Iron released from volcanic ash can perturb the biogeochemical cycles in the ocean. However, knowing that the emitted ash from a volcano contains insoluble iron, what processes can solubilize the ash iron while it is airborne? To answer this question, a numerical model is developed in this study to simulate the gas-ash-aerosol interactions within the eruption plume. Results show that the dissolution of the ash mediated by halogen acids exert the key control on ash iron mobilization.