Experimental study on dissolution of iodine from coastal sediments

Sato, Yuhi; Otosaka, Shigeyoshi  ; Suzuki, Takashi  

For elucidating a dissolution process of iodine from pelagic coastal sediments, a dissolution experiment of iodine from sediments in an system simulating a natural environment was conducted using surface sediments collented from Ibaraki and Fukushima coasts and artificial seawater. In the experiment, concentrations of each chemical species of iodine and dissolved organic matter (DOM) in seawater was monitored for 70 days. The result showed characteristic behavoirs which were high concentration of iodine until 21 days, decreasing of it through 35 days, and dominance of dissolved organic iodine (DOI) after 35 days. These were potentially regulated by (1) supplying iodide caused by diffuidon of porewater, (2) supplying labile DOI within a few days, (3) attachment of iodide to sediment, and (4) exchenging of recalcitrant DOI between sediment and seawater, judging from the composition of iodine chemical species and fluorescent DOM analysis. It is suggested that these factors regulate the dissolution of iodine from sediment in a natural environment also.