11:00 〜 13:00
[ACG46-P01] 西部北太平洋熱帯域における表面水中のヨウ素の化学状態別の濃度分布
キーワード：ヨウ素酸イオン、ヨウ化物イオン、熱帯太平洋、イオンクロマトグラフ法
Iodine in seawater exists mainly as iodate (IO3-) and iodide (I-) ions, with a total reported to be approximately 0.4 μM. Iodine is present mostly as IO3- below 200 m, and approximately half of the iodine in the surface layer exists as I-, as reduced by organisms. It is well known that iodine in the atmosphere is oceanic origin and involved in various chemical reaction in the atmosphere. Tropospheric ozone, known as one of the greenhouse gases, is reported to be efficiently depleted by the reaction with iodine species over the tropical oceans, where SST reaches nearly 30 ℃. However, the mechanism of the reaction is not fully understood. To understand the iodine cycle in the oceans and evaluate its impact on the atmospheric environment, it is essential to use methods for quantifying iodine in seawater according to its chemical state. The objective of this study is to obtain spatial distributions of iodine in the western North Pacific with high SST, using an originally developed ion chromatography method.
Surface seawater samples were collected during R/V Mirai MR21-03 cruise which sailed the tropical western North Pacific in early summer. The water samples were collected from the faucet for research use on board. All the seawater samples were collected in 125-mL HDPE bottles. The bottles were stored at ∼4 ℃ on board. An ion chromatography combing a high ion exchange capacity column and a UV detector were used for determination of five anionic species (IO3-, I-, NO2-, NO3- and Br-) in samples.
Previous studies have indicated that the I- concentration in surface water is related to SST. In this study, however, although oceanic region with SST of 30 ℃ or higher were continuously sampled, the concentration of I- varied relatively largely and SST alone could not explain the concentration fluctuation. The relationship with other dissolved substances and organic iodine will also be discussed in the presentation.
Surface seawater samples were collected during R/V Mirai MR21-03 cruise which sailed the tropical western North Pacific in early summer. The water samples were collected from the faucet for research use on board. All the seawater samples were collected in 125-mL HDPE bottles. The bottles were stored at ∼4 ℃ on board. An ion chromatography combing a high ion exchange capacity column and a UV detector were used for determination of five anionic species (IO3-, I-, NO2-, NO3- and Br-) in samples.
Previous studies have indicated that the I- concentration in surface water is related to SST. In this study, however, although oceanic region with SST of 30 ℃ or higher were continuously sampled, the concentration of I- varied relatively largely and SST alone could not explain the concentration fluctuation. The relationship with other dissolved substances and organic iodine will also be discussed in the presentation.