<table><caption>**Table 4.** Mean observed δ¹⁵N data of NO₂ (δ¹⁵N(NO₂)) and NO₃⁻ (δ¹⁵N(NO₃⁻)), calculated atmospheric δ¹⁵N of NOₓ (δ¹⁵N(NOₓ)), and δ¹⁵N shift between δ¹⁵N(NO₃⁻) and δ¹⁵N(NO₂) (Δ¹⁵(NO₃⁻ - NO₂)).</caption><thead><tr><th></th><th></th><th>δ¹⁵N(NO₂) (‰)</th><th>δ¹⁵N(NO₃⁻) (‰)</th><th>δ¹⁵N(NOₓ) (‰)</th><th>Δ¹⁵N(NO₃⁻ - NO₂) (‰)</th></tr></thead><tbody><tr><td rowspan="2">Daytime (07:30–18:00)</td><td>SP 1</td><td>7.4 ± 4.7</td><td>7.0 ± 6.7</td><td>-9.9 ± 2.9</td><td>-0.4</td></tr><tr><td>SP 2</td><td>14.0 ± 13.9</td><td>4.0 ± 6.4</td><td>-10.8 ± 2.1</td><td>-10.0</td></tr><tr><td rowspan="2">Nighttime (18:00–07:30)</td><td>SP 1</td><td>-5.1 ± 2.3</td><td>1.4 ± 1.2</td><td>-9.0 ± 0.8</td><td>6.3</td></tr><tr><td>SP 2</td><td>-2.5 ± 4.2</td><td>-1.1 ± 0.4</td><td>-9.9 ± 1.9</td><td>1.4</td></tr></tbody></table>

were conducted at high temporal resolution (~3 h) in Chamonix, the French Alps, over 2 distinct days in late February 2021. The isotopic signals of both NO₂ and NO₃⁻ show substantial diurnal variabilities, which are investigated in the light of local meteorological parameters and atmospheric observations (NO, NO₂, O₃, and PM).

The observed variability in Δ¹⁷O(NO₂) can be well explained using Δ¹⁷O mass balance equations and corroborates the analysis of previous observations carried out in Grenoble, the French Alps, over a single day in spring (Albertin et al., 2021). On average, the high levels of NO₂ at our site are primarily driven by the oxidation of local NO emissions by O₃. The observed diurnal variability in Δ¹⁷O(NO₂) appears to be consistent with the diurnal variability expected in the NOₓ/O₃/RO₂ chemistry, with RO₂ levels of the order of pmol mol⁻¹, which is in agreement with the range of direct winter RO₂ measurements reported in the literature. RO₂ is thought to contribute significantly to the formation of NO₂ in the early morning under high-NOₓ conditions, which is in line with the effective morning production of radical species reported in urban areas in winter. At night, Δ¹⁷O(NO₂) reflects the nocturnal oxidation of surface NO emissions by O₃. These results provide additional evidence that Δ¹⁷O(NO₂) measurements represent valuable constraints in the study of the reactive NOₓ chemistry, down to the sub-daily temporal scales.

A clear linear relationship is found between δ¹⁵N(NO₂) and the NO₂/NOₓ ratio, indicating significant post-emission N fractionation effects. Theoretical N isotopic fractionation factors between NO and NO₂ at equilibrium and fractionation factors derived from the isotopic observations are found to be in good agreement, providing further support for the N isotopic fractionation theoretical framework commonly applied to the Leighton cycle. Observed δ¹⁵N(NO₂) corrected for N fractionation effects allows us to estimate the overall δ¹⁵N signature of ambient NOₓ at our site. Based on the existing δ¹⁵N fingerprints of different NOₓ emission sources, the main contribution at our site is very likely to be vehicle exhaust, which is confirmed by local emission inventories.

We use Δ¹⁷O mass balance equations of NO₃⁻ constrained by observed Δ¹⁷O(NO₂) to assess whether NO₃⁻ could originate locally from the oxidation of NO₂ at our site. During the first day of sampling, Δ¹⁷O records of NO₂ and NO₃⁻

support the local oxidation of NO₂ to NO₃⁻ by OH radicals during the day and via the heterogeneous hydrolysis of N₂O₅ during the night. The second day of sampling was affected by a Saharan dust event, accompanied by notable changes in the isotopic composition of NO₃⁻. We propose that the formation of a surface inversion layer at night could have influenced the vertical distribution of Δ¹⁷O(NO₂) and resulted in a positive gradient of Δ¹⁷O(NO₃⁻) with altitude, independently of the local NO₂-to-NO₃⁻ conversion processes near the surface. In such a scenario, the presence of Saharan dust could have promoted heterogeneous NO₂ oxidation, leading to higher Δ¹⁷O in NO₃⁻ formed aloft. The latter would have then mixed with the NO₃⁻ formed near the surface when the inversion broke up during the day. Although still uncertain, the influence of the boundary layer dynamics on the distribution of Δ¹⁷O in NO₃⁻ should be investigated in the future, notably for urban areas in winter.

The combined analysis of the first concurrent observations of δ¹⁵N in NO₂ and NO₃⁻ highlights persistent uncertainties in the current estimates of the N fractionation factors associated with NO₂ and NO₃⁻ conversion processes. However, δ¹⁵N(NO₃⁻) records need to be corrected for N fractionation effects if they are to be used to trace back the δ¹⁵N fingerprint of the primary NOₓ emission sources. Detailed simulation chamber experiments could provide more kinetic data on the various N fractionation processes in order to better exploit δ¹⁵N(NO₃⁻) records to identify and quantify of the sources of reactive nitrogen.

The present thorough investigation of the Δ¹⁷O and δ¹⁵N in NO₂ and NO₃⁻ highlights (1) the potential to use sub-daily Δ¹⁷O and δ¹⁵N records to trace the sources and formation chemistry of NO₃⁻, (2) the importance of measuring the NO₂ isotopic composition to avoid misinterpretation of NO₃⁻ isotopic records, and (3) the persistent knowledge gaps that prevent a complete assessment of the factors driving the variability in NO₃⁻ isotopic records. In most studies, the NO₃⁻ isotopic composition is interpreted on the basis of estimates of the isotopic composition of its precursor gases, assuming that both the chemistry of NO₂ (including its conversion to NO₃⁻) and N isotopic fractionation effects are known. However, these assumptions are subject to very significant uncertainties, mainly in urban atmospheres. Hence, given the recent development of a method for measuring the multi-
isotopic composition of NO₂, the accuracy and validity of the current interpretation framework of NO₃⁻ isotopic records should be tested in various environments. Such investigation can be performed by simultaneously collecting NO₂ and NO₃⁻, as done here. We recommend using this combined isotopic record in order to avoid biased interpretations of NO₃⁻ isotopic records, particularly in urban areas during winter, preferably at high temporal resolution (< 24 h). In addition, the vertical distribution of NO₂ and NO₃⁻ isotopic composition should be documented in order to explore the possible role of the boundary layer dynamics in the variability in NO₂ and NO₃⁻ isotopic composition observed at the surface.

## Appendix A: Reaction chemical rate

<table><caption>**Table A1.** Kinetic constants used in this study.</caption><thead><tr><th>Reactions</th><th>Rate constants (cm<sup>3</sup> mol<sup>-1</sup> s<sup>-1</sup>)</th><th>References</th></tr></thead><tbody><tr><td>NO + O<sub>3</sub> → NO<sub>2</sub> + O<sub>2</sub></td><td>k<sub>NO+O<sub>3</sub></sub> = 1.4 × 10<sup>-12</sup> exp(-1310(K)/T)</td><td>Atkinson et al. (2004)</td></tr><tr><td>NO + RO<sub>2</sub> → NO<sub>2</sub> + RO</td><td>k<sub>NO+RO<sub>2</sub></sub> = 2.3 × 10<sup>-12</sup> exp(360(K)/T)</td><td>Atkinson et al. (2006)</td></tr><tr><td>NO<sub>2</sub> + O<sub>3</sub> → NO<sub>3</sub><sup>-</sup> + O<sub>2</sub></td><td>k<sub>NO<sub>2</sub>+O<sub>3</sub></sub> = 1.4 × 10<sup>-13</sup> exp(-2470(K)/T)</td><td>Atkinson et al. (2004)</td></tr><tr><td><sup>15</sup>NO<sub>2</sub> + <sup>14</sup>NO → <sup>14</sup>NO<sub>2</sub> + <sup>15</sup>NO</td><td>k<sub>NO+NO<sub>2</sub></sub> = 8.14 × 10<sup>-14</sup></td><td>Sharma et al. (1970)</td></tr></tbody></table>

## Appendix B: Atmospheric lifetime of NO₂ and NO₃⁻

<table><caption>**Table B1.** Mean daytime (07:30–18:00 LT) and nighttime (18:00–07:30 LT) atmospheric lifetime of NO₂ ($\tau_{NO_2}$) and NO₃⁻ ($\tau_{NO_3^-}$) and dry-deposition constant ($k_d = V_d \times BLH$, where $V_d$ is the dry-deposition velocity and BLH is the boundary layer height).</caption><thead><tr><th></th><th>τ<sub>NO₂</sub><sup>a</sup></th><th>τ<sub>NO₃⁻</sub><sup>b</sup></th><th>k<sub>d(NO₂)</sub> (s<sup>-1</sup>)</th><th>k<sub>d(NO₃⁻)</sub> (s<sup>-1</sup>)</th></tr></thead><tbody><tr><td>Daytime (07:30–18:00)</td><td>5.1 min</td><td>27.8 h</td><td>0.5 × 10<sup>-5</sup></td><td>1.0 × 10<sup>-5</sup></td></tr><tr><td>Nighttime (18:00–07:30)</td><td>10.0 h</td><td>5.6 h</td><td>2.5 × 10<sup>-5</sup></td><td>5.0 × 10<sup>-5</sup></td></tr></tbody></table>

<footnote><sup>a</sup> Atmospheric lifetime relative to photolysis during the day (dry deposition and reaction NO₂ + OH are negligible) and to dry deposition and oxidation via O₃ during the night. <sup>b</sup> Atmospheric lifetime relative to dry deposition. The boundary layer is fixed at 500 m during the day and at 100 m during the night. The dry-deposition velocity ($V_d$) is fixed at 0.25 and 0.50 cm s⁻¹ for NO₂ and NO₃⁻, respectively (Holland et al., 1999; Zhang et al., 2009).</footnote>
isotopic composition of NO₂, the accuracy and validity of the current interpretation framework of NO₃⁻ isotopic records should be tested in various environments. Such investigation can be performed by simultaneously collecting NO₂ and NO₃⁻, as done here. We recommend using this combined isotopic record in order to avoid biased interpretations of NO₃⁻ isotopic records, particularly in urban areas during winter, preferably at high temporal resolution (< 24 h). In addition, the vertical distribution of NO₂ and NO₃⁻ isotopic composition should be documented in order to explore the possible role of the boundary layer dynamics in the variability in NO₂ and NO₃⁻ isotopic composition observed at the surface.

## Appendix A: Reaction chemical rate

<table><caption>**Table A1.** Kinetic constants used in this study.</caption><thead><tr><th>Reactions</th><th>Rate constants (cm<sup>3</sup> mol<sup>-1</sup> s<sup>-1</sup>)</th><th>References</th></tr></thead><tbody><tr><td>NO + O<sub>3</sub> → NO<sub>2</sub> + O<sub>2</sub></td><td>k<sub>NO+O<sub>3</sub></sub> = 1.4 × 10<sup>-12</sup> exp(-1310(K)/T)</td><td>Atkinson et al. (2004)</td></tr><tr><td>NO + RO<sub>2</sub> → NO<sub>2</sub> + RO</td><td>k<sub>NO+RO<sub>2</sub></sub> = 2.3 × 10<sup>-12</sup> exp(360(K)/T)</td><td>Atkinson et al. (2006)</td></tr><tr><td>NO<sub>2</sub> + O<sub>3</sub> → NO<sub>3</sub><sup>-</sup> + O<sub>2</sub></td><td>k<sub>NO<sub>2</sub>+O<sub>3</sub></sub> = 1.4 × 10<sup>-13</sup> exp(-2470(K)/T)</td><td>Atkinson et al. (2004)</td></tr><tr><td><sup>15</sup>NO<sub>2</sub> + <sup>14</sup>NO → <sup>14</sup>NO<sub>2</sub> + <sup>15</sup>NO</td><td>k<sub>NO+NO<sub>2</sub></sub> = 8.14 × 10<sup>-14</sup></td><td>Sharma et al. (1970)</td></tr></tbody></table>

## Appendix B: Atmospheric lifetime of NO₂ and NO₃⁻

<table><caption>**Table B1.** Mean daytime (07:30–18:00 LT) and nighttime (18:00–07:30 LT) atmospheric lifetime of NO₂ ($\tau_{NO_2}$) and NO₃⁻ ($\tau_{NO_3^-}$) and dry-deposition constant ($k_d = V_d \times BLH$, where $V_d$ is the dry-deposition velocity and BLH is the boundary layer height).</caption><thead><tr><th></th><th>τ<sub>NO₂</sub><sup>a</sup></th><th>τ<sub>NO₃⁻</sub><sup>b</sup></th><th>k<sub>d(NO₂)</sub> (s<sup>-1</sup>)</th><th>k<sub>d(NO₃⁻)</sub> (s<sup>-1</sup>)</th></tr></thead><tbody><tr><td>Daytime (07:30–18:00)</td><td>5.1 min</td><td>27.8 h</td><td>0.5 × 10<sup>-5</sup></td><td>1.0 × 10<sup>-5</sup></td></tr><tr><td>Nighttime (18:00–07:30)</td><td>10.0 h</td><td>5.6 h</td><td>2.5 × 10<sup>-5</sup></td><td>5.0 × 10<sup>-5</sup></td></tr></tbody></table>

<footnote><sup>a</sup> Atmospheric lifetime relative to photolysis during the day (dry deposition and reaction NO₂ + OH are negligible) and to dry deposition and oxidation via O₃ during the night. <sup>b</sup> Atmospheric lifetime relative to dry deposition. The boundary layer is fixed at 500 m during the day and at 100 m during the night. The dry-deposition velocity ($V_d$) is fixed at 0.25 and 0.50 cm s⁻¹ for NO₂ and NO₃⁻, respectively (Holland et al., 1999; Zhang et al., 2009).</footnote>
## Appendix C: Schematic of the N reactive cycle and associated Δ¹⁷O transfers and N enrichment factors

<figure><img src="image_8.png" /></figure>

**Figure C1.** Adapted from Elliott et al. (2019). Sketch of dominant daytime (thick yellow arrows) and nighttime (thick cyan arrows) NOₓ-to-NO₃⁻ conversion processes and associated quantified N fractionation effects at 298 K (thin red arrows and text) and Δ¹⁷O transfers (yellow and cyan boxes).

## Appendix D: Equilibrium N fractionation factors

**Table D1.** Calculated regression coefficients for the N isotope exchange between NO₂/NO and N₂O₅/NO₂ over the temperature range of 150 to 450 K (Walters and Michalski, 2015) and for the N kinetic fractionation for the reaction NO + O₃ over the temperature range of 220 to 320 K (Fang et al., 2021).

<table><tbody><tr><td colspan="5">($\alpha_{\text{EIE}}(X/Y) - 1) \times 1000 = \frac{A}{T^4} \times 10^{10} + \frac{B}{T^3} \times 10^8 + \frac{C}{T^2} \times 10^6 + \frac{D}{T} \times 10^4$</td></tr><tr><th>X/Y</th><th>A</th><th>B</th><th>C</th><th>D</th></tr><tr><td>NO₂/NO</td><td>3.847</td><td>-7.680</td><td>6.003</td><td>-0.118</td></tr><tr><td>N₂O₅/NO₂</td><td>1.004</td><td>-2.525</td><td>2.718</td><td>0.135</td></tr><tr><td colspan="5">($\alpha_{\text{KIE}}(X+Y) - 1) \times 1000 = A \times \exp(B/T)$</td></tr><tr><th>X + Y</th><th>A</th><th>B</th><td></td><td></td></tr><tr><td>NO + O₃</td><td>0.982</td><td>3.352</td><td></td><td></td></tr></tbody></table>

**Data availability.** Data presented in this article are included in the Supplement.

**Supplement.** The supplement related to this article is available online at: https://doi.org/10.5194/acp-24-1361-2024-supplement.

**Author contributions.** Grants obtained by KL and JS funded the project. AB, RG, QF, and IV performed the calibration of IBBCEAS and OFCEAS instruments, data acquisition, and post-processing. SA conducted the sampling and laboratory analysis. NC provided technical support for isotopic mass spectrometry analysis. The study was designed as part of SA's PhD thesis supervised by SB and JS. The paper was written by SA under the supervision of JS and SB and with contributions from all co-authors.
## Appendix C: Schematic of the N reactive cycle and associated Δ¹⁷O transfers and N enrichment factors

<figure><img src="image_8.png" /></figure>

**Figure C1.** Adapted from Elliott et al. (2019). Sketch of dominant daytime (thick yellow arrows) and nighttime (thick cyan arrows) NOₓ-to-NO₃⁻ conversion processes and associated quantified N fractionation effects at 298 K (thin red arrows and text) and Δ¹⁷O transfers (yellow and cyan boxes).

