Concentrations of iodine isotopes (129I and 127I) and their isotopic ratios in aerosol samples from Northern Germany

• Emissions from Sellafield and La Hague drastically changed natural abundances of I-129.
• Dominant sources of aerosol I-129 at Braunschweig are the two reprocessing plants.
• I-129 bound to aerosols can be used as radioactive tracer in the environment.

New data about 129I, 127I concentrations and their isotopic ratios in aerosol samples from the trace survey station of the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig, Northern Germany, are presented and discussed in this paper. The investigated samples were collected on a weekly basis during the years 2011 to 2013. Iodine was extracted from aerosol filters using a strong basic solution and was separated from the matrix elements with chloroform and was analysed by accelerator mass spectrometry (AMS) for 129I and by inductively coupled plasma mass spectrometry (ICP-MS) for 127I. The concentrations of 127I and 129I in aerosol filters ranged from 0.31 to 3.71 ng m−3 and from 0.06 to 0.75 fg m−3, respectively. The results of 129I/127I isotopic ratios were in the order 10−8 to 10−7. The 129I originated directly from gaseous emissions and indirectly from liquid emissions (via sea spray) from the reprocessing plants in Sellafield and La Hague. In comparison with the results of 131I after the Fukushima accident, no contribution of 129I from this accident was detectable in Central Europe due to the high background originating from the 129I releases of the European reprocessing plants. 129I atmospheric activity concentrations were compared with those of an anthropogenic radionuclide (85Kr). We did not find any correlation between 129I and 85Kr, both having nuclear reprocessing plant as the main source.