Source Of Reactive Nitrogen Research Articles

Nitrate–nitrogen and oxygen isotope ratios for identification of nitrate sources and dominant nitrogen cycle processes in a tile-drained dryland agricultural field

Agricultural systems are a leading source of reactive nitrogen to aquatic and atmospheric ecosystems. In this study environmental δ15Nnitrate and δ18Onitrate are used to identify the dominant nitrogen cycle processes and sources of NO3− leached from a tile-drained, dryland agricultural field. Tile-drain water discharge δ18Onitrate values suggest nitrification is the dominant soil nitrogen cycle process throughout the 5-year study period, because the expected δ18Onitrate from nitrification is indistinguishable from the measured value of −1.3 ± 1.5‰. Given this there is no evidence that denitrification was occurring at a large enough scale to influence [NO3−]. Values for δ15Nnitrate varied seasonally during the high-discharge season (January through May) and low-discharge season (June through December) with weighted means of 1.0 ± 1.0‰ and 4.7 ± 2.3‰ respectively. This suggests that during the high-discharge season NO3− originates from nitrification of NH4+ fertilizer, and during the low-discharge season NO3− originates from mineralized soil organic nitrogen. The estimated travel time through the soil for nitrified NH4+ fertilizer leached during the high-discharge season is less than 6 months, from fall fertilizer application to leaching through the tile-drain. This study suggests that understanding the hydrology of a region is necessary before dominant nitrogen cycling processes can be reliably determined.

Nitrogen–climate interactions in US agriculture

Agriculture in the United States (US) cycles large quantities of nitrogen (N) to produce food, fuel, and fiber and is a major source of excess reactive nitrogen (Nr) in the environment. Nitrogen lost from cropping systems and animal operations moves to waterways, groundwater, and the atmosphere. Changes in climate and climate variability may further affect the ability of agricultural systems to conserve N. The N that escapes affects climate directly through the emissions of nitrous oxide (N2O), and indirectly through the loss of nitrate (NO3−), nitrogen oxides (NOx) and ammonia to downstream and downwind ecosystems that then emit some of the N received as N2O and NOx. Emissions of NOx lead to the formation of tropospheric ozone, a greenhouse gas that can also harm crops directly. There are many opportunities to mitigate the impact of agricultural N on climate and the impact of climate on agricultural N. Some are available today; many need further research; and all await effective incentives to become adopted. Research needs can be grouped into four major categories: (1) an improved understanding of agricultural N cycle responses to changing climate; (2) a systems-level understanding of important crop and animal systems sufficient to identify key interactions and feedbacks; (3) the further development and testing of quantitative models capable of predicting N-climate interactions with confidence across a wide variety of crop-soil-climate combinations; and (4) socioecological research to better understand the incentives necessary to achieve meaningful deployment of realistic solutions.

Observations of atmospheric reactive nitrogen species in Rocky Mountain National Park and across northern Colorado

Increasing rates of nitrogen deposition are a concern in many protected ecosystems. Understanding the sources influencing these regions can be a challenge as there are often few observations available to understand the transport of key species. Several field campaigns were conducted in and around Rocky Mountain National Park (RMNP) from 2006 to 2009 to assess the impacts of various reactive nitrogen sources and regional meteorology on reactive nitrogen deposition. Measurements of ammonia, ammonium, nitric acid, and nitrate at ground-level sites across northern Colorado were used to examine spatial gradients in atmospheric reactive nitrogen concentrations, the influence of wind direction on reactive nitrogen transport in the regional atmosphere, and anthropogenic contributions to reactive nitrogen concentrations in RMNP. The highest concentrations of reduced nitrogen occurred on the eastern plains of Colorado while oxidized nitrogen concentrations were highest along the Front Range urban corridor. Both regions lie east of RMNP. Upslope (easterly) winds associated with mountain–valley wind patterns and larger, synoptic scale forcing, transport emissions from these sources westward up the eastern slope of the Rockies and into RMNP; the highest ammonium and nitrate concentrations in RMNP were clearly associated with this upslope transport pattern. Concentrations of key reactive nitrogen species east of the Continental Divide in RMNP were, on average, more than 50% higher than those observed at a background site located west of the park, further indicating large contributions from sources east of the park. These observations highlight the need to focus on controlling reactive nitrogen emissions east of the park as part of ongoing efforts to reduce reactive nitrogen deposition in RMNP.

