Redox chemical processes of iodine species with inorganic compounds in ice

Ice is ubiquitous and one of the most important environmental reaction media on earth. Generally, chemical reactions take place slowly when temperature decreases according to Arrhenius Equation(k=A·e^-EA/RT). Recently, it has been found that several chemical processes are accelerated by freezing compared to those in aqueous phase. Reactive iodine species (I, I₂, IO, OIO, HOI) in atmosphere are related to ozone depletion event (ODE) and new particle formation (NPF) in polar troposphere, and finally affect climate change. It was reported that the high concentration of halogen compounds(IO, BrO) in austral spring in Antarctica but the exact mechanism and sources are not fully understood. The biological production of halogens are regarded as the major source of organic and I2. However, the (photo)chemical reactions to produce reactive iodine species are also regarded as possible mechanism to explain the high atmospheric iodine budget. In this presentation, I want to introduce enhanced chemical reaction with laboratory experimental results such as 1)accelerated oxidation of iodide(I^-) in ice to produce molecular iodine(I₂) and tri-iodide(I₃^-), 2)nitrite-induced activation of iodate(IO₃^-) into molecular iodine in frozen solution. The detailed experimental conditions and mechanism will be discussed in the presentation.