Fig 1 - uploaded by Denise L. Mauzerall
Content may be subject to copyright.
Illustration of the nitrogen cascade showing the sequential effects that a single atom of N can have in various reservoirs after it has been converted from nonreactive N 2 to a reactive form (yellow arrows) and examples of existing international management policies. Adapted with permission from the GEO Yearbook 2003, United Nations Environment Programme (UNEP), 2004 (8) which was based on Galloway et al., 2003 (7).
Source publication
Nitrous oxide (N(2)O) is the largest known remaining anthropogenic threat to the stratospheric ozone layer. However, it is currently only regulated under the 1997 Kyoto Protocol because of its simultaneous ability to warm the climate. The threat N(2)O poses to the stratospheric ozone layer, coupled with the uncertain future of the international cli...
Context in source publication
Context 1
... oxide (N 2 O) contributes to two distinct global environmental problems: climate change and stratospheric ozone layer depletion. It is currently the third most signi fi cant greenhouse gas (GHG) in terms of climate forcing after carbon dioxide (CO 2 ) and methane (CH 4 ) (1), and its current emissions will contribute more to stratospheric ozone depletion than the current emissions of any other substance (2). N 2 O is not alone in having these dual impacts — for example, chloro fl uorocarbons (CFCs) also exacerbate both environmental problems, and CFC controls have reduced both ozone layer depletion and anthropogenic climate change. However, CFCs and N 2 O are controlled under different international treaties: CFCs under the universally accepted 1987 Montreal Protocol on Substances that Deplete the Ozone Layer and N 2 O under the 1997 Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC). The latter has not been universally rati fi ed, and its fi rst phase commitments expired at the end of 2012. Although a second commitment period will run through 2020, its emissions reduction targets remain unclear, and the Protocol ’ s membership has shrunk. Because N 2 O emissions are the largest remaining anthropogenic threat to the stratospheric ozone layer, this paper examines the issues that we regard as most relevant if the Parties to the ozone regime decide to consider future N 2 O controls. Our aim should not, however, be interpreted as implicitly endorsing such an outcome. The ozone regime (the 1985 Vienna Convention and its 1987 Montreal Protocol) is widely regarded as the most effective international environmental institution ever established. The Montreal Protocol has reduced the production and consumption of the ozone-depleting substances (ODSs) it controls by 98% since its inception, while simultaneously delaying the growth of overall anthropogenic radiative forcing by an amount equivalent to 7 – 12 y of increased CO 2 emissions in the early 21st century (3). Its institutional architecture has elements that various Parties regard as essential to their participation. Every country in the world has rati fi ed the Protocol, and all Parties have legally binding commitments (with developing countries given longer to comply with their commitments, which are often identical to developed country commitments). There is a strong fi nancial mechanism, the Multilateral Fund, funded by developed countries that fi nances projects in developing countries to cover their incremental costs of complying with their Montreal Protocol commitments. There is also an enforcement mechanism re- stricting trade in ODS. Well-respected assessment panels, made up of experts from industry, government, international organ- izations, private consultancies, and academia, provide valuable information and advice to the Parties on the science and environmental effects of ozone depletion as well as the technical and economic feasibility of chemical and process alternatives. The Parties may wish to use this existing institutional architecture if they decide to adopt future N 2 O controls. For example, the Parties could request a scoping report from the Technology and Economics Assessment Panel on the technical and economic feasibility of speci fi c N 2 O control strategies before deciding on a course of action (and possibly establish an N 2 O Technical Options Committee if they do decide to adopt controls) (4). Likewise, the Multilateral Fund could apply general lessons learned from successful projects in the agricultural sector that helped farmers adopt methods to reduce or replace use of the pesticide methyl bromide (5). N 2 O is a part of the tightly coupled nitrogen (N) cycle. Increases in anthropogenic emissions have come mainly from agriculture because of the biogeochemical processes of nitri fi cation and denitri fi cation, with additional contributions from stationary and mobile combustion, biomass burning, nitric and adipic acid production, and wastewater treatment (6). The N cycle is best char- acterized as a chemical cascade, with one N atom able to transform