Study of soil to plant transfer factors of 226Ra, 232Th, 40K and 137Cs in Vietnamese crops

The study of staple food products is crucial to assure public safety and provides input for predictive dose assessment models. To further this goal, the activity concentrations, transfer factors, and radiological hazards of Ra-226, Th-232, K-40 and Cs-137 were studied for ten pairs of selected vegetables and soils in Tien Le near Hanoi in Vietnam. This is the first study in this area for Vietnamese vegetable samples. The ten most popular vegetables in Vietnamese diet were selected, namely choy sum, crown daisy, lettuce, cabbage, Malabar spinach, beans, sweet potato, potato, kohlrabi and carrot. The research results showed that the activity concentrations observed in vegetable crops did not present the previously reported strong correlation to those in soil. The ranges of TFs of Ra-226, Th-232 and K-40 were 4 x 10(-2) - 6.9 x 10(-1), 8 x 10(-2) - 9.7 x 10(-1); and 1.0 x 10(0)-1.6 x 10(1), respectively. Values for leafy vegetables and tubers exceed previous world range figures for Th and K. The soil has been evaluated for radiological hazard indices, which predict almost no risk to human health in the study area.