating soil N2O emissions mitigation approaches, in SSA, policymakers should consider site-specific targeting approaches, and (ii) more empirical studies need to be conducted in diverse agroecological zones of SSA to qualify various mitigation options on N2O emissions, yield-scaled N2O emissions, and N2O emission factors which are essential in improving national and regional GHG inventories. [ABSTRACT FROM AUTHOR]

The precise measurement of the amount fraction of atmospheric nitrous oxide (N 2 O) is required to understand global emission trends. Analysis of the site-specific stable isotopic composition of N 2 O provides a means to differentiate emission sources. The availability of accurate reference materials of known N 2 O amount fractions and isotopic composition is critical for achieving these goals. We present the development of nitrous oxide gas reference materials for underpinning measurements of atmospheric composition and isotope ratio. Uncertainties target the World Metrological Organisation Global Atmosphere Watch (WMO-GAW) compatibility goal of 0.1 nmol mol -1 and extended compatibility goal of 0.3 nmol mol -1 , for atmospheric N 2 O measurements in an amount fraction range of 325–335 nmol mol -1. We also demonstrate the stability of amount fraction and isotope ratio of these reference materials and present a characterisation study of the cavity ring-down spectrometer used for analysis of the reference materials. [ABSTRACT FROM AUTHOR]

Agricultural soils are the largest anthropogenic source of atmospheric nitrous oxide (N 2 O) that causes global warming and stratospheric ozone depletion. In addition to the well-known emission associated with fertilization, significant N 2 O emission during the harvest season has been reported for soybean fields. Because soybean production is increasing, it is important to understand the production and consumption mechanisms of N 2 O in soybean fields. This study aimed to identify the microbial production processes using the ratios of isotopically substituted molecules, isotopocules. We also investigated the effectiveness of inoculating soybean with symbiotic nitrogen-fixing soil bacteria (rhizobia) with a high N 2 O-reducing ability, which was suggested as a mitigation option for N 2 O emission from soybean fields, on the basis of the characteristic isotope effect during N 2 O reduction. Along with semi-continuous flux measurements, weekly sampling and analysis of soil-emitted gas and soils were conducted in an experimental soybean field for two periods, after fertilization and before harvest, in two successive years. The isotopocule ratios of N 2 O emitted after fertilization suggested that it was produced by bacterial denitrification and nitrifier denitrification with smaller contributions from nitrification and fungal denitrification. Those for preharvest emission showed that N 2 O was produced by bacterial denitrification, including the process mediated by nodule rhizobia, with little progress of N 2 O reduction. We could not detect any difference between soybeans inoculated with rhizobia with different N 2 O reducing activity (nosZ − dominant, nosZ +, and nosZ ++) because of the weak N 2 O reduction, probably due to relatively aerobic soil conditions. Since temporal changes in the N 2 O isotopocule ratios further implied that the rate of N 2 O reduction decreased in the later phase of autumn emission, suitable soil conditions are crucial for effective N 2 O reduction by inoculation of high nosZ -expressing rhizobia. • Autumn N 2 O emission from soybean field is caused by bacterial denitrification. • Bacterial N 2 O reduction is very sensitive to soil conditions. • Nitrate in soils and soybean nodules could be distinct in isotopic signature. [ABSTRACT FROM AUTHOR]

The article discusses the impact of the healthcare sector on climate change, particularly in relation to anesthesia practices. Volatile anesthetic agents (VAAs) are potent greenhouse gases and contribute to global warming. The article suggests several strategies to minimize the carbon footprint of anesthesia practices, including the use of total intravenous anesthesia (TIVA) and low-flow anesthesia (LFA), limiting the use of high-GWP VAAs, opting for regional anesthesia, and adopting reusable devices. The article also highlights the importance of proper disposal of anesthetic waste and the need for research and collaboration to develop more sustainable practices. The responsibility to address these issues is shared by both the government and the healthcare industry. [Extracted from the article]

