Articles | Volume 26, issue 15
https://doi.org/10.5194/acp-26-10947-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-26-10947-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
06 Aug 2026
Research article |
| 06 Aug 2026
| 06 Aug 2026
Size-resolved isotope analysis reveals anthropogenic reactive nitrogen transport and transformation in Taiwan mountain forests: A case study
Wen-Chien Lee
Department of Atmospheric Sciences, National Taiwan University, Taipei, 10617, Taiwan
Ming-Hao Huang
Department of Atmospheric Sciences, National Taiwan University, Taipei, 10617, Taiwan
Wei-Chieh Huang
Department of Atmospheric Sciences, National Taiwan University, Taipei, 10617, Taiwan
Jen-Ping Chen
Department of Atmospheric Sciences, National Taiwan University, Taipei, 10617, Taiwan
Yen-Jen Lai
Experimental Forest, National Taiwan University, Nantou, 557004, Taiwan
Haojia Ren
CORRESPONDING AUTHOR
Department of Geosciences, National Taiwan University, Taipei, 10617, Taiwan
Department of Atmospheric Sciences, National Taiwan University, Taipei, 10617, Taiwan
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Geosci. Model Dev., 19, 6231–6257, https://doi.org/10.5194/gmd-19-6231-2026, https://doi.org/10.5194/gmd-19-6231-2026, 2026
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We developed a new cloud microphysics scheme that links simulated cloud and precipitation particles with radar signals. Idealized squall line and a real thunderstorm case in Taiwan show that the scheme produces physically meaningful storm structures and encouraging radar comparisons, while further refinement is still needed for ice particles, hydrometeor orientation, and radar-viewing assumptions.
Jen-Ping Chen, I-Chun Tsai, Li-Wei Kuo, and Gong-Do Hwang
Atmos. Chem. Phys., 26, 6909–6927, https://doi.org/10.5194/acp-26-6909-2026, https://doi.org/10.5194/acp-26-6909-2026, 2026
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Thomas M. DeCarlo, Oliwia Jasnos, Avi Strange, Andreas Andersson, Angel T. Bautista VII, Sierra Bloomer, Isaiah W. Bolden, Maartje Bosman, Thomas C. Brachert, Giulia B. Braz, Gabriel O. Cardoso, Juan P. Carricart-Ganivet, Jessica E. Carilli, Karl D. Castillo, Leticia Cavole, Sylvia Chan, Xuefei Chen, Ben Chomitz, Thierry Correge, Travis A. Courtney, Mikayla Deigan, Juan Pablo D'Olivo, Robert Dunbar, Ian C. Enochs, Ludmilla Falsarella, Thomas Felis, Gabriela Gutierrez-Estrada, Brighton Hedger, Shijian Hu, Seamus Jameson, Stacy Jupiter, Paul Kench, Diego K. Kersting, Ke Lin, Yi-Wei Liu, Carla A. B. Lorigados, Derek P. Manzello, Malcolm T. McCulloch, Miguel Mies, Rodrigo L. Moura, Ferdinand Oberle, Natan Pereira, Nancy Prouty, Riovie D. Ramos, Haojia Ren, Emma Ryan, Diane M. Thompson, Lauren T. Toth, Marina J. Vergotti, Jody M. Webster, and Jens Zinke
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We present CoralCache, a virtual coral core repository with global coverage. This repository fills a key gap by enabling researchers to transparently archive and share the raw core image datasets and the visual interpretations of those images, rather than simply the summarized growth rate data, which on their own cannot be traced or precisely reproduced. CoralCache is designed to meet the data-sharing principles of findability, accessibility, interoperability, and reusability (FAIR).
