DETERMINATION OF PARTICULATE IODINE IN AEROSOLS FROM DIFFERENT REGIONS BY SIZE FRACTIONATING IMPACTOR SAMPLING AND IDMS

Concentrations of particulate iodine in aerosols depending on the particle size were determined after sampling with an impactor system by isotope dilution mass spectrometry (IDMS) using the production of negative GAMMA thermal ions. The collection efficiency of the impactor system was compared with a filter system by parallel samplings and agreed well. By different leaching processes, using sodium sulfite solution and distilled water, it was shown that various iodine species are incorporated in the aerosol particles. Determinations were carried out with samples from different areas, two continental places in Germany, which are more or less anthropogenically influenced, one location with marine and anthropogenic influences (North Sea) and one in the Weddell Sea, Antarctica, not anthropogenically influenced. In all cases we found the major part of the total iodine in the smallest aerosol particles with an aerodynamic diameter of < 0.49 mum. Investigations of the continental iodine in aerosols over a two-year period resulted in an average of (2.1 +/- 1.2) ng m-3 with significantly higher spots during winter only. The total iodine concentration of a sample from Antarctica is about one order of magnitude lower than the mean of the continental samples from Germany, whereas the contents of the North Sea samples are little higher. In an anthropogenically influenced area of Germany the proportion of the total iodine, which was not iodide but iodate and organoiodine leached by sulfite solution, was determined to be 15%, whereas in an Antarctic sample this portion was about 77%. Detection limits down to 1.8 pg m-3 for the impactor system and down to 6 pg m-3 for the other filter systems were obtained. Natural and anthropogenic sources, which can contribute to the inorganic and organic iodine compounds in the aerosol particles, are discussed.