A Preliminary Study on the Behavior and Flux of Dissolved Iodine in the Jiulong River Estuary, China

TDI (Total Dissolved Iodine) may occur as three species-iodate, iodide and dissolved organic iodine (DOI), they are precursors for forming disinfection byproducts in finished drinking waters, hence, the investigation of iodine species is then important for understanding the transport and transfer process of iodine. This study focuses the distribution and behavior of iodine in the JRE (Jiulong River Estuary) surface waters. Iodide is determined by CSSWV (cathodic stripping square wave voltammetry), iodate is measured by spectrophotometric method, DOI is measured as reduced iodide. The results showed that, TDI (Total Dissolved Iodine) in the freshwater end-member of JRE was 197.6 × 10–9 mol L−1, existed as iodide (~140 × 10–9 mol L−1, or ~75%) and DOI (Dissolved Organic Iodine, ~45 × 10–9 mol L−1, or ~25%). The surface TDI behavior of the JRE was basically conservative in June, meaning only very small part of the dissolved iodine in the water was transformed into iodine in other phases, with the exception in the low salinity waters, which an additive behavior was discovered. Overall there is a loss of TII during mixing in the waters of salinity below ~10. Iodate was removed in surface waters, especially below the middle salinity (~10), where iodate disappeared, while at the same salinity zone, iodide showed additive behavior. DOI showed both addtive (0 < Salinity < 6.3, 15.6 < Salinity < 23.7) and removal behavior (6.3 < Salinity < 15.6, 23.7 < Salinity < 29.1). The annual flux of iodine in the Jiulong River was 3.8 × 108 g (~0.4% of the annual global flux).