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Babette A.A. Hoogakker, Catherine Davis, Yi Wang, Stephanie Kusch, Katrina Nilsson-Kerr, Dalton S. Hardisty, Allison Jacobel, Dharma Reyes Macaya, Nicolaas Glock, Sha Ni, Julio Sepúlveda, Abby Ren, Alexandra Auderset, Anya V. Hess, Katrin J. Meissner, Jorge Cardich, Robert Anderson, Christine Barras, Chandranath Basak, Harold J. Bradbury, Inda Brinkmann, Alexis Castillo, Madelyn Cook, Kassandra Costa, Constance Choquel, Paula Diz, Jonas Donnenfield, Felix J. Elling, Zeynep Erdem, Helena L. Filipsson, Sebastián Garrido, Julia Gottschalk, Anjaly Govindankutty Menon, Jeroen Groeneveld, Christian Hallmann, Ingrid Hendy, Rick Hennekam, Wanyi Lu, Jean Lynch-Stieglitz, Lélia Matos, Alfredo Martínez-García, Giulia Molina, Práxedes Muñoz, Simone Moretti, Jennifer Morford, Sophie Nuber, Svetlana Radionovskaya, Morgan Reed Raven, Christopher J. Somes, Anja S. Studer, Kazuyo Tachikawa, Raúl Tapia, Martin Tetard, Tyler Vollmer, Xingchen Wang, Shuzhuang Wu, Yan Zhang, Xin-Yuan Zheng, and Yuxin Zhou
Biogeosciences, 22, 863–957, https://doi.org/10.5194/bg-22-863-2025, https://doi.org/10.5194/bg-22-863-2025, 2025
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Paleo-oxygen proxies can extend current records, constrain pre-anthropogenic baselines, provide datasets necessary to test climate models under different boundary conditions, and ultimately understand how ocean oxygenation responds on longer timescales. Here we summarize current proxies used for the reconstruction of Cenozoic seawater oxygen levels. This includes an overview of the proxy's history, how it works, resources required, limitations, and future recommendations.
Wei-Chieh Huang, Hui-Ming Hung, Ching-Wei Chu, Wei-Chun Hwang, and Shih-Chun Candice Lung
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Ping-Chieh Huang, Hui-Ming Hung, Hsin-Chih Lai, and Charles C.-K. Chou
Atmos. Chem. Phys., 24, 10759–10772, https://doi.org/10.5194/acp-24-10759-2024, https://doi.org/10.5194/acp-24-10759-2024, 2024
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Models were used to study ways to reduce particulate matter (PM) pollution in Taiwan during winter. After considering various factors, such as physical processes and chemical reactions, we found that reducing NOx or NH3 emissions is more effective at mitigating PM2.5 than reducing SO2 emissions. When considering both efficiency and cost, reducing NH3 emissions seems to be a more suitable policy for the studied environment in Taiwan.
Ting-Yu Chen, Chia-Li Chen, Yi-Chi Chen, Charles C.-K. Chou, Haojia Ren, and Hui-Ming Hung
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By presenting an approach using EMeRGe-Asia airborne field measurements and surface observations, this study shows that the fraction of OH reactivity due to SO2-OH reaction has a significant correlation with the sulfate concentration. Approximately 30 % of sulfate is produced by SO2-OH reaction. Our results underline the importance of SO2-OH gas-phase oxidation in sulfate formation, and demonstrate that the method can be applied to other regions and under different meteorological conditions.
Cited articles
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.
Aschmann, S. M., Arey, J., and Atkinson, R.: OH radical formation from the gas-phase reactions of O3 with a series of terpenes, Atmos. Environ., 36, 4347–4355, https://doi.org/10.1016/S1352-2310(02)00355-2, 2002.
Böhlke, J. K., Mroczkowski, S. J., and Coplen, T. B.: Oxygen isotopes in nitrate: new reference materials for
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 NO
Chang, Y., Zhang, Y., Wang, Q., Shao, S., Bao, M., Zhang, C., and Lehmann, M. F.: Nitrogen isotope fractionation associated with ammonia gas-to-aerosol conversion and implications for determining isotopic source signatures and tracing atmospheric ammonium origins, Environ. Sci. Technol., 59, 22110–22121, https://doi.org/10.1021/acs.est.5c11271, 2025.
Chen, C.-L., Chen, T.-Y., Hung, H.-M., Tsai, P.-W., Chou, C. C. K., and Chen, W.-N.: The influence of upslope fog on hygroscopicity and chemical composition of aerosols at a forest site in Taiwan, Atmos. Environ., 246, 118150, https://doi.org/10.1016/j.atmosenv.2020.118150, 2021.
