TITLE:
Determination of 224Ra and 226Ra Activities in Soil and Sediment Using Interference Correction Method by Ultra Low-Level Gamma Spectrometry
AUTHORS:
Abdul J. Khan, Umme-Farzana Syed, Cynthia A. Costello
KEYWORDS:
224Ra, 226Ra, Soil, Sediment, CRMs, IAEA-312, Low Background Gamma Spectrometry
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.14 No.1,
January
23,
2026
ABSTRACT: Radium isotopes, particularly 226Ra and 228Ra, pose environmental concerns due to their long half-lives (1600 years and 6 years, respectively) and their persistence in soils and sediments, especially in regions affected by coal combustion and uranium mining. This study introduces a novel deconvolution method using ultra-low-background gamma spectrometry to directly quantify 224Ra (240.99 keV) and 226Ra (186.21 keV) in soil and sediment samples, effectively correcting for spectral interferences from 214Pb (241.99 keV) and 235U (185.71 keV). By measuring multiple gamma lines of 235U (143.76, 163.33, 205.31 keV), the method enables precise interference correction. Samples collected from Lake Ontario sediments (2018-2023) and certified reference materials (IAEA-312, IAEA-385, IAEA-412, IAEA-447, and an IAEA 2006 proficiency testing (PT) soil sample) underwent gamma counting for up to 240,000 s. Results showed 224Ra activities in sediments ranging from 23.1 - 23.8 Bq·kg−1 (mean 23.5 ± 0.2), closely matching 228Ra levels, indicating secular equilibrium. Corrected 226Ra activities (22.6 - 24.6 Bq·kg−1; mean 24.2 ± 0.9) aligned well with radon progeny 214Pb and 214Bi measurements. CRM analyses confirmed method accuracy: 226Ra in IAEA-312 was 296 ± 28 Bq·kg−1 (certified 250 - 287 Bq·kg−1), while other radionuclides (40K, 137Cs, 241Am, 234Th, 234mPa, 235U, and 210Pb) measured in samples and CRMs showed strong agreement with certified values. This validated deconvolution approach provides a reliable and time-efficient alternative for direct radium isotope quantification in environmental matrices, thereby enhancing the capability for monitoring both natural and anthropogenic radionuclide distributions.