Disproportionation and reduction of molecular iodine added to seawater

An oceanic, near-surface seawater sample has been found to sustain the formation of iodate through the disproportionation of the 1.5 μM added molecular iodine. Some 17% of the added molecular iodine was converted to iodate while the remainder was reduced. Even so, a kinetic model of the competing reactions, developed specifically for the purpose, shows that the disproportionation reaction will have little geochemical significance as it is unable to compete effectively at the much lower concentrations of iodine possibly existing naturally in the oceans. The kinetic model is described and its use in the classification of ocean waters according to their ability to reduce added iodine, is discussed. The model is probably applicable to the chlorination and ozonation of seawater during anti-fouling procedures.