Chen, T.-Y., Chen, C.-L., Chen, Y.-C., Chou, C. C.-K., Ren, H., and Hung, H.-M.: Source apportionment and evolution of N-containing aerosols at a rural cloud forest in Taiwan by isotope analysis, Atmos. Chem. Phys., 22, 13001–13012, https://doi.org/10.5194/acp-22-13001-2022, 2022.
Chen, Z.-L., Song, W., Hu, C.-C., Liu, X.-J., Chen, G.-Y., Walters, W. W., Michalski, G., Liu, C.-Q., Fowler, D., and Liu, X.-Y.: Significant contributions of combustion-related sources to ammonia emissions, Nat. Commun., 13, 7710, https://doi.org/10.1038/s41467-022-35381-4, 2022.
Cheng, Y., Zheng, G., Wei, C., Mu, Q., Zheng, B., Wang, Z., Gao, M., Zhang, Q., He, K., Carmichael, G., Pöschl, U., and Su, H.: Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China, Sci. Adv., 2, e1601530, https://doi.org/10.1126/sciadv.1601530, 2016.
Doney, S. C., Mahowald, N., Lima, I., Feely, R. A., Mackenzie, F. T., Lamarque, J.-F., and Rasch, P. J.: Impact of anthropogenic atmospheric nitrogen and sulfur deposition on ocean acidification and the inorganic carbon system, P. Natl. Acad. Sci. USA, 104, 14580–14585, https://doi.org/10.1073/pnas.0702218104, 2007.
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.
Ervens, B.: Modeling the processing of aerosol and trace gases in clouds and fogs, Chem. Rev., 115, 4157–4198, https://doi.org/10.1021/cr5005887, 2015.
Fan, M.-Y., Zhang, Y.-L., Lin, Y.-C., Cao, F., Zhao, Z.-Y., Sun, Y., Qiu, Y., Fu, P., and Wang, Y.: Changes of emission sources to nitrate aerosols in Beijing after the clean air actions: Evidence from dual isotope compositions, J. Geophys. Res.-Atmos., 125, e2019JD031998, https://doi.org/10.1029/2019JD031998, 2020.
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.
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.
Gobel, A. R., Altieri, K. E., Peters, A. J., Hastings, M. G., and Sigman, D. M.: Insights into anthropogenic nitrogen deposition to the North Atlantic investigated using the isotopic composition of aerosol and rainwater nitrate, Geophys. Res. Lett., 40, 5977–5982, https://doi.org/10.1002/2013GL058167, 2013.
Gong, C., Tian, H., Liao, H., Pan, N., Pan, S., Ito, A., Jain, A. K., Kou-Giesbrecht, S., Joos, F., Sun, Q., Shi, H., Vuichard, N., Zhu, Q., Peng, C., Maggi, F., Tang, F. H. M., and Zaehle, S.: Global net climate effects of anthropogenic reactive nitrogen, Nature, 632, 557–563, https://doi.org/10.1038/s41586-024-07714-4, 2024.
Guha, T., Lin, C. T., Bhattacharya, S. K., Mahajan, A. S., Ou-Yang, C.-F., Lan, Y.-P., Hsu, S. C., and Liang, M.-C.: Isotopic ratios of nitrate in aerosol samples from Mt. Lulin, a high-altitude station in Central Taiwan, Atmos. Environ., 154, 53–69, https://doi.org/10.1016/j.atmosenv.2017.01.036, 2017.
Guo, F., Bui, A. A. T., Schulze, B. C., Dai, Q., Yoon, S., Shrestha, S., Wallace, H. W., Sanchez, N. P., Alvarez, S., Erickson, M. H., Sheesley, R. J., Usenko, S., Flynn, J., and Griffin, R. J.: Airmass history, night-time particulate organonitrates, and meteorology impact urban SOA formation rate, Atmos. Environ., 322, 120362, https://doi.org/10.1016/j.atmosenv.2024.120362, 2024.
Haagen-Smit, A. J., Bradley, C. E., and Fox, M. M.: Ozone formation in photochemical oxidation of organic substances, Ind. Eng. Chem., 45, 2086–2089, https://doi.org/10.1021/ie50525a044, 1953.