The precise measurement of the amount fraction of atmospheric nitrous oxide (N2O) is required to understand global emission trends. Analysis of the site-specific stable isotopic composition of N2O provides a means to differentiate emission sources. The availability of accurate reference materials of known N2O amount fractions and isotopic composition is critical for achieving these goals. We present the development of nitrous oxide gas reference materials for underpinning measurements of atmospheric composition and isotope ratio. Uncertainties target the World Metrological Organisation Global Atmosphere Watch (WMO-GAW) compatibility goal of 0.1 nmol mol-1 and extended compatibility goal of 0.3 nmol mol-1, for atmospheric N2O measurements in an amount fraction range of 325-335 nmol mol-1. We also demonstrate the stability of amount fraction and isotope ratio of these reference materials and present a characterisation study of the cavity ring down spectrometer used for analysis of the reference materials. [ABSTRACT FROM AUTHOR]

Temperate desert soils are an important source of atmospheric nitrous oxide (N2O). However, it is uncertain how N2O emissions respond to warming, increased rainfall and nitrogen (N) addition in such soils. A multifactorial field manipulation study was carried out in the Gurbantunggut Desert, China's second largest desert, to investigate how these factors influence desert soil N2O emissions and to assess inter‐year variation. In our 3‐year study, under current climatic conditions, the annual flux of N2O in this temperate desert soil was 0.13 ± 0.02 kg N ha−1 yr−1, with the period of no plant growth contributing 43% of the annual emission. Surprisingly, there was no significant change in annual N2O flux under warming (+1°C) or increased precipitation (30%, +60 mm yr−1). In contrast, N2O emissions were significantly affected by extreme drought followed by precipitation. Additional N input, at 30 or 60 kg N ha−1 yr−1, greatly elevated annual N2O emission by 55–133%. The combined impact of N deposition and increasing rainfall on N2O emission was greater than that of any single factor, except for N deposition. This suggests that N2O emissions in this desert are driven primarily by soil available N content and are less sensitive to variations in soil temperature and moisture. [ABSTRACT FROM AUTHOR]

Nitrous 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. [ABSTRACT FROM AUTHOR]

When science and politics come together: From depletion to recovery of the stratospheric ozone hole: This article belongs to Ambio's 50th Anniversary Collection. Entered into force in 1989, this international treaty was designed to protect the ozone layer by phasing out the production of ozone-depleting substances, such as CFCs. Another article, written in 1977 together with Dieter H. Ehhalt, focuses in more detail on the effect of nitrous oxide (N SB 2 sb O) emissions on ozone destruction (Crutzen and Ehhalt [3]). [Extracted from the article]

The impact of the rise in atmospheric nitrous oxide on stratospheric ozone: This article belongs to Ambio's 50th Anniversary Collection. At that time, many aspects of atmospheric N SB 2 sb O were not known and the knowledge of the budget and of sources and sinks of atmospheric N SB 2 sb O was very incomplete (e.g. Bolin and Arrhenius [2]; Crutzen and Ehhalt [6]). Further, the role of the ocean was unclear, it was stated that "a smaller source or even a sink of N SB 2 sb O [at the ocean surface] during larger concentrations of N SB 2 sb O should be considered" (Crutzen and Ehhalt [6]). Further, Crutzen and Ehhalt ([6]) stated that it "seems possible that present agricultural and waste treatment practices will lead gradually to more N SB 2 sb O in the atmosphere by denitrification of the increasing amounts of fixed nitrogen being put in circulation by intensive agricultural methods". [Extracted from the article]