Vertical segregation and phylogenetic characterization of ammonia-oxidizing Archaea in a deep oligotrophic lake

Freshwater habitats have been identified as one of the largest reservoirs of archaeal genetic diversity, with specific lineages of ammonia-oxidizing archaea (AOA) populations different from soils and seas. The ecology and biology of lacustrine AOA is, however, poorly known. In the present study, vertical changes in archaeal abundance by CARD-FISH, quantitative PCR (qPCR) analyses and identity by clone libraries were correlated with environmental parameters in the deep glacial high-altitude Lake Redon. The lake is located in the central Spanish Pyrenees where atmospheric depositions are the main source of reactive nitrogen. Strong correlations were found between abundance of thaumarchaeotal 16S rRNA gene, archaeal amoA gene and nitrite concentrations, indicating an ammonium oxidation potential by these microorganisms. The bacterial amoA gene was not detected. Three depths with potential ammonia-oxidation activity were unveiled along the vertical gradient, (i) on the top of the lake in winter-spring (that is, the 0 (o)C slush layers above the ice-covered sheet), (ii) at the thermocline and (iii) the bottom waters in summer-autumn. Overall, up to 90% of the 16S rRNA gene sequences matched Thaumarchaeota, mostly from both the Marine Group (MG) 1.1a (Nitrosoarchaeum-like) and the sister clade SAGMGC-1 (Nitrosotalea-like). Clone-libraries analysis showed the two clades changed their relative abundances with water depth being higher in surface and lower in depth for SAGMGC-1 than for MG 1.1a, reflecting a vertical phylogenetic segregation. Overall, the relative abundance and recurrent appearance of SAGMGC-1 suggests a significant environmental role of this clade in alpine lakes. These results expand the set of ecological and thermal conditions where Thaumarchaeota are distributed, unveiling vertical positioning in the water column as a key factor to understand the ecology of different thaumarchaeotal clades in lacustrine environments.

Pathways involved in the generation of reactive oxygen and nitrogen species during glucose deprivation and its role on the death of cultured hippocampal neurons

Oxidative stress has been suggested as a mechanism contributing to neuronal death induced by hypoglycemia, and an early production of reactive species (RS) during the hypoglycemic episode has been observed. However, the sources of reactive oxygen (ROS) and nitrogen (RNS) species have not been fully identified. In the present study we have examined the contribution of various enzymatic pathways to RS production and neuronal death induced by glucose deprivation (GD) in hippocampal cultures. We have observed a rapid increase in RS during GD, which depends on the activation of NMDA and non-NMDA receptors and on the influx of calcium from the extracellular space. Accordingly, intracellular calcium concentration [Ca2+]i progressively increases more than 30-fold during the GD period. It was observed that superoxide production through the activation of the calcium-dependent enzymes, phospholipase A2 (cPLA2) and xanthine oxidase (XaO), contributes to neuronal damage, while nitric oxide synthase (NOS) is apparently not involved. Inhibition of cPLA2 decreased RS at early times of GD whereas inhibition of XaO diminished RS at more delayed times. The antioxidants trolox and ebselen also showed a protective effect against neuronal death and diminished RS generation. Inhibition of NADPH oxidase also contributed to the early generation of superoxide. Taking together, the present results suggest that the early activation of calcium-dependent ROS producing pathways is involved in neuronal death associated with glucose deprivation.

Atmospheric nitrogen deposition in south-east Scotland: Quantification of the organic nitrogen fraction in wet, dry and bulk deposition

Water soluble organic nitrogen (WSON) compounds are ubiquitous in precipitation and in the planetary boundary layer, and therefore are a potential source of bioavailable reactive nitrogen. This paper examines weekly rain data over a period of 22 months from June 2005 to March 2007 collected in 2 types of rain collector (bulk deposition and “dry + wet” deposition) located in a semi-rural area 15 km southwest of Edinburgh, UK (N55°51′44″, W3°12′19″). Bulk deposition collectors are denoted in this paper as “standard rain gauges”, and they are the design used in the UK national network for monitoring precipitation composition. “Dry + wet” deposition collectors are flushing rain gauges and they are equipped with a rain detector (conductivity array), a spray nozzle, a 2-way valve and two independent bottles to collect funnel washings (dry deposition) and true wet deposition. On average, for the 27 weekly samples with 3 valid replicates for the 2 types of collectors, dissolved organic nitrogen (DON) represented 23% of the total dissolved nitrogen (TDN) in bulk deposition. Dry deposition of particles and gas on the funnel surface, rather than rain, contributed over half of all N-containing species (inorganic and organic). Some discrepancies were found between bulk rain gauges and flushing rain gauges, for deposition of both TDN and DON, suggesting biological conversion and loss of inorganic N in the flushing samplers.

