International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Soil contamination with radionuclides poses a serious threat to the health of the population. It can occur in radioactive incidents and accidents and improper management of radioactive waste. The mobile and bioavailable forms of radioactive contaminants are critical in predicting their transfer through food chains. This study presents the influence of soil organic matter on the leaching of 241Am, 60Co and 137Cs by distilled water from soils, taken from six regions in Bulgaria. The experiment was carried out by Chromic Cambisol, Eutric Fluvisol, two Calcaric Chernozem soils, Gleyic Fluvisol and Vertisol, taken from the surface soil layer 0-10 cm. The initial soil samples did not contain radionuclides and were contaminated by radioactive solution in the laboratory. The soil organic matter was removed from aliquot of the samples by treatment with 6 % NaClO and heating at 96 oC. The investigation aimed to examine the water-soluble forms of the radionuclides in soils, containing aliquots with removed organic substances as well as in natural soils. The contaminated soils were stored at 18 oC and water extraction of the radionuclides was performed after 75 min and 3 weeks after radioactive pollution. The radioactivity of the samples was measured by gamma spectrometry. The results showed that removing soil organic matter has different effects on the watersoluble forms of radiocesium and radiocobalt. No changes in the water-soluble forms of americium were measured. Adding soil with removed organic matter to Calcaric Chernozem soil was found to be an efficient approach to decrease the water-soluble forms of 60Co in the first three weeks after contamination.

Europium is widely used in industry and improper waste management in its recycling can cause environmental pollution. 152Eu is obtained as a result of neutron activation of the control rods of nuclear reactors and may enter the soils after nuclear accident. The distribution of 152Eu in the environment and its transfer through the food chain can threaten the human health through its beta and gamma radiation. Therefore, knowledge of the geochemical forms of Eu and its transfer from soil to plants is important for the risk assessment in case of environmental pollution. The paper presents the results of a model study on the mobile geochemical forms and bioaccumulation of 152Eu from chernozem soil to peppermint (Mentha Piperita L.). Peppermint plant was planted in a pot with Calcaric Chernozem soil, taken from the 0-10 cm surface layer. Aqueous solution of 152EuCl3 was spiked in the soil, simulating radioactive contamination. The peppermint was grown during 8 months and samples of the soil and peppermint stems and leaves were taken at the 5th and 8th month after the radioactive contamination. The transfer factors (TFs) soil-to-plant were determined. The water-soluble, exchangeable and bound to humic and fulvic acids forms of 152Eu were studied after the 1st, 5th and 8th month after the contamination. The transfer of 152Eu from the mint leaves to tea and tincture was examined. The results showed higher TFs for the soil-leaves than soil-stems system. More than 40% of 152Eu, accumulated in the dry leaves was found to be extracted in the tea, while no radioactive europium was found in mint tincture.