Iodine speciation in marine aerosols along a 15000-km round-trip cruise path from Shanghai, China,to the Arctic Ocean

Total iodine (TI) and water-soluble iodine species in the total suspended particle samples collected onboard a round-trip cruise from Shanghai, China to the Arctic Ocean were measured using inductively coupled plasma mass spectrometry and ion chromatography-inductively coupled plasma mass spectrometry respectively. TI and total soluble iodine (TSI) levels varied considerably both spatially and temporally over the length of the voyage. The maximum iodine levels occurred in the Arctic Ocean in September, whereas the minimum levels occurred in the Western and Northern Pacific Ocean in July. Iodate (IO3-) was found to be the dominant species in most samples, accounting for 57.8% of TSI on average, whereas iodide and soluble organic iodine only accounted for 16.8% of TSI on average. There was also a significant fraction of insoluble iodine. This finding confirms model predictions of atmospheric iodine speciation, i.e. the predominant iodine species is iodate rather than iodide.