Human activities have caused considerable perturbations of the nitrogen (N) cycle, leading to a ~20% increase in the concentration of atmospheric nitrous oxide (N2O) since the preindustrial era. While substantial efforts have been made to quantify global and regional N2O emissions from cropland, there is large uncertainty regarding how climate change and variability have altered net N2O fluxes at annual and decadal time scales. Herein, we applied a process‐based dynamic land ecosystem model (DLEM) to estimate global N2O emissions from cropland driven by synthetic N fertilizer application and multiple environmental factors (i.e., elevated CO2, atmospheric N deposition, and climate change). We estimate that global cropland N2O emissions increased by 180% (from 1.1 ± 0.2 to 3.3 ± 0.1 Tg N year−1; mean ±1 standard deviation) during 1961–2014. Synthetic N fertilizer applications accounted for ~70% of total emissions during 2000–2014. At the regional scale, Europe and North America were two leading regions for N2O emissions in the 1960s. However, East Asia became the largest emitter after the 1990s. Compared with estimates based on linear and nonlinear emission factors, our results were 150% and 186% larger, respectively, at the global scale during 2000–2014. Our higher estimates of N2O emissions could be attributable to the legacy effect from previous N addition to cropland as well as the interactive effect of N addition and climate change. To reduce future cropland N2O emissions, effective mitigation strategies should be implemented in regions that have received high levels of N fertilizer and regions that would be more vulnerable to future climate change. Key Points: Synthetic N fertilizer contributed to N2O emissions of 2.0 ± 0.1 Tg N year−1 from global cropland between 2000 and 2014Uncertainty remains in fertilizer‐induced N2O emissions due to temporal and spatial differences in current N fertilizer data setsChanges in environmental factors increased cropland N2O emissions; however, the magnitude of environmental effects remain highly uncertain [ABSTRACT FROM AUTHOR]

Ice core measurements of the concentration and stable isotopic composition of atmospheric nitrous oxide (N2O) 74,000–59,000 years ago constrain marine and terrestrial emissions. The data include two major Dansgaard‐Oeschger (D‐O) events and the N2O decrease during global cooling at the Marine Isotope Stage (MIS) 5a‐4 transition. The N2O increase associated with D‐O 19 (~73–71.5 ka) was driven by equal contributions from marine and terrestrial emissions. The N2O decrease during the transition into MIS 4 (~71.5–67.5 ka) was caused by gradual reductions of similar magnitude in both marine and terrestrial sources. A 50 ppb increase in N2O concentration at the end of MIS 4 was caused by gradual increases in marine and terrestrial emissions between ~64 and 61 ka, followed by an abrupt increase in marine emissions at the onset of D‐O 16/17 (59.5 ka). This suggests that the importance of marine versus terrestrial emissions in controlling millennial‐scale N2O fluctuations varied in time. Plain Language Summary: Nitrous oxide is a powerful greenhouse gas that is produced naturally in soils and oceans. An important unresolved question is the extent to which anthropogenic warming will stimulate additional emissions from these sources, further adding to the warming. Past variations in the abundance of nitrous oxide have been observed using ice core reconstructions, but the reasons for the variations are not well understood. Nitrous oxide produced in soils is isotopically distinct from nitrous oxide produced in oceans. New measurements of the isotopes of atmospheric nitrous oxide provide constraints on how marine and terrestrial sources must have changed, driving fluctuations in nitrous oxide concentration during two intervals of rapid warming and a prolonged period of global cooling. The reconstructed changes in nitrous oxide sources provide insights into relationships between marine and terrestrial ecosystems and climate. Key Points: Stable isotopes of nitrous oxide constrain marine versus terrestrial production 74,000–59,000 years agoMarine and terrestrial sources varied similarly across Dansgaard‐Oeschger 19 and during the Marine Isotope Stage 5‐4 transitionMarine emissions dominated across Dansgaard‐Oeschger 16/17; thus, abrupt N2O increases were not all identical during the last glacial period [ABSTRACT FROM AUTHOR]

