Environmental monitoring of plutonium at ultratrace level in natural water (Sea of Galilee—Israel) by ICP-SFMS and MC-ICP-MS

Abstract

An analytical method for the determination of plutonium concentration and its isotope ratio at ultratrace level in natural water by inductively coupled plasma mass spectrometry (ICP-MS) is proposed. In order to preconcentrate Pu and to avoid matrix effects and clogging effects on the cones during the mass spectrometric measurements, an effective Pu separation procedure (on TEVA resin) from the matrix was applied. Studies of the separation procedure for 2.1 pg of ²⁴²Pu spiked into 100 L of lake water from the Sea of Galilee result in a recovery of 62%. The detection limits of ²³⁹Pu in 100 L lake water were determined as 1 × 10⁻¹⁹ g mL⁻¹ and 3 × 10⁻²⁰ g mL⁻¹ using ICP-SFMS and MC-ICP-MS, respectively. ²³⁹Pu was detected in the Sea of Galilee at a concentration level of about 3.6 × 10⁻¹⁹g mL⁻¹ with a ²⁴⁰Pu/²³⁹Pu isotope ratio of 0.17. This measured plutonium isotope ratio is the most probable evidence of plutonium contamination of the Sea of Galilee as a result of global nuclear fallout after the nuclear weapons tests in the sixties. This paper discusses applications of double-focusing sector field ICP-MS with single and multiple ion collection for the quantitative determination of plutonium and its isotope ratio at the 10⁻¹⁹ g mL⁻¹ level in natural water.