Reactive iodine species in a semi-polluted environment

Iodine chemistry in the marine boundary layer has attracted increasing attention over the last few years because iodine oxides cause ozone destruction, change the atmospheric oxidising capacity, and can form ultrafine particles. However, the chemistry of iodine in polluted environments is not well understood: its effects are assumed to be inhibited by reactions involving NOx (NO2 & NO). This paper describes Differential Optical Absorption Spectroscopy (DOAS) observations of iodine species (I2, OIO and IO) and the nitrate radical (NO3) at a semi‐polluted coastal site in Roscoff, France. Significant concentrations of IO and I2 were measured during daytime, indicating efficient recycling of iodine from iodine nitrate (IONO2). I2, IO, OIO and NO3 were observed at night. These observations are interpreted using a one dimensional model to demonstrate that iodine plays an important role even in polluted environments due to recycling mechanisms not considered previously.