We present analyses of nitrogen and oxygen isotopic ratios and site‐preference (SP) values of atmospheric nitrous oxide samples obtained from Taiwan in west Pacific. Air samples were collected during September 2013 to January 2016 from Taipei and during November 2011 to December 2014 from Keelung, located in the northeastern coast of Taiwan. The average values of δ15N, δ18O, and SP are 6.4 ± 0.3 ‰, 44.0 ± 0.4 ‰, and 17.1 ± 1.0 ‰, respectively, at Taipei and 6.4 ± 0.2 ‰, 44.6 ± 0.4 ‰, and 17.9 ± 1.3 ‰, for δ15N, δ18O, and SP respectively, at Keelung, comparable to the average values (6.6 ± 0.2, 44.2 ± 0.2, and 18.1 ± 0.5 ‰, scaled to year 2014) from Hateruma, an open ocean station in western Pacific. Strong temporal variations in the delta values, however, are seen. During a subtropical jet‐strengthening period in October to mid‐December 2014, the δ15N, δ18O and SP values increased at the rate of 0.006 ± 0.002 ‰/day, 0.010 ± 0.002 ‰/day and 0.008 ± 0.002 ‰/day, respectively at Taipei and 0.013 ± 0.005 ‰/day, 0.011 ± 0.005 ‰/day and 0.011 ± 0.027 ‰/day at Keelung. This suggests intrusion of air to the lower troposphere from the stratosphere where δ15N, δ18O and SP values are higher. This is consistent with earlier observations of oxygen isotope anomaly in atmospheric CO2 and elevated 35S in sulfate aerosols, indicating frequent stratospheric intrusions in this region. The observed δ15N and δ18O values, along with the oxygen isotope anomaly in CO2 and multiple sulfur isotopes in sulfate, can be used to constrain local emissions from the surface, improving our knowledge of anthropogenic contribution to the global budget of N2O. Key Points: Temporal variations in isotopic ratios of atmospheric N2O from TaiwanIsotopic ratio increase is concurrent with strengthening of the subtropical jetPositive trends suggest intrusion of air from the stratosphere [ABSTRACT FROM AUTHOR]

Aims: Environmental factors controlling nitrous oxide (N2O) uptake in forest soils are poorly known, and the atmospheric impact of the forest N2O sink is not well constrained compared to that of methane (CH4). Methods: We compared nitrous oxide (N2O) and CH4 fluxes over two growing seasons in boreal forest soils located in Eastern Finland. Within a spruce forest, we compared plots with long-term nitrogen (N) fertilization history and non-fertilized plots, and additionally pine forest plots without a fertilization history. The flux data was complemented with measurements of climatic conditions and soil physical and chemical characteristics, in order to identify factors affecting N2O and CH4 fluxes. Results: Non-fertilized spruce forest soils showed the highest cumulative N2O uptake among the sites, whereas the pine forest site displayed low cumulative N2O emission. Nitrous oxide uptake was favored by high soil silt and water content. The low temperature seasons, spring and autumn, had the highest N2O uptake, likely associated with high soil water content typical for these seasons. In the spruce forest the N2O uptake was seasonally decoupled from the CH4 uptake. Conclusions: Applying the Global Warming Potential (GWP) approach, the cooling effect of N2O uptake in the spruce forest was on average 35% of that of CH4 uptake showing that N2O uptake should be considered when evaluating the atmospheric impact of boreal forests. [ABSTRACT FROM AUTHOR]

