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.

Gamma radiation treatment for the destruction of biological pests is a widely applied method, due to its high efficiency, penetrating power of gamma rays, the ability to control the absorbed dose, speed and absence of toxic residual products. The application of gamma irradiation processing for preservation and conservation of artefacts made of wood requires knowledge of the possible radiation effects on the structure of its components and the selection of an appropriate absorbed dose and dose rate. Тhe present study is devoted to the side effects of gamma irradiation decontamination on the structure of two ebony woods dated to different radiocarbon ages. The changes induced by gamma irradiation at two dose rates: 0.037 Gy/s and 1 Gy/s with absorbed doses from 5 to 25 kGy using differential scanning calorimetry are presented. The effects of the absorbed dose, the dose rate and the age of the samples on the observed radiation effects are considered. Higher effects on the enthalpy of water loss were registered in the younger ebony wood after irradiation at low dose rate. Slight changes of the temperatures of water loss were found in the younger ebony wood sample. No significant changes in the temperatures of thermal decomposition in both ebony wood samples were measured.

The paper presents the applicability of gamma irradiation for the degradation of mycotoxins ochratoxin A, zearalenone and deoxynivalenol in wheat flour. The experiment was carried out by contamination of wheat flour samples with mixture of the mycotoxins and their gamma irradiaton with doses of 5 kGy, 10 kGy and 20 kGy using industrial gamma irradiation facility BULGAMMA. The concentrations of the mycotoxins before and after the radiation processing were measured by HPLC. The results showed that the application of a dose of 10 kGy resulted in incomplete decomposition of the investigated mycotoxins: 12 % of deoxynivalenol, 13 % of ochratoxin A and 37 % of zearalenone. The decomposition of the investigated mycotoxins in wheat flour achieved after gamma irradiation with a dose of 20 kGy was found to increase in the following order: ochratoxin A (48 %) > zearalenone (66 %) > deoxynivalenol (97 %).

The article presents the effects of different doses of gamma irradiation on the degradation of aflatoxins B1, B2, G1 and G2 in wheat flour. The experiment was conducted after contamination of wheat flour samples with mixture of aflatoxins with concentrations from 3 μg/kg to 12 μg/kg using reference material. Irradiation of flour aliquots with absorbed doses from 5.8 kGy to 27 kGy was carried out in an industrial gamma irradiation facility BULGAMMA. The concentrations of the aflatoxins before and after the radiation processing were measured by HPLC. The results showed that gamma irradiation with 27 kGy caused the highest degree of destruction of aflatoxins B2 (82 %) and G2 (81 %), followed by aflatoxin G1 (65 %) and to the lowest extend of aflatoxin B1 (59 %). Gamma irradiation with the maximum allowable dose for commercial food irradiation of 10 kGy was not sufficient to destroy the studied aflatoxins to the maximum permissible concentrations in wheat flour.