Speciation of dissolved iodine in the waters of a humic-rich estuary

This paper reports the findings of a study into iodine speciation in the humic-rich waters of the Huon Estuary, Tasmania, Australia. Water samples were taken from the estuary at various locations during both summer and winter. The samples were analysed for a range of parameters including iodate, iodide, total iodine, nutrients, chlorophyll a, dissolved organic carbon (DOC) and salinity. Total iodine behaved conservatively within the estuary irrespective of season. Iodate concentrations varied linearly with salinity but became undetectable in the low salinity end of the estuary. Iodide concentrations showed no correlation with salinity, but showed a positive correlation with total dissolved phosphorus during summer suggesting iodide concentrations within the estuary are controlled by biological activity during, or immediately after, periods of high productivity. “Organic” iodine is produced within the estuary and the fraction of iodine present in this form increases in the low salinity waters where DOC concentrations are highest.