The continuous growth of atmospheric nitrous oxide (N2O) is of concern for its potential role in global warming and future stratospheric ozone destruction. Climate feedbacks that enhance N2O emissions in response to global warming are not well understood, and past records of N2O from ice cores are not sufficiently well resolved to examine the underlying climate‐N2O feedbacks on societally relevant time scales. Here, we present a new high‐resolution and high‐precision N2O reconstruction obtained from the Greenland NEEM (North Greenland Eemian Ice Drilling) and the Antarctic Styx Glacier ice cores. Covering the N2O history of the past two millennia, our reconstruction shows a centennial‐scale variability of ~10 ppb. A pronounced minimum at ~600 CE coincides with the reorganizations of tropical hydroclimate and ocean productivity changes. Comparisons with proxy records suggest association of centennial‐ to millennial‐scale variations in N2O with changes in tropical and subtropical land hydrology and marine productivity. Plain Language Summary: Nitrous oxide (N2O) is a greenhouse and ozone‐depleting gas. The growing level of N2O in the atmosphere is of global concern, and records of past N2O variations can provide an important context for understanding the links between N2O and climate change. In this study, we report new, high‐quality N2O records covering the last two millennia using ice cores obtained from Greenland and Antarctica. Our N2O records show rapid centennial‐scale changes in atmospheric N2O and confirm a pronounced minimum near 600 CE. Comparison with climate records suggests that hydroclimate change on land and changes in marine productivity contribute to centennial‐ to millennial‐scale N2O variations. Key Points: We report records of N2O concentration for the last 2,000 yr from the Styx ice core in Antarctca and NEEM ice core in GreenlandThe data accurately reveal the timing and magnitude of N2O variations on centennial time scalesVariations in N2O are associated with changes in tropical and subtropical land hydrology and marine productivity [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Epilithic mosses are early colonizers of the terrestrial biosphere, which constitute a special ecosystem regulating rock‐atmosphere interactions. Terrestrial mosses can take up nitrate (NO3−), a major form of bioavailable N, from soil substrates. However, the importance of substrate NO3− relative to atmospheric NO3− remains unclear in moss NO3− utilization. This has prevented the understanding of moss NO3− dynamics and their responses to environmental N loadings. This study investigated monthly concentrations, δ15N, and δ18O of NO3− in four epilithic moss species from August 2006 to August 2007 in Guiyang, southwestern China. We developed a non‐steady state isotope mass‐balance model to evaluate fractional contributions of atmospheric NO3− (Фatm) and soil NO3− (Фsoil), moss NO3− uptake flux (Finflux), moss NO3− reduction flux (Freduction), and the percentage of NO3− reduction in moss NO3− uptake (freduced). The monthly Фsoil values averaged 53 ± 13% and the monthly freduced values averaged 50 ± 35%. Both the monthly Freduction and freduced increased as the monthly Finflux increased, particularly when the Фsoil values were higher than Фatm values. However, the amount of annual NO3− reduction (219.7 ± 30.5 μg‐N/g, dw) accounted for only 1.0 ± 0.2% of the bulk N of the mosses. We conclude that half of the NO3− in epilithic mosses is derived from the soil NO3− and that NO3− uptake from the soil induces moss NO3− reduction, but the total NO3− assimilation contributed a low fraction of the total N in the studied mosses. These findings are important for understanding N sources and N dynamics in terrestrial mosses. Key Points: A non‐steady state isotope mass‐balance model was used to evaluate moss nitrate sources and reductionEpilithic mosses acquire about half of their nitrate from the underlying soil substratesNitrate contributed a low fraction of the total N in the studied mosses [ABSTRACT FROM AUTHOR]

Background: Covariances among major anthropogenic greenhouse gases were studied during three cold-air pool episodes in the Pannonian Basin to better constrain their emission factors for Europe. Results: On the base of observed covariance between carbon dioxide, methane, carbon monoxide and nitrous oxide atmospheric dry air mole fraction in a region of the Pannonian (Carpathian) Basin during three cold-air pool episodes in January–February 2017, emission factors relative to carbon dioxide were determined. For the determination of the emission of carbon dioxide, a simple boundary-layer budget model was compiled. The model gave 6.3 g m−2 day−1 carbon dioxide emission for the footprint area of the measurements on average for the period of the episodes. The 6.7–13.8 nmol μmol−1, 0.15–0.31 nmol μmol−1 and 15.0–25.8 nmol μmol−1 ratios for CH4:CO2, N2O:CO2 and CO:CO2, respectively, correspond to 15.3–31.7 mg m−2 day−1 methane, 0.9–2.0 mg m−2 day−1 nitrous oxide and 60.0–103.4 mg m−2 day−1 carbon monoxide emissions for the region. These values are somewhat higher than the officially reported bottom-up annual national averages for Hungary, which are explained by the winter conditions and intensive domestic heating. Conclusions: The study indicated the high share of biomass burning in residential heating in rural environment that results in high carbon monoxide emission relative to that of carbon dioxide. It also indicated that the actual emission factor for nitrous oxide may exceed the range given in the guidelines for inventory compilation, which should be taken into account in reporting. It is shown that even a simple boundary-layer budget model might give realistic emission estimation under cool-air pool episodes. [ABSTRACT FROM AUTHOR]