On the Effect of Atmospheric Ozone by the Human Activities

The phenomenon on issue of the ozone hole or ozone reduction in the South Pole or north hole and other mid-latitude areas happens in recent years,and more and more attentions are paid to this big phenomenon caused by the human activities.In this paper we give a brief introduction to the impact of the atmospheric ozone by aircraft emissions and potential nonlinear response by source of reactive chlorine or source of reactive nitrogen caused by human activities.

On the Nonlinear Response of Lower Stratospheric Ozone to Nox and Clox Perturbations

AbstractThe impact of H2O‐H2SO4 aerosol, ClOx and NOx perturbations on stratospheric ozone is researched by using the heterogeneous chemical system, which consists of 19 species belonging to 5 chemical families. The results show that, just in terms of aerosol, it is not an important factor to decide the nonlinear behaviors of the heterogeneous system under the current conditions. However, if the heterogeneous system is controlled together by aerosol and a source of reactive chlorine (ClOx) or a source of reactive nitrogen (NOx), the heterogeneous chemistry may produce significant influence on nonlinear behaviors of the system through chlorine chemistry and nitrogen chemistry. And in some parameters range, it can be presented as the existence of multi‐equilibrium solutions which could produce a folding transition.

Young’s modulus, Poisson’s ratio, and residual stress and strain in (111)-oriented scandium nitride thin films on silicon

Epitaxial scandium nitride films (225nm thick) were grown on silicon by molecular beam epitaxy, using ammonia as a reactive nitrogen source. The main crystallographic orientation of ScN with respect to Si is (111)ScN‖(111)Si and [1–10]ScN‖[0–11]Si; however, some twinning is also present in the films. The films displayed a columnar morphology with rough surfaces, due to low adatom mobility during growth. The strain-free lattice parameter of ScN films grown under optimized conditions was found to be 4.5047±0.0005Å, as determined using high-resolution x-ray diffraction (HRXRD). In-plane and out-of-plane strains were subsequently evaluated using HRXRD and were used to determine the Poisson ratio of ScN along the ⟨111⟩ direction, which is found to be 0.188±0.005. Wafer curvature measurements were made and combined with the strain information to determine the average Young’s modulus of the films, which is found to be 270±25GPa. Residual film stresses ranged from −1to1GPa (depending on film growth temperature and film thickness) due to competition between the tensile stress (induced by the differential thermal contraction between the ScN film and the Si substrate) and intrinsic compressive stresses generated during growth.

Sources of reactive nitrogen affecting ecosystems in Latin America and the Caribbean: current trends and future perspectives

While the amount of reactive nitrogen circulating at the global level has increased markedly in the last century, the effects of this increase are largely seen at the regional level due to interacting ecological and socio-economic factors. In contrast with most other regions of the world, Latin America and the Caribbean (LA-Ca) stand out due to the fact that the major input of reactive nitrogen (Nr) still occurs naturally via biological nitrogen fixation (BNF) in natural ecosystems as opposed to anthropogenic inputs of synthetic fertilizer, fossil fuel combustion and cropping with leguminous species. Largely due to economic reasons, the consumption of fertilizer N in the LA-Ca region is still low in comparison with the average consumption of the world. However, the fertilizer N consumption is increasing at a much faster rate than that in developed regions of the world, like USA and Canada. The Nr production through BNF in cultivated plants that fix nitrogen (C-BNF) is 5 times lower than that occurring naturally in Latin America, but is still equivalent to 16% of the world C-BNF. The cultivation of nitrogen-fixing crop species in the LA-Ca region is also increasing, almost entirely due to the expansion of soybean fields in the central and northern regions of Brazil and the Pampa region of Argentina. Other anthropogenic activities in the region that contribute to an increase in the circulation of reactive nitrogen include the impact of biomass burning and urbanization. In the last decade, an average of 47,000 km2 per year of forests was burned in the LACa region. The environmental impact of urban centers in the LA-Ca region has become very important, since an intense urbanization process is occurring in this region, at an intensity that far exceeds urban development in the northern hemisphere. The consequences of increased urbanization include increased emissions of NOx to the atmosphere due to the fossil fuel combustion, and the lack of sewage treatment facilities in most cities of the LA-Ca result in a large volume of untreated sewage discharged into surface waters, creating serious environmental problems. The combination of rapid urbanization and agricultural intensification in this region suggest that concern is warranted for the potential for increase in the circulation of reactive nitrogen in the very near future. At the same time, the opportunity still exists to mitigate some of the consequences of human impact on the nitrogen cycle in a region that still maintains a large fraction of its natural ecosystems intact.

