16:15 〜 17:30
[MTT42-P04] 新しい海洋生態系トレーサーとしての魚中ヨウ素129の分析法確立
キーワード：ヨウ素129, トレーサー, 海洋生態系, 魚, AMS
The availability of 129I as a new tracer for marine ecosystem was examined.
The iodine isotopic ratio (129I/127I) in seawater is determined by the anthropogenic 129I transferred from the atmosphere, i.e., it shows very high ratio as the order of 10-10 for 129I/127I at the surface or surface mixing layer and suddenly decreases going deeper to some of 10-12 or lower. Iodine isotopic ratio (129I/127I) of marine lives like fish should be determined by their habitats and the ways exchanging iodine with seawater. This means that the iodine isotopic ratio is potential indicator of marine ecosystem. However there have been only few studies using 129I for marine ecosystem. This is because 129I is so trace in the marine lives that ordinary analytical techniques cannot detect.
Recent development of analytical technique for 129I using AMS (Accelerator Mass Spectrometry) enables determine trace amount of 129I concentration in environmental samples.
In this study the pyrohydrolysis method was applied to extract iodine from fish samples. A freeze-dried and homogenized fish sample, 0.1g to 0.5g, was combusted in the quartz tube under oxygen and water vapor flow. Iodine was extracted into an alkaline solution. An aliquot of this solution was taken for ICP-MS analysis to determine the stable iodine (127I) concentration. The remaining was, added with carrier iodine (about 1 mg), purified by solvent extraction and collected as AgI precipitation. 129I/127I ratio was determined by AMS. From the AMS result and the 127I concentration, the 129I/127I ratio of the fish samples themselves can be calculated.
The extraction yield was evaluated using IAEA-414 fish standard sample. Background in the pyrohydrolysis was also examined.
The preliminary results of fish samples, collected from Suruga-bay (located on Pacific coast in the middle of Honshu, Japan) showed 1×10-10 to 7×10-10, which was consistent with that of surface seawater.
The iodine isotopic ratio (129I/127I) in seawater is determined by the anthropogenic 129I transferred from the atmosphere, i.e., it shows very high ratio as the order of 10-10 for 129I/127I at the surface or surface mixing layer and suddenly decreases going deeper to some of 10-12 or lower. Iodine isotopic ratio (129I/127I) of marine lives like fish should be determined by their habitats and the ways exchanging iodine with seawater. This means that the iodine isotopic ratio is potential indicator of marine ecosystem. However there have been only few studies using 129I for marine ecosystem. This is because 129I is so trace in the marine lives that ordinary analytical techniques cannot detect.
Recent development of analytical technique for 129I using AMS (Accelerator Mass Spectrometry) enables determine trace amount of 129I concentration in environmental samples.
In this study the pyrohydrolysis method was applied to extract iodine from fish samples. A freeze-dried and homogenized fish sample, 0.1g to 0.5g, was combusted in the quartz tube under oxygen and water vapor flow. Iodine was extracted into an alkaline solution. An aliquot of this solution was taken for ICP-MS analysis to determine the stable iodine (127I) concentration. The remaining was, added with carrier iodine (about 1 mg), purified by solvent extraction and collected as AgI precipitation. 129I/127I ratio was determined by AMS. From the AMS result and the 127I concentration, the 129I/127I ratio of the fish samples themselves can be calculated.
The extraction yield was evaluated using IAEA-414 fish standard sample. Background in the pyrohydrolysis was also examined.
The preliminary results of fish samples, collected from Suruga-bay (located on Pacific coast in the middle of Honshu, Japan) showed 1×10-10 to 7×10-10, which was consistent with that of surface seawater.