2009 年 43 巻 3 号 p. 103-112
In this paper, various studies done by myself and my co-workers are reviewed with the related works by other researchers in terms of nondestructive speciation by Mössbauer spectroscopy and X-ray absorption fine structure (XAFS) to understand various geochemical conditions. These methods were first applied to the sediments collected from the Tama River estuary in Tokyo, Japan. Prior to speciation, concentrations of 33 elements in the estuarine sediments were determined by activation analyses. The speciation of iron in the sediments was conducted by using Mössbauer spectroscopy in order to clarify the vertical change of iron species. Although XAFS can be applied to measure many elements unlike Mössbauer spectroscopy, the XAFS spectra of different species often have severe overlap in the whole spectral region. For quantifying the species from the whole XAFS spectra, partial least-squares (PLS) and artificial neural networks (ANN) were employed. The overlapping spectra were successfully deconvoluted, and the relative abundances of iron species determined were consistent with the results of Mössbauer spectroscopy. Applications of the Mössbauer spectroscopy to the other materials were demonstrated; e.g., the distribution of pyrite of the sediment column collected from salt lakes in China suggested the past climatic changes.