A comparative study on the structure and hardness enhancement of a-BON/nc-TiN films prepared by low and high RF frequency PAMOCVD

Amorphous (a)-BON/nanocrystal (nc)-TiN bilayer coatings were deposited on a p-type silicon(1 0 0) substrate by low and high RF frequency plasma-assisted metal–organic chemical vapor deposition(PAMOCVD) system, using tetrakisdimethylaminotitanium(TDMAT, [(CH 3) 2N] 4Ti) and trimethylborate(TMB, (CH 3O) 3B) as TiN and BON precursors, respectively. We used Ar gas as a plasma source and N 2 gas as a reactive and additional nitrogen source. In this study, we have mainly investigated the relationship between the hardness and the structure of the coating layers by the effects of deposition parameters such as frequency, deposition time and substrate temperature. The results show that the surface structure of the top layer and the interface structure of layer-by-layer affect the hardness enhancement in bilayered a-BON/nc-TiN thin films. The as-grown films were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM) and nano indenter.

Microstructure of epitaxial scandium nitride films grown on silicon

Epitaxial scandium nitride films (225 nm thick) were grown on (1 1 1)-oriented silicon substrates by molecular beam epitaxy (MBE), using ammonia as a reactive nitrogen source. Film microstructure was investigated using X-ray diffraction (XRD). The (1 1 1) ω-scan FWHM of 0.551° obtained for films grown at 850 °C is the lowest reported so far for ScN thin films. The principal orientation of ScN with respect to Si is (1 1 1) ScN//(1 1 1) Si and [ 1 1 ¯ 0 ] ScN//[ 0 1 ¯ 1 ] Si, representing a 60° in-plane rotation of the ScN layer with respect to the Si substrate. However, some twinning is also present in the films; the orientation of the twinned component is (1 1 1) ScN//(1 1 1) Si and [ 1 1 ¯ 0 ] ScN//[ 1 1 ¯ 0 ] Si, representing a ‘cube-on-cube’ orientation. The volume percentage of these twins in the films decreases with increasing film growth temperature.

Microstructure and Strain-Free Lattice Parameters of SCxGa1-xN Films

Epitaxial ScxGa1-xN films of low Sc concentration (x = 0.08 ± 0.01) were deposited on MOCVD-grown GaN films (using an Al2O3 substrate) at 800oC using molecular beam epitaxy employing ammonia as a reactive nitrogen source (NH3-MBE). The strain-free lattice parameters of the films were determined using a method based on high-resolution X-ray diffraction (HRXRD) in conjunction with an in-situ elastic tester. It is found that the c:a lattice parameter ratio increases slightly and that the Poisson's ratio decreases with increasing Sc concentration. The crystalline quality and long-range ordering of the ScxGa1-xN films (as indicated by HRXRD peak intensities and full width at half maximum values) is improved considerably relative to the GaN template. Our results indicate that threading dislocations do not propagate effectively into the ScxGa1-xN films and that these may therefore potentially find application as dislocation blocking layers in GaN-based optoelectronic devices.

Is the atmosphere really an important source of reactive nitrogen to coastal waters?

Increasing inputs of reactive nitrogen have led to excessive phytoplankton growth in some coastal waters. Until recently, rivers were thought to be the most important nitrogen source but we now know that atmospheric inputs are large and can equal, or exceed, those from the rivers. These atmospheric nitrogen compounds have both agricultural sources (ammonia emitted from animal wastes) and combustion sources (nitrate derived from NO x emitted by vehicles and power stations). Our hypothesis is that atmospheric nitrogen deposition in summer to nutrient depleted, well lit, surface waters in coastal seas stimulates phytoplankton blooms. This paper summarises and compares studies conducted in the North Sea, the North East Atlantic Ocean and the Kattegat Sea. Budgeting approaches imply that the atmosphere can, under certain meteorological conditions and over short time periods, provide enough nitrogen to support a large increase in phytoplankton growth. This is not true in all areas and at all times and this emphasises the highly episodic nature of atmospheric deposition. However, productivity-based approaches suggest that atmospheric nitrogen inputs have little effect on phytoplankton growth. This may be because productivity in the North Sea and the Kattegat is controlled by internal recycling of nitrogen, even in the summer when inorganic nitrogen levels are very low. Over longer time scales, atmospheric inputs do increase the overall nitrogen stock in the water column. Reducing the input of nitrogen from the atmosphere will, therefore, reduce total nitrogen loads to coastal seas and hence may decrease eutrophication problems.