readily among different forms (7) (Fig. 1). As a result, N [speci fi cally, reactive nitrogen (Nr) — all N compounds except N 2 ] can contribute to a myriad of environmental problems. In princi- ple, therefore, it can be controlled at a number of points along the cascade. For example, nitrogen oxides (NO x = NO + NO 2 ), nitrate (NO 3 − ), and N 2 O are all forms of Nr, which can be controlled as air, water, and ozone and climate pollutants, respectively. Because of the cascade effect, reductions in one form of Nr likely reduce total Nr levels (9). Consequently, controlling N 2 O provides environmental cobene fi ts (e.g., improved air and water quality) in addition to the direct bene fi ts of reducing ozone depletion and climate change. The following sections examine the scienti fi c, legal, technical and policy-related issues surrounding potential N 2 O controls under the ozone regime. N 2 O Emission Sources. With natural emissions assumed to have remained unchanged, it is believed that anthropogenic activity alone is responsible for the ∼ 20% increase in atmospheric N 2 O concentrations [from 270 to 325 parts per billion by volume (ppbv)] since 1860 (8). Natural emissions are estimated at 10.2 Tg N per year (10) compared with current anthropogenic emissions estimates of 5.5 – 8.2 Tg N per year (6, 10 – 12). Consequently, the current stratospheric photochemical sink of N 2 O of ∼ 13.3 Tg N per year (given an atmospheric abundance of 325 ppbv and an atmospheric lifetime of 119 y) is not large enough to offset total annual emissions of 15.7 – 18.4 Tg N (12); the atmospheric abundance of N 2 O continues to increase as a result. Although the magnitude of total N 2 O anthropogenic emissions is reasonably well-known, attributing anthropogenic N 2 O emissions to various activities or sectors has signi fi cant uncertainties. N 2 O from natural and agricultural sources is a product of denitri fi cation (the transformation of NO 3 − into N 2 ) and nitri fi cation [the transformation of ammonium (NH 4+ ) into NO 3 − ] (13). N 2 O is also emitted as an industrial byproduct from other anthropogenic sources ( Feasibility of N 2 O Reductions: Sector-By-Sector Emissions and Mitigation Opportunities ). Source attribution is dif- fi cult, because the larger sources are diffuse, variable in time, dispersed across the globe, and occur above a large natural background. In addition, new anthropogenic sources of N 2 O, such as aquaculture, may be growing rapidly (14). Uncertainty in the magnitude of individual sources makes it challenging to predict emission reductions from speci fi c mitigation actions, particularly in agriculture. Contribution of N 2 O to Stratospheric Ozone Layer Depletion. Both natural and anthropogenic N 2 O emissions are transported to the stratosphere, where ∼ 10% is oxidized by excited atomic oxygen [O( 1 D )] to form nitric oxide (NO), which together with nitrogen dioxide (NO 2 ), forms a catalytic cycle for ozone destruction (15). There is a balance between ozone production and loss, with NO x catalysis a major ozone loss process in the mid- to upper stratosphere. Indeed, NO x was found to catalyze stratospheric ozone destruction several years before similar concerns emerged about CFCs (16). Ravishankara et al. (2) calculated an ozone depletion potential (ODP) for N 2 O. ODP is a metric used to evaluate the ef fi cacy of a species ’ stratospheric ozone destruction relative to CFC-11. Ravishankara et al. (2) reported an ODP for N 2 O of ∼ 0.02 (i.e., 1 kg N 2 O emissions destroy ∼ 2% of the stratospheric ozone that 1 kg CFC-11 emissions destroy). This value changes slightly with atmospheric conditions ( SI Text ) but is comparable with the ODPs of several substances already controlled under the Montreal Protocol [e.g., hydrochloro fl uorocarbon-123 (0.02)]. N 2 O ’ s small ODP can be deceptive, because the mass of N 2 O emitted from anthropogenic activities is much larger than past or projected future CFC emissions (e.g., in 2008, ODP-weighted emissions of N 2 O were approximately double the ODP-weighted emissions of CFC-11). Ravishankara et al. (2) note that, based on ODP- weighted emissions, anthropogenic N 2 O was the fourth most important ODS at the height of CFC emissions, is the most important ODS emitted today, and is projected to remain the most important throughout the 21st century. Furthermore, Ravishankara et al. (2) suggest that, by 2050, N 2 O ODP-weighted emissions could be as large as one-third of the peak of the CFC ODP-weighted emissions, which occurred in the late 1980s. As a result, N 2 O emissions are currently the largest remaining anthropogenic threat to the stratospheric ozone layer. Considering together future projections of CO 2 , CH 4 , and N 2 O increases and ODS decreases, it is estimated that the ozone layer should eventually return to its pre-1980 levels, despite continued emissions of N 2 O and other ODSs (17). However, the Parties to the Montreal Protocol continue to consider and pursue ways to ...
