EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-3780 Isotopic composition of aerosol iron from anthropogenic sources: implications for source apportionment of aerosol iron Zhang Yifan 1 6 8 Zhu Guanhong 2 8 Li Rui 3 Liu Mingyuan https://orcid.org/0000-0003-4391-3929 4 Yang Yi 5 Zhang Tianyu 1 Chen Yizhu 1 Ma Jinlong 2 Wang Xinming https://orcid.org/0000-0002-1982-0928 1 Tang Mingjin https://orcid.org/0000-0002-8756-8445 1 7 State Key Laboratory of Advanced Environmental Technology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China Department of Environmental Health, School of Public Health, Shanxi Medical University, Taiyuan, China Division of Ambient Air Monitoring, China National Environmental Monitoring Centre, Beijing, China Key Laboratory of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai, China College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin, China These authors contributed equally to this work. 14 07 2026 2026 1 28 Copyright: © 2026 Yifan Zhang et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-3780/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-3780/egusphere-2026-3780.pdf

Aerosol iron (Fe) significantly impacts human health, atmospheric chemistry and marine biogeochemistry. The stable isotope ratio of Fe, typically reported as &delta;<sup>56</sup>Fe, has emerged as a promising method for source apportionment of total and soluble aerosol Fe. However, the &delta;<sup>56</sup>Fe endmember values remain poorly constrained for aerosol Fe from various non-dust sources, impeding the application of Fe isotopes in atmospheric research. This work measured isotopic compositions for aerosol Fe from desert dust and several anthropogenic sources. The average &delta;<sup>56</sup>Fe was determined to be +0.14 &plusmn; 0.10 &permil; for the seven dust samples we examined, in good agreement with previous work. We found that different anthropogenic aerosols exhibit a wide range of Fe isotopic composition. Compared to desert dust, the average &delta;<sup>56</sup>Fe was found to be higher for power plant coal fly ash (+0.26 &plusmn; 0.18 &permil;, n = 28), slightly lower for steelwork fly ash (<span>&minus;</span>0.07 &plusmn; 0.41 &permil;, n = 18), and considerably lower for biofuel burning aerosol (<span>&minus;</span>0.28 &plusmn; 0.39 &permil;, n = 11). In addition, the average &delta;<sup>56</sup>Fe was determined to be +0.20 &plusmn; 0.12 &permil; (n = 2) for municipal incineration fly ash, +0.38 &plusmn; 0.13 &permil; (n = 1) for heavy oil bottom ash, and +0.08 &plusmn; 0.13 &permil; for certificated urban particulate matter sample (n = 1). We suggest that not all the anthropogenic aerosol Fe is isotopically lighter than natural dust Fe, in contrast to what is conventionally assumed. Our findings also imply that Fe isotope-based source apportionment must account for the &delta;<sup>56</sup>Fe endmember variability both among and within different anthropogenic aerosols. Overall, our work substantially improves our ability to constrain &delta;<sup>56</sup>Fe endmember values from various anthropogenic sources.