Impacts of biomass burning in Southeast Asia on ozone and reactive nitrogen over the western Pacific in spring

Aircraft measurements of ozone (O3) and its precursors (reactive nitrogen, CO, nonmethane hydrocarbons) were made over the western Pacific during the Transport and Chemical Evolution Over the Pacific (TRACE‐P) campaign, which was conducted during February–April 2001. Biomass burning activity was high over Southeast Asia (SEA) during this period (dry season), and convective activity over SEA frequently transported air from the boundary layer to the free troposphere, followed by eastward transport to the sampling region over the western Pacific south of 30°N. This data set allows for systematic investigations of the chemical and physical processes in the outflow from SEA. Methyl chloride (CH3Cl) and CO are chosen as primary and secondary tracers, respectively, to gauge the degree of the impact of emissions of trace species from biomass burning. Biomass burning is found to be a major source of reactive nitrogen (NOx, PAN, HNO3, and nitrate) and O3 in this region from correlations of these species with the tracers. Changes in the abundance of reactive nitrogen during upward transport are quantified from the altitude change of the slopes of the correlations of these species with CO. NOx decreased with altitude due to its oxidation to HNO3. On the other hand, PAN was conserved during transport from the lower to the middle troposphere, consistent with its low water solubility and chemical stability at low temperatures. Large losses of HNO3 and nitrate, which are highly water soluble, occurred in the free troposphere, most likely due to wet removal by precipitation. This has been shown to be the major pathway of NOy loss in the middle troposphere. Increases in the mixing ratios of O3 and its precursors due to biomass burning in SEA are estimated using the tracers. Enhancements of CO and total reactive nitrogen (NOy), which are directly emitted from biomass burning, were largest at 2–4 km. At this altitude the increases in NOy and O3 were 810 parts per trillion by volume (pptv) and 26 parts per billion by volume (ppbv) above their background values of 240 pptv and 31 ppbv, respectively. The slope of the O3‐CO correlation in biomass burning plumes was similar to those observed in fire plumes in northern Australia, Africa, and Canada. The O3 production efficiency (OPE) derived from the O3‐CO slope and NOx/CO emission ratio (ER) is shown to be positively correlated with the C2H4/NOx ER, indicating that the C2H4/NOx ER is a critical parameter in determining the OPE. Comparison of the net O3 flux across the western Pacific region and total O3 production due to biomass burning in SEA suggests that about 70% of O3 produced was transported to the western Pacific.

Effects of biomass burning and lightning on atmospheric chemistry over Australia and South-east Asia

In situ aircraft measurements of trace gases and aerosols were made in the boundary layer (BL) and free troposphere (FT) over Indonesia and Australia during the Biomass Burning and Lightning Experiment (BIBLE)-A and B conducted in August–October 1998 and 1999.Concentrations of ozone (O3) and its precursors [CO, reactive nitrogen (NOx), non-methane hydrocarbons (NMHCs)] were measured in these campaigns to identify the sources of NOx and to estimate the effects of biomass burning and lightning on photochemical production of O3. Over Indonesia, in-situ production of NOx by lightning was found to be a major source of reactive nitrogen in the upper troposphere during BIBLE-A. In some circumstances, increases in reactive nitrogen were often associated with enhancements in CO and NMHCs, suggesting that the sources were biomass burning and fossil fuel combustion, followed by upward transport by cumulus convection. Over Australia the levels of O3, CO, reactive nitrogen, and NMHCs were elevated throughout the troposphere compared to those observed in the tropical Pacific. However, the mechanisms responsible for the enhanced concentrations in the BL and FT are distinctly different. The emissions from biomass burning that occurred in northern Australia were restricted to the BL because of strong subsidence in the period. In the FT over Australia, elevated concentrations of O3 and its precursors result from injections of emissions as the air masses travel over Africa, South America, the Indian Ocean, and Indonesia en route to Australia. In all cases, O3 levels in the biomass burning plumes were enhanced due to photochemical production.

