Alkyl nitrate production and persistence in the Mexico City Plume (original) (raw)
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Journal of Geophysical Research, 2007
Histories of atmospheric N 2 Oconcentration and its d 15 Nand d 18 Owere reconstructed for the period 1952-2001 on the basis of the analyses of firn air collected at the North Greenland Ice Core Project (NGRIP), Greenland, and Dome Fuji and H72, Antarctica. The N 2 Oconcentration increased from 290 ppbv in 1952 to 316 ppbv in 2001, which agrees well with the results from atmospheric observations and polar ice core analyses. The d 15 Na nd d 18 Os howed as ecular decrease, the respective values being 8.9 and 21.5% in 1952 and 7.0 and 20.5% in 2001. Their rates of change also varied, from about À 0.02% yr À 1 in the 1950s to about À 0.04% yr À 1 in 1960-2001 for d 15 N, and from about 0 % yr À 1 to À 0.02% yr À 1 for d 18 O. The isotopic budgetary calculations using at wo-box model indicated that anthropogenic N 2 Oe mission from soils played a main role in the atmospheric N 2 Oi ncrease after industrialization, as well as that the average isotopic ratio of anthropogenic N 2 Oh as potentially been changed temporally.
2016
Formation of organic nitrates (RONO 2) during oxidation of biogenic volatile organic compounds (BVOCs: isoprene, monoterpenes) is a significant loss pathway for atmospheric nitrogen oxide radicals (NO x), but the chemistry of RONO 2 formation and degradation remains uncertain. Here we implement a new BVOC oxidation mechanism (including updated isoprene chemistry, new monoterpene chemistry, and particle uptake of RONO 2) in the GEOS-Chem global chemical transport model with ∼25×25 km 2 resolution over North America. We evaluate the model using aircraft (SEAC 4 RS) and ground-based (SOAS) observations of NO x , BVOCs, and RONO 2 from the Southeast US in summer 2013. The updated simulation successfully reproduces the concentrations of individual gas-and particle-phase RONO 2 species measured during the campaigns. Gas-phase isoprene nitrates account for 25-50% of observed RONO 2 in surface air, and we find that another 10% is contributed by gas-phase monoterpene nitrates. Observations in the free troposphere show an important contribution from long-lived nitrates derived from anthropogenic VOCs. During both campaigns, at least 10% of observed boundary layer RONO 2 were in the particle phase. We find that aerosol uptake followed by hydrolysis to HNO 3 accounts for 60% of simulated gas-phase RONO 2 loss in the boundary layer. Other losses are 20% by photolysis to recycle NO x and 15% by dry deposition. RONO 2 production accounts for 20% of the net regional NO x sink in the Southeast US in summer, limited by the spatial segregation between BVOC and NO x emissions. This segregation implies that RONO 2 production will remain a minor sink for NO x in the Southeast US in the future even as NO x emissions continue to decline. 1 Introduction Nitrogen oxide radicals (NO x ≡ NO + NO 2) are critical in controlling tropospheric ozone production (Monks et al., 2015, and references therein) and influencing aerosol formation (Rollins et al., 2012; Ayres et al., 2015; Xu et al., 2015), with indirect impacts on atmospheric oxidation capacity, air quality, climate forcing, and ecosystem health. The ability of NO x to influence ozone and aerosol budgets is tied to its atmospheric fate. In continental regions, a significant loss pathway for NO x is reaction with peroxy radicals derived from biogenic volatile organic compounds (BVOCs) to form organic nitrates (Liang et al., 1998; Browne and Cohen, 2012). NO x loss to organic nitrate formation is predicted to become increasingly important as NO x abundance declines (Browne and Cohen, 2012), as has occurred in the US over the past two decades (Hidy et al., 2014; Simon et al., 2015). Despite this increasing influence on the NO x budget, the chemistry of organic nitrates remains the subject of debate, with key uncertainties surrounding the organic nitrate yield from BVOC oxidation, the recycling of NO x from organic nitrate degradation, and the role of organic nitrates in secondary organic aerosol formation (Paulot et al., 2012; Perring et al., 2013). Two campaigns in the Southeast US in summer 2013 provided datasets of unprecedented chemical detail for addressing these uncertainties: the airborne NASA SEAC 4 RS (Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys; Toon et al., 2016) and the ground-based SOAS (Southern Oxidants and Aerosols Study). Here we use a ∼25×25 km 2 resolution 3-D chemical transport model (GEOS-Chem) to interpret organic nitrate observations from both campaigns, with focus on their impacts on atmospheric nitrogen (N) budgets. Nitrogen oxides are emitted from natural and anthropogenic sources primarily as NO, which rapidly achieves steady state with NO 2. Globally, the dominant loss pathway for NO x is reaction with the hydroxyl radical (OH) to form nitric acid (HNO 3).
