Accumulation of Natural and Artificial Radionuclides by Medicinal Plant Raw Materials Using Nettle Leaves as an Example

The purpose of the present research was to study peculiarities in the accumulation of natural and artificial radioisotopes in medicinal plant raw material using nettle (Urtica dioica L.) leaves as an example. The specific activities of the main long-lived artificial radioisotopes (cesium-137 and strontium-90) and naturally occurring radionuclides (thorium-232, potassium-40, and radium-226) in experimental samples of upper soil layers and nettle leaves were determined on a RADEK MKGB-01 spectrometer-radiometer. All studied samples of nettle leaves collected in natural and artificial phytocenoses of Voronezh Region met existing radiation safety requirements (first group). A correlation analysis of the specific activities of artificial and natural radionuclides in the soil and nettle leaves showed a close relationship between these numerical indicators that confirmed their contamination primarily through soil. The specific activities of strontium-90, cesium-137, thorium-232, potassium-40, and radium-226 in the medicinal plant raw material increased as their specific activities in the soil increased. High accumulations of cesium-137 and potassium-40 from the upper soil layers were noted for nettle leaves growing in Voronezh Region. A detailed analysis of the dependence of the calculated accumulation coefficients of natural and artificial radioisotopes in nettle leaves revealed trends toward their decrease with increases in the specific activities of the radionuclides in the soil, which indicated physical mechanisms for regulating their uptake into the plant were present.