## Appendix D: Equilibrium N fractionation factors

**Table D1.** Calculated regression coefficients for the N isotope exchange between NO₂/NO and N₂O₅/NO₂ over the temperature range of 150 to 450 K (Walters and Michalski, 2015) and for the N kinetic fractionation for the reaction NO + O₃ over the temperature range of 220 to 320 K (Fang et al., 2021).

<table><tbody><tr><td colspan="5">($\alpha_{\text{EIE}}(X/Y) - 1) \times 1000 = \frac{A}{T^4} \times 10^{10} + \frac{B}{T^3} \times 10^8 + \frac{C}{T^2} \times 10^6 + \frac{D}{T} \times 10^4$</td></tr><tr><td>X/Y</td><td>A</td><td>B</td><td>C</td><td>D</td></tr><tr><td>NO₂/NO</td><td>3.847</td><td>-7.680</td><td>6.003</td><td>-0.118</td></tr><tr><td>N₂O₅/NO₂</td><td>1.004</td><td>-2.525</td><td>2.718</td><td>0.135</td></tr><tr><td colspan="5">($\alpha_{\text{KIE}}(X+Y) - 1) \times 1000 = A \times \exp(B/T)$</td></tr><tr><td>X + Y</td><td>A</td><td>B</td><td></td><td></td></tr><tr><td>NO + O₃</td><td>0.982</td><td>3.352</td><td></td><td></td></tr></tbody></table>

**Data availability.** Data presented in this article are included in the Supplement.

**Supplement.** The supplement related to this article is available online at: https://doi.org/10.5194/acp-24-1361-2024-supplement.

**Author contributions.** Grants obtained by KL and JS funded the project. AB, RG, QF, and IV performed the calibration of IBBCEAS and OFCEAS instruments, data acquisition, and post-processing. SA conducted the sampling and laboratory analysis. NC provided technical support for isotopic mass spectrometry analysis. The study was designed as part of SA's PhD thesis supervised by SB and JS. The paper was written by SA under the supervision of JS and SB and with contributions from all co-authors.
**Competing interests.** The contact author has declared that none of the authors has any competing interests.

**Disclaimer.** Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors.

**Acknowledgements.** This work benefited from CNRS and IGE infrastructures and laboratory platforms. The authors acknowledge the support of the CASPA programme (Climate-relevant Aerosol Sources and Processes in the Arctic). The authors gratefully acknowledge Catherine Coulaud for providing temperature data in Chamonix; Jean-Luc Jaffrezo for providing data of previous filter measurements in Chamonix; and Anthony Lemoine, Matthieu Lafaysse and Louis Le Toumelin for providing S2M re-analysis and meteorological data. The authors particularly thank Patrick Ginot, Anthony Vella, Armelle Crouzet, and Bruno Jourdain for instrumental and laboratory technical support. Finally, the authors thank Alexis Lamothe for assistance during the sampling campaign and Pete Akers for his thorough proofreading of the manuscript and his constructive comments.

**Financial support.** This research has been supported by the Agence Nationale de la Recherche (ANR) via contract ANR-21-CE01-0017 CASPA and INSU/CNRS (National Institute of Sciences of the Universe) via its national LEFE programme (Les Enveloppes Fluides et l'Environnement) and by a grant from LabEx OSUG@2020 (Investissements d'avenir – ANR10 LABX56) and the IDEX-UGA ANR project ANR-15-IDEX-02.

**Review statement.** This paper was edited by Markus Ammann and reviewed by Lei Geng and one anonymous referee.

## References

Albertin, S.: Author Comment 2, Reply on RC2, https://doi.org/10.5194/egusphere-2023-744-AC2, 2023.

Albertin, S., Savarino, J., Bekki, S., Barbero, A., and Caillon, N.: Measurement report: Nitrogen isotopes ($\delta^{15}$N) and first quantification of oxygen isotope anomalies ($\Delta^{17}$O, $\delta^{18}$O) in atmospheric nitrogen dioxide, Atmos. Chem. Phys., 21, 10477–10497, https://doi.org/10.5194/acp-21-10477-2021, 2021.

Alexander, B., Hastings, M. G., Allman, D. J., Dachs, J., Thornton, J. A., and Kunasek, S. A.: Quantifying atmospheric nitrate formation pathways based on a global model of the oxygen isotope composition ($\Delta^{17}$O) of atmospheric nitrate, Atmos. Chem. Phys., 9, 5043–5056, https://doi.org/10.5194/acp-9-5043-2009, 2009.

Alexander, B., Sherwen, T., Holmes, C. D., Fisher, J. A., Chen, Q., Evans, M. J., and Kasibhatla, P.: Global inorganic nitrate production mechanisms: comparison of a global model with nitrate

isotope observations, Atmos. Chem. Phys., 20, 3859–3877, https://doi.org/10.5194/acp-20-3859-2020, 2020.

Alicke, B., Geyer, A., Hofzumahaus, A., Holland, F., Konrad, S., Pätz, H. W., Schäfer, J., Stutz, J., Volz-Thomas, A., and Platt, U.: OH formation by HONO photolysis during the BERLIOZ experiment, J. Geophys. Res.-Atmos., 108, PHO 3-1–PHO 3-17, https://doi.org/10.1029/2001JD000579, 2003.

Allard, J.: Qualité de l'air dans la Vallée de l'Arve: météorologie locale et mesures des réductions des émissions liées au chauffage au bois, PhD Thesis, Université Grenoble Alpes, https://theses.hal.science/tel-01901636 (last access: 25 January 2024), 2018.

Ammann, M., Siegwolf, R., Pichlmayer, F., Suter, M., Saurer, M., and Brunold, C.: Estimating the uptake of traffic-derived NO₂ from ¹⁵N abundance in Norway spruce needles, Oecologia, 118, 124–131, https://doi.org/10.1007/s004420050710, 1999.

Angelisi, M. D. and Gaudichet, A.: Saharan dust deposition over Mont Blanc (French Alps) during the last 30 years, Tellus B, 43, 61–75, https://doi.org/10.1034/j.1600-0889.1991.00005.x, 1991.

Appel, B. R., Wall, S. M., Tokiwa, Y., and Haik, M.: Simultaneous nitric acid, particulate nitrate and acidity measurements in ambient air, Atmos. Environ., 14, 549–554, https://doi.org/10.1016/0004-6981(80)90084-0, 1980.

Appel, B. R., Tokiwa, Y., and Haik, M.: Sampling of nitrates in ambient air, Atmos. Environ., 15, 283–289, https://doi.org/10.1016/0004-6981(81)90029-9, 1981.

Atkinson, R., Baulch, D. L., Cox, R. A., Crowley, J. N., Hampson, R. F., Hynes, R. G., Jenkin, M. E., Rossi, M. J., and Troe, J.: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume I – gas phase reactions of Oₓ, HOx, NOₓ and SOₓ species, Atmos. Chem. Phys., 4, 1461–1738, https://doi.org/10.5194/acp-4-1461-2004, 2004.

Atkinson, R., Baulch, D. L., Cox, R. A., Crowley, J. N., Hampson, R. F., Hynes, R. G., Jenkin, M. E., Rossi, M. J., Troe, J., and IUPAC Subcommittee: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II – gas phase reactions of organic species, Atmos. Chem. Phys., 6, 3625–4055, https://doi.org/10.5194/acp-6-3625-2006, 2006.

Atmo-Auvergne-Rhône-Alpes: Bilan des connaissances sur la qualité de l'air dans la vallée de l'Arve, Atmo-Auvergne-Rhône-Alpes, https://www.atmo-auvergnerhonealpes.fr/publications/bilan-des-connaissances-sur-la-qualite-de-lair-dans-la-vallee-de-larve (last access: July 2021), 2018.

Aumont, B., Chervier, F., and Laval, S.: Contribution of HONO sources to the NOₓ/HOx/O₃ chemistry in the polluted boundary layer, Atmos. Environ., 37, 487–498, https://doi.org/10.1016/S1352-2310(02)00920-2, 2003.

Aymoz, G., Jaffrezo, J.-L., Jacob, V., Colomb, A., and George, Ch.: Evolution of organic and inorganic components of aerosol during a Saharan dust episode observed in the French Alps, Atmos. Chem. Phys., 4, 2499–2512, https://doi.org/10.5194/acp-4-2499-2004, 2004.

Aymoz, G., Jaffrezo, J. L., Chapuis, D., Cozic, J., and Maenhaut, W.: Seasonal variation of PM₁₀ main constituents in two valleys of the French Alps: I. EC/OC fractions, Atmos. Chem. Phys., 7, 661–675, https://doi.org/10.5194/acp-7-661-2007, 2007.

Barbero, A., Blouzon, C., Savarino, J., Caillon, N., Dommergue, A., and Grilli, R.: A compact incoherent broadband cavity-enhanced absorption spectrometer for trace detection of nitrogen
**Competing interests.** The contact author has declared that none of the authors has any competing interests.

**Disclaimer.** Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors.

**Acknowledgements.** This work benefited from CNRS and IGE infrastructures and laboratory platforms. The authors acknowledge the support of the CASPA programme (Climate-relevant Aerosol Sources and Processes in the Arctic). The authors gratefully acknowledge Catherine Coulaud for providing temperature data in Chamonix; Jean-Luc Jaffrezo for providing data of previous filter measurements in Chamonix; and Anthony Lemoine, Matthieu Lafaysse and Louis Le Toumelin for providing S2M re-analysis and meteorological data. The authors particularly thank Patrick Ginot, Anthony Vella, Armelle Crouzet, and Bruno Jourdain for instrumental and laboratory technical support. Finally, the authors thank Alexis Lamothe for assistance during the sampling campaign and Pete Akers for his thorough proofreading of the manuscript and his constructive comments.

**Financial support.** This research has been supported by the Agence Nationale de la Recherche (ANR) via contract ANR-21-CE01-0017 CASPA and INSU/CNRS (National Institute of Sciences of the Universe) via its national LEFE programme (Les Enveloppes Fluides et l'Environnement) and by a grant from LabEx OSUG@2020 (Investissements d'avenir - ANR10 LABX56) and the IDEX-UGA ANR project ANR-15-IDEX-02.

**Review statement.** This paper was edited by Markus Ammann and reviewed by Lei Geng and one anonymous referee.

## References

Albertin, S.: Author Comment 2, Reply on RC2, https://doi.org/10.5194/egusphere-2023-744-AC2, 2023.

Albertin, S., Savarino, J., Bekki, S., Barbero, A., and Caillon, N.: Measurement report: Nitrogen isotopes ($\delta^{15}$N) and first quantification of oxygen isotope anomalies ($\Delta^{17}$O, $\delta^{18}$O) in atmospheric nitrogen dioxide, Atmos. Chem. Phys., 21, 10477–10497, https://doi.org/10.5194/acp-21-10477-2021, 2021.

Alexander, B., Hastings, M. G., Allman, D. J., Dachs, J., Thornton, J. A., and Kunasek, S. A.: Quantifying atmospheric nitrate formation pathways based on a global model of the oxygen isotope composition ($\Delta^{17}$O) of atmospheric nitrate, Atmos. Chem. Phys., 9, 5043–5056, https://doi.org/10.5194/acp-9-5043-2009, 2009.

Alexander, B., Sherwen, T., Holmes, C. D., Fisher, J. A., Chen, Q., Evans, M. J., and Kasibhatla, P.: Global inorganic nitrate production mechanisms: comparison of a global model with nitrate

isotope observations, Atmos. Chem. Phys., 20, 3859–3877, https://doi.org/10.5194/acp-20-3859-2020, 2020.

Alicke, B., Geyer, A., Hofzumahaus, A., Holland, F., Konrad, S., Pätz, H. W., Schäfer, J., Stutz, J., Volz-Thomas, A., and Platt, U.: OH formation by HONO photolysis during the BERLIOZ experiment, J. Geophys. Res.-Atmos., 108, PHO 3-1–PHO 3-17, https://doi.org/10.1029/2001JD000579, 2003.

Allard, J.: Qualité de l'air dans la Vallée de l'Arve: météorologie locale et mesures des réductions des émissions liées au chauffage au bois, PhD Thesis, Université Grenoble Alpes, https://theses.hal.science/tel-01901636 (last access: 25 January 2024), 2018.

Ammann, M., Siegwolf, R., Pichlmayer, F., Suter, M., Saurer, M., and Brunold, C.: Estimating the uptake of traffic-derived NO₂ from $^{15}$N abundance in Norway spruce needles, Oecologia, 118, 124–131, https://doi.org/10.1007/s004420050710, 1999.

Angelisi, M. D. and Gaudichet, A.: Saharan dust deposition over Mont Blanc (French Alps) during the last 30 years, Tellus B, 43, 61–75, https://doi.org/10.1034/j.1600-0889.1991.00005.x, 1991.

Appel, B. R., Wall, S. M., Tokiwa, Y., and Haik, M.: Simultaneous nitric acid, particulate nitrate and acidity measurements in ambient air, Atmos. Environ., 14, 549–554, https://doi.org/10.1016/0004-6981(80)90084-0, 1980.

Appel, B. R., Tokiwa, Y., and Haik, M.: Sampling of nitrates in ambient air, Atmos. Environ., 15, 283–289, https://doi.org/10.1016/0004-6981(81)90029-9, 1981.

Atkinson, R., Baulch, D. L., Cox, R. A., Crowley, J. N., Hampson, R. F., Hynes, R. G., Jenkin, M. E., Rossi, M. J., and Troe, J.: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume I – gas phase reactions of Oₓ, HOx, NOₓ and SOₓ species, Atmos. Chem. Phys., 4, 1461–1738, https://doi.org/10.5194/acp-4-1461-2004, 2004.

Atkinson, R., Baulch, D. L., Cox, R. A., Crowley, J. N., Hampson, R. F., Hynes, R. G., Jenkin, M. E., Rossi, M. J., Troe, J., and IUPAC Subcommittee: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II – gas phase reactions of organic species, Atmos. Chem. Phys., 6, 3625–4055, https://doi.org/10.5194/acp-6-3625-2006, 2006.

Atmo-Auvergne-Rhône-Alpes: Bilan des connaissances sur la qualité de l'air dans la vallée de l'Arve, Atmo-Auvergne-Rhône-Alpes, https://www.atmo-auvergnerhonealpes.fr/publications/bilan-des-connaissances-sur-la-qualite-de-lair-dans-la-vallee-de-larve (last access: July 2021), 2018.

Aumont, B., Chervier, F., and Laval, S.: Contribution of HONO sources to the NOₓ/HOx/O₃ chemistry in the polluted boundary layer, Atmos. Environ., 37, 487–498, https://doi.org/10.1016/S1352-2310(02)00920-2, 2003.

Aymoz, G., Jaffrezo, J.-L., Jacob, V., Colomb, A., and George, Ch.: Evolution of organic and inorganic components of aerosol during a Saharan dust episode observed in the French Alps, Atmos. Chem. Phys., 4, 2499–2512, https://doi.org/10.5194/acp-4-2499-2004, 2004.

Aymoz, G., Jaffrezo, J. L., Chapuis, D., Cozic, J., and Maenhaut, W.: Seasonal variation of PM₁₀ main constituents in two valleys of the French Alps: I. EC/OC fractions, Atmos. Chem. Phys., 7, 661–675, https://doi.org/10.5194/acp-7-661-2007, 2007.

Barbero, A., Blouzon, C., Savarino, J., Caillon, N., Dommergue, A., and Grilli, R.: A compact incoherent broadband cavity-enhanced absorption spectrometer for trace detection of nitrogen
oxides, iodine oxide and glyoxal at levels below parts per billion for field applications, Atmos. Meas. Tech., 13, 4317–4331, https://doi.org/10.5194/amt-13-4317-2020, 2020.

Barkan, E. and Luz, B.: High-precision measurements of ¹⁷O/¹⁶O and ¹⁸O/¹⁶O of O₂ and O₂/Ar ratio in air, Rapid Commun. Mass Sp., 17, 2809–2814, https://doi.org/10.1002/rcm.1267, 2003.

Bauer, S. E., Koch, D., Unger, N., Metzger, S. M., Shindell, D. T., and Streets, D. G.: Nitrate aerosols today and in 2030: a global simulation including aerosols and tropospheric ozone, Atmos. Chem. Phys., 7, 5043–5059, https://doi.org/10.5194/acp-7-5043-2007, 2007.

Bekker, C., Walters, W. W., Murray, L. T., and Hastings, M. G.: Nitrate chemistry in the northeast US – Part 1: Nitrogen isotope seasonality tracks nitrate formation chemistry, Atmos. Chem. Phys., 23, 4185–4201, https://doi.org/10.5194/acp-23-4185-2023, 2023.

Berhanu, T. A., Savarino, J., Bhattacharya, S. K., and Vicars, W. C.: ¹⁷O excess transfer during the NO₂ + O₃ → NO₃ + O₂ reaction, J. Chem. Phys., 136, 044311, https://doi.org/10.1063/1.3666852, 2012.

Brown, S. S. and Stutz, J.: Nighttime radical observations and chemistry, Chem. Soc. Rev., 41, 6405–6447, https://doi.org/10.1039/c2cs35181a, 2012.

Brown, S. S., Ryerson, T. B., Wollny, A. G., Brock, C. A., Peltier, R., Sullivan, A. P., Weber, R. J., Dubé, W. P., Trainer, M., Meagher, J. F., Fehsenfeld, F. C., and Ravishankara, A. R.: Variability in Nocturnal Nitrogen Oxide Processing and Its Role in Regional Air Quality, Science, 311, 67–70, https://doi.org/10.1126/science.1120120, 2006.