Through the microbial breakdown of organic matter and production of greenhouse gases (GHGs), small agricultural dams or ponds have recently been shown to make a relatively large contribution to freshwater ecosystem carbon cycling. However, current estimates of their total carbon dioxide- equivalent (CO2-e) emissions lack inclusion of both seasonal and diel fluctuations. In addition, the atmospheric emissions of nitrous oxide from these often eutrophic systems have yet to be established. Here, we quantified the diffusive winter emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from 12 small agricultural dams within southeast Australia over a 24-h period. The winter CO2-e emissions of small agricultural water bodies were ~92% lower than previous summer estimates, at 1.02 g·m-2·d-1, while N2O contributed just 3.2% of this total. We also show that diel cycles do not significantly affect winter CO2, CH4, or N2O emission rates, and we discuss the likely carbon sources to these systems, through analyses of stable carbon isotopes (δ13C). The results from this study fill key gaps in our knowledge of agricultural dam GHG production and global atmospheric emissions, aiding their inclusion into future GHG budgets. [ABSTRACT FROM AUTHOR]

Using high-precision and centennial-resolution ice core information on atmospheric nitrous oxide concentrations and its stable nitrogen and oxygen isotopic composition, we quantitatively reconstruct changes in the terrestrial and marine N2O emissions over the last 21 000 years. Our reconstruction indicates that N2O emissions from land and ocean increased over the deglaciation largely in parallel by 1.7±0.3 and 0.7±0.3 TgN yr -1 , respectively, relative to the Last Glacial Maximum level. However, during the abrupt Northern Hemisphere warmings at the onset of the Bølling–Allerød warming and the end of the Younger Dryas, terrestrial emissions respond more rapidly to the northward shift in the Intertropical Convergence Zone connected to the resumption of the Atlantic Meridional Overturning Circulation. About 90 % of these large step increases were realized within 2 centuries at maximum. In contrast, marine emissions start to slowly increase already many centuries before the rapid warmings, possibly connected to a re-equilibration of subsurface oxygen in response to previous changes. Marine emissions decreased, concomitantly with changes in atmospheric CO2 and δ13C(CO2) , at the onset of the termination and remained minimal during the early phase of Heinrich Stadial 1. During the early Holocene a slow decline in marine N2O emission of 0.4 TgN yr -1 is reconstructed, which suggests an improvement of subsurface water ventilation in line with slowly increasing Atlantic overturning circulation. In the second half of the Holocene total emissions remain on a relatively constant level, but with significant millennial variability. The latter is still difficult to attribute to marine or terrestrial sources. Our N2O emission records provide important quantitative benchmarks for ocean and terrestrial nitrogen cycle models to study the influence of climate on nitrogen turnover on timescales from several decades to glacial–interglacial changes. [ABSTRACT FROM AUTHOR]

Abstract This study aims to quantify the differences between the standard laboratory-based NO x emissions factor (EF) and on-road measurements, and to estimate how much NO x emissions exceed the current EF under typical Korean road traffic conditions. Four Euro 4 light-duty diesel vehicles (LDVs) manufactured in Korea were driven on a chassis dynamometer and on test routes that included urban and rural roads and a motorway. NO x emissions, average speed, and acceleration were measured and calculated for each 1 km trip. We focused in particular on the possibility of vehicle malfunctions causing increased NO x emissions, and compared NO x emissions before and after the repair of faulty exhaust gas recirculation (EGR) valves, which are a key NO x reduction system for LDVs. The current NO x EF for Euro 4 LDVs only estimates 27–31% of on their on-road NO x emissions, and low acceleration during the standard driving cycle is a part of the reason for this weak representativeness. Another is the lack of tools with which to monitor EGR valve degradation. Even with fully functioning EGR valve hardware, the capability of vehicles to control NO x emissions differ in laboratory and on-road conditions; it is weaker for the latter compared to the former because the software controls are different. The findings here provide insights for different regions where Euro 4 LDVs are still in use, depending on their age. For Korea and the EU, where the fleet is old, accurate assessments of the real risk of NO x emissions are beneficial in terms of increasing the effectiveness of control measures. In countries where the Euro 4 fleet is still young, comprehensive changes are recommended for the on-board diagnostic system and the subsequent maintenance of the hardware and software of EGR valve. Graphical abstract Image 1 Highlights • Korean standard emission factors only estimate 27–31% of on-road NOx emissions. • Incorrect lab-based tests and ineffective hardware surveillance tools are the issue. • Faster acceleration during standard driving cycles would improve representativeness. • Repairing hardware and modifying software will reduce emissions from test vehicles. [ABSTRACT FROM AUTHOR]

