Evaluation of straightforward and rapid multi-element analyses of stream sediments for geochemical mapping in the remote islands of Japan — Seto Inland Sea region —

Abstract

The straightforward and rapid determination of 53 elements in stream sediments using ICP-AES (inductively coupled plasma atomic emission spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), and AAS (atomic absorption spectrometry) were evaluated for the geochemical mapping of isolated islands. Samples of 0.1 g were decomposed with HF, HNO3, and HClO4 at 125–145°C for 3 h to improve the determination of elements, including refractory minerals. The concentrations of rare earth elements (REEs), Nb, and Ta increased by 5–15% on average, and those of Zr and Hf increased by 30% on average. For arsenic determination, 0.1 g samples were digested using a mixed acid solution with an oxidizing reagent (KMnO4) at 120°C for 20 min. Decomposition without using the oxidizing reagent and/or extended decomposition times has been shown to cause a decrease in As concentrations in geochemical reference materials. However, similar As concentrations in stream sediment samples were obtained irrespective of KMnO4 addition and decomposition time. AAS was used to Hg measurement after thermal decomposition of about 50 mg samples without pre-treatment. The estimated concentrations of 53 elements in geochemical reference materials measured using ICP-AES, ICP-MS and AAS were agreement with the recommended values. Thus, it is concluded that the precision and accuracy of the rapid and straightforward analysis for geochemical mapping were satisfactory.