In situ chemical speciation of iron in estuarine sediments using XANES spectroscopy with partial least-squares regression

Abstract

X-ray absorption near-edge structure (XANES) spectroscopy has been applied to the quantitative determination of iron species in estuarine sediments. Mixtures of pyrite, olivine, and goethite were prepared as model mixtures containing ferrous sulfides, ferrous silicates, and ferric oxides and/or hydroxides, respectively. For resolving XANES spectra of these mixtures and quantifying the Fe-bearing minerals, partial least-squares (PLS) regression has been employed. The obtained PLS regression gave sufficient precision and this technique was applied to the XANES spectra of estuarine sediments collected from the Tama River in Tokyo, Japan. The relative abundances of iron species thus determined were consistent with the Mössbauer spectroscopic results.