Water Science and Technology (Sep 2023)
Dissolved iodine in the Changjiang River Estuary, China
Abstract
The distribution and behavior of total dissolved iodine (TDI) and its species-iodate, iodide, and dissolved organic iodine (DOI) in the Changjiang River Estuary (CJE) surface and subsurface waters were studied along the salinity gradient. Results showed that TDI concentration in the freshwater endmember of CJE was 0.037 μM and existed as iodide. Although the transformation of dissolved iodine forms was active, TDI showed a conservative behavior, ranging from 0.037 μM to 0.42 μM in the estuary. Iodate showed removal behavior (ranging within 0–0.277 μM), iodide showed additive behavior (ranging within 0.037–0.131 μM), whereas DOI showed additive (0 10. The iodine–carbon ratios in DOI from different sources were more than 10 times different. The annual flux of iodine in the Changjiang River was 4.0 × 109g, accounting for about 4% of the global river iodine flux. HIGHLIGHTS Total dissolved iodine concentration in the freshwater endmember of the Changjiang River Estuary was 0.037 μM.; Iodate and iodide showed removal and additive behaviors in the estuary.; The iodine atoms in dissolved organic iodine are mainly supplied by iodide when salinity is >10 but by iodate in waters of salinity between 10 and 33.5.; The annual flux of iodine in the Changjiang River was 4.0 × 109 g.;
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