Brown, S. S., Dubé, W. P., Peischl, J., Ryerson, T. B., Atlas, E., Warneke, C., de Gouw, J. A., te Lintel Hekkert, S., Brock, C. A., Flocke, F., Trainer, M., Parrish, D. D., Feshenfeld, F. C., and Ravishankara, A. R.: Budgets for nocturnal VOC oxidation by nitrate radicals aloft during the 2006 Texas Air Quality Study, J. Geophys. Res.-Atmos., 116, D24305, https://doi.org/10.1029/2011JD016544, 2011.

Brulfert, G., Chemel, C., Chaxel, E., and Chollet, J. P.: Modelling photochemistry in alpine valleys, Atmos. Chem. Phys., 5, 2341–2355, https://doi.org/10.5194/acp-5-2341-2005, 2005.

Casciotti, K. L., Sigman, D. M., Hastings, M. G., Böhlke, J. K., and Hilkert, A.: Measurement of the oxygen isotopic composition of nitrate in seawater and freshwater using the denitrifier method, Anal. Chem., 74, 4905–4912, https://doi.org/10.1021/ac020113w, 2002.

Casciotti, K. L., Böhlke, J. K., McIlvin, M. R., Mroczkowski, S. J., and Hannon, J. E.: Oxygen Isotopes in Nitrite: Analysis, Calibration, and Equilibration, Anal. Chem., 79, 2427–2436, https://doi.org/10.1021/ac061598h, 2007.

Chai, J., Miller, D. J., Scheuer, E., Dibb, J., Selimovic, V., Yokelson, R., Zarzana, K. J., Brown, S. S., Koss, A. R., Warneke, C., and Hastings, M.: Isotopic characterization of nitrogen oxides (NOₓ), nitrous acid (HONO), and nitrate (pNO₃⁻) from laboratory biomass burning during FIREX, Atmos. Meas. Tech., 12, 6303–6317, https://doi.org/10.5194/amt-12-6303-2019, 2019.

Chan, Y.-C., Evans, M. J., He, P., Holmes, C. D., Jaeglé, L., Kassibhatla, P., Liu, X.-Y., Sherwen, T., Thornton, J. A., Wang, X., Xie, Z., Zhai, S., and Alexander, B.: Heterogeneous Nitrate Production Mechanisms in Intense Haze Events in the North China Plain, J. Geophys. Res.-Atmos., 126, e2021JD034688, https://doi.org/10.1029/2021JD034688, 2021.

Chang, Y., Zhang, Y., Tian, C., Zhang, S., Ma, X., Cao, F., Liu, X., Zhang, W., Kuhn, T., and Lehmann, M. F.: Nitrogen isotope fractionation during gas-to-particle conversion of NOₓ to NO₃⁻ in the atmosphere – implications for isotope-based NOₓ source apportionment, Atmos. Chem. Phys., 18, 11647–11661, https://doi.org/10.5194/acp-18-11647-2018, 2018.

Chazette, P., Couvert, P., Randriamiarisoa, H., Sanak, J., Bonsang, B., Moral, P., Berthier, S., Salanave, S., and Tousaint, F.: Three-dimensional survey of pollution during winter in French Alps valleys, Atmos. Environ., 39, 1035–1047, https://doi.org/10.1016/j.atmosenv.2004.10.014, 2005.

Crutzen, P. J.: The Role of NO and NO₂ in the Chemistry of the Troposphere and Stratosphere, Annu. Rev. Earth Planet. Sc., 7, 443–472, https://doi.org/10.1146/annurev.ea.07.050179.002303, 1979.

Delmas, R. J.: Snow chemistry of high altitude glaciers in the French Alps, Tellus B, 46, 304–324, https://doi.org/10.3402/tellusb.v46i4.15806, 1994.

Dentener, F. J. and Crutzen, P. J.: Reaction of N₂O₅ on tropospheric aerosols: Impact on the global distributions of NOₓ, O₃, and OH, J. Geophys. Res.-Atmos., 98, 7149–7163, https://doi.org/10.1029/92JD02979, 1993.

Di Mauro, B., Garzonio, R., Rossini, M., Filippa, G., Pogliotti, P., Galvagno, M., Morra di Cella, U., Migliavacca, M., Baccolo, G., Clemenza, M., Delmonte, B., Maggi, V., Dumont, M., Tuzet, F., Lafaysse, M., Morin, S., Cremonese, E., and Colombo, R.: Saharan dust events in the European Alps: role in snowmelt and geochemical characterization, The Cryosphere, 13, 1147–1165, https://doi.org/10.5194/tc-13-1147-2019, 2019.

Dubey, M. K., Mohrschladt, R., Donahue, N. M., and Anderson, J. G.: Isotope Specific Kinetics of Hydroxyl Radical (OH) with Water (H₂O): Testing Models of Reactivity and Atmospheric Fractionation, J. Phys. Chem. A, 101, 1494–1500, https://doi.org/10.1021/jp962332p, 1997.

Edwards, P. M., Brown, S. S., Roberts, J. M., Ahmadov, R., Banta, R. M., deGouw, J. A., Dubé, W. P., Field, R. A., Flynn, J. H., Gilman, J. B., Graus, M., Helmig, D., Koss, A., Langford, A. O., Lefer, B. L., Lerner, B. M., Li, R., Li, S.-M., McKeen, S. A., Murphy, S. M., Parrish, D. D., Senff, C. J., Soltis, J., Stutz, J., Sweeney, C., Thompson, C. R., Trainer, M. K., Tsai, C., Veres, P. R., Washenfelder, R. A., Warneke, C., Wild, R. J., Young, C. J., Yuan, B., and Zamora, R.: High winter ozone pollution from carbonyl photolysis in an oil and gas basin, Nature, 514, 351–354, https://doi.org/10.1038/nature13767, 2014.

Elliott, E. M., Yu, Z., Cole, A. S., and Coughlin, J. G.: Isotopic advances in understanding reactive nitrogen deposition and atmospheric processing, Sci. Total Environ., 662, 393–403, https://doi.org/10.1016/j.scitotenv.2018.12.177, 2019.

Emmerson, K. M., Carslaw, N., Carpenter, L. J., Heard, D. E., Lee, J. D., and Pilling, M. J.: Urban Atmospheric Chemistry During the PUMA Campaign 1: Comparison of Modelled OH and HO₂ Concentrations with Measurements, J. Atmos. Chem., 52, 143–164, https://doi.org/10.1007/s10874-005-1322-3, 2005.

Fan, M.-Y., Zhang, Y.-L., Lin, Y.-C., Chang, Y.-H., Cao, F., Zhang, W.-Q., Hu, Y.-B., Bao, M.-Y., Liu, X.-Y., Zhai, X.-Y., Lin, X., Zhao, Z.-Y., and Song, W.-H.: Isotope-based source apportionment of nitrogen-containing aerosols: A case study in
oxides, iodine oxide and glyoxal at levels below parts per billion for field applications, Atmos. Meas. Tech., 13, 4317–4331, https://doi.org/10.5194/amt-13-4317-2020, 2020.

Barkan, E. and Luz, B.: High-precision measurements of ¹⁷O/¹⁶O and ¹⁸O/¹⁶O of O₂ and O₂/Ar ratio in air, Rapid Commun. Mass Sp., 17, 2809–2814, https://doi.org/10.1002/rcm.1267, 2003.

Bauer, S. E., Koch, D., Unger, N., Metzger, S. M., Shindell, D. T., and Streets, D. G.: Nitrate aerosols today and in 2030: a global simulation including aerosols and tropospheric ozone, Atmos. Chem. Phys., 7, 5043–5059, https://doi.org/10.5194/acp-7-5043-2007, 2007.

Bekker, C., Walters, W. W., Murray, L. T., and Hastings, M. G.: Nitrate chemistry in the northeast US – Part 1: Nitrogen isotope seasonality tracks nitrate formation chemistry, Atmos. Chem. Phys., 23, 4185–4201, https://doi.org/10.5194/acp-23-4185-2023, 2023.

Berhanu, T. A., Savarino, J., Bhattacharya, S. K., and Vicars, W. C.: ¹⁷O excess transfer during the NO₂ + O₃ → NO₃ + O₂ reaction, J. Chem. Phys., 136, 044311, https://doi.org/10.1063/1.3666852, 2012.

Brown, S. S. and Stutz, J.: Nighttime radical observations and chemistry, Chem. Soc. Rev., 41, 6405–6447, https://doi.org/10.1039/c2cs35181a, 2012.

Brown, S. S., Ryerson, T. B., Wollny, A. G., Brock, C. A., Peltier, R., Sullivan, A. P., Weber, R. J., Dubé, W. P., Trainer, M., Meagher, J. F., Fehsenfeld, F. C., and Ravishankara, A. R.: Variability in Nocturnal Nitrogen Oxide Processing and Its Role in Regional Air Quality, Science, 311, 67–70, https://doi.org/10.1126/science.1120120, 2006.

Brown, S. S., Dubé, W. P., Peischl, J., Ryerson, T. B., Atolas, E., Warneke, C., de Gouw, J. A., te Lintel Hekkert, S., Brock, C. A., Flocke, F., Trainer, M., Parrish, D. D., Feshenfeld, F. C., and Ravishankara, A. R.: Budgets for nocturnal VOC oxidation by nitrate radicals aloft during the 2006 Texas Air Quality Study, J. Geophys. Res.-Atmos., 116, D24305, https://doi.org/10.1029/2011JD016544, 2011.

Brulfert, G., Chemel, C., Chaxel, E., and Chollet, J. P.: Modelling photochemistry in alpine valleys, Atmos. Chem. Phys., 5, 2341–2355, https://doi.org/10.5194/acp-5-2341-2005, 2005.

Casciotti, K. L., Sigman, D. M., Hastings, M. G., Böhlke, J. K., and Hilkert, A.: Measurement of the oxygen isotopic composition of nitrate in seawater and freshwater using the denitrifier method, Anal. Chem., 74, 4905–4912, https://doi.org/10.1021/ac020113w, 2002.

Casciotti, K. L., Böhlke, J. K., McIlvin, M. R., Mroczkowski, S. J., and Hannon, J. E.: Oxygen Isotopes in Nitrite: Analysis, Calibration, and Equilibration, Anal. Chem., 79, 2427–2436, https://doi.org/10.1021/ac061598h, 2007.

Chai, J., Miller, D. J., Scheuer, E., Dibb, J., Selimovic, V., Yokelson, R., Zarzana, K. J., Brown, S. S., Koss, A. R., Warneke, C., and Hastings, M.: Isotopic characterization of nitrogen oxides (NOₓ), nitrous acid (HONO), and nitrate (pNO₃⁻) from laboratory biomass burning during FIREX, Atmos. Meas. Tech., 12, 6303–6317, https://doi.org/10.5194/amt-12-6303-2019, 2019.

Chan, Y.-C., Evans, M. J., He, P., Holmes, C. D., Jaeglé, L., Kasibhatla, P., Liu, X.-Y., Sherwen, T., Thornton, J. A., Wang, X., Xie, Z., Zhai, S., and Alexander, B.: Heterogeneous Nitrate Production Mechanisms in Intense Haze Events in the North

China Plain, J. Geophys. Res.-Atmos., 126, e2021JD034688, https://doi.org/10.1029/2021JD034688, 2021.

Chang, Y., Zhang, Y., Tian, C., Zhang, S., Ma, X., Cao, F., Liu, X., Zhang, W., Kuhn, T., and Lehmann, M. F.: Nitrogen isotope fractionation during gas-to-particle conversion of NOₓ to NO₃⁻ in the atmosphere – implications for isotope-based NOₓ source apportionment, Atmos. Chem. Phys., 18, 11647–11661, https://doi.org/10.5194/acp-18-11647-2018, 2018.

Chazette, P., Couvert, P., Randriamiarisoa, H., Sanak, J., Bonsang, B., Moral, P., Berthier, S., Salanave, S., and Tousaint, F.: Three-dimensional survey of pollution during winter in French Alps valleys, Atmos. Environ., 39, 1035–1047, https://doi.org/10.1016/j.atmosenv.2004.10.014, 2005.

Crutzen, P. J.: The Role of NO and NO₂ in the Chemistry of the Troposphere and Stratosphere, Annu. Rev. Earth Planet. Sc., 7, 443–472, https://doi.org/10.1146/annurev.ea.07.050179.002303, 1979.

Delmas, R. J.: Snow chemistry of high altitude glaciers in the French Alps, Tellus B, 46, 304–324, https://doi.org/10.3402/tellusb.v46i4.15806, 1994.

Dentener, F. J. and Crutzen, P. J.: Reaction of N₂O₅ on tropospheric aerosols: Impact on the global distributions of NOₓ, O₃, and OH, J. Geophys. Res.-Atmos., 98, 7149–7163, https://doi.org/10.1029/92JD02979, 1993.

Di Mauro, B., Garzonio, R., Rossini, M., Filippa, G., Pogliotti, P., Galvagno, M., Morra di Cella, U., Migliavacca, M., Baccolo, G., Clemenza, M., Delmonte, B., Maggi, V., Dumont, M., Tuzet, F., Lafaysse, M., Morin, S., Cremonese, E., and Colombo, R.: Saharan dust events in the European Alps: role in snowmelt and geochemical characterization, The Cryosphere, 13, 1147–1165, https://doi.org/10.5194/tc-13-1147-2019, 2019.

Dubey, M. K., Mohrschladt, R., Donahue, N. M., and Anderson, J. G.: Isotope Specific Kinetics of Hydroxyl Radical (OH) with Water (H₂O): Testing Models of Reactivity and Atmospheric Fractionation, J. Phys. Chem. A, 101, 1494–1500, https://doi.org/10.1021/jp962332p, 1997.

Edwards, P. M., Brown, S. S., Roberts, J. M., Ahmadov, R., Banta, R. M., deGouw, J. A., Dubé, W. P., Field, R. A., Flynn, J. H., Gilman, J. B., Graus, M., Helmig, D., Koss, A., Langford, A. O., Lefer, B. L., Lerner, B. M., Li, R., Li, S.-M., McKeen, S. A., Murphy, S. M., Parrish, D. D., Senff, C. J., Soltis, J., Stutz, J., Sweeney, C., Thompson, C. R., Trainer, M. K., Tsai, C., Veres, P. R., Washenfelder, R. A., Warneke, C., Wild, R. J., Young, C. J., Yuan, B., and Zamora, R.: High winter ozone pollution from carbonyl photolysis in an oil and gas basin, Nature, 514, 351–354, https://doi.org/10.1038/nature13767, 2014.

Elliott, E. M., Yu, Z., Cole, A. S., and Coughlin, J. G.: Isotopic advances in understanding reactive nitrogen deposition and atmospheric processing, Sci. Total Environ., 662, 393–403, https://doi.org/10.1016/j.scitotenv.2018.12.177, 2019.

Emmerson, K. M., Carslaw, N., Carpenter, L. J., Heard, D. E., Lee, J. D., and Pilling, M. J.: Urban Atmospheric Chemistry During the PUMA Campaign 1: Comparison of Modelled OH and HO₂ Concentrations with Measurements, J. Atmos. Chem., 52, 143–164, https://doi.org/10.1007/s10874-005-1322-3, 2005.

Fan, M.-Y., Zhang, Y.-L., Lin, Y.-C., Chang, Y.-H., Cao, F., Zhang, W.-Q., Hu, Y.-B., Bao, M.-Y., Liu, X.-Y., Zhai, X.-Y., Lin, X., Zhao, Z.-Y., and Song, W.-H.: Isotope-based source apportionment of nitrogen-containing aerosols: A case study in
an industrial city in China, Atmos. Environ., 212, 96–105, https://doi.org/10.1016/j.atmosenv.2019.05.020, 2019.

Fan, M.-Y., Zhang, Y.-L., Lin, Y.-C., Hong, Y., Zhao, Z.-Y., Xie, F., Du, W., Cao, F., Sun, Y., and Fu, P.: Important Role of NO₃ Radical to Nitrate Formation Aloft in Urban Beijing: Insights from Triple Oxygen Isotopes Measured at the Tower, Environ. Sci. Technol., 56, 6870–6879, https://doi.org/10.1021/acs.est.1c02843, 2022.

Fan, M.-Y., Zhang, W., Zhang, Y.-L., Li, J., Fang, H., Cao, F., Yan, M., Hong, Y., Guo, H., and Michalski, G.: Formation Mechanisms and Source Apportionments of Nitrate Aerosols in a Megacity of Eastern China Based On Multiple Isotope Observations, J. Geophys. Res.-Atmos., 128, e2022JD038129, https://doi.org/10.1029/2022JD038129, 2023.

Fang, H., Walters, W. W., Mase, D., and Michalski, G.: iңRACM: incorporating ¹⁵N into the Regional Atmospheric Chemistry Mechanism (RACM) for assessing the role photochemistry plays in controlling the isotopic composition of NOₓ, NOᵧ, and atmospheric nitrate, Geosci. Model Dev., 14, 5001–5022, https://doi.org/10.5194/gmd-14-5001-2021, 2021.

Felix, J. D. and Elliott, E. M.: Isotopic composition of passively collected nitrogen dioxide emissions: Vehicle, soil and livestock source signatures, Atmos. Environ., 92, 359–366, https://doi.org/10.1016/j.atmosenv.2014.04.005, 2014.