Abundance of NO3 Derived Organo-Nitrates and Their Importance in the Atmosphere
Atmosphere
The chemistry of the nitrate radical and its contribution to organo-nitrate formation in the troposphere has been investigated using a mesoscale 3-D chemistry and transport model, WRF-Chem-CRI. The model-measurement comparisons of NO2, ozone and night-time N2O5 mixing ratios show good agreement supporting the model’s ability to represent nitrate (NO3) chemistry reasonably. Thirty-nine organo-nitrates in the model are formed exclusively either from the reaction of RO2 with NO or by the reaction of NO3 with alkenes. Temporal analysis highlighted a significant contribution of NO3-derived organo-nitrates, even during daylight hours. Night-time NO3-derived organo-nitrates were found to be 3-fold higher than that in the daytime. The reactivity of daytime NO3 could be more competitive than previously thought, with losses due to reaction with VOCs (and subsequent organo-nitrate formation) likely to be just as important as photolysis. This has highlighted the significance of NO3 in daytime o...
Governing processes for reactive nitrogen compounds in the European atmosphere
Biogeosciences, 2012
Reactive nitrogen (N r) compounds have different fates in the atmosphere due to differences in governing processes of physical transport, deposition and chemical transformation. N r compounds addressed here include reduced nitrogen (NH x : ammonia (NH 3) and its reaction product ammonium (NH + 4)), oxidized nitrogen (NO y : nitrogen monoxide (NO) + nitrogen dioxide (NO 2) and their reaction products) as well as organic nitrogen compounds (organic N). Pollution abatement strategies need to take into account these differences in the governing processes of these compounds when assessing their impact on ecosystem services, biodiversity, human health and climate. NO x (NO + NO 2) emitted from traffic affects human health in urban areas where the presence of buildings increases the residence time in streets. In urban areas this leads to enhanced exposure of the population to NO x concentrations. NO x emissions have little impact on nearby ecosystems because of the small dry deposition rates of NO x. These compounds need to be converted into nitric acid (HNO 3) before removal through deposition is efficient. HNO 3 sticks quickly to any surface and is thereby either dry deposited or incorporated into aerosols as nitrate (NO − 3). In contrast to NO x compounds, NH 3 has potentially high impacts on ecosystems near the main agricultural sources of NH 3 because of its large ground-level concentrations along with large dry deposition rates. Aerosol phase NH + 4 and NO − 3 contribute significantly to background PM 2.5 and PM 10 (mass of aerosols with a diameter of less than 2.5 and 10 µm, respectively) with an impact on radiation balance as well as potentially on human health. Little is known quantitatively and qualitatively about organic N in the atmosphere, other than that it contributes a significant fraction of wet-deposited N, and is present in both gaseous and particulate forms in the atmosphere. Further studies are needed to characterize the sources, air chemistry and removal rates of organic N emissions.
npj Climate and Atmospheric Science
Inorganic nitrate production is critical in atmospheric chemistry that reflects the oxidation capacity and the acidity of the atmosphere. Here we use the oxygen anomaly of nitrate (Δ17O($$\rm{NO}_{3}^{-}$$ NO 3 − )) in high-time-resolved (3 h) aerosols to explore the chemical mechanisms of nitrate evolution in fine particles during the winter in Nanjing, a megacity of China. The continuous Δ17O($$\rm{NO}_{3}^{-}$$ NO 3 − ) observation suggested the dominance of nocturnal chemistry (NO3 + HC/H2O and N2O5 + H2O/Cl−) in nitrate formation in the wintertime. Significant diurnal variations of nitrate formation pathways were found. The contribution of nocturnal chemistry increased at night and peaked (72%) at midnight. Particularly, nocturnal pathways became more important for the formation of nitrate in the process of air pollution aggravation. In contrast, the contribution of daytime chemistry (NO2 + OH/H2O) increased with the sunrise and showed a highest fraction (48%) around noon. The ...
