Efficient uranium sequestration ability and mechanism of live and inactivated strain of Streptomyces sp. HX-1 isolated from uranium wastewater.

Prokaryotes are effective biosorbents for the recovery of uranium and other heavy metals. However, the potential mechanism of uranium bioaccumulation by filamentous strain (actinobacteria) remains unclear. This study demonstrates the potential for and mechanism of uranium bioaccumulation by living (L-SS) and inactivated (I-SS) Streptomyces sp. HX-1 isolated from uranium mine waste streams. Uranium accumulation experiments showed that L-SS and I-SS had efficient uranium adsorption potentials, with removal rates of 92.93 and 97.42%, respectively. Kinetic and equilibrium data indicated that the bioaccumulation process was consistent with the pseudo-second-order kinetic, Langmuir, and Sips isotherm models. FTIR indicated that the main functional groups of L-SS and I-SS binding uranium were uranyl, carboxyl, and phosphate groups. Moreover, the results of XRD, XPS, SEM-EDS, and TEM-EDS analyses revealed for the first time that L-SS has biomineralization and bioreduction capacity against uranium. L-SS mineralize U(VI) into NH4UO2PO4 and [Formula: see text] through the metabolic activity of biological enzymes (phosphatases). In summary, Streptomyces sp. HX-1 is a novel and efficient uranium-fixing biosorbent for the treatment of uranium-contaminated wastewater.

Bioremediation of uranium (â ¥) using a native strain Halomonas campaniensis ZFSY-04 isolated from uranium mining and milling effluent: Potential and mechanism.

A significant surge in the exploitation of uranium resources has resulted in considerable amounts of radioactive effluents. Thus, efficient and eco-friendly uranium removal strategies need to be explored to ensure ecological safety and resource recovery. In this study, we investigated the resistance of Halomonas campaniensis strain ZFSY-04, isolated from an evaporation pool at a uranium mine site, and its potential mechanism of uranium (Ⅵ) removal. The results showed that the strain exhibited unique uranium tolerance and its growth was not significantly inhibited under a uranium concentration of 700 mg/L. It had a maximum loading capacity of 865.40 mg/g (dry weight), achieved following incubation under uranium concentration of 100 mg/L, pH 6.0, and temperature 30 °C, for 2 h, indicating that the removal of uranium by the strain was efficient and rapid. Combined with kinetic, isothermal, thermodynamic, and microspectral analyses, the mechanism of uranium loading by strain ZFSY-04 was metabolism-dependent and diverse, including, physical and chemical adsorption on the cell surface, extracellular biomineralisation, intracellular bioaccumulation, and biomineralisation. Our results highlight the unique properties of indigenous strains, including high resistance, high efficiency, rapid uranium removal, and various uranium removal strategies, which make it suitable as a new tool for in situ bioremediation and uranium-contaminated environmental resource recovery.

Study on the thermoluminescence and optically stimulated luminescence of LiMgPO4:Dy phosphors synthesized by different methods.

LiMgPO4:Dy phosphors were synthesized by high-temperature solid-state method and sol-gel method. The effects of different synthesis methods on crystal structure, morphology, thermoluminescence (TL) properties, and optically stimulated luminescence (OSL) properties of LiMgPO4:Dy were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), TL glow curve and continuous wave OSL (CW-OSL) curves. XRD patterns showed that the crystal phase of the samples synthesized by the two methods is LiMgPO4. The morphology of the samples synthesized by sol-gel method was better than that synthesized by high-temperature solid-state method. The TL sensitivity of the samples synthesized by sol-gel method was higher than that synthesized by high-temperature solid-state method. The TL strongest glow peak of the LiMgPO4:Dy sample synthesized by high-temperature solid-state method was 363 K, while that the LiMgPO4:Dy sample synthesized by sol-gel method was 380 K. The OSL sensitivity of the samples synthesized by sol-gel method was significantly higher than that synthesized by high-temperature solid-state method. The synthesis method had no effect on the OSL decay of the sample. LiMgPO4:Dy phosphor synthesized by sol-gel method may be a suitable candidate material for radiation dosimetry.

Equilibrium, kinetics and thermodynamics of biosorption of U(VI) by Jonesia quinghaiensis strain ZFSY-01 isolated from the wastewater of a uranium mine.

The adsorption ability of a native Jonesia quinghaiensis strain ZFSY-01, a microorganism isolated from uranium tailing wastewater, to U(VI) in wastewater under different conditions was studied in this work. The results showed that 391.5 mg U/g and 78.3% of adsorption capacity and efficiency were achieved under an optimum adsorption condition, respectively. Especially, the adsorption capacity of this strain reached the maximum (Q=788.9 mg U/g) under 100 mg/L of strain dosage. Simultaneously, the linear regression coefficients for the used isothermal sorption model indicate that the biosorption process is compatible with the Freundlich isotherm, the Temkin isotherm and the Halsey isotherm model. Based on the fitted kinetic parameters, the data from the experiments fit well with models of pseudo-second-order kinetics and intraparticle diffusion, suggesting that the strain ZFSY-01 immobilized U(VI) by physical and chemical adsorption. In addition, thermodynamic parameters demonstrated that the sequestration of U(VI) by the strain is spontaneous and endothermic. Based on the above analysis, strain ZFSY-01 can effectively remove U(VI) ions from high- or low-concentration uranium-containing wastewater and is expected to become a promising biological adsorbent.

