Insights into the Stabilization of Atmospheric Iron(II) by Water-Soluble Organic Matter: Role of Aliphatic Organosulfates

Understanding the behavior of soluble Fe(II) in the atmosphere is essential for unraveling global biogeochemical cycles of iron and its bioavailability. In this study, we conducted redox experiments to investigate the stabilizing effect of water-soluble organic matter (WSOM) on soluble iron(II) (Fe(II)) in the atmosphere. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to analyze the molecular composition of WSOM, specifically focusing on molecules that showed positive correlations with Fe(II) concentrations during the redox transformation of iron. Our study indicates that aliphatic organosulfates/nitrooxy-organosulfates, especially those with unsaturated structures, play a significant role in stabilizing Fe(II). Their sources primarily include secondary organic aerosols derived from naphthalene, unsaturated fatty acids, benzene, long-chain alkanes, and monoterpenes. This discovery advances our understanding of the mechanisms underlying the presence of atmospheric Fe(II) and provides new insights into the processes governing its stabilization and cycling, highlighting the intricate interplay between iron chemistry and atmospheric organic matter.