Development of a new method for the analysis of individual biological history of the aquatic creatures using synchrotron radiation X-ray fluorescence imaging

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After the investigation for three years, the following results have been obtained.1.Sample Preparation : Methods of sample preparation for synchrotron radiation X-ray fluorescence microprobe analysis was developed. For the fish otolith preparation, sagaital plane with otolith core of 30mum thick was revealed to be suitable for the analysis.2.Investigation of finger-print elements : ICP-AES analysis of otoliths of various fishes of different origin disclosed that they contain Sr, Zn, Fe, Mg, Mn and Al as trace components, among which Sr is found to be most suitable for the indicator of the salinity change of their environmental water.3.Application of Synchrotron Radiation : Two-dimensional distributions of Ca, Sr and Fe were clarified by synchrotron radiation X-ray fluorescence microprobe. Measurements were made at Photon Factory, High Energy Accelerator Research Organization. Samples were excited by an X-ray of 17 keV generated by a Si (111) double-crystal monochromator. Two dimensional analysis of trace elemenls such as iron (average : around 100 ppm) was successfully carried out by using X-ray microbeam under the following condition : beam size, ca 100x1OO um2 and counting time of 10sec/step. Thus we have established the XRF imaging technique as a new important tool for characterization of the trace elements in the otoliths.4.Instrumentation : We have developed a new X-ray fluorescence imaging system for routine analysis of the trace elements in the hard tissues by using conventional laboratory X-ray source. This system utilizes monochromatic Mo Ka X-ray obtained by a curved Graphite monochoromator, which enables us to carry out high sensitivity analysis.5.Validation of the methods : To verify the method developed here, otoliths of the freshwater eel, masu salmon and lantern fish were analyzed. As the results, the individual migratory history was well demonstrated and thus, we conclude this method was sufficiently verified.