Results of an IAEA inter-comparison exercise to assess 137Cs and total 210Pb analytical performance in soil

Abstract

Fallout radionuclides (FRNs) such as 210Pb and 137Cs have been widely used to assess soil erosion and sedimentation processes. It is of major importance to obtain accurate analytical results of FRNs by gamma analysis before any data treatment through conversion model and to allow subsequent comparison of erosion and sedimentation rates from different case studies. Therefore, IAEA organized an inter-comparison exercise to assess the validity and reliability of the analytical results of 137Cs and total 210Pb using γ-spectrometry in the various laboratories participating in the IAEA Co-ordinated Research Project on “Assess the effectiveness of soil conservation measures for sustainable watershed management using fallout radionuclides”. Reference materials were distributed to 14 participating laboratories and, using a rating system, their analytical results were compared to the reference values assigned. In the case of 137Cs, the analytical results were satisfactory with 66% of the laboratories producing acceptable results. Only the sample with low 137Cs activity (2.6±0.2 Bq kg −1) gave less accurate results with more than 25% not acceptable results. The total 210Pb analysis indicated a clear need for corrective actions in the analysis process as only 36% of the laboratories involved in the proficiency test was able to access total 210Pb with occurrence (bias ⩽10%). This inter-laboratory test underlines that further inter-comparison exercises should be organized by IAEA or regional laboratories to ensure the quality of the analytical data produced in Member States. As a result of the above-mentioned proficiency test, some recommendations have been provided to improve accurate gamma measurement of both 137Cs and total 210Pb.