Atmospheric Chemistry and Physics, 2016
Formation of organic nitrates (RONO 2) during oxidation of biogenic volatile organic compounds (BVOCs: isoprene, monoterpenes) is a significant loss pathway for atmospheric nitrogen oxide radicals (NO x), but the chemistry of RONO 2 formation and degradation remains uncertain. Here we implement a new BVOC oxidation mechanism (including updated isoprene chemistry, new monoterpene chemistry, and particle uptake of RONO 2) in the GEOS-Chem global chemical transport model with ∼ 25 × 25 km 2 resolution over North America. We evaluate the model using aircraft (SEAC 4 RS) and ground-based (SOAS) observations of NO x , BVOCs, and RONO 2 from the Southeast US in summer 2013. The updated simulation successfully reproduces the concentrations of individual gas-and particlephase RONO 2 species measured during the campaigns. Gasphase isoprene nitrates account for 25-50 % of observed RONO 2 in surface air, and we find that another 10 % is contributed by gas-phase monoterpene nitrates. Observations in the free troposphere show an important contribution from long-lived nitrates derived from anthropogenic VOCs. During both campaigns, at least 10 % of observed boundary layer RONO 2 were in the particle phase. We find that aerosol uptake followed by hydrolysis to HNO 3 accounts for 60 % of simulated gas-phase RONO 2 loss in the boundary layer. Other losses are 20 % by photolysis to recycle NO x and 15 % by dry deposition. RONO 2 production accounts for 20 % of the net regional NO x sink in the Southeast US in summer, limited by the spatial segregation between BVOC and NO x emissions. This segregation implies that RONO 2 production will remain a minor sink for NO x in the Southeast US in the future even as NO x emissions continue to decline.
Journal of Geophysical Research, 1986
Measurements of NO, Na2, HNa3, particulate nitrate, peroxyacetyl nitrate (PAN), 03, and total reactive odd nitrogen (Nay) were made in the nonurban troposphere during the summer and fall of 1984. The field site was located near Niwot Ridge, Colorado, at an elevation of 3 km. Nay was measured by catalytic reduction to NO, followed by the detection of NO with a chemiluminescence instrument. The other species were measured with conventional techniques. The data and interpretation presented focus primarily on the relationships between a measurement of Nay and concurrent measurements of the individual species, as examined through ratio and correlation plots. Through the separate display of daytime and nighttime data, the plots provide insight into the photochemical nature of the individual species. In addition, the composition of Nay is addressed through a comparison of the measured Nay level with that found for the sum of the measured component species. The Nay level systematically exceeded the sum level, with the difference being larger in the summer than in the fall. The presence of organic nitrate species other than PAN is proposed as one way to account for the observed difference. 1. INTRODUCTION The important role of the nitrogen oxides in atmospheric chemistry has long been recognized [Haagan-Smit, 1952]. Current modeling efforts in both the stratosphere and the troposphere give the details of this role [Logan et al., 1981; Solomon and Garcia, 1983; National Research Council (NRC), 1984]. In the troposphere the chemistry of the nitrogen oxides leads to local oxidant and acid production. In the stratosphere the chemistry contributes to the maintenance of the ozone layer. The current level of understanding of nitrogen oxide chemistry has been provided in part by the development and use of specific detection techniques, of which those for NO, NO2, HNO3, and peroxyacetyl nitrate (PAN) are important examples. In contrast, the measurement of total reactive odd nitrogen NOy is a more recent development. NOy is defined to be the sum of the important component species: NOy = NO + NO2 + HNO3 + HONO + HO2NO2 + NO3 + 2N205 + PAN + particulate nitrate (NO3-) + ... (1) The need for a comprehensive budget experiment to understand the chemistry of nitrogen species has been cited by the Global Tropospheric Chemistry Program [NRC, 1984, p. 35].