EC-08. Reduction of Iodate in aqueous organic and inorganic aerosol particle proxies

Abstract
Iodine is released from the ocean into the atmosphere, undergoing photolysis and subsequently reacting with ozone forming oxidized iodine species. These further react producing iodic acid, a source of particle-phase iodate. However, iodine resides primarily in the gas-phase (~ 90%) even in aged tropospheric air, suggesting a recycling mechanism in which particle-phase iodine is reduced and re-emitted to the gas-phase. The reduction of iodate in atmospheric aerosol proxies is explored in coated wall flow tube (CWFT) experiments, using aqueous iodate films in an organic or inorganic matrix. Released I2 is measured by cavity enhanced differential optical absorption spectroscopy (CE-DOAS). Three types of experiments were conducted: films were (1) reacted with H2O2 in the dark, (2) separately irradiated with visible and UVA light; and (3) reacted with H2O2 in the dark, then irradiated with visible light. Results show that iodate reduction and re-emission in the form of I2 occurs for all studied systems, but to higher extents under visible light versus in the dark.