Gamma-ray spectrometry of ²¹⁰Pb in rainwater using preconcentration with iminodiacetate extraction disk

Abstract

An analytical method for ²¹⁰Pb in rainwater using a γ-ray spectrometry combined with solid-phase extraction on iminodiacetate extraction disk has been developed. A rainwater sample was adjusted to pH 5.6 with HNO₃ and 1 M CH₃CO₂NH₄, and then passed through an Empore™ chelating resin disk pretreated by 0.1 M CH₃CO₂NH₄. The chelating resin disk was packed into acrylic containers (38 mmφ) having a window of a thin Mylar film (1 mg cm⁻²) for a non-distractive γ-ray measurement. Radioactivity of ²¹⁰Pb was determined by the 46.5 keV γ-ray with an HP-Ge spectrometer. The radioactivity of ²¹⁰Pb in rainwater sample collected on the chelating resin disk ranged from 28 to 54 mBq l⁻¹, which was a lower level than those observed at several sites along the Japan sea. The present method is more simple and rapid than the conventional method, and is applicable to short-lived ²¹²Pb and cosmogenicaly-produced ⁷Be in environmental water.