Citations
... The current growth rate is estimated at 2% per decade, extensively discussed in studies such as Prather et al. [25](2015) and Ciais et al. [9](2013). Ravishankara et al., [26](2009); Kanter et al., [18](2013) Research by Ravishankara et al. [26](2009) and Kanter et al. [18](2013) emphasizes that Nitrous oxide holds the position of the third-largest contributor to global warming and has been a predominant ozone-depleting substance throughout the century. Algeria, due to its geographical position and climate, experiences a notable impact from climate change, with greenhouse gases, particularly N 2 O, originating from energy, industry, and agriculture (Sahnoune et al. [30]2013). ...
... The current growth rate is estimated at 2% per decade, extensively discussed in studies such as Prather et al. [25](2015) and Ciais et al. [9](2013). Ravishankara et al., [26](2009); Kanter et al., [18](2013) Research by Ravishankara et al. [26](2009) and Kanter et al. [18](2013) emphasizes that Nitrous oxide holds the position of the third-largest contributor to global warming and has been a predominant ozone-depleting substance throughout the century. Algeria, due to its geographical position and climate, experiences a notable impact from climate change, with greenhouse gases, particularly N 2 O, originating from energy, industry, and agriculture (Sahnoune et al. [30]2013). ...
This paper is devoted to a predictive study on Nitrous oxide emissions per capita in Algeria, we implement a hybrid approach in order to handle complex patterns such as nonlinearity, long memory and other components. We use Singular spectrum analysis to decompose data into trend and residuals then we apply ARTFIMA process which has the capacity to deal with short and long memory, this hybridizing technique allow us to handle various components. We use some performance measures in order to validate the models adopted. This study enhances our understanding of potential future behavior and risk management for this issue.
... The majority of N 2 O emissions come from agriculture, largely through the overuse of fertilizers, with wastewater, biomass burning, transport and industrial emissions also contributing significantly (Kanter et al. 2013). In 2020, industrial N 2 O process emissions from the manufacture of nitric acid, adipic acid and caprolactam, were estimated at 47.4 MtCO 2 e in industrialized countries alone. ...
Action under the Montreal Protocol has contributed to climate change mitigation for almost 35 years. The phase-out of ozone-depleting substances (ODS) has set the ozone layer on a path to recovery, protecting the world’s biosphere from harmful ultraviolet radiation. The 2016 Kigali Amendment to the Montreal Protocol is expected to avoid 5.6–8.7 gigatonnes of carbon-dioxide equivalent (GtCO2e) emissions of hydrofluorocarbons (HFC) per year by 2100, reducing the impact of HFCs on global average warming by up to 0.4°C. Despite its successes, unexpected emissions of phased out ODS – notably the chlorofluorocarbon, CFC-11 - have brought attention to shortcomings in the Protocol’s monitoring, reporting, verification and enforcement (MRV+E) which must be addressed to guarantee its controls are sustained. Meanwhile, additional significant mitigation could be achieved by accelerating the phase-down of HFCs under the Kigali Amendment, by tackling ODS and HFC emissions from leaking banks of equipment and products and by controlling feedstocks, which are not subject to Montreal Protocol phase-out controls. Recent scientific papers have linked almost 870 million tCO2 per year of greenhouse gases (GHG) and ODS to fluorochemical industrial processes and illegal fluorochemical production. Expanding the scope of the Montreal Protocol to address nitrous oxide (N2O), itself an ODS and GHG, would also contribute substantial ozone and climate benefits. This perspective essay discusses new and strengthened policy measures that governments can consider under the Montreal Protocol in order to maximize early, cost-effective reductions in emissions of non-CO2 greenhouse gases and ensure future implementation.
... Hintergrund ist, dass institutionelle Fragmentierung zu Effizienzverlusten führen kann, beispielsweise wenn Bestimmungen des internationalen Handelsregimes effektive Maßnahmen im Rahmen der globalen Umweltgovernance verhindern (Eckersley 2004). Umgekehrt kann es zu einer produktiven Arbeitsteilung zwischen internationalen Organisationen kommen (Gehring 2011), etwa wenn im Rahmen des Ozonregimes auch Treibhausgase reduziert werden (Kanter et al. 2013). ...
