Mixing state and distribution of iodine-containing particles in Arctic Ocean during summertime.

Iodine chemistry plays a key role in ozone destruction and new aerosol formation in the marine boundary layer (MBL), especially in polar regions. We investigated iodine-containing particles (0.2-2 µm) in the Arctic Ocean using a ship-based single particle aerosol mass spectrometer from July to August 2017. Seven main particle types were identified: dust, biomass combustion particles, sea salt, organic S, aromatics, hydrocarbon-like compounds, and amines. The number fraction of iodine-containing particles was higher inside the Arctic Circle (>65°N) than outside (55-65°N). According to the air mass back trajectories, the latitudinal distribution of iodine-containing particles can be mainly attributed to iodine emissions from the sea ice edge region. Diurnal trends were found, especially during the second half of cruise, with peak iodine-containing particle number fractions during low-light conditions and relatively low number fractions at midday. These results imply that solar radiation plays a significant role in modulating particulate iodine in the Arctic atmosphere.