Particle size distribution effects on radionuclide concentration in TENORM and $ ^{137}\mathrm{Cs} $ contaminated soil

This study investigates the radioactivity concentrations in contaminated soil samples, comprising TENORM-contaminated soil from an oilfield and artificially contaminated soil containing 137Cs. The primary objective was to examine the correlation between soil grain size distribution and radionuclide concentrations within these samples. Radioactivity measurements were conducted using a broad-energy HPGe gamma-spectroscopy system with 50 % relative efficiency. Both soil samples were systematically fractionated into seven distinct size categories through mechanical sieving, ranging from < 37 ?m (400 mesh) to >900?m (20 mesh) in diameter. Results demonstrate that radionuclide activity concentrations in TENORM samples exhibit significant variation across particle size fractions, with the exception of ^{40}\mathrm{K} . The highest activity concentrations were consistently observed in the finest particle fraction (?37.5 ?m). Similarly, ^{137}\mathrm{Cs} activity in the artificially contaminated soil exhibits fraction-dependent distribution, with peak concentrations in particles ?63 ?m. Statistical analysis revealed strong reverse correlations between particle size and radionuclide concentration: correlation coefficients of r = -0.647 and r = -0.710 were obtained for ^{228}\mathrm{Ra} and ^{226}\mathrm{Ra} , respectively (p-value ? 0.008 and p ? 0.04), while ^{137}\mathrm{Cs} demonstrated an even stronger reverse correlation (r = -0.930, p ? 0.02). These findings provide essential guidance for advancing targeted soil remediation strategies and optimizing mechanical separation techniques at radioactively contaminated sites, with direct implications for radiation protection practices and environmental risk assessment.