Volume 90A (2012) Pages 167-188
This study extends a comprehensive modeling study by Ito and Feng to investigate the effect of iron mobilization in size-segregated particles on soluble iron deposition to the open ocean using a global aerosol chemistry transport model. The iron dissolution from relatively insoluble iron in mineral aerosols due to chemical reactions with acidic species is calculated from the online simulation of our aerosol chemistry model. In addition, the iron from combustion sources such as biomass and fossil fuels burning is readily released into solutions in aerosols assuming constant iron solubility (i.e., the mass fraction of dissolved to total iron). The simulation results indicate that fine particles play a major role in soluble iron supply to the Pacific and Atlantic oceans in the Northern Hemisphere (70-100%) due to acid mobilization. In significant portions of the Southern Ocean, in contrast, the amount of acidic trace gases is not high enough to promote the iron dissolution in the fine aerosols. Consequently, coarse particles are important source of soluble iron in the South Atlantic Ocean (40-60%) downwind of regions from Patagonian desert in South America. The model response of soluble iron deposition to perturbation by iron solubility suggests that large fires may supply a potentially important source of soluble iron to the open ocean, compared to dust.