Evaluation of lightning flash rate parameterizations for use in a global chemical transport model

Model simulations of tropospheric O3 require an accurate specification of the reactive odd nitrogen (NOx) source from lightning that is consistent in time and space with convective transport of O3 precursors. Lightning NOx production in global models is often parameterized in terms of convective cloud top heights (CLDHT). However, a closer relationship may exist between flash rate and other measures of convective intensity. In this study, flash rates are parameterized in terms of CLDHT, convective precipitation (PRECON), and upward convective mass flux (MFLUX) from the Goddard Earth Observing System Data Assimilation System (GEOS DAS). GEOS‐based flash rates are compared to flash rates from the National Lightning Detection Network (NLDN) and Long Range Flash (LRF) network and the Optical Transient Detector (OTD). Overall, MFLUX‐based flash rates are most realistic. PRECON‐ and CLDHT‐based flash rates are too large in the tropics. The MFLUX‐ and PRECON‐based flash rates are a factor of 3 too high (low) over the equatorial western Pacific (central and southern Africa), while CLDHT‐based flash rates are much too low at nearly all marine locations. In many cases, biases in the flash rate distributions can be traced to biases in the GEOS DAS convective fields. Improvements in flash rate parameterizations will be tied closely to improvements in model physics as well as to increases in the amount of tropical data that are available for assimilation. Flash rates calculated from the 6‐hour averaged CLDHTs are much less variable than observed, and O3 production rates calculated using the NOx produced from these flash rates are likely to be larger than observed.

Structures and properties of BON and multilayered TiN/BON thin films prepared by PAMOCVD method

Hard multilayered TiN/BON thin films have been deposited on steel and copper substrates in the deposition temperature range of RT∼300 °C by low frequency RF derived plasma assisted MOCVD. Trimethylborate and tetrakisdimethylaminotitanium precursors were used to grow multilayered TiN/BON thin films. We used Ar gas for a plasma source and N2 gas as a reactive and additional nitrogen source. In this study, we have mainly investigated the relationship between hardness and structures of the coating layers by the effects of deposition parameters such as deposition time and substrate temperature. We found that the microhardness strongly depended on film thickness and structures of the bilayer films. In addition, the sequence of deposition procedure for the TiN/BON bilayers highly affected the hardness. The maximum hardness obtained from TiN/BON bilayer was 30 GPa.

A marine source of methyl nitrate

Methyl nitrate (CH3ONO2) is known to be an important source of reactive nitrogen in the remote marine atmosphere, and it has been speculated that its atmospheric distribution might be explained in part by an ocean source. Measurements made in the N. Atlantic show that dissolved CH3ONO2 is present at depths up to 600–800 m. Maximum concentrations are typically found in the upper water column, indicative of an in situ source. Although we show that CH3ONO2 can be produced photochemically in seawater in the presence of nitrite, and that this reaction may account for some production in the uppermost waters of the ocean, the maxima below this zone indicate that an additional production mechanism exists.

Stratospheric N2O–NOy system: Testing uncertainties in a three‐dimensional framework

Nitrous oxide (N2O) is an important greenhouse gas and the major source of stratospheric reactive nitrogen (NOy), an active participant in the stratospheric chemistry controlling ozone depletion. Tropospheric N2O abundances are increasing at nearly 0.3% yr−1 and this increase is expected to continue in the near future as are direct stratospheric NOy perturbations, for example, from aircraft. In order to test and gain confidence in three‐dimensional (3‐D) model simulations of the stratospheric N2O‐NOy system, a simplified photochemistry for N2O and NOy is developed for use in chemistry transport models (CTMs). This chemical model allows for extensive CTM simulations focusing on uncertainties in chemistry and transport. We compare 3‐D model simulations with measurements and evaluate the effect on N2O and NOy of potential errors in model transport, in column and local ozone, and in stratospheric temperatures. For example, with the three different 3‐D wind fields used here, modeled N2O lifetimes vary from 173 to 115 years, and the unrealistically long lifetimes produce clear errors in equatorial N2O profiles. The impact of Antarctic denitrification and an in situ atmospheric N2O source are also evaluated. The modeled N2O and NOy distributions are obviously sensitive to model transport, particularly the strength of tropical upwelling in the stratosphere. Midlatitude, lower‐stratospheric NO2/N2O correlations, including seasonal amplitudes, are well reproduced by the standard model when denitrification is included. These correlations are sensitive to changes in stratospheric chemistry but relatively insensitive to model transport. The lower stratospheric NOy/N2O correlation slope gives the correct net NOy production of about 0.5 Tg N yr−1 (i.e., the cross‐tropopause flux as in the Plumb‐Ko relation) only when N2O values from 250 to 310 ppb are used. As a consequence, the Synoz calibration of the flux of O3 from the stratosphere to the troposphere needs to be corrected to 550±140 Tg O3 yr−1.