Hall, S. J., Ogata, E. M., Weintraub, S. R., Baker, M. A., Ehleringer, J. R., Czimczik, C. I., and Bowling, D. R.: Convergence in nitrogen deposition and cryptic isotopic variation across urban and agricultural valleys in northern Utah, J. Geophys. Res.-Biogeo., 121, 2340–2355, https://doi.org/10.1002/2016JG003354, 2016.
Hastings, M. G., Sigman, D. M., and Lipschultz, F.: Isotopic evidence for source changes of nitrate in rain at Bermuda, J. Geophys. Res.-Atmos., 108, 4790, https://doi.org/10.1029/2003JD003789, 2003.
Heaton, T. H. E., Spiro, B., and Robertson, S. M. C.: Potential canopy influences on the isotopic composition of nitrogen and sulphur in atmospheric deposition, Oecologia, 109, 600–607, https://doi.org/10.1007/s004420050122, 1997.
Holmes, R. M., Aminot, A., Kérouel, R., Hooker, B. A., and Peterson, B. J.: A simple and precise method for measuring ammonium in marine and freshwater ecosystems, Can. J. Fish. Aquat. Sci., 56, 1801–1808, https://doi.org/10.1139/f99-128, 1999.
Huang, P.-C., Hung, H.-M., Lai, H.-C., and Chou, C. C.-K.: Assessing the effectiveness of SO2, NOx, and NH3 emission reductions in mitigating winter PM2.5 in Taiwan using CMAQ, Atmos. Chem. Phys., 24, 10759–10772, https://doi.org/10.5194/acp-24-10759-2024, 2024.
Huang, W.-C., Hung, H.-M., Chu, C.-W., Hwang, W.-C., and Lung, S.-C. C.: Deriving the hygroscopicity of ambient particles using low-cost optical particle counters, Atmos. Meas. Tech., 17, 6073–6084, https://doi.org/10.5194/amt-17-6073-2024, 2024.
Humbert, J. Y., Dwyer, J. M., Andrey, A., and Arlettaz, R.: Impacts of nitrogen addition on plant biodiversity in mountain grasslands depend on dose, application duration and climate: a systematic review, Glob. Change Biol., 22, 110–120, https://doi.org/10.1111/gcb.12986, 2016.
Kanaya, Y., Cao, R., Kato, S., Miyakawa, Y., Kajii, Y., Tanimoto, H., Yokouchi, Y., Mochida, M., Kawamura, K., and Akimoto, H.: Chemistry of OH and HO2 radicals observed at Rishiri Island, Japan, in September 2003: Missing daytime sink of HO2 and positive nighttime correlations with monoterpenes, J. Geophys. Res.-Atmos., 112, D11308, https://doi.org/10.1029/2006JD007987, 2007.
Kawashima, H., Yoshida, O., and Suto, N.: Long-term source apportionment of ammonium in PM2.5 at a suburban and a rural site using stable nitrogen isotopes, Environ. Sci. Technol., 57, 1268–1277, https://doi.org/10.1021/acs.est.2c06311, 2023.
Kroll, J. H., Clarke, J. S., Donahue, N. M., Anderson, J. G., and Demerjian, K. L.: Mechanism of HOx formation in the gas-phase ozone–alkene reaction. 1. Direct, pressure-dependent measurements of prompt OH yields, J. Phys. Chem. A, 105, 1554–1560, https://doi.org/10.1021/jp002121r, 2001.
Kroopnick, P. and Craig, H.: Atmospheric oxygen: Isotopic composition and solubility fractionation, Science, 175, 54–55, https://doi.org/10.1126/science.175.4017.54, 1972.
Kundu, S., Kawamura, K., and Lee, M.: Seasonal variation of the concentrations of nitrogenous species and their nitrogen isotopic ratios in aerosols at Gosan, Jeju Island: Implications for atmospheric processing and source changes of aerosols, J. Geophys. Res.-Atmos., 115, D20305, https://doi.org/10.1029/2009JD013323, 2010.
Lee, W.-C., Huang, M.-H., Huang, W.-C., Chen, J.-P., Ren, H.-J., and Hung, H.-M.: Size-resolved isotope analysis reveals anthropogenic reactive nitrogen transport and transformation in Taiwan mountain forests: A case study, Zenodo [data set], https://doi.org/10.5281/zenodo.20787090, 2026.
