Thesis for the Degree of Doctor of Philosophy - DTU Orbit

maximum values is at 0.03-0.06×10 9 atoms/L and 0.5-0.7 ×10 9 atoms/L in the studied lakes (Tables 1
and 2).
Discussion
Because of the low concentration of organic iodine encountered in seawater, recently works on
speciation analysis in seawater are focused on iodide and iodate while organic iodine being calculated
as difference between the total inorganic iodine and total iodine. Although high concentrations of
organic iodine have been reported in fresh water compared to seawater (Reifenhäuser and Heumann,
1990), studies concerning quantification of aquatic organic iodine are still very limited. Photochemical
decomposition (H2O2)/UV or dehydrohalogenation (NaOH/ ethanol) of aquatic organic iodine has been
previously employed (Wong & Cheng, 2001; Schwehr, 2003) and the results show a discrepancy of up
to 40% or higher, depending on methods. Photochemical decomposition ((H2O2)/UV) of dissolved
organic iodine in seawater have shown to produce iodide (Wong & Cheng, 2001). A question of
whether photochemical destruction of organic matter occurs in the same time with formation in small
proportion of iodine organic matter remains uncertain (Wong & Cheng, 2001; Moore & Zafiriou,
1994).
Conventional, organic matter destruction can be performed by hydrolysis, reductions, thermal and wet
oxidation and thermal methods (Stevenson, 1994). Oxidation methods include oxidizing agents, such as
potassium permanganate (KMnO4), disodium peroxodisulphate (Na2S2O8), or sodium hypochlorite
(NaOCl). In this study the iodine organic matter was destroyed by using NaClO in alkaline medium at
150 0 C for 3h. Excepting few locations in Denmark were organic iodine-127 accounts for 50% of the
total iodine-127 and the precipitation sample collected form Rasback, Sweden the iodine (both
isotopes) associated organic matter calculated by subtracting inorganic iodine (iodide + iodate) from
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