Dr Rosie Chance
University of York, UK
Topic: Measurement of total iodine and iodine speciation in marine aerosol (report)
Host: Ben Gilfedder, Technische Universität, Braunschweig GERMANY
Date of STSM: 27/04/2009 to 15/05/2009
STSM code: 4309
Dr Chance visited the Institute of Environmental Geology, Technische Universität, Braunschweig, Germany, in order to use a new thermo-extraction spectrophotometric method developed by Dr Gilfedder for determination of particulate iodine. Following training, a set of marine aerosol samples collected in the tropical east Atlantic was analysed for total particulate iodine. The precision of the method was 5% or less and the limit of detection equivalent to 6 pmol I m-3 air. Sample concentrations ranged from 16 to 97 pmol m-3, with a median value of 46 pmol m-3. Aqueous extracts of the samples were prepared and will be analysed for water soluble iodine by inductively coupled plasma mass spectrometry (ICP-MS) by Dr Gilfedder. It is anticipated that these measurements will form the basis of a publication. Total iodine and was also measured in phytoplankton material prepared from laboratory cultures. Total carbon in these samples was measured using a Euro EA Elemental Analyser, and iodine:carbon ratios calculated. Initial results suggest molar iodine:carbon ratios between 2 x 10-7 and 1 x 10-5, which is lower than has been reported for marine particulate. Whether these low values are an accurate reflection of the iodine content of laboratory grown phytoplankton cultures or the result of unanticipated losses during sampling and measurement is currently under investigation. Ongoing collaboration with the host will develop the use of the thermo-extraction method as a means of determining iodine content of phytoplankton. Participation in the STSM has strengthened links between the research groups involved and it is anticipated that this may lead to further collaborations in the future.