Felix, J. D., Elliott, E. M., and Shaw, S. L.: Nitrogen Isotopic Composition of Coal-Fired Power Plant NOₓ: Influence of Emission Controls and Implications for Global Emission Inventories, Environ. Sci. Technol., 46, 3528–3535, https://doi.org/10.1021/es203355v, 2012.

Fibiger, D. L. and Hastings, M. G.: First Measurements of the Nitrogen Isotopic Composition of NOₓ from Biomass Burning, Environ. Sci. Technol., 50, 11569–11574, https://doi.org/10.1021/acs.est.6b03510, 2016.

Finlayson-Pitts, B. J. and Pitts, J. N.: Chemistry of the upper and lower troposphere, Academic Press, San Diego, California, https://doi.org/10.1016/B978-0-12-257060-5.X5000-X, 2000.

Frey, M. M., Savarino, J., Morin, S., Erbland, J., and Martins, J. M. F.: Photolysis imprint in the nitrate stable isotope signal in snow and atmosphere of East Antarctica and implications for reactive nitrogen cycling, Atmos. Chem. Phys., 9, 8681–8696, https://doi.org/10.5194/acp-9-8681-2009, 2009.

Freyer, H. D.: Seasonal variation of ¹⁵N/¹⁴N ratios in atmospheric nitrate species, Tellus B, 43, 30–44, https://doi.org/10.1034/j.1600-0889.1991.00003.x, 1991.

Freyer, H. D., Kley, D., Volz-Thomas, A., and Kobel, K.: On the interaction of isotopic exchange processes with photochemical reactions in atmospheric oxides of nitrogen, J. Geophys. Res.-Atmos., 98, 14791–14796, https://doi.org/10.1029/93JD00874, 1993.

Fu, X., Wang, T., Gao, J., Wang, P., Liu, Y., Wang, S., Zhao, B., and Xue, L.: Persistent Heavy Winter Nitrate Pollution Driven by Increased Photochemical Oxidants in Northern China, Environ. Sci. Technol., 54, 3881–3889, https://doi.org/10.1021/acs.est.9b07248, 2020.

Galeazzo, T., Bekki, S., Martin, E., Savarino, J., and Arnold, S. R.: Photochemical box modelling of volcanic SO₂ oxidation: isotopic constraints, Atmos. Chem. Phys., 18, 17909–17931, https://doi.org/10.5194/acp-18-17909-2018, 2018.

Galloway, J. N., Townsend, A. R., Erisman, J. W., Bekunda, M., Cai, Z., Freney, J. R., Martinelli, L. A., Seitzinger, S. P., and Sutton, M. A.: Transformation of the Nitrogen Cycle: Recent Trends, Questions, and Potential Solutions, Science, 320, 889–892, https://doi.org/10.1126/science.1136674, 2008.

Gaudel, A., Cooper, O. R., Ancellet, G., Barret, B., Boynard, A., Burrows, J. P., Clerbaux, C., Coheur, P.-F., Cuesta, J., Cuevas, E., Doniki, S., Dufour, G., Ebojie, F., Foret, G., Garcia, O., Granados-Muñoz, M. J., Hannigan, J. W., Hase, F., Hassler, B., Huang, G., Hurtmans, D., Jaffe, D., Jones, N., Kalabokas, P., Keridge, B., Kulawik, S., Latter, B., Leblanc, T., Le Flochmoën, E., Lin, W., Liu, J., Liu, X., Mahieu, E., McClure-Begley, A., Neu, J. L., Osman, M., Palm, M., Petetin, H., Petropavlovskikh, I., Querel, R., Rahpoe, N., Rozanov, A., Schultz, M. G., Schwab, J., Siddans, R., Smale, D., Steinbacher, M., Tanimoto, H., Tarasick, D. W., Thouret, V., Thompson, A. M., Trickl, T., Weatherhead, E., Wespes, C., Worden, H. M., Vigouroux, C., Xu, X., Zeng, G., and Ziemke, J.: Tropospheric Ozone Assessment Report: Present-day distribution and trends of tropospheric ozone relevant to climate and global atmospheric chemistry model evaluation, Elementa, 6, 39, https://doi.org/10.1525/elementa.291, 2018.

Geng, L., Alexander, B., Cole-Dai, J., Steig, E. J., Savarino, J., Sofen, E. D., and Schauer, A. J.: Nitrogen isotopes in ice core nitrate linked to anthropogenic atmospheric acidity change, P. Natl. Acad. Sci. USA, 111, 5808–5812, https://doi.org/10.1073/pnas.1319441111, 2014.

Goudie, A. S. and Middleton, N. J.: Saharan dust storms: nature and consequences, Earth-Sci. Rev., 56, 179–204, https://doi.org/10.1016/S0012-8252(01)00067-8, 2001.

Grannas, A. M., Jones, A. E., Dibb, J., Ammann, M., Anastasio, C., Beine, H. J., Bergin, M., Bottenheim, J., Boxe, C. S., Carver, G., Chen, G., Crawford, J. H., Dominé, F., Frey, M. M., Guzmán, M. I., Heard, D. E., Helmig, D., Hoffmann, M. R., Honrath, R. E., Huey, L. G., Hutterli, M., Jacobi, H. W., Klán, P., Lefer, B., McConnell, J., Plane, J., Sander, R., Savarino, J., Shepson, P. B., Simpson, W. R., Sodeau, J. R., von Glasow, R., Weller, R., Wolff, E. W., and Zhu, T.: An overview of snow photochemistry: evidence, mechanisms and impacts, Atmos. Chem. Phys., 7, 4329–4373, https://doi.org/10.5194/acp-7-4329-2007, 2007.

Greilinger, M., Schauer, G., Baumann-Stanzer, K., Skomorowski, P., Schöner, W., and Kasper-Giebl, A.: Contribution of Saharan Dust to Ion Deposition Loads of High Alpine Snow Packs in Austria (1987–2017), Front. Earth Sci., 6, 126, https://doi.org/10.3389/feart.2018.00126, 2018.

Gu, P., Dallmann, T. R., Li, H. Z., Tan, Y., and Presto, A. A.: Quantifying Urban Spatial Variations of Anthropogenic VOC Concentrations and Source Contributions with a Mobile Sampling Platform, Int. J. Environ. Res. Pu., 16, 1632, https://doi.org/10.3390/ijerph16091632, 2019.

He, P., Xie, Z., Chi, X., Yu, X., Fan, S., Kang, H., Liu, C., and Zhan, H.: Atmospheric Δ¹⁷O(NO₃⁻) reveals nocturnal chemistry dominates nitrate production in Beijing haze, Atmos. Chem. Phys., 18, 14465–14476, https://doi.org/10.5194/acp-18-14465-2018, 2018.

He, P., Xie, Z., Yu, X., Wang, L., Kang, H., and Yue, F.: The observation of isotopic compositions of atmospheric nitrate in Shanghai China and its implication for reac-
an industrial city in China, Atmos. Environ., 212, 96–105, https://doi.org/10.1016/j.atmosenv.2019.05.020, 2019.

Fan, M.-Y., Zhang, Y.-L., Lin, Y.-C., Hong, Y., Zhao, Z.-Y., Xie, F., Du, W., Cao, F., Sun, Y., and Fu, P.: Important Role of NO₃ Radical to Nitrate Formation Aloft in Urban Beijing: Insights from Triple Oxygen Isotopes Measured at the Tower, Environ. Sci. Technol., 56, 6870–6879, https://doi.org/10.1021/acs.est.1c02843, 2022.

Fan, M.-Y., Zhang, W., Zhang, Y.-L., Li, J., Fang, H., Cao, F., Yan, M., Hong, Y., Guo, H., and Michalski, G.: Formation Mechanisms and Source Apportionments of Nitrate Aerosols in a Megacity of Eastern China Based On Multiple Isotope Observations, J. Geophys. Res.-Atmos., 128, e2022JD038129, https://doi.org/10.1029/2022JD038129, 2023.

Fang, H., Walters, W. W., Mase, D., and Michalski, G.: iN<sub>x</sub>RACM: incorporating <sup>15</sup>N into the Regional Atmospheric Chemistry Mechanism (RACM) for assessing the role photochemistry plays in controlling the isotopic composition of NO<sub>x</sub>, NO<sub>y</sub>, and atmospheric nitrate, Geosci. Model Dev., 14, 5001–5022, https://doi.org/10.5194/gmd-14-5001-2021, 2021.

Felix, J. D. and Elliott, E. M.: Isotopic composition of passively collected nitrogen dioxide emissions: Vehicle, soil and livestock source signatures, Atmos. Environ., 92, 359–366, https://doi.org/10.1016/j.atmosenv.2014.04.005, 2014.

Felix, J. D., Elliott, E. M., and Shaw, S. L.: Nitrogen Isotopic Composition of Coal-Fired Power Plant NOₓ: Influence of Emission Controls and Implications for Global Emission Inventories, Environ. Sci. Technol., 46, 3528–3535, https://doi.org/10.1021/es203355v, 2012.

Fibiger, D. L. and Hastings, M. G.: First Measurements of the Nitrogen Isotopic Composition of NOₓ from Biomass Burning, Environ. Sci. Technol., 50, 11569–11574, https://doi.org/10.1021/acs.est.6b03510, 2016.

Finlayson-Pitts, B. J. and Pitts, J. N.: Chemistry of the upper and lower troposphere, Academic Press, San Diego, California, https://doi.org/10.1016/B978-0-12-257060-5.X5000-X, 2000.

Frey, M. M., Savarino, J., Morin, S., Erbland, J., and Martins, J. M. F.: Photolysis imprint in the nitrate stable isotope signal in snow and atmosphere of East Antarctica and implications for reactive nitrogen cycling, Atmos. Chem. Phys., 9, 8681–8696, https://doi.org/10.5194/acp-9-8681-2009, 2009.

Freyer, H. D.: Seasonal variation of <sup>15</sup>N/<sup>14</sup>N ratios in atmospheric nitrate species, Tellus B, 43, 30–44, https://doi.org/10.1034/j.1600-0889.1991.00003.x, 1991.

Freyer, H. D., Kley, D., Volz-Thomas, A., and Kobel, K.: On the interaction of isotopic exchange processes with photochemical reactions in atmospheric oxides of nitrogen, J. Geophys. Res.-Atmos., 98, 14791–14796, https://doi.org/10.1029/93JD00874, 1993.

Fu, X., Wang, T., Gao, J., Wang, P., Liu, Y., Wang, S., Zhao, B., and Xue, L.: Persistent Heavy Winter Nitrate Pollution Driven by Increased Photochemical Oxidants in Northern China, Environ. Sci. Technol., 54, 3881–3889, https://doi.org/10.1021/acs.est.9b07248, 2020.

Galeazzo, T., Bekki, S., Martin, E., Savarino, J., and Arnold, S. R.: Photochemical box modelling of volcanic SO₂ oxidation: isotopic constraints, Atmos. Chem. Phys., 18, 17909–17931, https://doi.org/10.5194/acp-18-17909-2018, 2018.

Galloway, J. N., Townsend, A. R., Erisman, J. W., Bekunda, M., Cai, Z., Freney, J. R., Martinelli, L. A., Seitzinger, S. P., and Sutton, M. A.: Transformation of the Nitrogen Cycle: Recent Trends, Questions, and Potential Solutions, Science, 320, 889–892, https://doi.org/10.1126/science.1136674, 2008.

Gaudel, A., Cooper, O. R., Ancellet, G., Barret, B., Boynard, A., Burrows, J. P., Clerbaux, C., Coheur, P.-F., Cuesta, J., Cuevas, E., Doniki, S., Dufour, G., Ebojie, F., Foret, G., Garcia, O., Granados-Muñoz, M. J., Hannigan, J. W., Hase, F., Hassler, B., Huang, G., Hurtmans, D., Jaffe, D., Jones, N., Kalabokas, P., Keridge, B., Kulawik, S., Latter, B., Leblanc, T., Le Flochmoën, E., Lin, W., Liu, J., Liu, X., Mahieu, E., McClure-Begley, A., Neu, J. L., Osman, M., Palm, M., Petetin, H., Petropavlovskikh, I., Querel, R., Rahpoe, N., Rozanov, A., Schultz, M. G., Schwab, J., Siddans, R., Smale, D., Steinbacher, M., Tanimoto, H., Tarsick, D. W., Thouret, V., Thompson, A. M., Trickl, T., Weatherhead, E., Wespes, C., Worden, H. M., Vigouroux, C., Xu, X., Zeng, G., and Ziemke, J.: Tropospheric Ozone Assessment Report: Present-day distribution and trends of tropospheric ozone relevant to climate and global atmospheric chemistry model evaluation, Elementa, 6, 39, https://doi.org/10.1525/elementa.291, 2018.

Geng, L., Alexander, B., Cole-Dai, J., Steig, E. J., Savarino, J., Sofen, E. D., and Schauer, A. J.: Nitrogen isotopes in ice core nitrate linked to anthropogenic atmospheric acidity change, P. Natl. Acad. Sci. USA, 111, 5808–5812, https://doi.org/10.1073/pnas.1319441111, 2014.

Goudie, A. S. and Middleton, N. J.: Saharan dust storms: nature and consequences, Earth-Sci. Rev., 56, 179–204, https://doi.org/10.1016/S0012-8252(01)00067-8, 2001.

Grannas, A. M., Jones, A. E., Dibb, J., Ammann, M., Anastasio, C., Beine, H. J., Bergin, M., Bottenheim, J., Boxe, C. S., Carver, G., Chen, G., Crawford, J. H., Dominé, F., Frey, M. M., Guzmán, M. I., Heard, D. E., Helmig, D., Hoffmann, M. R., Honrath, R. E., Huey, L. G., Hutterli, M., Jacobi, H. W., Klán, P., Lefer, B., McConnell, J., Plane, J., Sander, R., Savarino, J., Shepson, P. B., Simpson, W. R., Sodeau, J. R., von Glasow, R., Weller, R., Wolff, E. W., and Zhu, T.: An overview of snow photochemistry: evidence, mechanisms and impacts, Atmos. Chem. Phys., 7, 4329–4373, https://doi.org/10.5194/acp-7-4329-2007, 2007.

Greilinger, M., Schauer, G., Baumann-Stanzer, K., Skomorowski, P., Schöner, W., and Kasper-Giebl, A.: Contribution of Saharan Dust to Ion Deposition Loads of High Alpine Snow Packs in Austria (1987–2017), Front. Earth Sci., 6, 126, https://doi.org/10.3389/feart.2018.00126, 2018.

Gu, P., Dallmann, T. R., Li, H. Z., Tan, Y., and Presto, A. A.: Quantifying Urban Spatial Variations of Anthropogenic VOC Concentrations and Source Contributions with a Mobile Sampling Platform, Int. J. Environ. Res. Pu., 16, 1632, https://doi.org/10.3390/ijerph16091632, 2019.

He, P., Xie, Z., Chi, X., Yu, X., Fan, S., Kang, H., Liu, C., and Zhan, H.: Atmospheric Δ<sup>17</sup>O(NO<sub>3</sub><sup>-</sup>) reveals nocturnal chemistry dominates nitrate production in Beijing haze, Atmos. Chem. Phys., 18, 14465–14476, https://doi.org/10.5194/acp-18-14465-2018, 2018.

He, P., Xie, Z., Yu, X., Wang, L., Kang, H., and Yue, F.: The observation of isotopic compositions of atmospheric nitrate in Shanghai China and its implication for reac-
tive nitrogen chemistry, Sci. Total Environ., 714, 136727, https://doi.org/10.1016/j.scitotenv.2020.136727, 2020.

Heaton, T. H. E.: $^{15}$N/$^{14}$N ratios of NO$_x$ from vehicle engines and coal-fired power stations, Tellus B, 42, 304–307, https://doi.org/10.1034/j.1600-0889.1990.00007.x-i1, 1990.

Hoesly, R. M., Smith, S. J., Feng, L., Klimont, Z., Janssens-Maenhout, G., Pitkanen, T., Seibert, J. J., Vu, L., Andres, R. J., Bolt, R. M., Bond, T. C., Dawidowski, L., Kholod, N., Kurokawa, J.-I., Li, M., Liu, L., Lu, Z., Moura, M. C. P., O'Rourke, P. R., and Zhang, Q.: Historical (1750–2014) anthropogenic emissions of reactive gases and aerosols from the Community Emissions Data System (CEDS), Geosci. Model Dev., 11, 369–408, https://doi.org/10.5194/gmd-11-369-2018, 2018.

Holland, E. A., Dentener, F. J., Braswell, B. H., and Sulzman, J. M.: Contemporary and pre-industrial global reactive nitrogen budgets, Biogeochemistry, 46, 7–43, https://doi.org/10.1023/A:1006148011944, 1999.

Huang, R.-J., Zhang, Y., Bozzetti, C., Ho, K.-F., Cao, J.-J., Han, Y., Daellenbach, K. R., Slowik, J. G., Platt, S. M., Canonaco, F., Zotter, P., Wolf, R., Pieber, S. M., Bruns, E. A., Crippa, M., Ciarelli, G., Piazzalunga, A., Schwikowski, M., Abbaszade, G., Schnelle-Kreis, J., Zimmermann, R., An, Z., Szidat, S., Baltensperger, U., Haddad, I. E., and Prévôt, A. S. H.: High secondary aerosol contribution to particulate pollution during haze events in China, Nature, 514, 218–222, https://doi.org/10.1038/nature13774, 2014.