Deutschland hat sich das Ziel gesetzt, bis 2045 klimaneutral zu werden. Der Weg dorthin erfordert neben technischen Innovationen und wirtschaftlichem Wandel auch eine tiefe gesellschaftliche Transformation, die existierende gesellschaftliche Konfliktlinien aktiviert und auch neue Spannungen schafft. Die Klimawende bedarf daher neben umsichtiger politischer Steuerung auch einer breiten gesellschaftlichen Beteiligung und Trägerschaft. Ausgehend von diesem Befund entwickelt die Mercator-Stiftungsprofessur für Soziologie an der Universität Hamburg Methoden zur Analyse und Synthese relevanter gesellschaftlicher Prozesse, um abschätzen zu können, inwieweit die tiefe und schnelle Dekarbonisierung der deutschen Gesellschaft nicht nur technisch und ökonomisch machbar, sondern auch sozial und politisch plausibel ist. Dazu wird eine jährliche Studie erstellt, die den Fokus auf jeweils neue gesellschaftliche Treiber der Klimawende legt. Förderung durch die Stiftung Mercator Die Professur und der Klimawende Ausblick werden durch die Stiftung Mercator gefördert. Die Stiftung Mer-cator ist eine private, unabhängige und gemeinnützige Stiftung, die auf der Grundlage wissenschaftlicher Expertise und praktischer Projekterfahrung handelt. Seit 1996 tritt sie für eine solidarische und partizipative Gesellschaft ein. Dazu fördert und entwickelt sie Projekte, die Chancen auf Teilhabe und den Zusammenhalt in einem diverser werdenden Gemeinwesen verbessern. Die Stiftung Mercator setzt sich für ein weltoffenes, demokratisches Europa ein, eine an den Grundrechten orientierte digitale Transformation von Staat und Gesellschaft sowie einen sozial gerechten Klimaschutz. Die Stiftung Mercator engagiert sich in Deutschland, Europa und weltweit. Dem Ruhrgebiet, Heimat der Stifterfamilie und Stiftungssitz, fühlt sie sich besonders verbunden. Das Exzellenzcluster Klima, Klimawandel, und Gesellschaft Im Exzellenzcluster CLICCS (Climate, Climatic Change and Society) haben sich Forscherinnen und Forscher verschiedenster Disziplinen zusammengeschlossen, um zu untersuchen, wie sich Klima und Gesellschaft gemeinsam entwickeln. Das CLICCS-Programm wird durch das Zentrum für Erdsystemforschung und Nachhaltigkeit (CEN) der Universität Hamburg in enger Zusammenarbeit mit mehreren Partnerinstitutionen koordi-niert und von der Deutschen Forschungsgemeinschaft (DFG) gefördert (EXC 2037 "CLICCS-Climate, Climatic Change, and Society"-Projektnummer: 390683824).
... Since the invention of the Haber-Bosch process, the use of N-containing fertilisers has massively increased the nitrous oxide concentration in the atmosphere (> 20 % since 1750 to 330 ppb in 2018). [1][2][3] Fuel combustion, wastewater management, and synthesis of nitric and adipic acids have also contributed (and continue to do so) to the emission of N 2 O. This gas is a long-lived stratospheric ozonedepleting substance and greenhouse gas with an impact on global warming 300 times larger than that of carbon dioxide (CO 2 ). ...
Decomposition of the environmentally harmful gas nitrous oxide (N2O) is usually performed thermally or catalytically. Selective catalytic reduction (SCR) is currently the most promising technology for N2O mitigation, a multicomponent heterogeneous catalytic system that employs reducing agents such as ammonia, hydrogen, hydrocarbons, or a combination thereof. This study reports the first homogenous catalyst that performs the reduction of nitrous oxide employing readily available and cheap light alcohols such as methanol, ethanol or ethylene glycol derivatives. During the reaction, these alcohols are transformed in a dehydrogenative coupling reaction to carboxylate derivatives, while N2O is converted to N2 and H2O, later entering the reaction as substrate. The reaction is catalysed by the low‐valent dinuclear ruthenium complex [Ru2H(μ‐H)(Me2dad)(dbcot)2] that carries a diazabutadiene, Me2dad, and two rigid dienes, dbcot, as ligands. The reduction of nitrous oxide proceeds with low catalyst loadings under relatively mild conditions (65–80 °C, 1.4 bar N2O) achieving turnover numbers of up to 480 and turnover frequencies of up to 56 h⁻¹.