Using high precision and centennial resolution ice core information on atmospheric nitrous oxide concentrations and its stable nitrogen and oxygen isotopic composition, we quantitatively reconstruct changes in the terrestrial and marine N2O emissions over the last 21,000 years. We show that N2O emissions from land and ocean increased largely in parallel by 1.7±0.3TgNyr-1 and 0.7±0.3TgNyr-1 over the deglaciation, respectively. However, during the abrupt Northern Hemisphere warmings at the onset of the B⊘lling/Aller⊘d and the end of the Younger Dryas, terrestrial emissions respond more rapidly to the northward shift in the Intertropical Convergence Zone connected to the resumption of the Atlantic Meridional Overturning Circulation. 90% of these large step increases were realized within maximum two centuries. In contrast, marine emissions start to slowly increase already many centuries before the rapid warmings, possibly connected to a re-equilibration of subsurface oxygen in response to previous changes. Marine emissions decreased, concomitantly with changes in atmospheric CO2 and δ13C(CO2), at the onset of the termination and remained minimal during the early phase of Heinrich Stadial 1. During the early Holocene a slow decline in marine N2O emission of 0.4TgNyr-1 is reconstructed, suggesting an improvement of subsurface water ventilation in line with slowly increasing Atlantic overturning circulation. In the second half of the Holocene total emissions remain on a relatively constant level, however with significant millennial variability which is currently still difficult to attribute to marine or terrestrial sources. Our N2O emission records provide important quantitative benchmarks for ocean and terrestrial nitrogen cycle models to study the influence of climate on nitrogen turnover on time scales from several decades to glacial/interglacial changes. [ABSTRACT FROM AUTHOR]

Abstract Agricultural soils are a dominant source of atmospheric nitrous oxide (N 2 O). A clear understanding of N 2 O emission from fruit cropping systems is urgently needed to improve the global budget and establish mitigation options. The primary aims of this study were to (i) quantify the variations in N 2 O emissions from fruit orchards, (ii) evaluate the major controls of N 2 O emissions, and (iii) discuss potential mitigation strategies across climates, soil types and field managements. We summarized 123 determinations of N 2 O emissions under perennial fruit trees from peer-reviewed publications from 1997 to 2019, with measurement periods covering at least one whole growing season. Cumulative N 2 O emissions ranged widely from −0.116–26 kg N ha−1 per year or growing season and increased linearly with nitrogen (N) fertilizer input rates on a global basis (r2 = 0.39, p < 0.001). Climate and form of N fertilizers also contributed to the large variability. In particular, tropical orchards should be a priority for N 2 O management because they display a large emission factor (approximately 2% of applied fertilizer N). A meta-analysis revealed that the application of nitrification inhibitors significantly reduced N 2 O emissions by 73% on average (95% confidence intervals: −87% to −51%). The effects of mulching and cover cropping were not significant, mostly depending on the mulch material and species of cover crop along with the management of cropping, which modified the availability of soil water and nutrients. More measurements are highly needed to evaluate the effectiveness of mitigation options across diverse experimental environments. Highlights • A large variability in N 2 O emissions from fruit orchards worldwide was observed. • Cumulative N 2 O emissions increased with nitrogen input rates regardless of locations. • Emission factors and background emissions varied across climates. • The effectiveness of mitigation options was assessed by a meta-analysis. [ABSTRACT FROM AUTHOR]

