Tracing the Origin and Fate of NO
            <sub>x</sub>
            in the Arctic Atmosphere Using Stable Isotopes in Nitrate

Morin, Samuel; Savarino, Joël; Frey, M. M.; Yan, Nicolas; Bekki, Slimane; Bottenheim, J. W.; Martins, Jean M.F.

doi:10.1126/science.1161910

Cited by 201 publications

(348 citation statements)

References 31 publications

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“…It should also be noted that the Δ 17 O used for ozone has no impact on this estimation because all 17 O-excess transfer mechanisms scale identically with this parameter (15), thus conserving the Δ 17 O seasonality. Nevertheless, in this study, we used Δ 17 O(O 3 ) measured in the vicinity of the CVAO, applying our unique analytical approach (37), and thus did not adjust this variable to match the observed Δ 17 O, in contrast to previous studies (7,12,13,18 (Fig. 2), the CTM largely favored its daytime chemistry (i.e., NO 2 + OH), placing too much emphasis on the N 2 O 5 hydrolysis and not enough on the NO 3 pathways.…”

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confidence: 99%

“…For also Table S2) shows the different chemistries used by the different models, with DMS (CH 3 SCH 3 ) being the main atmospheric sink of NO 3 (detailed information on the models and data reductions can be found in Materials and Methods and SI Text). (12,13,17,18). In the present study, a chemical box model (SSM) and a 3D model (CTM) are confronted with the CVAO observations, first with the observed concentrations and then with the stable oxygen isotope compositions.…”

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confidence: 99%

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Isotopic composition of atmospheric nitrate in a tropical marine boundary layer

Savarino

Morin

Erbland

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Long-term observations of the reactive chemical composition of the tropical marine boundary layer (MBL) are rare, despite its crucial role for the chemical stability of the atmosphere. Recent observations of reactive bromine species in the tropical MBL showed unexpectedly high levels that could potentially have an impact on the ozone budget. Uncertainties in the ozone budget are amplified by our poor understanding of the fate of NO x (= NO + NO 2 ), particularly the importance of nighttime chemical NO x sinks. Here, we present year-round observations of the multiisotopic composition of atmospheric nitrate in the tropical MBL at the Cape Verde Atmospheric Observatory. We show that the observed oxygen isotope ratios of nitrate are compatible with nitrate formation chemistry, which includes the BrNO 3 sink at a level of ca. 20 ± 10% of nitrate formation pathways. The results also suggest that the N 2 O 5 pathway is a negligible NO x sink in this environment. Observations further indicate a possible link between the NO 2 /NO x ratio and the nitrogen isotopic content of nitrate in this low NO x environment, possibly reflecting the seasonal change in the photochemical equilibrium among NO x species. This study demonstrates the relevance of using the stable isotopes of oxygen and nitrogen of atmospheric nitrate in association with concentration measurements to identify and constrain chemical processes occurring in the MBL.monitoring | oxidation | tropic | bromine chemistry | aerosols T he tropical marine lower troposphere is one of the most photochemically active compartments of the global atmosphere. The year-round high solar radiation, temperature, and humidity render this region the second largest contributor to methane removal via the OH sink (1). A large proportion of tropospheric ozone loss also occurs in the tropical marine boundary layer (MBL), where the concentrations of precursors, such as NO x (= NO + NO 2 ) and volatile organic carbons (VOCs) (2), are generally too low to keep the ozone production rate above its destruction rate. The destruction of ozone is further highlighted by the recently discovered role of halogen chemistry at low latitudes (3), which is known to destroy ozone catalytically (4). The subtle oxidation chemistry coupling NO x , halogens, and VOCs with ozone production and destruction in the MBL is still not fully understood, as demonstrated by the historically overlooked bromine chemistry (3) or the role of heterogeneous N 2 O 5 hydrolysis as a NO x sink (5, 6).Being the end product of the NO x /O 3 /VOC interaction, atmospheric nitrate is particularly well suited to probe such chemistry, especially through its stable isotope composition (7). Indeed, isotopic measurements have proven to be instrumental in identifying and quantifying sources, processes affecting the formation of atmospheric nitrate [particulate NO 3 − plus gas-phase nitric acid (HNO 3 ); hereafter defined as NO 3 − ], and the role of its precursors (i.e., the complex chemical interactions between NO x , halogens, and ozone...

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confidence: 99%

Isotopic composition of atmospheric nitrate in a tropical marine boundary layer

Savarino

Morin

Erbland

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…But there are also some promising new advances using ''anomalous'' oxygen isotope signatures (2): anomalous meaning isotope distributions that cannot be predicted by means of the usual statistical and quantum mechanical techniques (4). For oxygen, the anomaly is defined as the excess 17 O over what is expected based on 18 O isotopic abundances. This excess 17 O is quantified by ⌬ 17 O Ϸ ␦ 17 O Ϫ 0.52␦ 18 O or more precisely using natural log scales (5).…”

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confidence: 99%

“…For oxygen, the anomaly is defined as the excess 17 O over what is expected based on 18 O isotopic abundances. This excess 17 O is quantified by ⌬ 17 O Ϸ ␦ 17 O Ϫ 0.52␦ 18 O or more precisely using natural log scales (5). The process, or processes, that generate ⌬ 17 O signals have been termed mass-independent fractionations (MIF) (2,6) because the enrichments appear to scale irrespective of the relative mass differences of 17 O with respect to 18 O when referenced to 16 O.…”

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The role of symmetry in the mass independent isotope effect in ozone

Michalski

Bhattacharya

2009

Proc. Natl. Acad. Sci. U.S.A.