... Nitrous oxide (N 2 O) is one of the six greenhouse gases specified in the Kyoto Protocol, contributing to quite a global warming effect, following CO 2 and CH 4 , but it has a much greater global warming effect per unit concentration than CO 2 and CH 4 . 1 With the continuous advancement of industrialization, the concentration of N 2 O in the atmosphere has reached an unprecedented level. 2−5 The majority of N 2 O from stationary sources comes from industrial processes such as biomass burning, nitric acid, and adipic acid production, while mobile sources (including private cars, cruise ships, etc.) also have a large amount of N 2 O emissions. ...
Nitrous oxide (N2O) has gained increasing attention as an important noncarbon dioxide greenhouse gas, and catalytic decomposition is an effective method of reducing its emissions. Here, Co3O4 was synthesized by the sol-gel method and single-atom Pr was confined in its matrix to improve the N2O decomposition performance. It was observed that the reaction rate varied in a volcano-like pattern with the amount of doped Pr. A N2O decomposition reaction rate 5-7.5 times greater than that of pure Co3O4 is achieved on the catalyst with a Pr/Co molar ratio of 0.06:1, and further Pr doping reduced the activity due to PrOx cluster formation. Combined with X-ray photoelectron spectroscopy, X-ray absorption fine structure, density functional theory and in situ near-ambient pressure X-ray photoelectron spectroscopy, it was demonstrated that the single-atom doped Pr in Co3O4 generates the "Pr 4f-O 2p-Co 3d" network, which redistributes the electrons in Co3O4 lattice and increases the t2g electrons at the tetracoordinated Co2+ sites. This coupling between the Pr 4f orbit and Co2+ 3d orbit triggers the formation of a 4f-3d electronic ladder, which accelerates the electron transfer from Co2+ to the 3π* antibonding orbital of N2O, thus contributing to the N-O bond cleavage. Moreover, the energy barrier for each elementary reaction in the decomposition process of N2O is reduced, especially for O2 desorption. Our work provides a theoretical grounding and reference for designing atomically modified catalysts for N2O decomposition.
... Nitrous oxide (N 2 O) is well known as the third important greenhouse gas [1][2][3] and the largest anthropogenic contributor to stratospheric ozone decomposition for the remainder of this century [4,5]. Its atmospheric concentration at present has increased by 20% compared to pre-industrial levels [1]. ...
Denitrification, as an important part of the soil nitrogen cycle, is widely considered to be a major source of nitrous oxide (N2O). Both biotic and abiotic denitrification processes contribute significantly to soil N2O emission, especially under acidic conditions. Increasing soil pH was found to suppress N2O emissions from denitrification, while the underlying mechanism remains uncertain. In this study, we incubated fresh forest soil anaerobically after increasing soil pH and adding nitrate (NO3−) under both sterilized and unsterilized conditions. The dynamic changes of NO3−, nitrite (NO2−), N2O and dinitrogen (N2) were monitored continuously during the 15 days of incubation. The results showed that nitrate reduction rates increased with soil pH in both sterilized and unsterilized soils, with the former having higher rates. The obvious production and consumption of nitrite were found at pH 7.1, rather than at pH 5.5, especially in sterilized soils. In both sterilized and unsterilized soils, accumulative emission of N2O and N2O-N/(N2O+N2)-N product ratios decreased significantly with increasing pH, while N2 showed the opposite trend. In sterilized soils, N2O was the dominant end gas product, accounting for 40.88% and 29.42% of the added nitrate at pH 5.5 and 7.1, respectively. In unsterilized soils, N2 was the only final gas product at pH 7.1 (59.34% of the added nitrate), whereas N2O dominated at pH 5.5 (26.67% of the added nitrate). Our results here showed that increasing soil pH promoted the conversion of N2O to N2 under both sterilized and unsterilized conditions, and highlighted the potential importance of abiotic denitrification on N2O emission.
