Speciation analysis of long-lived anthropogenic iodine isotopes (129
I) in time series Danish aerosols shows that secondary emission from heavily 129
I-contaminated seawater is a major source of 129
I in the Atmosphere, at least in North Europe. Iodide is the major form of water-soluble iodine, while NaOH-soluble iodine is the dominant species of iodine in aerosol, which is likely bound with organic substances. The contribution of Fukushima-derived 129
I is estimated to be negligible in Europe.