Thesis for the Degree of Doctor of Philosophy - DTU Orbit

In soils/sediments iodine occurs as organic and inorganic species depending on soil/sediment type, pH, Eh,
quantity and quality of organic matter, microbiological activity, soil matrix composition itself as well as
differences in contaminant origin and chemical speciation of both isotopes ( 127 I & 129 I) deposited on the
soil/sediment (in Paper IV; Englund, et al., 2010; Schlegel, et al., 2006; Sheppard and Thibault, 1992).
Results of speciation analysis in such reservoirs reveal that a considerable part of iodine is adsorbed on
oxides and hydroxides of iron and manganese, and that most of the iodine is associated with organic matter
(Hou, et al., 2003, Englund, et al., 2010; Schlegel, et al., 2006; Sheppard and Thibault, 1992; Paper IV). In
sedimentary rocks the iodine concentrations range between 0.2 and 10 mg/kg (Fuge & Johnson, 1986). In
soils, the iodine concentration depends on sampling location and ranges between 0.5 and 20 mg/kg
(Whitehead, 1984).
1.1.2 Radioactive iodine ( 129 I)
Iodine is a biophilic tracer element with forty-two isotopes and isomers at atomic numbers 108-141,
including only one long-lived isotope ( 129 I, 15,7 million years), and one stable isotope, 127 I (Table 2). In
nature iodine – 129 occurs naturally, but mainly originates from anthropogenic nuclear activities (Figure 3)
Natural Origin (250kg)
Nuclear weapon tests (57-63 kg)
Chernobyl accident (1.3–6 kg)
Marine discharges from reprocessing facilities (5200 kg)
Atmospheric discharges from reprocessing facilities (800 kg)
Fig.3 Sources and inventory, releases from reprocessing plants and environmental level of 129 I by 2007.
Marine discharge refers to the sum of discharges from La Hague and Sellafield reprocessing plants, whereas
the atmospheric release refers to the sum from La Hague, Sellafield, Marcoule, WAK and Hanford.
Reported marine discharges are 5200 kg and atmospheric releases of approximately 800 kg, both by 2007
(In Paper I).
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