Kaiser, J., Hastings, M. G., Houlton, B. Z., Röckmann, T., and Sigman, D. M.: Triple oxygen isotope analysis of nitrate using the denitrifier method and thermal decomposition of N$_2$O, Anal. Chem., 79, 599–607, https://doi.org/10.1021/ac061022s, 2007.

Kanaya, Y., Cao, R., Akimoto, H., Fukuda, M., Komazaki, Y., Yokouchi, Y., Koike, M., Tanimoto, H., Takegawa, N., and Kondo, Y.: Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO$_2$ radical concentrations during the winter and summer of 2004, J. Geophys. Res.-Atmos., 112, D21312, https://doi.org/10.1029/2007JD008670, 2007.

Karydis, V. A., Tsimpidi, A. P., Pozzer, A., Astitha, M., and Lelieveld, J.: Effects of mineral dust on global atmospheric nitrate concentrations, Atmos. Chem. Phys., 16, 1491–1509, https://doi.org/10.5194/acp-16-1491-2016, 2016.

Kim, H., Walters, W. W., Bekker, C., Murray, L. T., and Hastings, M. G.: Nitrate chemistry in the northeast US – Part 2: Oxygen isotopes reveal differences in particulate and gas-phase formation, Atmos. Chem. Phys., 23, 4203–4219, https://doi.org/10.5194/acp-23-4203-2023, 2023.

Kirchstetter, T. W., Harley, R. A., and Littlejohn, D.: Measurement of Nitrous Acid in Motor Vehicle Exhaust, Environ. Sci. Technol., 30, 2843–2849, https://doi.org/10.1021/es960135y, 1996.

Kurtenbach, R., Becker, K. H., Gomes, J. A. G., Kleffmann, J., Lörzer, J. C., Spittler, M., Wiesen, P., Ackermann, R., Geyer, A., and Platt, U.: Investigations of emissions and heterogeneous formation of HONO in a road traffic tunnel, Atmos. Environ., 35, 3385–3394, https://doi.org/10.1016/S1352-2310(01)00138-8, 2001.

Largeron, Y. and Staquet, C.: Persistent inversion dynamics and wintertime PM$_{10}$ air pollution in Alpine valleys, Atmos. Environ., 135, 92–108, https://doi.org/10.1016/j.atmosenv.2016.03.045, 2016.

Leighton, P. A.: Photochemistry of Air Pollution, Academic Press, ISBN 978-0124333345, 1961.

Li, J., Zhang, X., Orlando, J., Tyndall, G., and Michalski, G.: Quantifying the nitrogen isotope effects during photochemical equilibrium between NO and NO$_2$: implications for δ$^{15}$N in tropospheric reactive nitrogen, Atmos. Chem. Phys., 20, 9805–9819, https://doi.org/10.5194/acp-20-9805-2020, 2020.

Li, J., Davy, P., Harvey, M., Katzman, T., Mitchell, T., and Michalski, G.: Nitrogen isotopes in nitrate aerosols collected in the remote marine boundary layer: Implications for nitrogen isotopic fractionations among atmospheric reactive nitrogen species, Atmos. Environ., 245, 118028, https://doi.org/10.1016/j.atmosenv.2020.118028, 2021.

Li, K., Jacob, D. J., Liao, H., Qiu, Y., Shen, L., Zhai, S., Bates, K. H., Sulprizio, M. P., Song, S., Lu, X., Zhang, Q., Zheng, B., Zhang, Y., Zhang, J., Lee, H. C., and Kuk, S. K.: Ozone pollution in the North China Plain spreading into the late-winter haze season, P. Natl. Acad. Sci. USA, 118, e2015797118, https://doi.org/10.1073/pnas.2015797118, 2021.

Li, W., Ni, B. L., Jin, D. Q., and Zhang, Q. G.: Measurement of the absolute abundance of Oxygen-17 in SMOW, Kexue Tongboa, Chinese Sci. Bull., 33, 1610–1613, https://doi.org/10.1360/sb1988-33-19-1610, 1988.

Li, Y., Shi, G., Chen, Z., Lan, M., Ding, M., Li, Z., and Hastings, M. G.: Significant Latitudinal Gradient of Nitrate Production in the Marine Atmospheric Boundary Layer of the Northern Hemisphere, Geophys. Res. Lett., 49, e2022GL100503, https://doi.org/10.1029/2022GL100503, 2022.

Li, Z., Walters, W. W., Hastings, M. G., Song, L., Huang, S., Zhu, F., Liu, D., Shi, G., Li, Y., and Fang, Y.: Atmospheric nitrate formation pathways in urban and rural atmosphere of Northeast China: Implications for complicated anthropogenic effects, Environ. Pollut., 296, 118752, https://doi.org/10.1016/j.envpol.2021.118752, 2022.

Lim, S., Lee, M., Savarino, J., and Laj, P.: Oxidation pathways and emission sources of atmospheric particulate nitrate in Seoul: based on δ$^{15}$N and Δ$^{17}$O measurements, Atmos. Chem. Phys., 22, 5099–5115, https://doi.org/10.5194/acp-22-5099-2022, 2022.

Liu, J., Liu, Z., Ma, Z., Yang, S., Yao, D., Zhao, S., Hu, B., Tang, G., Sun, J., Cheng, M., Xu, Z., and Wang, Y.: Detailed budget analysis of HONO in Beijing, China: Implication on atmosphere oxidation capacity in polluted megacity, Atmos. Environ., 244, 117957, https://doi.org/10.1016/j.atmosenv.2020.117957, 2021.

Liu, Z., Hu, K., Zhang, K., Zhu, S., Wang, M., and Li, L.: VOCs sources and roles in O$_3$ formation in the central Yangtze River Delta region of China, Atmos. Environ., 302, 119755, https://doi.org/10.1016/j.atmosenv.2023.119755, 2023.

Luo, L., Wu, S., Zhang, R., Wu, Y., Li, J., and Kao, S.: What controls aerosol δ$^{15}$N-NO$_3$$^{-}$? NO$_x$ emission sources vs. nitrogen isotope fractionation, Sci. Total Environ., 871, 162185, https://doi.org/10.1016/j.scitotenv.2023.162185, 2023.

Mariotti, A.: Natural $^{15}$N abundance measurements and atmospheric nitrogen standard calibration, Nature, 311, 251–252, https://doi.org/10.1038/311251a0, 1984.

Martinelli, L. A., Piccolo, M. C., Townsend, A. R., Vitousek, P. M., Cuevas, E., McDowell, W., Robertson, G. P., Santos, O. C., and Treseder, K.: Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests, Biogeochemistry, 46, 45–65, https://doi.org/10.1023/A:1006100128782, 1999.
tive nitrogen chemistry, Sci. Total Environ., 714, 136727, https://doi.org/10.1016/j.scitotenv.2020.136727, 2020.

Heaton, T. H. E.: ¹⁵N/¹⁴N ratios of NOₓ from vehicle engines and coal-fired power stations, Tellus B, 42, 304–307, https://doi.org/10.1034/j.1600-0889.1990.00007.x-i1, 1990.

Hoesly, R. M., Smith, S. J., Feng, L., Klimont, Z., Janssens-Maenhout, G., Pitkanen, T., Seibert, J. J., Vu, L., Andres, R. J., Bolt, R. M., Bond, T. C., Dawidowski, L., Kholod, N., Kurokawa, J.-I., Li, M., Liu, L., Lu, Z., Moura, M. C. P., O'Rourke, P. R., and Zhang, Q.: Historical (1750–2014) anthropogenic emissions of reactive gases and aerosols from the Community Emissions Data System (CEDS), Geosci. Model Dev., 11, 369–408, https://doi.org/10.5194/gmd-11-369-2018, 2018.

Holland, E. A., Dentener, F. J., Braswell, B. H., and Sulzman, J. M.: Contemporary and pre-industrial global reactive nitrogen budgets, Biogeochemistry, 46, 7–43, https://doi.org/10.1023/A:1006148011944, 1999.

Huang, R.-J., Zhang, Y., Bozzetti, C., Ho, K.-F., Cao, J.-J., Han, Y., Daellenbach, K. R., Slowik, J. G., Platt, S. M., Canonaco, F., Zotter, P., Wolf, R., Pieber, S. M., Bruns, E. A., Crippa, M., Ciarelli, G., Piazzalunga, A., Schwikowski, M., Abbaszade, G., Schnelle-Kreis, J., Zimmermann, R., An, Z., Szidat, S., Baltensperger, U., Haddad, I. E., and Prévôt, A. S. H.: High secondary aerosol contribution to particulate pollution during haze events in China, Nature, 514, 218–222, https://doi.org/10.1038/nature13774, 2014.

Kaiser, J., Hastings, M. G., Houlton, B. Z., Röckmann, T., and Sigman, D. M.: Triple oxygen isotope analysis of nitrate using the denitrifier method and thermal decomposition of N₂O, Anal. Chem., 79, 599–607, https://doi.org/10.1021/ac061022s, 2007.

Kanaya, Y., Cao, R., Akimoto, H., Fukuda, M., Komazaki, Y., Yokouchi, Y., Koike, M., Tanimoto, H., Takegawa, N., and Kondo, Y.: Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO₂ radical concentrations during the winter and summer of 2004, J. Geophys. Res.-Atmos., 112, D21312, https://doi.org/10.1029/2007JD008670, 2007.

Karydis, V. A., Tsimpidi, A. P., Pozzer, A., Astitha, M., and Lelieveld, J.: Effects of mineral dust on global atmospheric nitrate concentrations, Atmos. Chem. Phys., 16, 1491–1509, https://doi.org/10.5194/acp-16-1491-2016, 2016.

Kim, H., Walters, W. W., Bekker, C., Murray, L. T., and Hastings, M. G.: Nitrate chemistry in the northeast US – Part 2: Oxygen isotopes reveal differences in particulate and gas-phase formation, Atmos. Chem. Phys., 23, 4203–4219, https://doi.org/10.5194/acp-23-4203-2023, 2023.

Kirchstetter, T. W., Harley, R. A., and Littlejohn, D.: Measurement of Nitrous Acid in Motor Vehicle Exhaust, Environ. Sci. Technol., 30, 2843–2849, https://doi.org/10.1021/es960135y, 1996.

Kurtenbach, R., Becker, K. H., Gomes, J. A. G., Kleffmann, J., Lörzer, J. C., Spittler, M., Wiesen, P., Ackermann, R., Geyer, A., and Platt, U.: Investigations of emissions and heterogeneous formation of HONO in a road traffic tunnel, Atmos. Environ., 35, 3385–3394, https://doi.org/10.1016/S1352-2310(01)00138-8, 2001.

Largeron, Y. and Staquet, C.: Persistent inversion dynamics and wintertime PM₁₀ air pollution in Alpine valleys, Atmos. Environ., 135, 92–108, https://doi.org/10.1016/j.atmosenv.2016.03.045, 2016.

Leighton, P. A.: Photochemistry of Air Pollution, Academic Press, ISBN 978-0124333345, 1961.

Li, J., Zhang, X., Orlando, J., Tyndall, G., and Michalski, G.: Quantifying the nitrogen isotope effects during photochemical equilibrium between NO and NO₂: implications for δ¹⁵N in tropospheric reactive nitrogen, Atmos. Chem. Phys., 20, 9805–9819, https://doi.org/10.5194/acp-20-9805-2020, 2020.

Li, J., Davy, P., Harvey, M., Katzman, T., Mitchell, T., and Michalski, G.: Nitrogen isotopes in nitrate aerosols collected in the remote marine boundary layer: Implications for nitrogen isotopic fractionations among atmospheric reactive nitrogen species, Atmos. Environ., 245, 118028, https://doi.org/10.1016/j.atmosenv.2020.118028, 2021.

Li, K., Jacob, D. J., Liao, H., Qiu, Y., Shen, L., Zhai, S., Bates, K. H., Sulprizio, M. P., Song, S., Lu, X., Zhang, Q., Zheng, B., Zhang, Y., Zhang, J., Lee, H. C., and Kuk, S. K.: Ozone pollution in the North China Plain spreading into the late-winter haze season, P. Natl. Acad. Sci. USA, 118, e2015797118, https://doi.org/10.1073/pnas.2015797118, 2021.

Li, W., Ni, B. L., Jin, D. Q., and Zhang, Q. G.: Measurement of the absolute abundance of Oxygen-17 in SMOW, Kexue Tongboa, Chinese Sci. Bull., 33, 1610–1613, https://doi.org/10.1360/sb1988-33-19-1610, 1988.

Li, Y., Shi, G., Chen, Z., Lan, M., Ding, M., Li, Z., and Hastings, M. G.: Significant Latitudinal Gradient of Nitrate Production in the Marine Atmospheric Boundary Layer of the Northern Hemisphere, Geophys. Res. Lett., 49, e2022GL100503, https://doi.org/10.1029/2022GL100503, 2022.

Li, Z., Walters, W. W., Hastings, M. G., Song, L., Huang, S., Zhu, F., Liu, D., Shi, G., Li, Y., and Fang, Y.: Atmospheric nitrate formation pathways in urban and rural atmosphere of Northeast China: Implications for complicated anthropogenic effects, Environ. Pollut., 296, 118752, https://doi.org/10.1016/j.envpol.2021.118752, 2022.

Lim, S., Lee, M., Savarino, J., and Laj, P.: Oxidation pathways and emission sources of atmospheric particulate nitrate in Seoul: based on δ¹⁵N and Δ¹⁷O measurements, Atmos. Chem. Phys., 22, 5099–5115, https://doi.org/10.5194/acp-22-5099-2022, 2022.

Liu, J., Liu, Z., Ma, Z., Yang, S., Yao, D., Zhao, S., Hu, B., Tang, G., Sun, J., Cheng, M., Xu, Z., and Wang, Y.: Detailed budget analysis of HONO in Beijing, China: Implication on atmosphere oxidation capacity in polluted megacity, Atmos. Environ., 244, 117957, https://doi.org/10.1016/j.atmosenv.2020.117957, 2021.

Liu, Z., Hu, K., Zhang, K., Zhu, S., Wang, M., and Li, L.: VOCs sources and roles in O₃ formation in the central Yangtze River Delta region of China, Atmos. Environ., 302, 119755, https://doi.org/10.1016/j.atmosenv.2023.119755, 2023.

Luo, L., Wu, S., Zhang, R., Wu, Y., Li, J., and Kao, S.: What controls aerosol δ¹⁵N-NO₃⁻? NOₓ emission sources vs. nitrogen isotope fractionation, Sci. Total Environ., 871, 162185, https://doi.org/10.1016/j.scitotenv.2023.162185, 2023.

Mariotti, A.: Natural ¹⁵N abundance measurements and atmospheric nitrogen standard calibration, Nature, 311, 251–252, https://doi.org/10.1038/311251a0, 1984.

Martinelli, L. A., Piccolo, M. C., Townsend, A. R., Vitousek, P. M., Cuevas, E., McDowell, W., Robertson, G. P., Santos, O. C., and Treseder, K.: Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests, Biogeochemistry, 46, 45–65, https://doi.org/10.1023/A:1006100128782, 1999.
Masson-Delmotte, V., Zhai, A., Pirani, A., Connors, S. L., Péan, C., Berger, S., Caud, N., Chen, Y., Goldfarb, L., Gomis, M. I., Huang, M., Leitzell, K., Lonnoy, E., Matthews, J. B. R., Maycock, T. K., Waterfield, T., Yelekçi, O., Yu, R., and Zhou, B. (Eds.): Climate Change 2021: The Physical Science Basis, Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 147–286, https://doi.org/10.1017/9781009157896.003, 2021.

Mayer, H.: Air pollution in cities, Atmos. Environ., 33, 4029–4037, https://doi.org/10.1016/S1352-2310(99)00144-2, 1999.

McIlvin, M. R. and Altabet, M. A.: Chemical Conversion of Nitrate and Nitrite to Nitrous Oxide for Nitrogen and Oxygen Isotopic Analysis in Freshwater and Seawater, Anal. Chem., 77, 5589–5595, https://doi.org/10.1021/ac050528s, 2005.

Michalski, G., Scott, Z., Kabiling, M., and Thiemens, M. H.: First measurements and modeling of $\Delta^{17}O$ in atmospheric nitrate, Geophys. Res. Lett., 30, 1870, https://doi.org/10.1029/2003GL017015, 2003.

Michalski, G., Bhattacharya, S. K., and Girsch, G.: NOₓ cycle and the tropospheric ozone isotope anomaly: an experimental investigation, Atmos. Chem. Phys., 14, 4935–4953, https://doi.org/10.5194/acp-14-4935-2014, 2014.

Michoud, V., Doussin, J.-F., Colomb, A., Afif, C., Borden, A., Camredon, M., Aumont, B., Legrand, M., and Beekmann, M.: Strong HONO formation in a suburban site during snowy days, Atmos. Environ., 116, 155–158, https://doi.org/10.1016/j.atmosenv.2015.06.040, 2015.

Miller, C. E. and Yung, Y. L.: Photo-induced isotopic fractionation, J. Geophys. Res.-Atmos., 105, 29039–29051, https://doi.org/10.1029/2000JD090388, 2000.

