Investigation of naturally occurring radionuclides in selected medicinal plants and associated soils, and calculation of soil-to-plant transfer factors

This study investigated the activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K and their soil-to-plant transfer factors in some medicinal plants located in Nepal. The geometric mean values of soil-to-plant transfer factors (TFs) for ²²⁶Ra, ²³²Th, and ⁴⁰K were 0.37, 0.96, and 3.50, respectively. This indicated that medicinal plants absorbed the highest amount of ⁴⁰K from the soil, followed by ²³²Th, while ²²⁶Ra was absorbed the least. The average radium equivalent activities for medicinal plants (189 Bq/kg) and associated soils (182 Bq/kg) were within the international acceptable limit of 370 Bq/kg. According to the activity concentrations found in the medicinal plants, they do not present any radiological health hazards unless consumed in excessive quantities; however, continuous investigations are essential.