PHYTOREMEDIATION OF URANIUM TAILINGS: ROLE OF CHELATORS IN TRIGGERING URANIUM ACCUMULATION IN WHEAT

Chelator-assisted phytoextraction has been proposed as a potential tool for phytoremediation of uranium contaminated tailings. The purpose of the present investigation was to test the efficiency of the four various chelators namely, citric acid (CA), oxalic acid (OA), NTA and EDTA and to screen out the most effective chelator with promising concentration of it in increasing the U uptake and accumulation for phytoremedial programmes. Three kilograms of mixture (25:75; tailing: garden soil) was filled in the earthen pots. Treatment pots were prepared by applying- 0.1, 0.5, 2.5 and 12.5 mmol kg-1 concentrations of each of the chelator (CA, OA, NTA and EDTA). Optimum concentrations of the chelators were recorded considering biomass production, tolerance index and U uptake. Each chelator produced severe toxicity symptoms at 12.5 mmol kg-1 treatment level. Lowest depression in respect of growth was observed with NTA while OA and CA were proved less toxic than EDTA. Highest inhibition was recorded in EDTA treatments at respective levels. U uptake and accumulation was concentration dependent for each of the chelator amendment. Maximum U uptake (3.4-fold) in the roots occurred at 2.5 mmol kg-1 of CA while NTA proved to be the weakest for the same purpose. Not with standing, EDTA and NTA are stronger complexion agents than CA but in contrary, the use of CA proved beneficial in U tailing phytoremediation in the present investigation. The growth of the wheat plants was affected by each of the chelator, which in general follows the order: NTA ? OA ? CA ? EDTA, whereas the order for U accumulation was recorded as- CA > EDTA > OA > NTA. On the basis of this study it can be suggested that the use CA over EDTA is better, as it is easily biodegradable, less toxic and has lower leaching risk..

Application of gamma-ray spectroscopy and IR-spectroscopy methods for the purposes of ore geology in the Timan-Pechora Oil and Gas Province (the case of Ukhta Region)

Two express methods are presented in this paper. The first method is a high-resolution gamma-spectroscopic method based on a germanium detector, the second method is an IR-spectroscopic method. The applied complex of methods allows to determine the sources of uranium and thorium, identify the rhythms of uranium accumulation associated with regional events; identify areas with a high content of uranium due to the influence of local sources (faults, hydrothermal, etc.); determine the amount of authigenous uranium in the composition of total uranium; determine thermal maturity of organic matter in shales without their preliminary demineralization. To identify levels of increased uranium intensity in the high-carbon strata, a set of indicators has been proposed, which includes both applied indicators in practice of geological work and new indicators. New indicators have been tested on the collection of shale reference samples. For them, values ​​were established that characterize the processes of uranium accumulation and uranium removal. On the example of Ukhta Region according to the proposed indicators, the sections from the Vendian-Riphean to Domanic inclusive were interpreted. The performed work showed the possibility of comparing the calculated gamma-spectroscopic data with the data of other methods. This opens up a broader perspective for the use of express non-destructive gamma-spectroscopic method for detecting levels with a high content of uranium in the shale rocks, to which ore-bearing concentrations of a number of metals are also confined.

The Use of Edible Plants for Rhizofiltration under Different Hydroponic Conditions

<p>This study conducted a rhizofiltration experiment for uranium-removal with the edible plants (<em>Lactuca sativa, Brassica campestris </em>L., <em>Raphanus sativus </em>L., and <em>Oenanthe javanica</em>) which generally consumed in South Korea. Various batch experiments were performed with different initial uranium concentrations, pH conditions, and genuine groundwater. The results showed the uranium accumulation and bioconcentration factor (BCF) of plant roots increase with an increase in initial uranium concentrations in the solution. Of the four plants, the amount of uranium accumulated in <em>Raphanus sativus </em>L. roots was 1215.8 μg/g DW with the maximum BCF value of 2692.7. The BCF value based on various pH conditions (pHs 3, 5, 7 and 9) of artificial solutions was highest at pH 3 for all four plants, and the BCF value of <em>Brassica campestris </em>L. was the maximum of 11580.3 at pH 3. As a result of rhizofiltration experiments with genuine groundwater contaminated with uranium, the BCF values of <em>Raphanus sativus </em>L. were 1684.7 and 1700.1, the highest among the four species, in Oesam-dong and Bugokdong groundwater samples with uranium concentration of 83 and 173 μg/L. From SEM/EDS analysis, it was confirmed that uranium in contaminated groundwater was adsorbed as a solid phase on the root surface. These results demonstrate that <em>Raphanus sativus </em>L. not only has a high tolerance to high concentrations of uranium and low pH conditions but also has a remarkable potential for uranium accumulation capacity.</p>

Uranium Rhizofiltration by Lactuca sativa, Brassica campestris L., Raphanus sativus L., Oenanthe javanica under Different Hydroponic Conditions

Rhizofiltration experiments were conducted using uranium-contaminated groundwater and lettuce (Lactuca sativa), Chinese cabbage (Brassica campestris L.), radish (Raphanus sativus L.), and buttercup (Oenanthe javanica), which are commonly grown and consumed in South Korea. The results of the rhizofiltration experiments with artificial solutions with different initial uranium concentrations (18, 32, 84, 116, 173, and 263 μg/L) show that the uranium accumulation and bioconcentration factor (BCF) of plant roots increase with increasing uranium concentration in the groundwater. Among the four plants, the uranium concentration in the roots of Raphanus sativus L. is 1215.8 μg/g dry weight, with a maximum BCF value of 2692.7. The BCF value of the artificial solutions with various pH values (pH 3, 5, 7, and 9) is the highest under acidic conditions (pH 3) for all four plants. The uranium BCF values based on different hydroponic conditions range from 170.5 to 11580.3 and the results are comparable with those of other studies using similar methods; the highest BCF value was determined for Brassica campestris L. at pH 3. The BCF values of Raphanus sativus L. after the rhizofiltration experiments with genuine groundwater contaminated with uranium are the highest among the four species; that is, 1684.7 and 1700.1 in Oesam-dong and Bugokdong groundwater samples with uranium concentrations of 83 and 173 μg/L, respectively. The results of the scanning electron microscope/electron dispersive X-ray spectroscope analyses show that uranium in contaminated groundwater is adsorbed as a solid phase on the root surface. These results demonstrate that Raphanus sativus L. has a high tolerance to high concentrations of uranium and low pH conditions and a remarkable potential for uranium accumulation.