Naslov
Prenos naravnih radionuklidov v izbrane organizme iz tal onesnaženih s hidrometalirško jalovino
(Transfer of natural radionuclides to selected organisms from soil contaminated with U-mill tailings)

Autori
Černe, Marko

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Međunarodna poslijediplomska škola Jožefa Stefana

Mjesto
Ljubljana

Datum
05.05

Godina
2014

Stranica
135

Mentor
Smodiš, Borut

Ključne riječi
Natural radionuclides ; Transfer ; Bioaccumulation ; Organisms ; U-mill tailings

Sažetak
Environmental contamination due to radionuclide released is a common phenomenon in uranium mining and milling areas. Disposal of uranium-ore processing materials may result in environmental contamination if inappropriate waste management is applied. Radionuclides retained in the soil may be subsequently taken-up by various organisms which depend on the soil properties, physicochemical conditions and microbial activity of soil. Organisms, such as certain plant species growing on soils naturally abundant with uranium series radionuclides or soils contaminated with uranium- mill tailings may accumulate radionuclides in above-ground organs in higher quantities due to adaptation in the extreme conditions. In this doctoral thesis, a transfer of natural radionuclides to various organisms was investigated from soils contaminated with uranium- mill tailings in site-specific in-situ conditions and in laboratory-based conditions. For in-situ conditions, a wetland plant species from the Žirovski vrh influential area, such as the common reed (Phragmites australis (Cav.) Trin. ex Steud.), soft rush (Juncus effusus L.), marsh- marigolds (Caltha palustris L.) and tall moor grass (Molinia arundinacea Schrank) growing in marsh habitat continuously flooded by tailings seepage waters were tested for their radionuclide activity concentrations as they may be useful for phytoremediation or biomonitoring of soils contaminated with natural radionuclides. Ra-226 activity concentrations in plants were 1200 ± 100, 70 ± 7, 40 ± 3 and 12.4 ± 1.1 Bq kg-1 dry mass, for the common reed (leaves), soft rush, tall moor grass and marsh-marigolds (leaves), respectively. Activity concentrations of other radionuclides in wetland plants, i.e. U-238, Pb-210, Th-230 and K- 40, are briefly shown and discussed in this doctoral thesis and in the attached scientific articles in more detail. The ERICA Tool was applied for the assessment of environmental radiological risk to wetland plants from the Žirovski vrh influential area due to their exposure to natural radionuclides emitted from the Boršt tailings pile. Total dose rates to plants were 0.83, 3.49 and 2.65 μGy h-1 for marsh marigolds, soft rush and tall moor grass, respectively.The results showed that no risk from ionizing radiation to the studied plant species was found. Dose rates to other organisms from the Žirovski vrh influential area are also shown and discussed in the attached scientific article. For laboratory-based conditions, the soil-to-plant transfer of U-238, Ra-226 and Pb-210 for Chinese cabbage (Brassica pekinensis Rupr.) was investigated on soils contaminated with uranium- mill tailings. Tested plants were growing in pots in the controlled conditions as big variability in concentration ratios may arise in field conditions due to variable natural conditions. Different levels of soil contamination under various growing conditions were applied in the pot experiment to simulate different contamination scenarios. U-238, Ra-226 and Pb-210 were determined in above-ground organs to calculate the plant-to-soil radionuclide concentration ratios. The macro-elements and alkaline earth metals in tested plants were also considered due to their role in the uptake process. Pedological parameters were taken into account as they directly affect the availability of radionuclides in the soil. The study was conducted in a Hot Cells Facility of the Jožef Stefan Institute in Ljubljana. The statistical ANOVA design was used as the experimental basis where three different soils (A, B and C) and four levels of soil contamination (0, 20, 40 and 60 % of UMT in the soil) were applied in a two-factor design in four replicates. Activity concentrations of Ra-226 in Chinese cabbage varied from 56–276, 156–502 and 277–877 Bq kg-1 dry mass for 20, 40 and 60 % of UMT content in the soil, respectively. The results showed increased accumulation of Ra- 226 in cabbage leaves on more contaminated soil. The activity concentrations of Ra-226 in Chinese cabbage indicated that caution is needed when growing Brassica crops at the mine areas potentially contaminated by natural radionuclides due to possible transfer of Ra-226 to food chain and the related dose absorbed by the nearby living inhabitants. Activity concentrations of other radionuclides in Chinese cabbage i.e. U-238 and Pb-210 are also shown and discussed in this doctoral thesis and their concentration ratios for different contamination levels at various growing conditions are presented and critically evaluated.

Izvorni jezik
Engleski

Znanstvena područja
Kemija, Poljoprivreda (agronomija), Interdisciplinarne biotehničke znanosti

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