... Furthermore, the total anthropogenic N 2 O emissions in East Asia were estimated at about 2.2 Tg in 2016, accounting for around 18% of global human-induced emissions (Tian et al., 2020). Owing to the cascade effect of reactive nitrogen (Nr), increase of N 2 O may perk up NO X , PM, and ground-level O 3 , thereby deteriorating air quality and eliciting eutrophication (Kanter et al., 2013). CO and O 3 , the main species of air pollutants, are indirect and direct contributors to global warming, respectively (Yarragunta et al., 2017;de Richter and Caillol, 2011). ...
... Fossil fuel combustion generates N 2 O as a byproduct. SCR can lower N 2 O emissions from stationary combustion sources by as much as 80% (Kanter et al., 2013). In addition, oxy-fuel combustion with circulating fluidized bed (CFB) can promoted carbon sequestration (Shi et al., 2020). ...
As apanoramic overview of the multipronged national-scale regulations of China to synchronously decelerate climate change and improve air quality, this study pores through a constellation of China's strategies aimed to obtain coinstantaneous reductions in the emissions of atmospheric pollution and greenhouse gases (GHGs). These strategies, inclusive of afforestation and silviculture, ultra-low industrial emissions, energy structure reform, renewable energy development, household emission reductions, transportation emission control, and shutdown of cryptocurrency mining, have vouchsafed China new pragmatic dimensions in pursuit of its climate goals and have established a roadmap to bide time for the future. Here we show blow-by-blow the pros and cons of these pathways to illustrate the reasons why they best serve China's long-term targets and dovetail with China's geopolitical realities. Because of the interactions between air pollutants and GHGs, cooperatively reducing the emissions of both air pollutants and climate change gases have mutual benefits and are efficacious for the enhancement of air quality and mitigation of global warming.
... Nitrous oxide (N 2 O) is one of the three major greenhouse gases with 298 times the warming potential of CO 2 and is considered a major destroyer of the stratospheric ozone layer (Ravishankara et al., 2009;Kanter et al., 2013;Greaver et al., 2016). Atmospheric N 2 O concentrations have increased from 270 ppb in 1750 to 332 ppb in 2020 (Hall et al., 2007;Reay et al., 2012;Prinn et al., 2018;Tian et al., 2020). ...
As nitrous oxide (N2O) is one of the most important greenhouse gases, N2O emission pathways and regulation techniques in soils with different vegetation types have become a research focus. Currently, a diverse array of research exists on the N2O emissions from soils of different vegetation types, e.g., forest, grassland, and agriculture. Few studies have investigated the microbial processes of N2O emissions from lawn soils. Fertilization levels in lawn soils are often similar to or much higher than those in agricultural ecosystems, thus fertilized lawn is an important source of atmospheric N2O. In the study, we employed the ¹⁵N-nitrate labelling method combined with the nitrification inhibition technique to distinguish microbial processes and their contribution to N2O emissions in long-term nitrogen fertilised lawns. We found that the N2O emission rate from the control treatment was 1.0 nmol g⁻¹ h⁻¹ over the incubation, with autotrophic nitrification contributing 60%. The N2O emission rate increased to 1.4 nmol g⁻¹ h⁻¹ from the soil treated with long-term N fertilization, and the contribution of autotrophic nitrification increased to 69%. N fertilization did not significantly increase the contribution of denitrification (24–26%) in the total N2O emissions. However, N fertilization substantially decreased the contribution of heterotrophic nitrification from 13 to 0.4% in the total N2O emissions. Co-denitrification to N2O was detected but the overall contribution was of minor importance (3–5%). The correlation analysis revealed that soil NO3 ⁻ levels were the main influencing factors in the N2O producing microbial processes. Our results suggest that N fertilization altered both N2O production rates and the contribution pattern of microbial processes, and indicate the autotrophic nitrification and heterotrophic nitrification are more sensitive to N fertilization than denitrification and co-denitrification.
... In China, ammonia emission from fertilized cropland causes secondary particulate pollution and enhanced N deposition [14] . Nitrate leaching and N runoff lead to nitrate pollution in groundwater and eutrophication in surface water (e.g., coastal seas, rivers and lakes) [15] , and nitrous oxide emissions will accelerate global warming and also destroy the stratospheric ozone layer [16] . Excessive application of N fertilizer has further accelerated soil acidification [17] , which will threaten cereal production in China if acidification continues [18] . ...
