Atmospheric soluble iron

This thesis investigates the role of atmospheric soluble iron (Fe) in multiphase chemical processes and its interactions with secondary organic aerosol (SOA). Soluble Fe is an important driver for tropospheric aqueous-phase reactions like the hydroxyl radical formation through Fenton chemistry. These processes drive the interaction of iron with soluble organic compounds, leading to the formation and chemical transformation of SOA, thus affecting the Earth’s radiation budget. However, the sources of soluble iron, its transformation pathways, and its chemical interactions with SOA remain insufficiently understood. To address these gaps, a novel analytical setup for the online speciation of water-soluble Fe in ambient aerosols was developed, enabling the simultaneous quantification of Fe(II) and total water-soluble Fe. Field applications demonstrated its suitability for urban environments, while highlighting limitations in remote regions with very low iron concentrations. Complementary laboratory experiments investigated the multiphase interactions between soluble Fe and organic aerosol components under varying conditions. Results show that iron-driven chemistry enhances SOA formation and further plays a key role in the formation of light-absorbing compounds, including secondary brown carbon. Overall, this thesis provides methodological advances and systematically characterizes key aspects of atmospheric iron chemistry under controlled and ambient conditions.