Influence of extraction process on Cs isotope ratios for Fukushima Daiichi nuclear power plant accident-contaminated soil.

The influence of extraction process on Cs isotope ratios was investigated by thermal ionization mass spectrometry (TIMS) for nitric-acid (HNO3) treatments of Fukushima Daiichi nuclear power plant accident-contaminated soil samples. In contrast to the consistent TIMS results for conc. HNO3 treatments at 90–200 °C, dilute HNO3 treatment provided a statistically significant 3.0‰-higher 135Cs/137Cs average isotope ratio than the conc. HNO3 treatment conducted at the same temperature. The higher isotope ratio is caused by a specific extraction process making detectable the deviated distribution of Cs isotopes in clay minerals or leading to matrix effects responsible for instrumental mass bias. [ABSTRACT FROM AUTHOR]