Research on leaching behavior of uranium from a uranium tailing and its adsorption behavior in geotechnical media.

The release of uranium from uranium tailings into the aqueous environment is a complex process controlled by a series of interacting geochemical reactions. In this paper, uranium tailings from a uranium tailings pond in southern China were collected at different depths by means of borehole sampling and mixed to analyze the fugacity state of U. Static leaching experiments of U at different pH, oxidant concentration and solid-to-liquid ratios and dynamic leaching experiments of U at different pH were carried out, and the adsorption and desorption behaviour of U in five representative stratigraphic media were investigated. The results show that U is mainly present in the residue state in uranium tailings, that U release is strong in the lower pH range, that the leached U is mainly in the form of U(VI), mainly from the water-soluble, Fe/Mn oxides and exchangeable fraction of uranium tailings, and that the reduction in U leaching at higher pH is mainly due to the combined effect of precipitation formation and larger particle size of platelets in uranium tailings. Experiments with different oxidant concentrations and solid-liquid ratios showed that the oxygen-enriched state and low solid-liquid ratios were favorable for the leaching of U from uranium tailings. Adsorption and desorption experiments show that U is weakly adsorbed in representative strata, reversibly adsorbed, and that U is highly migratory in groundwater. The present research results have important guiding significance for the management of existing uranium tailings ponds and the control of U migration in groundwater, which is conducive to ensuring the long-term safety, stability and sustainability of uranium mining sites.

Leaching behaviour and mechanism of U, 226Ra and 210Pb from uranium tailings at different pH conditions.

A large number of radionuclides remain in uranium tailings, and U, 226Ra and 210Pb leach out with water chemistry, causing potential radioactive contamination to the surrounding environment. In this paper, uranium tailings from a uranium tailings pond in southern China were collected at different depths by means of borehole sampling, mixed and homogenised, and analysed for mineral and chemical composition, microscopic morphology, U, 226Ra and 210Pb fugacity, static leaching and dynamic leaching of U, 226Ra and 210Pb in uranium tailings at different pH conditions. The variation of U, 226Ra and 210Pb concentrations in the leachate under different pH conditions with time was obtained, and the leaching mechanism was analysed. The results showed that the uranium tailings were dominated by quartz, plagioclase and other minerals, of which SiO2 and Al2O3 accounted for 65.45% and 13.32% respectively, and U, 226Ra and 210Pb were mainly present in the residue form. The results of the static leaching experiments show that pH mainly influences the leaching of U, 226Ra and 210Pb by changing their chemical forms and the particle properties of the tailings, and that the lower the pH the more favourable the leaching. The results of dynamic leaching experiments during the experimental cycle showed that the leaching concentration and cumulative release of U, 226Ra and 210Pb in the leach solution were greater at lower pH conditions than at higher pH conditions, and the leaching of U, 226Ra and 210Pb at different pH conditions was mainly from the water-soluble and exchangeable states. The present research results are of great significance for the environmental risk management and control of radioactive contamination in existing uranium tailings ponds, and are conducive to ensuring the long-term safety, stability and sustainability of uranium mining sites.

Effects of the coupling water and fertilizer on soil phosphorus components in alfalfa field in Eastern Inner Mongolia, China.

Soil phosphorus (P) could be categorized into organic and inorganic forms, with diffe-rent capabilities of nutrient supply. Exploring soil P components through liquid 31P-NMR would provide an important theoretical basis for soil P nutrition regulation. This study addressed the characteristic of P in alfalfa (Medicago sativa) soil via the pot experiment. There were two scenarios of treatments with conventional and dry water combined with different P fertilizer levels (P0-P4: 0, 0.025, 0.05, 0.1, and 0.2 g P2O5·kg-1soil). The characteristics of P components in alfalfa soil under water-fertilizer coupling conditions were measured by liquid 31P-NMR. Results showed that under different water and fertilizer treatments, soil inorganic P was mainly composed of inorganic orthophosphate, pyrophosphate and inorganic polyphosphate. Inorganic orthophosphate was the dominant component of inorganic P, which could be reduced by drought. High P application (P4) could increase the contents of soil inorganic polyphosphates and inorganic pyrophosphates. Among the organic P components, monoester orthophosphate was dominant, the conversion and utilization of which in alfalfa soil were affected by drought. Overall, the rational management of water and fertilizer could effectively regulate the conversion and utilization of P nutrients in alfalfa soil in Eastern Inner Mongolia.

Remyelination is enhanced by Astragalus polysaccharides through inducing the differentiation of oligodendrocytes from neural stem cells in cuprizone model of demyelination.

Demyelination is the hallmark of multiple sclerosis (MS). Promoting remyelination is an important strategy to treat MS. Our previous study showed that Astragalus polysaccharides (APS), the main bioactive component of Astragalus membranaceus, could prevent demyelination in experimental autoimmune encephalomyelitis mice. To investigate the effects of APS on remyelination and the underlying mechanisms, in this study we set up a cuprizone-induced demyelination model in mice and treated them with APS. It was found that APS relieved the neurobehavioral dysfunctions caused by demyelination, and efficaciously facilitated remyelination in vivo. In order to determine whether the mechanism of enhancing remyelination was associated with the differentiation of neural stem cells (NSCs), biomarkers of NSCs, astrocytes, oligodendrocytes and neurons were measured in the corpus callosum tissues of mice through Real-time PCR, Western blot and immunohistochemistry assays. Data revealed that APS suppressed the stemness of NSCs, reduced the differentiation of NSCs into astrocytes, and promoted the differentiation into oligodendrocytes and neurons. This phenomenon was confirmed in the differentiation model of C17.2 NSCs cultured in vitro. Since Sonic hedgehog signaling pathway has been proven to be crucial to the differentiation of NSCs into oligodendrocytes, we examined expression levels of the key molecules in this pathway in vivo and in vitro, and eventually found APS activated this signaling pathway. Together, our results demonstrated that APS probably activated Sonic hedgehog signaling pathway first, then induced NSCs to differentiate into oligodendrocytes and promoted remyelination, which suggested that APS might be a potential candidate in treating MS.

[Selection of sodium chloride tolerant mutants in Chrysanthemum morifolium in Anhui].

OBJECTIVE: To select the sodium chloride tolerant mutants of the Chrysanthemum morifolium callus through tissue culture and EMS (ethylmethane sulfonate) treatment. METHOD: Calli were induced from the leaves of C. morifolium. The calli were treated with 0.2% and 0.5% EMS, respectively. After 15 days' culture, the calli were transplanted to selection media with 0.5%, 1.0% and 1.5% NaCl, and the sodium chloride tolerant mutants were selected out. RESULT AND CONCLUSION: After tested the sodium chloride tolerant stability, the callus selected are found to be the mutants indeed.