Lin, Y.-C., Zhang, Y.-L., Yu, M., Fan, M.-Y., Xie, F., Zhang, W.-Q., Wu, G., Cong, Z., and Michalski, G.: Formation mechanisms and source apportionments of airborne nitrate aerosols at a Himalayan-Tibetan Plateau site: Insights from nitrogen and oxygen isotopic compositions, Environ. Sci. Technol., 55, 12261–12271, https://doi.org/10.1021/acs.est.1c03957, 2021.
Lin, Z., Ji, X., Xu, L., Chen, G., Yang, C., Zhang, K., Zhang, F., Li, L., Chen, Y., and Chen, J.: Enhanced NO2-driven multiphase formation of particulate nitrate and sulfate under high-humidity conditions, npj Clim. Atmos. Sci., 9, 76, https://doi.org/10.1038/s41612-026-01352-5, 2026.
Meng, W., Zhong, Q., Yun, X., Zhu, X., Huang, T., Shen, H., Chen, Y., Chen, H., Zhou, F., Liu, J., Wang, X., Zeng, E. Y., and Tao, S.: Improvement of a global high-resolution ammonia emission inventory for combustion and industrial sources with new data from the residential and transportation sectors, Environ. Sci. Technol., 51, 2821–2829, https://doi.org/10.1021/acs.est.6b03694, 2017.
Moore, H.: The isotopic composition of ammonia, nitrogen dioxide and nitrate in the atmosphere, Atmos. Environ., 11, 1239–1243, https://doi.org/10.1016/0004-6981(77)90102-0, 1977.
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.
Murphy, S. E., Buenconsejo, R. S., Draper, D. C., Crounse, J. D., Baliaka, H. D., Ward, R. X., Schulze, B. C., Rezgui, S. P., Ball, K., Susskind, T., Kappaganthula, G., and Wennberg, P. O.: Multi-functional organic nitrogen in the Los Angeles Air Basin, ACS ES&T Air, 2, 2009–2027, https://doi.org/10.1021/acsestair.5c00206, 2025.
Pan, Y., Tian, S., Liu, D., Fang, Y., Zhu, X., Zhang, Q., Zheng, B., Michalski, G., and Wang, Y.: Fossil fuel combustion-related emissions dominate atmospheric ammonia sources during severe haze episodes: Evidence from 15N-stable isotope in size-resolved aerosol ammonium, Environ. Sci. Technol., 50, 8049–8056, https://doi.org/10.1021/acs.est.6b00634, 2016.
Pinder, R. W., Davidson, E. A., Goodale, C. L., Greaver, T. L., Herrick, J. D., and Liu, L.: Climate change impacts of US reactive nitrogen, P. Natl. Acad. Sci. USA, 109, 7671–7675, https://doi.org/10.1073/pnas.1114243109, 2012.
Proemse, B. C., Mayer, B., Chow, J. C., and Watson, J. G.: Isotopic characterization of nitrate, ammonium and sulfate in stack PM2.5 emissions in the Athabasca Oil Sands Region, Alberta, Canada, Atmos. Environ., 60, 555–563, https://doi.org/10.1016/j.atmosenv.2012.06.046, 2012.
Pye, H. O. T., Nenes, A., Alexander, B., Ault, A. P., Barth, M. C., Clegg, S. L., Collett Jr., J. L., Fahey, K. M., Hennigan, C. J., Herrmann, H., Kanakidou, M., Kelly, J. T., Ku, I.-T., McNeill, V. F., Riemer, N., Schaefer, T., Shi, G., Tilgner, A., Walker, J. T., Wang, T., Weber, R., Xing, J., Zaveri, R. A., and Zuend, A.: The acidity of atmospheric particles and clouds, Atmos. Chem. Phys., 20, 4809–4888, https://doi.org/10.5194/acp-20-4809-2020, 2020.
Romer, P. S., Duffey, K. C., Wooldridge, P. J., Allen, H. M., Ayres, B. R., Brown, S. S., Brune, W. H., Crounse, J. D., de Gouw, J., Draper, D. C., Feiner, P. A., Fry, J. L., Goldstein, A. H., Koss, A., Misztal, P. K., Nguyen, T. B., Olson, K., Teng, A. P., Wennberg, P. O., Wild, R. J., Zhang, L., and Cohen, R. C.: The lifetime of nitrogen oxides in an isoprene-dominated forest, Atmos. Chem. Phys., 16, 7623–7637, https://doi.org/10.5194/acp-16-7623-2016, 2016.