Miller, D. J., Wojtal, P. K., Clark, S. C., and Hastings, M. G.: Vehicle NOₓ emission plume isotopic signatures: Spatial variability across the eastern United States, J. Geophys. Res.-Atmos., 122, 4698–4717, https://doi.org/10.1002/2016JD025877, 2017.

Miller, D. J., Chai, J., Guo, F., Dell, C. J., Karsten, H., and Hastings, M. G.: Isotopic Composition of In Situ Soil NOₓ Emissions in Manure-Fertilized Cropland, Geophys. Res. Lett., 45, 12058–12066, https://doi.org/10.1029/2018GL079619, 2018.

Morin, S., Savarino, J., Bekki, S., Cavender, A., Shepson, P. B., and Bottenheim, J. W.: Major influence of BrO on the NO₃ and nitrate budgets in the Arctic spring, inferred from $\Delta^{17}O(NO_3)$ measurements during ozone depletion events, Environ. Chem., 4, 238–241, https://doi.org/10.1071/EN07003, 2007a.

Morin, S., Savarino, J., Bekki, S., Gong, S., and Bottenheim, J. W.: Signature of Arctic surface ozone depletion events in the isotope anomaly ($\Delta^{17}O$) of atmospheric nitrate, Atmos. Chem. Phys., 7, 1451–1469, https://doi.org/10.5194/acp-7-1451-2007, 2007b.

Morin, S., Savarino, J., Frey, M. M., Domine, F., Jacobi, H.-W., Kaleschke, L., and Martins, J. M. F.: Comprehensive isotopic composition of atmospheric nitrate in the Atlantic Ocean boundary layer from 65° S to 79° N, J. Geophys. Res.-Atmos., 114, D05303, https://doi.org/10.1029/2008JD010696, 2009.

Morin, S., Sander, R., and Savarino, J.: Simulation of the diurnal variations of the oxygen isotope anomaly ($\Delta^{17}O$) of reactive atmospheric species, Atmos. Chem. Phys., 11, 3653–3671, https://doi.org/10.5194/acp-11-3653-2011, 2011.

Newsome, B. and Evans, M.: Impact of uncertainties in inorganic chemical rate constants on tropospheric composition and ozone radiative forcing, Atmos. Chem. Phys., 17, 14333–14352, https://doi.org/10.5194/acp-17-14333-2017, 2017.

Olofson, K. F. G., Andersson, P. U., Hallquist, M., Ljungström, E., Tang, L., Chen, D., and Pettersson, J. B. C.: Urban aerosol evolution and particle formation during winter-time temperature inversions, Atmos. Environ., 43, 340–346, https://doi.org/10.1016/j.atmosenv.2008.09.080, 2009.

ORCAE: Rapport des profils climat air énergie de la communauté de communes de la Vallée de Chamonix-Mont-Blanc, https://www.orcae-auvergne-rhone-alpes.fr/ (last access: July 2021), 2022.

Park, R. J., Jacob, D. J., Field, B. D., Yantosca, R. M., and Chin, M.: Natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosols in the United States: Implications for policy, J. Geophys. Res.-Atmos., 109, D15204, https://doi.org/10.1029/2003JD004473, 2004.

Patris, N., Cliff, S., Quinn, P., Kasem, M., and Thiemens, M.: Isotopic analysis of aerosol sulfate and nitrate during ITCT-2k2: Determination of different formation pathways as a function of particle size, J. Geophys. Res., 112, D23301, https://doi.org/10.1029/2005JD006214, 2007.

Penkett, S. A., Burgess, R. A., Coe, H., Coll, I., Hov, Ø., Lindskog, A., Schmidbauer, N., Solberg, S., Roemer, M., Thijsse, T., Beck, J., and Reeves, C. E.: Evidence for large average concentrations of the nitrate radical (NO₃) in Western Europe from the HANSA hydrocarbon database, Atmos. Environ., 41, 3465–3478, https://doi.org/10.1016/j.atmosenv.2006.11.055, 2007.

Prabhakar, G., Parworth, C. L., Zhang, X., Kim, H., Young, D. E., Beyersdorf, A. J., Ziemba, L. D., Nowak, J. B., Bertram, T. H., Faloona, I. C., Zhang, Q., and Cappa, C. D.: Observational assessment of the role of nocturnal residual-layer chemistry in determining daytime surface particulate nitrate concentrations, Atmos. Chem. Phys., 17, 14747–14770, https://doi.org/10.5194/acp-17-14747-2017, 2017.

Prospero, J. M. and Savoie, D. L.: Effect of continental sources on nitrate concentrations over the Pacific Ocean, Nature, 339, 687–689, https://doi.org/10.1038/339687a0, 1989.

Pugh, T. A. M., Cain, M., Methven, J., Wild, O., Arnold, S. R., Real, E., Law, K. S., Emmerson, K. M., Owen, S. M., Pyle, J. A., Hewitt, C. N., and MacKenzie, A. R.: A Lagrangian model of air-mass photochemistry and mixing using a trajectory ensemble: the Cambridge Tropospheric Trajectory model of Chemistry And Transport (CiTTYCAT) version 4.2, Geosci. Model Dev., 5, 193–221, https://doi.org/10.5194/gmd-5-193-2012, 2012.

Quimbayo-Duarte, J., Chemel, C., Staquet, C., Troude, F., and Arduini, G.: Drivers of severe air pollution events in a deep valley during wintertime: A case study from the Arve river valley, France, Atmos. Environ., 247, 118030, https://doi.org/10.1016/j.atmosenv.2020.118030, 2021.

Ren, J., Guo, F., and Xie, S.: Diagnosing ozone–NOₓ–VOC sensitivity and revealing causes of ozone increases in China based on 2013–2021 satellite retrievals, Atmos. Chem. Phys., 22, 15035–15047, https://doi.org/10.5194/acp-22-15035-2022, 2022.

Ren, X., Brune, W. H., Mao, J., Mitchell, M. J., Lesher, R. L., Simpas, J. B., Metcalf, A. R., Schwab, J. J., Cai, C., Li, Y., Demerjian, K. L., Felton, H. D., Boynton, G., Adams, A., Perry, J., He, Y., Zhou, X., and Hou, J.: Behavior of OH and HO₂ in the win-
Masson-Delmotte, V., Zhai, A., Pirani, A., Connors, S. L., Péan, C., Berger, S., Caud, N., Chen, Y., Goldfarb, L., Gomis, M. I., Huang, M., Leitzell, K., Lonnoy, E., Matthews, J. B. R., Maycock, T. K., Waterfield, T., Yelekçi, O., Yu, R., and Zhou, B. (Eds.): Climate Change 2021: The Physical Science Basis, Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 147–286, https://doi.org/10.1017/9781009157896.003, 2021.

Mayer, H.: Air pollution in cities, Atmos. Environ., 33, 4029–4037, https://doi.org/10.1016/S1352-2310(99)00144-2, 1999.

McIlvin, M. R. and Altabet, M. A.: Chemical Conversion of Nitrate and Nitrite to Nitrous Oxide for Nitrogen and Oxygen Isotopic Analysis in Freshwater and Seawater, Anal. Chem., 77, 5589–5595, https://doi.org/10.1021/ac050528s, 2005.

Michalski, G., Scott, Z., Kabiling, M., and Thiemens, M. H.: First measurements and modeling of $\Delta^{17}\text{O}$ in atmospheric nitrate, Geophys. Res. Lett., 30, 1870, https://doi.org/10.1029/2003GL017015, 2003.

Michalski, G., Bhattacharya, S. K., and Girsch, G.: NOₓ cycle and the tropospheric ozone isotope anomaly: an experimental investigation, Atmos. Chem. Phys., 14, 4935–4953, https://doi.org/10.5194/acp-14-4935-2014, 2014.

Michoud, V., Doussin, J.-F., Colomb, A., Afif, C., Borden, A., Camredon, M., Aumont, B., Legrand, M., and Beekmann, M.: Strong HONO formation in a suburban site during snowy days, Atmos. Environ., 116, 155–158, https://doi.org/10.1016/j.atmosenv.2015.06.040, 2015.

Miller, C. E. and Yung, Y. L.: Photo-induced isotopic fractionation, J. Geophys. Res.-Atmos., 105, 29039–29051, https://doi.org/10.1029/2000JD090388, 2000.

Miller, D. J., Wojtal, P. K., Clark, S. C., and Hastings, M. G.: Vehicle NOₓ emission plume isotopic signatures: Spatial variability across the eastern United States, J. Geophys. Res.-Atmos., 122, 4698–4717, https://doi.org/10.1002/2016JD025877, 2017.

Miller, D. J., Chai, J., Guo, F., Dell, C. J., Karsten, H., and Hastings, M. G.: Isotopic Composition of In Situ Soil NOₓ Emissions in Manure-Fertilized Cropland, Geophys. Res. Lett., 45, 12058–12066, https://doi.org/10.1029/2018GL079619, 2018.

Morin, S., Savarino, J., Bekki, S., Cavender, A., Shepson, P. B., and Bottenheim, J. W.: Major influence of BrO on the NO₃ and nitrate budgets in the Arctic spring, inferred from $\Delta^{17}\text{O}(NO_3)$ measurements during ozone depletion events, Environ. Chem., 4, 238–241, https://doi.org/10.1071/EN07003, 2007a.

Morin, S., Savarino, J., Bekki, S., Gong, S., and Bottenheim, J. W.: Signature of Arctic surface ozone depletion events in the isotope anomaly ($\Delta^{17}\text{O}$) of atmospheric nitrate, Atmos. Chem. Phys., 7, 1451–1469, https://doi.org/10.5194/acp-7-1451-2007, 2007b.

Morin, S., Savarino, J., Frey, M. M., Domine, F., Jacobi, H.-W., Kaleschke, L., and Martins, J. M. F.: Comprehensive isotopic composition of atmospheric nitrate in the Atlantic Ocean boundary layer from 65° S to 79° N, J. Geophys. Res.-Atmos., 114, D05303, https://doi.org/10.1029/2008JD010696, 2009.

Morin, S., Sander, R., and Savarino, J.: Simulation of the diurnal variations of the oxygen isotope anomaly ($\Delta^{17}\text{O}$) of reactive atmospheric species, Atmos. Chem. Phys., 11, 3653–3671, https://doi.org/10.5194/acp-11-3653-2011, 2011.

Newsome, B. and Evans, M.: Impact of uncertainties in inorganic chemical rate constants on tropospheric composition and ozone radiative forcing, Atmos. Chem. Phys., 17, 14333–14352, https://doi.org/10.5194/acp-17-14333-2017, 2017.

Olofson, K. F. G., Andersson, P. U., Hallquist, M., Ljungström, E., Tang, L., Chen, D., and Pettersson, J. B. C.: Urban aerosol evolution and particle formation during winter-time temperature inversions, Atmos. Environ., 43, 340–346, https://doi.org/10.1016/j.atmosenv.2008.09.080, 2009.

ORCAE: Rapport des profils climat air énergie de la communauté de communes de la Vallée de Chamonix-Mont-Blanc, https://www.orcae-auvergne-rhone-alpes.fr/ (last access: July 2021), 2022.

Park, R. J., Jacob, D. J., Field, B. D., Yantosca, R. M., and Chin, M.: Natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosols in the United States: Implications for policy, J. Geophys. Res.-Atmos., 109, D15204, https://doi.org/10.1029/2003JD004473, 2004.

Patris, N., Cliff, S., Quinn, P., Kasem, M., and Thiemens, M.: Isotopic analysis of aerosol sulfate and nitrate during ITCT-2k2: Determination of different formation pathways as a function of particle size, J. Geophys. Res., 112, D23301, https://doi.org/10.1029/2005JD006214, 2007.

Penkett, S. A., Burgess, R. A., Coe, H., Coll, I., Hov, Ø., Lindskog, A., Schmidbauer, N., Solberg, S., Roemer, M., Thijsse, T., Beck, J., and Reeves, C. E.: Evidence for large average concentrations of the nitrate radical (NO₃) in Western Europe from the HANSA hydrocarbon database, Atmos. Environ., 41, 3465–3478, https://doi.org/10.1016/j.atmosenv.2006.11.055, 2007.

Prabhakar, G., Parworth, C. L., Zhang, X., Kim, H., Young, D. E., Beyersdorf, A. J., Ziemba, L. D., Nowak, J. B., Bertram, T. H., Faloona, I. C., Zhang, Q., and Cappa, C. D.: Observational assessment of the role of nocturnal residual-layer chemistry in determining daytime surface particulate nitrate concentrations, Atmos. Chem. Phys., 17, 14747–14770, https://doi.org/10.5194/acp-17-14747-2017, 2017.

Prospero, J. M. and Savoie, D. L.: Effect of continental sources on nitrate concentrations over the Pacific Ocean, Nature, 339, 687–689, https://doi.org/10.1038/339687a0, 1989.

Pugh, T. A. M., Cain, M., Methven, J., Wild, O., Arnold, S. R., Real, E., Law, K. S., Emmerson, K. M., Owen, S. M., Pyle, J. A., Hewitt, C. N., and MacKenzie, A. R.: A Lagrangian model of air-mass photochemistry and mixing using a trajectory ensemble: the Cambridge Tropospheric Trajectory model of Chemistry And Transport (CiTTYCAT) version 4.2, Geosci. Model Dev., 5, 193–221, https://doi.org/10.5194/gmd-5-193-2012, 2012.

Quimbayo-Duarte, J., Chemel, C., Staquet, C., Troude, F., and Arduini, G.: Drivers of severe air pollution events in a deep valley during wintertime: A case study from the Arve river valley, France, Atmos. Environ., 247, 118030, https://doi.org/10.1016/j.atmosenv.2020.118030, 2021.

Ren, J., Guo, F., and Xie, S.: Diagnosing ozone–NOₓ–VOC sensitivity and revealing causes of ozone increases in China based on 2013–2021 satellite retrievals, Atmos. Chem. Phys., 22, 15035–15047, https://doi.org/10.5194/acp-22-15035-2022, 2022.

Ren, X., Brune, W. H., Mao, J., Mitchell, M. J., Lesher, R. L., Simpas, J. B., Metcalf, A. R., Schwab, J. J., Cai, C., Li, Y., Demerjian, K. L., Felton, H. D., Boynton, G., Adams, A., Perry, J., He, Y., Zhou, X., and Hou, J.: Behavior of OH and HO₂ in the win-
ter atmosphere in New York City, Atmos. Environ., 40, 252–263,
https://doi.org/10.1016/j.atmosenv.2005.11.073, 2006.

Richard, L., Romanini, D., and Ventrillard, I.: Nitric Oxide Analysis Down to ppt Levels by Optical-Feedback Cavity-Enhanced Absorption Spectroscopy, Sensors, 18, 1997, https://doi.org/10.3390/s18071997, 2018.

Savard, M. M., Cole, A. S., Vet, R., and Smirnoff, A.: The $\Delta^{17}O$ and $\delta^{18}O$ values of atmospheric nitrates simultaneously collected downwind of anthropogenic sources – implications for polluted air masses, Atmos. Chem. Phys., 18, 10373–10389, https://doi.org/10.5194/acp-18-10373-2018, 2018.

Savarino, J., Kaiser, J., Morin, S., Sigman, D. M., and Thiemens, M. H.: Nitrogen and oxygen isotopic constraints on the origin of atmospheric nitrate in coastal Antarctica, Atmos. Chem. Phys., 7, 1925–1945, https://doi.org/10.5194/acp-7-1925-2007, 2007.

Savarino, J., Bhattacharya, S. K., Morin, S., Baroni, M., and Doussin, J.-F.: The $NO + O_3$ reaction: A triple oxygen isotope perspective on the reaction dynamics and atmospheric implications for the transfer of the ozone isotope anomaly, J. Chem. Phys., 128, 194303, https://doi.org/10.1063/1.2917581, 2008.

Savarino, J., Morin, S., Erbland, J., Grannec, F., Patey, M. D., Vicars, W., Alexander, B., and Achterberg, E. P.: Isotopic composition of atmospheric nitrate in a tropical marine boundary layer, P. Natl. Acad. Sci. USA, 110, 17668–17673, https://doi.org/10.1073/pnas.1216639110, 2013.

Savarino, J., Vicars, W. C., Legrand, M., Preunkert, S., Jourdain, B., Frey, M. M., Kukui, A., Caillon, N., and Gil Roca, J.: Oxygen isotope mass balance of atmospheric nitrate at Dome C, East Antarctica, during the OPALE campaign, Atmos. Chem. Phys., 16, 2659–2673, https://doi.org/10.5194/acp-16-2659-2016, 2016.

Schaap, M., Müller, K., and ten Brink, H. M.: Constructing the European aerosol nitrate concentration field from quality analysed data, Atmos. Environ., 36, 1323–1335, https://doi.org/10.1016/S1352-2310(01)00556-8, 2002.

Schwikowski, M., Seibert, P., Baltensperger, U., and Gaggeler, H. W.: A study of an outstanding Saharan dust event at the high-alpine site Jungfraujoch, Switzerland, Atmos. Environ., 29, 1829–1842, https://doi.org/10.1016/1352-2310(95)00060-C, 1995.

