Iodine is a reactive element which participates in many different classes of reactions in waters, soils, sediments, and the atmosphere. It has been implicated in a variety of important processes which control the stability of pollutants in the atmosphere and the solubility of toxic metals in the ocean. This proposal has as its main objectives (1) the determination of the speciation of iodine in sedimentary pore waters and solids, (2) the identification of the major classes of reactions which control iodine speciation and distribution in sediments, and (3) determining the kinetic factors controlling iodine distributions in the environment. The results of this study will have utility in predicting both the distribution of iodine in the sediments, and, by analogy, the iodine distribution in soils, surface waters, and groundwaters as well. The proposed studies involve the determination of the speciation and distribution of iodine in sediments under a wide range of environmental conditions (Eh, ph, and temperature). Sediment samples will be incubated at in situ temperatures in the laboratory to determine the rates of production and consumption of total dissolved iodine and some individual reactive iodine species. Laboratory studies will be made of the interaction of iodine redox chemistry with the chemistry of other redox-sensitive species normally present in sedimentary pore waters. Together the results of this research will lead to a better understanding of iodine geochemistry and the way in which environmental conditions may control iodine cycling and the cycling of other important solutes.