Salvador, C. M., Chou, C. C.-K., Ho, T.-T., Tsai, C.-Y., Tsao, T.-M., Tsai, M.-J., and Su, T.-C.: Contribution of terpenes to ozone formation and secondary organic aerosols in a subtropical forest impacted by urban pollution, Atmosphere, 11, 1232, https://doi.org/10.3390/atmos11111232, 2020.
Savard, M. M., Cole, A., Smirnoff, A., and Vet, R.: δ15N values of atmospheric N species simultaneously collected using sector-based samplers distant from sources – Isotopic inheritance and fractionation, Atmos. Environ., 162, 11–22, https://doi.org/10.1016/j.atmosenv.2017.05.010, 2017.
Stock, B. C. and Semmens, B. X.: MixSIAR GUI User Manual, Version 3.1, https://doi.org/10.5281/zenodo.1209993, 2016.
Stock, B. C., Jackson, A. L., Ward, E. J., Parnell, A. C., Phillips, D. L., and Semmens, B. X.: Analyzing mixing systems using a new generation of Bayesian tracer mixing models, PeerJ, 6, e5096, https://doi.org/10.7717/peerj.5096, 2018 (code available at: https://brianstock.github.io/MixSIAR/, last access: 31 July 2026).
Ti, C., Gao, B., Luo, Y., Wang, X., Wang, S., and Yan, X.: Isotopic characterization of NHx-N in deposition and major emission sources, Biogeochemistry, 138, 85–102, https://doi.org/10.1007/s10533-018-0432-3, 2018.
Tsai, I.-C., Chen, J.-P., Lung, C. S.-C., Li, N., Chen, W.-N., Fu, T.-M., Chang, C.-C., and Hwang, G.-D.: Sources and formation pathways of organic aerosol in a subtropical metropolis during summer, Atmos. Environ., 117, 51–60, https://doi.org/10.1016/j.atmosenv.2015.07.005, 2015.
Tsai, I.-C., Hsieh, P.-R., Hsu, H.-H., Tung, Y.-S., Chen, Y.-M., and Cheng, C.-T.: Climate change-induced impacts on PM2.5 in Taiwan under 2 and 4 °C global warming, Atmos. Pollut. Res., 15, 102106, https://doi.org/10.1016/j.apr.2024.102106, 2024.
Vicars, W. C., Morin, S., Savarino, J., Wagner, N. L., Erbland, J., Vince, E., Martins, J. M. F., Lerner, B. M., Quinn, P. K., Coffman, D. J., Williams, E. J., and Brown, S. S.: Spatial and diurnal 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.
Walters, W. W. and Michalski, G.: Theoretical calculation of oxygen equilibrium isotope fractionation factors involving various NOy 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., Chai, J., and Hastings, M. G.: Theoretical phase resolved ammonia–ammonium nitrogen equilibrium isotope exchange fractionations: Applications for tracking atmospheric ammonia gas-to-particle conversion, ACS Earth Space Chem., 3, 79–89, https://doi.org/10.1021/acsearthspacechem.8b00140, 2019.
Walters, W. W., Karod, M., Willcocks, E., Baek, B. H., Blum, D. E., and Hastings, M. G.: Quantifying the importance of vehicle ammonia emissions in an urban area of northeastern USA utilizing nitrogen isotopes, Atmos. Chem. Phys., 22, 13431–13448, https://doi.org/10.5194/acp-22-13431-2022, 2022.
Walters, W. W., Song, L., Chai, J., Fang, Y., Colombi, N., and Hastings, M. G.: Characterizing the spatiotemporal nitrogen stable isotopic composition of ammonia in vehicle plumes, Atmos. Chem. Phys., 20, 11551–11567, https://doi.org/10.5194/acp-20-11551-2020, 2020.
