Marine Chemistry, 25 (1988) 95-106 95 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands Dissolved Iodine Behavior in Estuaries along the East Coast of the United States W.J. ULLMAN 1, G.W. LUTHER, IIP, R.C. ALLER ~ and J.E. MACKIN ~ ~CoUegeof Marine Studies, University of Delaware, Lewes, DE 19958 (U.S.A.) 2Marine Science Research Center, State University of New York, Stony Brook, N Y I 1794 (U.S.A.) (Received October 26, 1987; revision accepted February 2, 1988) ABSTRACT Ullman, W.J., Luther, III, G.W., Aller, R.C. and Mackin, J.E., 1988. Dissolved iodine behavior in estuaries along the east coast of the United States. Mar. Chem., 25: 95-106. Previous studies of dissolved iodine behavior in estuaries have shown no evidence of iodine's participation in biogeochemical processes. Three estuaries along the United States' Atlantic coast clearly show the results of iodine reactivity in biological and/or particle processes. Major factors involved in controlling the iodine speciation and distribution in estuaries include: (i) remineral- ization of iodine-containingorganic matter in sediment or anoxic bottom water; (ii) anthropo- genic inputs; (iii) resuspension of fine-grained sediments and their associated interstitial water: and (iv) estuarine flow regime and residence time. INTRODUCTION Previously published studies of the estuarine distribution of total dissolved iodine and the dissolved inorganic species iodide (I-) and iodate (IO~) have suggested that iodine is conservative and is unaffected by biogeochemical pro- cesses (Smith and Butler, 1979; Takayanagi and Cossa, 1985). These obser- vations are in contrast to the vast body of literature which indicates that iodine is an active participant in sediment-seawater exchange (Tsunogai, 1971; Ull- man and Aller, 1980 ), seawater-atmosphere exchange (Miyake and Tsunogai, 1963; Duce etal., 1963; Winchester and Duce, 1965), biological uptake and enrichment (Vinogradov, 1953; Shaw, 1959; Sugawara and Terada, 1967; Saenko et al., 1978), and inorganic scavenging reactions (Sugawara etal., 1958; Music et al., 1980; Strickert et al., 1980; Couture and Seitz, 1983). The pub- lished observations from estuaries can only be reconciled with the current un- derstanding of iodine biogeochemistry by assuming that the studied estuaries are ones in which the rates of mixing and flushing are far faster than the rates 0304-4203/88/$03.50 © 1988 Elsevier Science Publishers B.V.