... The efficiency of use of all N inputs to agriculture must be increased, combining maximal crop production with minimal emissions of Nr from farmland to natural and semi-natural environments, reducing ecological and environmental risks [15,24,25] . Optimized N management practices including the 4Rs (right source of N applied at the right rate, the right time and in the right place) [26] and ISSM (integrated soil-crop system management) [27] are increasingly important. ...
... Next to phosphorus, N is a key nutrient causing eutrophication in fresh and coastal waters [60,61] . With the rapidly increasing global population, more and more Nr is released into waters causing serious damage [15,62] . To quantify the anthropogenic Nr impact on waters, a conceptual model NANI (net anthropogenic nitrogen inputs, including atmospheric N deposition, synthetic N fertilizer, biological N fixation and N in net food and feed imports) has been developed and applied in a number of watersheds in the USA, Europe and Asia [61,63,64] . ...
Since the 1980s, the widespread use of N fertilizer has not only resulted in a strong increase in agricultural productivity but also caused a number of environmental problems, induced by excess reactive N emissions. A range of approaches to improve N management for increased agricultural production together with reduced environmental impacts has been proposed. The 4R principles (right product, right amount, right time and right place) for N fertilizer application have been essential for improving crop productivity and N use efficiency while reducing N losses. For example, site-specific N management (as part of 4R practice) reduced N fertilizer use by 32% and increased yield by 5% in China. However, it has not been enough to overcome the challenge of producing more food with reduced impact on the environment and health. This paper proposes a new framework of food-chain-nitrogen-management (FCNM). This involves good N management including the recycling of organic manures, optimized crop and animal production and improved human diets, with the aim of maximizing resource use efficiency and minimizing environmental emissions. FCNM could meet future challenges for food demand, resource sustainability and environmental safety, key issues for green agricultural transformation in China and other countries.
... As a dominant ozone-depleting emission [1-3] and a greenhouse gas with about 300 times the global warming potential than that of CO 2 (based on the 100-year timescale) [4][5][6], nitrous oxide (N 2 O) has been brought to the frontier of climate and environmental protection [7][8][9]. Efforts that aim to terminate environmentally detrimental N 2 O have been examined in the last few decades [10,11]. Beyond the commonly studied decomposition of N 2 O catalyzed by metal oxides (MOs) [12][13][14][15], a variety of possible conversions of N 2 O have also been investigated, including O-atom insertion into metal-H and metal-C bonds [16][17][18][19][20][21], cleavage of N-O and N-N bonds [22][23][24][25], and reactions with organic substrates [11,[26][27][28]. ...
As the overall turnover-limiting step (TOLS) in the homogeneous conversion of N2O, the oxygen-atom transfer (OAT) from an N2O to an Ru-H complex to generate an N2 and Ru-OH complex has been comprehensively investigated by density functional theory (DFT) computations. Theoretical results show that the proton transfer from Ru-H to the terminal N of endo N2O is most favorable pathway, and the generation of N2 via OAT is accomplished by a three-step mechanism [N2O-insertion into the Ru-H bond (TS-1-2, 24.1 kcal mol−1), change of geometry of the formed (Z)-O-bound oxyldiazene intermediate (TS-2-3, 5.5 kcal mol−1), and generation of N2 from the proton transfer (TS-3-4, 26.6 kcal mol−1)]. The Gibbs free energy of activation (ΔG‡) of 29.0 kcal mol−1 for the overall turnover-limiting step (TOLS) is determined. With the participation of potentially existing traces of water in the THF solvent serving as a proton shuttle, the Gibbs free energy of activation in the generation of N2 (TS-3-4-OH2) decreases to 15.1 kcal mol−1 from 26.6 kcal mol−1 (TS-3-4). To explore the structure–activity relationship in the conversion of N2O to N2, the catalytic activities of a series of Ru-H complexes (C1–C10) are investigated. The excellent linear relationships (R2 > 0.91) between the computed hydricities (ΔGH−) and ΔG‡ of TS-3-4, between the computed hydricities (ΔGH−) and the ΔG‡ of TOLS, were obtained. The utilization of hydricity as a potential parameter to predict the activity is consistent with other reports, and the current results suggest a more electron-donating ligand could lead to a more active Ru-H catalyst.
