Soil-to-plant transfer and radiological risk assessment of naturally occurring radionuclides in vegetables from Lay Gayint, Ethiopia.

This study examines how naturally occurring radionuclides (40K, 226Ra, 228Ra) transfer from soil into cabbage and spinach grown in Lay Gayint woreda, Amhara Region, Ethiopia. Activity concentrations of radionuclides were measured in irrigation water (n = 15), soil (n = 20), and vegetable samples using HPGe gamma spectrometry. Mean soil concentrations were 625 ± 152 Bq·kg-1 for 40K, 89 ± 30 Bq·kg-1 for 226Ra, and 85 ± 31 Bq·kg-1 for 228Ra. Transfer factors (TFs) were highest for 40K (cabbage: 0.78 ± 0.07; spinach: 1.04 ± 0.13), followed by 226Ra (0.12 ± 0.01; 0.11 ± 0.02) and 228Ra (0.13 ± 0.03; 0.09 ± 0.01). A strong negative correlation was observed between clay content and TFs (r = -0.992 to -0.997, P < 0.001), indicating that higher clay content reduces plant uptake. Regression analysis showed that clay content explained over 98% of the variance in TFs. All radiological hazard indices (radium equivalent activity, external hazard index, internal hazard index) remained below global limits. Annual effective doses from vegetable consumption ranged from 0.01-0.06 mSv y-1 (cabbage) and 0.03-0.13 mSv y-1 (spinach), while the excess lifetime cancer risk (ELCR) reached up to 3.7 × 10-4. Although annual effective dose values fall within international recommendations, the ELCR is slightly elevated, suggesting minimal but nonnegligible radiological risk for consumers. This study provides key baseline data on radionuclide transfer in Ethiopian agriculture, useful for broader radiological risk assessment and management.