Ward, R. X., Baliaka, H. D., Schulze, B. C., Kerr, G. H., Crounse, J. D., Hasheminassab, S., Bahreini, R., Dillner, A. M., Russell, A., Ng, N. L., Wennberg, P. O., Flagan, R. C., and Seinfeld, J. H.: Poorly quantified trends in ammonium nitrate remain critical to understand future urban aerosol control strategies, Sci. Adv., 11, eadt8957, https://doi.org/10.1126/sciadv.adt8957, 2025.
Weigand, M. A., Foriel, J., Barnett, B., Oleynik, S., and Sigman, D. M.: Updates to instrumentation and protocols for isotopic analysis of nitrate by the denitrifier method, Rapid Commun. Mass Spectrom., 30, 1365–1383, https://doi.org/10.1002/rcm.7570, 2016.
Wu, C., Cao, C., Li, J., Lv, S., Li, J., Liu, X., Zhang, S., Liu, S., Zhang, F., Meng, J., and Wang, G.: Different physicochemical behaviors of nitrate and ammonium during transport: a case study on Mt. Hua, China, Atmos. Chem. Phys., 22, 15621–15635, https://doi.org/10.5194/acp-22-15621-2022, 2022.
Xu, W., Kuang, Y., Xu, W., Liu, L., Xu, H., Wang, X., Liu, Y., Cheng, H., Zhang, X., Zhai, M., Liu, C., Liang, L., Zhang, G., Luo, B., Tao, J., Liu, J., Zhao, H., Ren, S., Zhou, G., Liu, P., Xu, X., and Sun, Y.: Efficient nitrate formation in fog events implicates fog interstitial aerosols as significant drivers of atmospheric chemistry, Environ. Sci. Technol., 58, 22298–22311, https://doi.org/10.1021/acs.est.4c09078, 2024.
Yu, H.-R., Zhang, Y.-L., Cao, F., Zhao, Z.-Y., Fan, M.-Y., and Yang, X.-Y.: Fog event is possibly a source rather than a sink of atmospheric nitrate aerosols: Insights from isotopic measurements in Nanjing, China, Appl. Geochem., 155, 105721, https://doi.org/10.1016/j.apgeochem.2023.105721, 2023.
Yu, X., Li, Q., Liao, K., Li, Y., Wang, X., Zhou, Y., Liang, Y., and Yu, J. Z.: New measurements reveal a large contribution of nitrogenous molecules to ambient organic aerosol, npj Clim. Atmos. Sci., 7, 72, https://doi.org/10.1038/s41612-024-00620-6, 2024.
Zhang, G., Hu, X., Sun, W., Yang, Y., Guo, Z., Fu, Y., Wang, H., Zhou, S., Li, L., Tang, M., Shi, Z., Chen, D., Bi, X., and Wang, X.: A comprehensive study about the in-cloud processing of nitrate through coupled measurements of individual cloud residuals and cloud water, Atmos. Chem. Phys., 22, 9571–9582, https://doi.org/10.5194/acp-22-9571-2022, 2022.
Zhang, Q., Jiang, X., Tong, D., Davis, S. J., Zhao, H., Geng, G., Feng, T., Zheng, B., Lu, Z., Streets, D. G., Ni, R., Brauer, M., van Donkelaar, A., Martin, R. V., Huo, H., Liu, Z., Pan, D., Kan, H., Yan, Y., Lin, J., He, K., and Guan, D.: Transboundary health impacts of transported global air pollution and international trade, Nature, 543, 705–709, https://doi.org/10.1038/nature21712, 2017.
Zhou, W., Xu, W., Kim, H., Zhang, Q., Fu, P., Worsnop, D. R., and Sun, Y.: A review of aerosol chemistry in Asia: Insights from aerosol mass spectrometer measurements, Environ. Sci. Processes Impacts, 22, 1616–1653, https://doi.org/10.1039/D0EM00212G, 2020.
Short summary
We studied nitrogen pollution in Taiwan's mountain forests to track how urban emissions reach and transform in remote areas. Isotope analysis and statistical modeling revealed that combustion sources contributed 50–83 % of ammonia, while nitrate forms continuously from urban to rural sampling sites. The findings show that persistent urban pollution strongly impacts mountain ecosystems, offering key insights for air quality management.
We studied nitrogen pollution in Taiwan's mountain forests to track how urban emissions reach...
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