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Understanding the internal distribution of ''anomalous'' isotope enrichments has important implications for validating theoretical postulates on the origin of these enrichments in molecules such as ozone and for understanding the transfer of these enrichments to other compounds in the atmosphere via mass transfer. Here, we present an approach, using the reaction NO 2 ؊ ؉ O3, for assessing the internal distribution of the (7) and non-mass-dependent (NOMAD) (8, 9).The most thoroughly studied MIF system is that of ozone formation. Ozone generated by electric discharge or UV photolysis can produce ⌬ 17 O values of 30-40‰ (‰ ϭ parts per thousand). There have also been numerous studies that have experimentally quantified the pressure and temperature dependence of the isotopic enrichments (10, 11). Most recently, the transfer of the ⌬ 17 O anomaly from ozone to other compounds during oxidation reactions (via atom transfer, e.g., mass balance) has been used to elucidate chemical oxidation pathways in modern atmospheres (16-21). These include ⌬ 17 O observations in atmospheric nitrate, sulfate, CO 2 , and N 2 O. ⌬ 17 O variations in atmospheric nitrate and sulfate are intriguing because they have opened the possibility of using these ⌬ 17 O variations in ice cores as a proxy for paleo-oxidation chemistry (22,23). Modeling such transfer reactions, however, requires knowledge of the internal distribution of the ⌬ 17 O anomaly, i.e., how much is contained in the central versus terminal atoms of ozone, because many atmospheric oxidations are thought to occur through terminal-only transition states.Theories as to the origin of the MIF effect have taken many turns (7,8,24,25), and some theories seem more adept at handling specific experimental cases than others. Most have symmetry as the main, albeit ad hoc, causal mechanism for producing MIF. Recent work by Marcus and coworkers (26-28) is perhaps the most thorough treatment, and they have suggested that nonstatistical RRKM effects arise because of differences in the rovibronic coupling efficiency of the asymmetric molecule when compared with the symmetric isomer. Recent NO 2 spectroscopic data appear to bear the theory out (29), but the uncertainties in that study remain significant, and no mass spectrometer isotope data on the unimolecular decay of NO 2 are available. Because the basis of the ozone MIF theory is symmetry driven, it is implied that the anomalous enrichment must be contained in the terminal atoms of ozone. To be clear, there maybe overall isotopic enrichment (␦ 18 O, ␦ 17 O) distributed throughout the molecule based on isotopologue zero-point energy differences (30), but the 17 O excess (⌬ 17 O) is expected to be only in the terminal position. Others, however, have argued against the symmetry theory (31-33) and have placed anomalous enrichments, even negative ⌬ 17 O values (34), throughout ozone in an attempt to reconcile experimental observations. Precise and accurate measurements of ozone's ⌬ 17 O internal distribution is therefore needed to test the symmet...

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“…Nitrogen oxides (NOx) are mainly produced by the combustion of fuels from mobile and stationary sources, which leads to serious air pollution in the form of acid rain, photochemical smog, and haze [1,2]. Currently, the removal of NOx from lean-burn exhausts remains a major challenge in environmental catalysis because, in the presence of excess oxygen, NOx cannot be efficiently removed by traditional three-way catalysts.…”

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Adsorption states of typical intermediates on Ag/Al2O3 catalyst employed in the selective catalytic reduction of NOx by ethanol

Deng

2015

Chinese Journal of Catalysis

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The adsorption of ethanol and important intermediates onto Ag/Al2O3 catalyst employed in the selective catalytic reduction of NOx by ethanol was simulated by density functional theory. Considering the interaction between Ag metal and Al2O3 support, typical Ag-O-Al entities, i.e., Ag-O-Altetra and Ag-O-Alocta, (tetra = tetrahedral and octa = octahedral refer to the coordination sites of Al), were selected as potential adsorption sites on the surface of the catalyst. Ethanol, and enolic and isocyanate species were preferentially adsorbed and activated by Ag-O-Altetra entities rather than by Ag-O-Alocta entities. The strong Lewis acidity of Altetra in the Ag-O-Altetra entity was very important, enabling the entity to accept an electron via forward donation from either the C-O σ bond in ethanol or the N-C σ bond in the −NCO species. Moreover, the hybridization of the Ag and Al orbitals was critical for electron back donation from the Ag-O-Altetra entity to the C-C π bond in the enolic species or N-C π bond in the −NCO species. The significant activation of the N-C bond in −NCO on the Ag-O-Altetra sites facilitated cleavage of −NCO to form N2. Thus, we can conclude that the acidity of the Al site and the interaction between Ag and Al play key roles in the selective catalytic reduction of NOx by ethanol over Ag/Al2O3.

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Tracing the Origin and Fate of NO _x in the Arctic Atmosphere Using Stable Isotopes in Nitrate

Cited by 201 publications

References 31 publications

Isotopic composition of atmospheric nitrate in a tropical marine boundary layer

Isotopic composition of atmospheric nitrate in a tropical marine boundary layer

The role of symmetry in the mass independent isotope effect in ozone

Adsorption states of typical intermediates on Ag/Al2O3 catalyst employed in the selective catalytic reduction of NOx by ethanol

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Tracing the Origin and Fate of NO x in the Arctic Atmosphere Using Stable Isotopes in Nitrate

Cited by 201 publications

References 31 publications

Isotopic composition of atmospheric nitrate in a tropical marine boundary layer

Isotopic composition of atmospheric nitrate in a tropical marine boundary layer

The role of symmetry in the mass independent isotope effect in ozone

Adsorption states of typical intermediates on Ag/Al2O3 catalyst employed in the selective catalytic reduction of NOx by ethanol

Contact Info

Product

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Tracing the Origin and Fate of NO _x in the Arctic Atmosphere Using Stable Isotopes in Nitrate