Approaches to ⁹⁰Sr determination in marine environmental materials

International Atomic Energy Agency, Marine Environment Laboratory, 4 quai Antoine 1, BP. 800, 98012 Monaco, Monaco

Abstract

The determination of ⁹⁰Sr in seawater, sediment and biota is carried out by radiochemical analysis. The choice of method is dependent on the amount of sample to be analyzed, the Ca/Sr mass ratio and the natural Sr content of the sample. For large volumes of seawater and sediment samples (e.g., coral) of high Ca content, 1 g (minimum) of Sr carrier and ⁸⁵Sr tracer are used. The Sr fraction is separated and purified chiefly by Sr(NO₃)₂ precipitations. After 2 - 3 weeks, the ingrown ⁹⁰Y is separated from the parent ⁹⁰Sr, and the ⁹⁰Y beta activity is measured by a gas-flow proportional counter. The detection limits obtained are 36 µBq/L for seawater and 0.36 Bq/kg for corals. For sediment and biota samples of low to moderate Ca content and low natural Sr content, 10 - 20 mg of stable Sr carrier are used without ⁸⁵Sr. The Sr fraction is separated and purified using crown ether extraction chromatography. The purified Sr fraction itself (containing ⁹⁰Sr together with in-growing ⁹⁰Y) is measured immediately using liquid scintillation counting. The detection limit obtained is 0.66 Bq/kg for 10g of sediment or biota ash.