Iodine speciation in chesapeake bay waters

Abstract

We report on the speciation of iodine in Chesapeake Bay during July 1986. Surface and bottom water samples were taken along the estuary at every 1–2% salinity division. At three locations in the upper bay, samples were taken above, at and below the pycnocline. All samples were analyzed by differential pulse polarography. Iodate was determined directly. Total iodine (including organic forms) was determined by hypochlorite oxidation to iodate. Iodide is defined as the difference between these two analyses. Total iodine appears to be conservative in the estuary. In all samples from the upper bay only reduced forms of iodine were present. Iodine is maintained in its reduced state by biological processes in the surface waters and by a combination of biological and chemical processes in the anoxic bottom waters. Iodate was present only in water samples at mid-depth and the bottom in the lower bay. Iodate comes from oceanic water intruding up the bay and decreases in concentration up the bay as the result of its reaction with reducing agents in the anoxic bottom waters. The forms of iodine in the waters of Chesapeake Bay can be used as a geochemical tracer. These result differ from previous reports in two other estuaries on the speciation of iodine in the water column.