Shah, V., Jaeglé, L., Thornton, J. A., Lopez-Hilfiker, F. D., Lee, B. H., Schroder, J. C., Campuzano-Jost, P., Jimenez, J. L., Guo, H., Sullivan, A. P., Weber, R. J., Green, J. R., Fiddler, M. N., Bililign, S., Campos, T. L., Stell, M., Weinheimer, A. J., Montzka, D. D., and Brown, S. S.: Chemical feedbacks weaken the wintertime response of particulate sulfate and nitrate to emissions reductions over the eastern United States, P. Natl. Acad. Sci. USA, 115, 8110–8115, https://doi.org/10.1073/pnas.1803295115, 2018.

Sharma, H. D., Jervis, R. E., and Wong, K. Y.: Isotopic exchange reactions in nitrogen oxides, J. Phys. Chem., 74, 923–933, https://doi.org/10.1021/j100699a044, 1970.

Shi, X., Nenes, A., Xiao, Z., Song, S., Yu, H., Shi, G., Zhao, Q., Chen, K., Feng, Y., and Russell, A. G.: High-Resolution Data Sets Unravel the Effects of Sources and Meteorological Conditions on Nitrate and Its Gas-Particle Partitioning, Environ. Sci. Technol., 53, 3048–3057, https://doi.org/10.1021/acs.est.8b06524, 2019.

Sigman, D. M., Casciotti, K. L., Andreani, M., Barford, C., Galanter, M., and Böhlke, J. K.: A Bacterial Method

for the Nitrogen Isotopic Analysis of Nitrate in Sea-water and Freshwater, Anal. Chem., 73, 4145–4153, https://doi.org/10.1021/ac010088e, 2001.

Simpson, W. R., Brown, S. S., Saiz-Lopez, A., Thornton, J. A., and von Glasow, R.: Tropospheric Halogen Chemistry: Sources, Cycling, and Impacts, Chem. Rev., 115, 4035–4062, https://doi.org/10.1021/cr5006638, 2015.

Sodemann, H., Palmer, A. S., Schwierz, C., Schwikowski, M., and Wernli, H.: The transport history of two Saharan dust events archived in an Alpine ice core, Atmos. Chem. Phys., 6, 667–688, https://doi.org/10.5194/acp-6-667-2006, 2006.

Song, W., Liu, X.-Y., Houlton, B. Z., and Liu, C.-Q.: Isotopic constraints confirm the significant role of microbial nitrogen oxides emissions from the land and ocean environment, Nat. Sci. Rev., 9, nwac106, https://doi.org/10.1093/nsr/nwc106, 2022.

Stone, D., Whalley, L. K., and Heard, D. E.: Tropospheric $OH$ and $HO_2$ radicals: field measurements and model comparisons, Chem. Soc. Rev., 41, 6348–6404, https://doi.org/10.1039/C2CS35140D, 2012.

Tan, Z., Rohrer, F., Lu, K., Ma, X., Bohn, B., Broch, S., Dong, H., Fuchs, H., Gkatzelis, G. I., Hofzumahaus, A., Holland, F., Li, X., Liu, Y., Liu, Y., Novelli, A., Shao, M., Wang, H., Wu, Y., Zeng, L., Hu, M., Kiendler-Scharr, A., Wahner, A., and Zhang, Y.: Wintertime photochemistry in Beijing: observations of $RO_x$ radical concentrations in the North China Plain during the BEST-ONE campaign, Atmos. Chem. Phys., 18, 12391–12411, https://doi.org/10.5194/acp-18-12391-2018, 2018.

Thiemens, M. H.: History and Applications of Mass-independent Isotope Effects, Annu. Rev. Earth Planet. Sc., 34, 217–262, https://doi.org/10.1146/annurev-earth.34.031405.125026, 2006.

Thornton, J. A., Kercher, J. P., Riedel, T. P., Wagner, N. L., Cozic, J., Holloway, J. S., Dubé, W. P., Wolfe, G. M., Quinn, P. K., Middlebrook, A. M., Alexander, B., and Brown, S. S.: A large atomic chlorine source inferred from mid-continental reactive nitrogen chemistry, Nature, 464, 271–274, https://doi.org/10.1038/nature08905, 2010.

Tørseth, K., Aas, W., Breivik, K., Fjæraa, A. M., Fiebig, M., Hjellbrekke, A. G., Lund Myhre, C., Solberg, S., and Yttri, K. E.: Introduction to the European Monitoring and Evaluation Programme (EMEP) and observed atmospheric composition change during 1972–2009, Atmos. Chem. Phys., 12, 5447–5481, https://doi.org/10.5194/acp-12-5447-2012, 2012.

Tsimpidi, A. P., Karydis, V. A., and Pandis, S. N.: Response of Fine Particulate Matter to Emission Changes of Oxides of Nitrogen and Anthropogenic Volatile Organic Compounds in the Eastern United States, J. Air Waste Manage., 58, 1463–1473, https://doi.org/10.3155/1047-3289.58.11.1463, 2008.

Usher, C. R., Michel, A. E., and Grassian, V. H.: Reactions on Mineral Dust, Chem. Rev., 103, 4883–4940, https://doi.org/10.1021/cr020657y, 2003.

Vicars, W. C. and Savarino, J.: Quantitative constraints on the $^{17}O$-excess ($\Delta^{17}O$) signature of surface ozone: Ambient measurements from 50°N to 50°S using the nitrite-coated filter technique, Geochim. Cosmochim. Ac., 135, 270–287, https://doi.org/10.1016/j.gca.2014.03.023, 2014.

Vicars, W. C., Bhattacharya, S. K., Erbland, J., and Savarino, J.: Measurement of the $^{17}O$-excess ($\Delta^{17}O$) of tropospheric ozone using a nitrite-coated filter, Rapid Commun. Mass Sp., 26, 1219–1231, https://doi.org/10.1002/rcm.6218, 2012.
ter atmosphere in New York City, Atmos. Environ., 40, 252–263,
https://doi.org/10.1016/j.atmosenv.2005.11.073, 2006.

Richard, L., Romanini, D., and Ventrillard, I.: Nitric Oxide Analysis Down to ppt Levels by Optical-Feedback Cavity-Enhanced Absorption Spectroscopy, Sensors, 18, 1997, https://doi.org/10.3390/s18071997, 2018.

Savard, M. M., Cole, A. S., Vet, R., and Smirnoff, A.: The Δ¹⁷O and δ¹⁸O values of atmospheric nitrates simultaneously collected downwind of anthropogenic sources – implications for polluted air masses, Atmos. Chem. Phys., 18, 10373–10389, https://doi.org/10.5194/acp-18-10373-2018, 2018.

Savarino, J., Kaiser, J., Morin, S., Sigman, D. M., and Thiemens, M. H.: Nitrogen and oxygen isotopic constraints on the origin of atmospheric nitrate in coastal Antarctica, Atmos. Chem. Phys., 7, 1925–1945, https://doi.org/10.5194/acp-7-1925-2007, 2007.

Savarino, J., Bhattacharya, S. K., Morin, S., Baroni, M., and Doussin, J.-F.: The NO + O₃ reaction: A triple oxygen isotope perspective on the reaction dynamics and atmospheric implications for the transfer of the ozone isotope anomaly, J. Chem. Phys., 128, 194303, https://doi.org/10.1063/1.2917581, 2008.

Savarino, J., Morin, S., Erbland, J., Grannec, F., Patey, M. D., Vicars, W., Alexander, B., and Achterberg, E. P.: Isotopic composition of atmospheric nitrate in a tropical marine boundary layer, P. Natl. Acad. Sci. USA, 110, 17668–17673, https://doi.org/10.1073/pnas.1216639110, 2013.

Savarino, J., Vicars, W. C., Legrand, M., Preunkert, S., Jourdain, B., Frey, M. M., Kukui, A., Caillon, N., and Gil Roca, J.: Oxygen isotope mass balance of atmospheric nitrate at Dome C, East Antarctica, during the OPALE campaign, Atmos. Chem. Phys., 16, 2659–2673, https://doi.org/10.5194/acp-16-2659-2016, 2016.

Schaap, M., Müller, K., and ten Brink, H. M.: Constructing the European aerosol nitrate concentration field from quality analysed data, Atmos. Environ., 36, 1323–1335, https://doi.org/10.1016/S1352-2310(01)00556-8, 2002.

Schwikowski, M., Seibert, P., Baltensperger, U., and Gaggeler, H. W.: A study of an outstanding Saharan dust event at the high-alpine site Jungfraujoch, Switzerland, Atmos. Environ., 29, 1829–1842, https://doi.org/10.1016/1352-2310(95)00060-C, 1995.

Shah, V., Jaeglé, L., Thornton, J. A., Lopez-Hilfiker, F. D., Lee, B. H., Schroder, J. C., Campuzano-Jost, P., Jimenez, J. L., Guo, H., Sullivan, A. P., Weber, R. J., Green, J. R., Fiddler, M. N., Bililign, S., Campos, T. L., Stell, M., Weinheimer, A. J., Montzka, D. D., and Brown, S. S.: Chemical feedbacks weaken the wintertime response of particulate sulfate and nitrate to emissions reductions over the eastern United States, P. Natl. Acad. Sci. USA, 115, 8110–8115, https://doi.org/10.1073/pnas.1803295115, 2018.

Sharma, H. D., Jervis, R. E., and Wong, K. Y.: Isotopic exchange reactions in nitrogen oxides, J. Phys. Chem., 74, 923–933, https://doi.org/10.1021/j100699a044, 1970.

Shi, X., Nenes, A., Xiao, Z., Song, S., Yu, H., Shi, G., Zhao, Q., Chen, K., Feng, Y., and Russell, A. G.: High-Resolution Data Sets Unravel the Effects of Sources and Meteorological Conditions on Nitrate and Its Gas-Particle Partitioning, Environ. Sci. Technol., 53, 3048–3057, https://doi.org/10.1021/acs.est.8b06524, 2019.

Sigman, D. M., Casciotti, K. L., Andreani, M., Barford, C., Galanter, M., and Böhlke, J. K.: A Bacterial Method

for the Nitrogen Isotopic Analysis of Nitrate in Sea-
water and Freshwater, Anal. Chem., 73, 4145–4153,
https://doi.org/10.1021/ac010088e, 2001.

Simpson, W. R., Brown, S. S., Saiz-Lopez, A., Thornton, J. A., and von Glasow, R.: Tropospheric Halogen Chemistry: Sources, Cycling, and Impacts, Chem. Rev., 115, 4035–4062, https://doi.org/10.1021/cr5006638, 2015.

Sodemann, H., Palmer, A. S., Schwierz, C., Schwikowski, M., and Wernli, H.: The transport history of two Saharan dust events archived in an Alpine ice core, Atmos. Chem. Phys., 6, 667–688, https://doi.org/10.5194/acp-6-667-2006, 2006.

Song, W., Liu, X.-Y., Houlton, B. Z., and Liu, C.-Q.: Isotopic con-
straints confirm the significant role of microbial nitrogen oxides
emissions from the land and ocean environment, Nat. Sci. Rev.,
9, nwac106, https://doi.org/10.1093/nsr/nwac106, 2022.

Stone, D., Whalley, L. K., and Heard, D. E.: Tropospheric OH and HO₂ radicals: field measurements and model comparisons, Chem. Soc. Rev., 41, 6348–6404, https://doi.org/10.1039/C2CS35140D, 2012.

Tan, Z., Rohrer, F., Lu, K., Ma, X., Bohn, B., Broch, S., Dong, H., Fuchs, H., Gkatzelis, G. I., Hofzumahaus, A., Holland, F., Li, X., Liu, Y., Liu, Y., Novelli, A., Shao, M., Wang, H., Wu, Y., Zeng, L., Hu, M., Kiendler-Scharr, A., Wahner, A., and Zhang, Y.: Wintertime photochemistry in Beijing: observations of ROₓ radical concentrations in the North China Plain during the BEST-ONE campaign, Atmos. Chem. Phys., 18, 12391–12411, https://doi.org/10.5194/acp-18-12391-2018, 2018.

Thiemens, M. H.: History and Applications of Mass-independent Isotope Effects, Annu. Rev. Earth Planet. Sc., 34, 217–262, https://doi.org/10.1146/annurev-earth.34.031405.125026, 2006.

Thornton, J. A., Kercher, J. P., Riedel, T. P., Wagner, N. L., Cozic, J., Holloway, J. S., Dubé, W. P., Wolfe, G. M., Quinn, P. K., Middlebrook, A. M., Alexander, B., and Brown, S. S.: A large atomic chlorine source inferred from mid-continental reactive nitrogen chemistry, Nature, 464, 271–274, https://doi.org/10.1038/nature08905, 2010.

Tørseth, K., Aas, W., Breivik, K., Fjæraa, A. M., Fiebig, M., Hjellbrekke, A. G., Lund Myhre, C., Solberg, S., and Yttri, K. E.: Introduction to the European Monitoring and Evaluation Programme (EMEP) and observed atmospheric composition change during 1972–2009, Atmos. Chem. Phys., 12, 5447–5481, https://doi.org/10.5194/acp-12-5447-2012, 2012.

Tsimpidi, A. P., Karydis, V. A., and Pandis, S. N.: Response of Fine Particulate Matter to Emission Changes of Oxides of Nitrogen and Anthropogenic Volatile Organic Compounds in the Eastern United States, J. Air Waste Manage., 58, 1463–1473, https://doi.org/10.3155/1047-3289.58.11.1463, 2008.

Usher, C. R., Michel, A. E., and Grassian, V. H.: Reactions on Mineral Dust, Chem. Rev., 103, 4883–4940, https://doi.org/10.1021/cr020657y, 2003.

Vicars, W. C. and Savarino, J.: Quantitative constraints on the ¹⁷O-excess (Δ¹⁷O) signature of surface ozone: Ambient measurements from 50°N to 50°S using the nitrite-coated filter technique, Geochim. Cosmochim. Ac., 135, 270–287, https://doi.org/10.1016/j.gca.2014.03.023, 2014.

Vicars, W. C., Bhattacharya, S. K., Erbland, J., and Savarino, J.: Measurement of the ¹⁷O-excess (Δ¹⁷O) of tropospheric ozone using a nitrite-coated filter, Rapid Commun. Mass Sp., 26, 1219–1231, https://doi.org/10.1002/rcm.6218, 2012.
Vicars, W. C., Morin, S., Savarino, J., Wagner, N. L., Erbland, J.,
Vince, E., Martins, J. M. F., Lerner, B. M., Quinn, P. K., Coff-
man, D. J., Williams, E. J., and Brown, S. S.: Spatial and diur-
nal variability in reactive nitrogen oxide chemistry as reflected in
the isotopic composition of atmospheric nitrate: Results from the
CalNex 2010 field study, J. Geophys. Res.-Atmos., 118, 10567-
10588, https://doi.org/10.1002/jgrd.50680, 2013.

Vitousek, P. M., Aber, J. D., Howarth, R. W., Likens, G. E., Matson, P. A., Schindler, D. W., Schlesinger, W. H., and Tilman, D. G.: Human Alteration of the Global Nitrogen Cycle: Sources and Consequences, Ecol. Appl., 7, 737–750, https://doi.org/10.1890/1051-0761(1997)007[0737:HAOTGN]2.0.CO;2, 1997.

Walters, W. W. and Michalski, G.: Theoretical calculation of nitro-
gen isotope equilibrium exchange fractionation factors for vari-
ous NO<sub>y</sub> molecules, Geochim. Cosmochim. Ac., 164, 284–297,
https://doi.org/10.1016/j.gca.2015.05.029, 2015.

Walters, W. W. and Michalski, G.: Theoretical calculation of oxygen equilibrium isotope fractionation factors involving various NOₓ molecules, OH, and H₂O and its implications for isotope variations in atmospheric nitrate, Geochim. Cosmochim. Ac., 191, 89–101, https://doi.org/10.1016/j.gca.2016.06.039, 2016.

Walters, W. W., Tharp, B. D., Fang, H., Kozak, B. J., and Michalski, G.: Nitrogen isotope composition of thermally produced NOₓ from various fossil-fuel combustion sources, Environ. Sci. Technol., 49, 11363–11371, https://doi.org/10.1021/acs.est.5b02769, 2015a.

Walters, W. W., Goodwin, S. R., and Michalski, G.: Nitrogen Stable Isotope Composition (δ¹⁵N) of Vehicle-Emitted NOₓ, Environ. Sci. Technol., 49, 2278–2285, https://doi.org/10.1021/es505580v, 2015b.

Walters, W. W., Simonini, D. S., and Michalski, G.: Nitrogen isotope exchange between NO and NO₂ and its implications for δ¹⁵N variations in tropospheric NOₓ and atmospheric nitrate, Geophys. Res. Lett., 43, 440–448, https://doi.org/10.1002/2015GL066438, 2016.

Walters, W. W., Fang, H., and Michalski, G.: Summertime diurnal variations in the isotopic composition of atmospheric nitrogen dioxide at a small midwestern United States city, Atmos. Environ., 179, 1–11, https://doi.org/10.1016/j.atmosenv.2018.01.047, 2018.

Wang, X., Jacob, D. J., Eastham, S. D., Sulprizio, M. P., Zhu, L., Chen, Q., Alexander, B., Sherwen, T., Evans, M. J., Lee, B. H., Haskins, J. D., Lopez-Hilfiker, F. D., Thornton, J. A., Huey, G. L., and Liao, H.: The role of chlorine in global tropospheric chemistry, Atmos. Chem. Phys., 19, 3981–4003, https://doi.org/10.5194/acp-19-3981-2019, 2019.