Abstract Nitrous oxide (N 2 O) and nitric oxide (NO) emissions from domestic wastewater treatment had been widely investigated due to their severe greenhouse effect and stratospheric ozone depletion. Researches concerning N 2 O and NO emissions from industrial wastewater treatment which usually contain high concentrations of nitrogen and refractory organics were still limited. In this study, N 2 O and NO emissions from a biological aerated filter (BAF) for coking wastewater treatment were investigated that achieved efficient nitrogen and chemical oxygen demand (COD) removal efficiency through short-cut nitrification and denitrification. Notably, emission factor of N 2 O and NO reached 23.58% and 0.09% respectively, much higher than those emitted from most domestic wastewater treatment plants. Moreover, batch experiments revealed that nitrifier denitrification contributed as high as 97.17% and 93.89% of the total generated N 2 O and NO, which was supposed to be the main source of green-house gases (GHGs) during coking wastewater treatment. The inhibition of denitrifying reductase by the toxic components in coking wastewater and the severe nitrite accumulations were key factors promoting the high emission of N 2 O and NO. Microbial community analysis based on high throughput sequencing of 16S rRNA gene revealed that ammonia-oxidizing bacteria and denitrifying bacteria distributed abundantly in the BAF reactor, while nitrite-oxidizing bacteria was almost absent. The huge imbalance between NO and N 2 O reductase was an underlying explanation for the high N 2 O emission in the present coking wastewater treatment according to Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) result. This study is of great significance to understanding the high N 2 O and NO emission and developing the control strategy when treating industrial wastewater with high-strength nitrogen and refractory organics. Graphical abstract Image 1 Highlights • Efficient nitrogen removal from coking wastewater was achieved in BAF. • N 2 O and NO emission factors reached 23.58% and 0.09% in the BAF. • Nitrifier denitrification contributed 97.17% of the total N 2 O generation. • Refractory organics decreased nitrogen removal and promoted N 2 O emission. • Large imbalance between NO and N 2 O reductase was revealed. [ABSTRACT FROM AUTHOR]

Highlights • Impact of a variety of agricultural cropping systems on the soil microbial gene abundance of key denitrification genes (nirK, nirS and nosZ). • The agroecosystems studied are a long term cropping systems project under chisel-till, no-till or organic management for over twenty years. • nirK copy number in soil was affected primarily by the phase of the crop rotation and secondarily by time of year, regardless of cropping system. • In contrast, nosZ gene copy number was primarily driven by cropping system. • Gene quantities did not correspond to N 2 O emissions patterns. Abstract While nitrogen fertilizers have helped increase crop yields substantially, they have also contributed to several environmental problems, including an increasing atmospheric concentration of nitrous oxide (N 2 O), a greenhouse gas (GHG) and catalyst of stratospheric ozone decay. The dominant source of atmospheric N 2 O in many agricultural soils is denitrification, a process carried out by soil microbes containing the genes for nitrate reductase (Nar), nitrite reductase (Nir), nitric oxide reductase (Nor) and/or nitrous oxide reductase (Nos). We monitored the abundance of soil nirK, nirS, and nosZ genes during the summer growing season. We sampled replicated field plots from a long-term agricultural research site that includes agroecosystems with corn/soybean/wheat/legume rotations: two tilled-organic systems (Org3 and Org6), and two conventional systems, one using a chisel plow for primary tillage (CT) and one using no-tillage (NT). We demonstrate that nirK copy number in soil was affected primarily by the phase of the crop rotation and secondarily by time of year, regardless of cropping system. In contrast, nosZ gene copy number was primarily driven by cropping system. Soil N 2 O emissions during the sampling period were highest in Org3 and lowest in NT. However, gene quantities did not correspond to N 2 O emissions patterns, indicating that quantitative PCR of key denitrification genes measured at the temporal resolution reported here is not a good predictor of soil N 2 O emissions. These results, nonetheless, show that cropping system management can affect microbial community composition, gene quantity of nir and nos genes and N 2 O emissions. We found cropping system and time of year captured variation in gene abundance among microbial denitrifier populations in these agricultural soils. [ABSTRACT FROM AUTHOR]