EGU General Assembly 2022
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Influence of ferrous and ferric ions in the aqueous phase on SOA formation in flow reactor experiments

Sabine Lüchtrath, Sven Klemer, and Andreas Held
Sabine Lüchtrath et al.
  • Department of Environmental Chemistry and Air Research, Institute of Environmental Science and Technology, Technische Universität Berlin, Germany

Aqueous-phase chemistry of fog and cloud waters plays an important role in the formation and aging of secondary organic aerosols (e.g. Ervens et al.,2011; Herrmann et al., 2015). Transitions metal ions driving Fenton chemistry in aqueous aerosols are one of the main sources of OH radicals besides direct uptake from the gas-phase (Ervens et al., 2003). The most abundant transition metal in aqueous aerosols is iron released from natural sources like sea salt spray and mineral dust or anthropogenic emissions. The generation of OH radicals by Fenton chemistry might drive or inhibit atmospheric new particle formation in cloud and fog water, or above salt lakes (e.g. Kamilli et al., 2015; Daumit et al., 2016), thus, having a direct impact on the climate system.

A first set of experiments has been carried out in a flow reactor investigating the influence of ferric and ferrous iron on new particle formation under dark and humid conditions (RH > 70%). α-Pinene was used as an organic precursor molecule for secondary organic aerosol (SOA) formation by dark ozonolysis. Droplets of FeSO4, FeCl3 and (NH4)2SO4 (as control) were produced by nebulizing solutions of varying concentrations between 0.1 µM and 30 mM using a custom-built atomizer. Particle size distributions were measured using a scanning mobility particle size spectrometer (SMPS, Grimm Aerosoltechnik).

First results show a significant decrease in geometric mean diameter of the produced particle population with increasing FeCl3 concentration. This effect neither occurs when nebulizing FeSO4 nor (NH4)2SO4. These results imply that Fe3+ might inhibit growth of SOA under dark conditions.

More data analysis is ongoing and further experiments are planned to better understand the influence of iron on aqueous-phase SOA.




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 Ervens, B., Turpin, B. J., & Weber, R. J. (2011). Secondary organic aerosol formation in cloud droplets and aqueous particles (aqSOA): a review of laboratory, field and model studies. Atmospheric Chemistry and Physics, 11(21), 11069-11102.

Herrmann, H., Schaefer, T., Tilgner, A., Styler, S. A., Weller, C., Teich, M., & Otto, T. (2015). Tropospheric aqueous-phase chemistry: kinetics, mechanisms, and its coupling to a changing gas phase. Chemical reviews, 115(10), 4259-4334.

Kamilli, K. A., Ofner, J., Lendl, B., Schmitt-Kopplin, P., & Held, A. (2015). New particle formation above a simulated salt lake in aerosol chamber experiments. Environmental Chemistry, 12(4), 489-503.


How to cite: Lüchtrath, S., Klemer, S., and Held, A.: Influence of ferrous and ferric ions in the aqueous phase on SOA formation in flow reactor experiments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3150,, 2022.