Atmospheric Chemistry in East Asia Determines the Iron Solubility of Aerosol Particles Supplied to the North Pacific Ocean

There is still considerable uncertainty in how dissolved iron (d-Fe) is supplied from East Asia to the North Pacific and how this varies seasonally. We conducted year-long, size-fractionated aerosol sampling at a background site in the Sea of Japan, strongly influenced by East Asian outflow, and analysed Fe concentrations and speciation. Our results show that Fe from mineral dust and combustion-derived oxides in submicron aerosols underwent chemical alterations during long-range transport, forming Fe-sulfates and Fe-oxalate. These species accounted for nearly 70% of d-Fe in total suspended particles. Using d-Fe from both dust and anthropogenic sources, we reconstructed atmospheric pH and showed that highly acidic conditions (pH < 3.0) are required for Fe solubilisation. These findings provide critical observational evidence that much of the d-Fe reaching the North Pacific is generated through in-transit chemical processing.

Reference: Sakata, K., Takano, S., Matsuki, A., et al. (2025). Atmospheric chemistry in East Asia determines the iron solubility of aerosol particles supplied to the North Pacific Ocean. Atmos. Chem. Phys., 25, 11087–11107, https://doi.org/10.5194/acp-25-11087-2025