Wang, Y., Zhang, Q. Q., He, K., Zhang, Q., and Chai, L.: Sulfate-nitrate-ammonium aerosols over China: response to 2000–2015 emission changes of sulfur dioxide, nitrogen oxides, and ammonia, Atmos. Chem. Phys., 13, 2635–2652, https://doi.org/10.5194/acp-13-2635-2013, 2013.

Wang, Y., Gao, W., Wang, S., Song, T., Gong, Z., Ji, D., Wang, L., Liu, Z., Tang, G., Huo, Y., Tian, S., Li, J., Li, M., Yang, Y., Chu, B., Petäjä, T., Kerminen, V.-M., He, H., Hao, J., Kulmala, M., Wang, Y., and Zhang, Y.: Contrasting trends of PM₂.₅ and surface-ozone concentrations in China from 2013 to 2017, Nat. Sci. Rev., 7, 1331–1339, https://doi.org/10.1093/nsr/nwaa032, 2020.

Wang, Y., Liu, J., Jiang, F., Chen, Z., Wu, L., Zhou, S., Pei, C., Kuang, Y., Cao, F., Zhang, Y., Fan, M., Zheng, J., Li, J., and Zhang, G.: Vertical measurements of stable nitrogen and oxygen isotope composition of fine particulate nitrate aerosol in Guangzhou city: Source apportionment and oxidation pathway, Sci. Total Environ., 865, 161239, https://doi.org/10.1016/j.scitotenv.2022.161239, 2023.

Wang, Y. L., Song, W., Yang, W., Sun, X. C., Tong, Y. D., Wang, X. M., Liu, C. Q., Bai, Z. P., and Liu, Z. Y.: Influences of Atmospheric Pollution on the Contributions of Major Oxidation Pathways to PM₂.₅ Nitrate Formation in Beijing, J. Geophys. Res.-Atmos., 124, 4174–4185, https://doi.org/10.1029/2019JD030284, 2019.

Wayne, R. P., Barnes, I., Biggs, P., Burrows, J. P., Canosa-Mas, C. E., Hjorth, J., Le Bras, G., Moortgat, G. K., Perner, D., Poulet, G., Restelli, G., and Sidebottom, H.: The nitrate radical: Physics, chemistry, and the atmosphere, Atmos. Environ. Pt. A-Gen., 25, 1–203, https://doi.org/10.1016/0960-1686(91)90192-A, 1991.

Weber, S., Uzu, G., Calas, A., Chevrier, F., Besombes, J.-L., Char-
ron, A., Salameh, D., Ježek, I., Močnik, G., and Jaffrezo, J.-
L.: An apportionment method for the oxidative potential of at-
mospheric particulate matter sources: application to a one-year
study in Chamonix, France, Atmos. Chem. Phys., 18, 9617-
9629, https://doi.org/10.5194/acp-18-9617-2018, 2018.

Whiteman, C. D.: Breakup of Temperature Inversions in Deep Mountain Valleys: Part I. Observations, J. Appl. Meteorol. Clim., 21, 270–289, https://doi.org/10.1175/1520-0450(1982)021<0270:BOTIID>2.0.CO;2, 1982.

WHO: World Health Organization global air quality guidelines. Particulate matter (PM<sub>2.5</sub> and PM<sub>10</sub>), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide, Geneva, World Health Organization, 2021.

Wild, O., Zhu, X., and Prather, M. J.: Fast-J: Accurate simulation of in- and below-cloud photolysis in tropospheric chemical models, J. Atmos. Chem., 37, 245–282, https://doi.org/10.1023/A:1006415919030, 2000.

Xue, C.: Substantially Growing Interest in the Chemistry of Nitrous Acid (HONO) in China: Current Achievements, Problems, and Future Directions, Environ. Sci. Technol., 56, 7375–7377, https://doi.org/10.1021/acs.est.2c02237, 2022.

Young, E. D., Galy, A., and Nagahara, H.: Kinetic and equilibrium mass-dependent isotope fractionation laws in nature and their geochemical and cosmochemical significance, Geochim. Cosmochim. Ac., 66, 1095–1104, https://doi.org/10.1016/S0016-7037(01)00832-8, 2002.

Yu, Z. and Elliott, E. M.: Novel Method for Nitrogen Isotopic Analysis of Soil-Emitted Nitric Oxide, Environ. Sci. Technol., 51, 6268–6278, https://doi.org/10.1021/acs.est.7b00592, 2017.

Zhang, L., Vet, R., O'Brien, J. M., Mihele, C., Liang, Z., and Wiebe, A.: Dry deposition of individual nitrogen species at eight Canadian rural sites, J. Geophys. Res.-Atmos., 114, D02301, https://doi.org/10.1029/2008JD010640, 2009.

Zhang, R., Wang, G., Guo, S., Zamora, M. L., Ying, Q., Lin, Y., Wang, W., Hu, M., and Wang, Y.: Formation of Urban Fine Particulate Matter, Chem. Rev., 115, 3803–3855, https://doi.org/10.1021/acs.chemrev.5b00067, 2015.

Zhang, W., Bi, X., Zhang, Y., Wu, J., and Feng, Y.: Diesel vehicle emission accounts for the dominate NOₓ source to atmospheric particulate nitrate in a coastal city: Insights from
Vicars, W. C., Morin, S., Savarino, J., Wagner, N. L., Erbland, J.,
Vince, E., Martins, J. M. F., Lerner, B. M., Quinn, P. K., Coff-
man, D. J., Williams, E. J., and Brown, S. S.: Spatial and diur-
nal variability in reactive nitrogen oxide chemistry as reflected in
the isotopic composition of atmospheric nitrate: Results from the
CalNex 2010 field study, J. Geophys. Res.-Atmos., 118, 10567-
10588, https://doi.org/10.1002/jgrd.50680, 2013.

Vitousek, P. M., Aber, J. D., Howarth, R. W., Likens, G. E., Matson, P. A., Schindler, D. W., Schlesinger, W. H., and Tilman, D. G.: Human Alteration of the Global Nitrogen Cycle: Sources and Consequences, Ecol. Appl., 7, 737–750, https://doi.org/10.1890/1051-0761(1997)007[0737:HAOTGN]2.0.CO;2, 1997.

Walters, W. W. and Michalski, G.: Theoretical calculation of nitro-
gen isotope equilibrium exchange fractionation factors for vari-
ous NO<sub>y</sub> molecules, Geochim. Cosmochim. Ac., 164, 284–297,
https://doi.org/10.1016/j.gca.2015.05.029, 2015.

Walters, W. W. and Michalski, G.: Theoretical calculation of oxygen equilibrium isotope fractionation factors involving various NOₓ molecules, OH, and H₂O and its implications for isotope variations in atmospheric nitrate, Geochim. Cosmochim. Ac., 191, 89–101, https://doi.org/10.1016/j.gca.2016.06.039, 2016.

Walters, W. W., Tharp, B. D., Fang, H., Kozak, B. J., and Michalski, G.: Nitrogen isotope composition of thermally produced NOₓ from various fossil-fuel combustion sources, Environ. Sci. Technol., 49, 11363–11371, https://doi.org/10.1021/acs.est.5b02769, 2015a.

Walters, W. W., Goodwin, S. R., and Michalski, G.: Nitrogen Stable Isotope Composition (δ¹⁵N) of Vehicle-Emitted NOₓ, Environ. Sci. Technol., 49, 2278–2285, https://doi.org/10.1021/es505580v, 2015b.

Walters, W. W., Simonini, D. S., and Michalski, G.: Nitrogen isotope exchange between NO and NO₂ and its implications for δ¹⁵N variations in tropospheric NOₓ and atmospheric nitrate, Geophys. Res. Lett., 43, 440–448, https://doi.org/10.1002/2015GL066438, 2016.

Walters, W. W., Fang, H., and Michalski, G.: Summertime diurnal variations in the isotopic composition of atmospheric nitrogen dioxide at a small midwestern United States city, Atmos. Environ., 179, 1–11, https://doi.org/10.1016/j.atmosenv.2018.01.047, 2018.

Wang, X., Jacob, D. J., Eastham, S. D., Sulprizio, M. P., Zhu, L., Chen, Q., Alexander, B., Sherwen, T., Evans, M. J., Lee, B. H., Haskins, J. D., Lopez-Hilfiker, F. D., Thornton, J. A., Huey, G. L., and Liao, H.: The role of chlorine in global tropospheric chemistry, Atmos. Chem. Phys., 19, 3981–4003, https://doi.org/10.5194/acp-19-3981-2019, 2019.

Wang, Y., Zhang, Q. Q., He, K., Zhang, Q., and Chai, L.: Sulfate-nitrate-ammonium aerosols over China: response to 2000–2015 emission changes of sulfur dioxide, nitrogen oxides, and ammonia, Atmos. Chem. Phys., 13, 2635–2652, https://doi.org/10.5194/acp-13-2635-2013, 2013.

Wang, Y., Gao, W., Wang, S., Song, T., Gong, Z., Ji, D., Wang, L., Liu, Z., Tang, G., Huo, Y., Tian, S., Li, J., Li, M., Yang, Y., Chu, B., Petäjä, T., Kerminen, V.-M., He, H., Hao, J., Kulmala, M., Wang, Y., and Zhang, Y.: Contrasting trends of PM₂.₅ and surface-ozone concentrations in China from 2013 to 2017, Nat. Sci. Rev., 7, 1331–1339, https://doi.org/10.1093/nsr/nwaa032, 2020.

Wang, Y., Liu, J., Jiang, F., Chen, Z., Wu, L., Zhou, S., Pei, C., Kuang, Y., Cao, F., Zhang, Y., Fan, M., Zheng, J., Li, J., and Zhang, G.: Vertical measurements of stable nitrogen and oxygen isotope composition of fine particulate nitrate aerosol in Guangzhou city: Source apportionment and oxidation pathway, Sci. Total Environ., 865, 161239, https://doi.org/10.1016/j.scitotenv.2022.161239, 2023.

Wang, Y. L., Song, W., Yang, W., Sun, X. C., Tong, Y. D., Wang, X. M., Liu, C. Q., Bai, Z. P., and Liu, Z. Y.: Influences of Atmospheric Pollution on the Contributions of Major Oxidation Pathways to PM₂.₅ Nitrate Formation in Beijing, J. Geophys. Res.-Atmos., 124, 4174–4185, https://doi.org/10.1029/2019JD030284, 2019.

Wayne, R. P., Barnes, I., Biggs, P., Burrows, J. P., Canosa-Mas, C. E., Hjorth, J., Le Bras, G., Moortgat, G. K., Perner, D., Poulet, G., Restelli, G., and Sidebottom, H.: The nitrate radical: Physics, chemistry, and the atmosphere, Atmos. Environ. Pt. A-Gen., 25, 1–203, https://doi.org/10.1016/0960-1686(91)90192-A, 1991.

Weber, S., Uzu, G., Calas, A., Chevrier, F., Besombes, J.-L., Char-
ron, A., Salameh, D., Ježek, I., Močnik, G., and Jaffrezo, J.-
L.: An apportionment method for the oxidative potential of at-
mospheric particulate matter sources: application to a one-year
study in Chamonix, France, Atmos. Chem. Phys., 18, 9617-
9629, https://doi.org/10.5194/acp-18-9617-2018, 2018.

Whiteman, C. D.: Breakup of Temperature Inversions in Deep Mountain Valleys: Part I. Observations, J. Appl. Meteorol. Clim., 21, 270–289, https://doi.org/10.1175/1520-0450(1982)021<0270:BOTIID>2.0.CO;2, 1982.

WHO: World Health Organization global air quality guidelines. Particulate matter (PM₂.₅ and PM₁₀), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide, Geneva, World Health Organization, 2021.

Wild, O., Zhu, X., and Prather, M. J.: Fast-J: Accurate simulation of in- and below-cloud photolysis in tropospheric chemical models, J. Atmos. Chem., 37, 245–282, https://doi.org/10.1023/A:1006415919030, 2000.

Xue, C.: Substantially Growing Interest in the Chemistry of Nitrous Acid (HONO) in China: Current Achievements, Problems, and Future Directions, Environ. Sci. Technol., 56, 7375–7377, https://doi.org/10.1021/acs.est.2c02237, 2022.

Young, E. D., Galy, A., and Nagahara, H.: Kinetic and equilibrium mass-dependent isotope fractionation laws in nature and their geochemical and cosmochemical significance, Geochim. Cosmochim. Ac., 66, 1095–1104, https://doi.org/10.1016/S0016-7037(01)00832-8, 2002.

Yu, Z. and Elliott, E. M.: Novel Method for Nitrogen Isotopic Analysis of Soil-Emitted Nitric Oxide, Environ. Sci. Technol., 51, 6268–6278, https://doi.org/10.1021/acs.est.7b00592, 2017.

Zhang, L., Vet, R., O'Brien, J. M., Mihele, C., Liang, Z., and Wiebe, A.: Dry deposition of individual nitrogen species at eight Canadian rural sites, J. Geophys. Res.-Atmos., 114, D02301, https://doi.org/10.1029/2008JD010640, 2009.

Zhang, R., Wang, G., Guo, S., Zamora, M. L., Ying, Q., Lin, Y., Wang, W., Hu, M., and Wang, Y.: Formation of Urban Fine Particulate Matter, Chem. Rev., 115, 3803–3855, https://doi.org/10.1021/acs.chemrev.5b00067, 2015.

Zhang, W., Bi, X., Zhang, Y., Wu, J., and Feng, Y.: Diesel vehicle emission accounts for the dominate NOₓ source to atmospheric particulate nitrate in a coastal city: Insights from
nitrate dual isotopes of PM₂.₅, Atmos. Res., 278, 106328, https://doi.org/10.1016/j.atmosres.2022.106328, 2022.

Zhang, Y.-L., Zhang, W., Fan, M.-Y., Li, J., Fang, H., Cao, F., Lin, Y.-C., Wilkins, B. P., Liu, X., Bao, M., Hong, Y., and Michalski, G.: A diurnal story of Δ¹⁷O(NO₃⁻) in urban Nanjing and its implication for nitrate aerosol formation, npj Clim. Atmos. Sci., 5, 1–10, https://doi.org/10.1038/s41612-022-00273-3, 2022.

Zhou, W., Gao, M., He, Y., Wang, Q., Xie, C., Xu, W., Zhao, J., Du, W., Qiu, Y., Lei, L., Fu, P., Wang, Z., Worsnop, D. R., Zhang, Q., and Sun, Y.: Response of aerosol chemistry to clean air action in Beijing, China: Insights from two-year ACSM measurements and model simulations, Environ. Pollut., 255, 113345, https://doi.org/10.1016/j.envpol.2019.113345, 2019.

Zong, Z., Wang, X., Tian, C., Chen, Y., Fang, Y., Zhang, F., Li, C., Sun, J., Li, J., and Zhang, G.: First Assessment of NOₓ Sources at a Regional Background Site in North China Using Isotopic Analysis Linked with Modeling, Environ. Sci. Technol., 51, 5923–5931, https://doi.org/10.1021/acs.est.6b06316, 2017.

Zong, Z., Sun, Z., Xiao, L., Tian, C., Liu, J., Sha, Q., Li, J., Fang, Y., Zheng, J., and Zhang, G.: Insight into the Variability of the Nitrogen Isotope Composition of Vehicular NOₓ in China, Environ. Sci. Technol., 54, 14246–14253, https://doi.org/10.1021/acs.est.0c04749, 2020.
nitrate dual isotopes of PM<sub>2.5</sub>, Atmos. Res., 278, 106328, https://doi.org/10.1016/j.atmosres.2022.106328, 2022.

Zhang, Y.-L., Zhang, W., Fan, M.-Y., Li, J., Fang, H., Cao, F., Lin, Y.-C., Wilkins, B. P., Liu, X., Bao, M., Hong, Y., and Michalski, G.: A diurnal story of Δ<sup>17</sup>O(NO<sub>3</sub><sup>-</sup>) in urban Nanjing and its implication for nitrate aerosol formation, npj Clim. Atmos. Sci., 5, 1–10, https://doi.org/10.1038/s41612-022-00273-3, 2022.

Zhou, W., Gao, M., He, Y., Wang, Q., Xie, C., Xu, W., Zhao, J., Du, W., Qiu, Y., Lei, L., Fu, P., Wang, Z., Worsnop, D. R., Zhang, Q., and Sun, Y.: Response of aerosol chemistry to clean air action in Beijing, China: Insights from two-year ACSM measurements and model simulations, Environ. Pollut., 255, 113345, https://doi.org/10.1016/j.envpol.2019.113345, 2019.

Zong, Z., Wang, X., Tian, C., Chen, Y., Fang, Y., Zhang, F., Li, C., Sun, J., Li, J., and Zhang, G.: First Assessment of NOx Sources at a Regional Background Site in North China Using Isotopic Analysis Linked with Modeling, Environ. Sci. Technol., 51, 5923–5931, https://doi.org/10.1021/acs.est.6b06316, 2017.

Zong, Z., Sun, Z., Xiao, L., Tian, C., Liu, J., Sha, Q., Li, J., Fang, Y., Zheng, J., and Zhang, G.: Insight into the Variability of the Nitrogen Isotope Composition of Vehicular NOₓ in China, Environ. Sci. Technol., 54, 14246–14253, https://doi.org/10.1021/acs.est.0c04749, 2020.