EGU25-10681, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-10681
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Measurements of photocatalytic chloride to chlorine conversion by iron-salt aerosols at the European Photoreactor (EUPHORE)
Luisa Pennacchio1, Marie K. Mikkelsen1, Chloe Brashear2, Rubén Soler3, Ezra Woods3,4, Mila Ródenas3, Amalia Muñoz3, Maarten van Herpen5, Thomas Röckmann2, and Matthew S. Johnson1
Luisa Pennacchio et al.
  • 1Department of Chemistry, University of Copenhagen, 2100 Copenhagen, Denmark
  • 2Institute for Marine and Atmospheric Research Utrecht, Utrecht University; Utrecht, the Netherlands
  • 3EUPHORE Labs., Atmospheric Chemistry Area, Fundación Centro de Estudios Ambientales del Mediterráneo (CEAM)
  • 4Department of Chemistry, Drexel University, Philadelphia, PA, USA
  • 5Acacia Impact Innovation BV; Heesch, The Netherlands

Recent studies have shown that when iron-containing mineral dust mixes with aerosols containing chloride, iron(III)chloride salts are formed enabling the photocatalytic production of Cl2 [1-3]. Work has shown that the iron salt aerosol mechanism is the largest source of chlorine radicals over the North Atlantic. The mechanism is catalytic both in iron and chlorine. Despite clear evidence from field studies, laboratory studies and modelling [2-5], significant questions remain (effect of RH, iron activity, pH limited behavior, etc.). The goal of this study is to answer these questions through experiments performed in the European Photoreactor (EUPHORE) in Valencia, Spain. The reactor is 200 m3 and utilizes natural sunlight and is therefore ideal for simulating atmospheric behavior. Measurements were collected with long-path FTIR, CIMS, OPS, SMPS, PTR-MS, ACSM, LIF-FAGE, Picarro G2108 and G2201-i as well as monitors for O3, CO, NO, NO2, NOx and HCHO. Furthermore, flask samples were collected for analysis of [CO], δ13C-CO, [CH4], δ13C-CH4 and VOCs at Utrecht University. Two sets of experiments were carried out, one to investigate the effect of the iron and chloride in the aerosols and one to investigate the mechanism using real dust samples. In the first set of experiments, solutions of FeCl3+NaCl, NaCl or FeSO4 were aerosolized to evaluate the effect of iron and chlorine separately and together. In the second set of experiments, acidic NaCl aerosols were introduced to the reactor along with aerosolized dust injections, for more realistic simulations. We will report our results concerning the rate of Cl2 production in the dark via the Fenton mechanism and by ISA.

[1] Chen et al. (2024) Environ. Sci. Technol., 58(28), 12585-12597

[2] van Herpen et al. (2023) PNAS, 120, 31

[3] Mikkelsen et al. (2024) Aerosol Research, 2, 31-47

[4] Wittmer et al. (2015) Environmental Chemistry, 12(4), 461-475

[5] Wittmer et al (2017) Journal of Atmospheric Chemistry, 74, 187-204

How to cite: Pennacchio, L., K. Mikkelsen, M., Brashear, C., Soler, R., Woods, E., Ródenas, M., Muñoz, A., van Herpen, M., Röckmann, T., and S. Johnson, M.: Measurements of photocatalytic chloride to chlorine conversion by iron-salt aerosols at the European Photoreactor (EUPHORE), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10681, https://doi.org/10.5194/egusphere-egu25-10681, 2025.