Observations of iodine speciation and cycling in the hydrosphere

• Main Author: Gilfedder, Benjamin Silas
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2008
• Subjects: 550; 550 Earth sciences; Greenland
• Online Access: https://archiv.ub.uni-heidelberg.de/volltextserver/8264/; https://archiv.ub.uni-heidelberg.de/volltextserver/8264/1/Observations_of_Iodine_Speciation_and_Cycling_in_the_Hydrosp.pdf; https://doi.org/10.11588/heidok.00008264; https://nbn-resolving.org/urn:nbn:de:bsz:16-opus-82645

Iodine is an important element in oceanic, atmospheric, and terrestrial systems. Firstly, radical reactions in the troposphere can lead to significant ozone depletion, and secondly, nucleation of gaseous iodine molecules can produce new aerosol formation events, presenting possible direct and indirect natural cooling effects on climate. In the terrestrial environment iodine is a vital micronutrient for all mammals, with a lack of iodine intake leading to several debilitating disorders such as goiter and cretinism. The aim of this study was to investigate iodine systematics, and particularly speciation, in the atmosphere (aerosols, rain, and snow) and terrestrial hydrosphere (lakes) in order to gain a better understanding of how iodine moves between and within each environmental compartment. A subsidiary aim was to develop an inexpensive, but sensitive and accurate method for iodine quantification in soils and sediments using conventional analytical equipment. Rain and snow samples were taken from both northern (Germany, Switzerland, Ireland, Greenland) and southern (Australia, New Zealand, Chile) hemispheres whereas aerosols were obtained from Mace Head, Ireland using cascade (5 stages) and PM 2.5 impactors. Iodine cycling in lakes was investigated in the Mummelsee, a small headwater lake in the Black Forest. Speciation measurements were conducted by coupling an ion chromatograph to an ICP-MS and the organic fraction calculated as total iodine minus the inorganic species iodide and iodate. Organically bound iodine was the most abundant fraction in the atmospheric aqueous phase, despite the fact that iodine oxides are currently thought to be the theoretical sink species. Aerosols from Mace Head, Ireland, contained a median of 50 pmol m-3 total iodine, with more than 90 % being associated with organic matter. Iodide was the next most abundant species (median 5 %) with iodate being the least abundant (median 0.8 %). Similar results were found in the precipitation samples from northern and southern hemispheres, with ...