Sensitive and accurate methods for determination of low activity level of 90Sr and 137Cs in grass/vegetable samples

Abstract

Sensitive, precise and accurate methods for determination of low activity level of 90Sr and 137Cs in grass/vegetable samples by a low background β-counter were developed. The method for 90Sr determination was based on coprecipitation as carbonate, elimination of 210Bi and iron with a Microthene-TOA column, separation of 90Y with a Microthene-HDEHP column, and source preparation as Y2(C2O4)3. The method for 137Cs determination was based on Cs adsorption on ammonium molybdophosphate and precipitation as Cs3Bi2I9 for source preparation. The quality control tests indicated that the methods could provide accurate results. The method application showed that: (1) The mean yields of yttrium and cesium were 79 ± 6% and 84 ± 2%, respectively. (2) The activity concentrations of 90Sr in 9 grass/vegetable samples were in the range of 0.04–1.8 Bq kg−1, while that of 137Cs in the range of 0.022–0.18 Bq kg−1. And (3) the uptake rate of 90Sr from soil to grass/vegetable was much higher than that of 137Cs.