Remedial effect and operating status of a decommissioned uranium mill tailings (UMT) repository: A micro-ecological perspective based on bacterial community.

From a radioecological perspective, increasing attention has been paid to the long-term stabilisation of decommissioned uranium mill tailings (UMT) repositories. However, little is known about the evaluation of decommissioning and remedial effects of UMT repositories from a microecological perspective based on bacterial communities. Here, we analysed the distribution and structure of soil community assemblies along different vertical soil profiles in a decommissioned UMT repository and explored the impact of soil properties, including physicochemical parameters, metal(loid)s, and radionuclides, on the bacterial assemblage. We found that the α diversity of the bacterial community was unaffected by variations in different soil profiles and taxa were classified at the phylum level with small significant differences. In contrast, the bacterial community structure in and around the UMT repository showed significant differences; however, this difference was significantly affected by soil metal(loid)s and physicochemical properties rather than soil radionuclides. In addition, seven bacterial genera with significant differences between the inner and surrounding regions of the repository could be used as potential indicators to further investigate the remedial effects on soil environmental quality. These findings provide novel insights into the construction of an assessment system and in situ biomonitoring of UMT repositories from a microecological perspective based on bacterial communities.

Response of soil microbial communities to natural radionuclides along specific-activity gradients.

Understanding the response of soil microbial community to abnormal natural radionuclides is important to maintain soil ecological function, but the underlying mechanism of tolerance and survival of microbes is poorly studied. The effects of natural radionuclides on the topsoil microbial communities in anomalous natural radiation area were investigated in this work, and it was found that microbial community composition was significantly influenced by the specific-activities of natural radionuclides. The results revealed that relative abundances of 10 major microbial phyla and genera displayed different patterns along specific-activity gradients, including decreasing, increasing, hump-shaped, U-shaped, and similar sinusoidal or cosine wave trends, which indicated that the natural radionuclides were the predominant driver for change of microbial community structure. At the phylum and genus level, microbial communities were divided into two special groups according to the tolerance to natural radionuclides, such as 238U and 232Th, including tolerant and sensitive groups. Taken together, our findings suggest that the high specific-activities of natural radionuclides can obviously drive changes in microbial communities, providing a possibility for future studies on the microbial tolerance genes and bioremediation strains.

Assessment of radiation dose hazards caused by radon and its progenies in tap water by the human dosimetric model.

Radon is readily soluble in water, and radon exposure caused by household water consumption may pose a threat to public health. In this study, the radon concentration in the tap water of residential buildings was measured, and the average value was 543.33 mBq L-1, which was in line with the radon concentration limit recommended by USEPA (11.11 Bq L-1) and EURATOM (100 Bq L-1), and also within the range of the results of radon concentration measurements in tap water in other countries or regions. Through water bath heating at different temperatures, the radon retention curves of multiple groups of samples at different temperatures were fitted and analyzed. The results showed that the radon retention continued to decrease between 25 and 70 °C, remained stable between 70 and 85 °C, and then continued to decline slowly. Combined with the measurement results, the effective doses of α- and ß-particles emitted by 222Rn and its progenies to residents respiratory and alimentary tissues and organs were calculated using the computational model provided by ICRP under two typical water scenarios of shower and drinking water, and the results show that radon exposure caused by normal water consumption will not pose a serious threat to public health.

Assessment of natural radioactivity and consequent radiological hazard in different brands of commercialized bottled mineral water produced in China.

As one of the drinking water quality parameters, natural radioactivity parameters are recommended to prevent a potential health threat to the public. In this study, the gross-α and gross-ß activity concentrations in 15 different brands of commercial bottled mineral water consumed in China were analyzed to evaluate the quality and corresponding health impact on the population. The activity concentrations of gross-α and gross-ß in different samples varied from 4.4 to 130.6 and 17.3-320.3 mBq L-1, respectively. The values of the annual effective dose equivalent rate (AED) for infants, children and adults ranged from 1.3 to 21.6, 2.9-52.5 and 5.5-97.8 µSv y-1, respectively. The average excess lifetime cancer risk caused by the consumption of bottled mineral water samples was estimated as 6.0 × 10-5. These results show that all the measured gross-α and gross-ß are found to be obviously less than the guidance level by WHO and the domestic standard. The values of AED are below the World Health Organization (WHO) recommended limit of 0.1 mSv y-1. Combined with the lifetime cancer risk assessment, it is concluded that there is no significant risk for consumption of the observed brands of bottled mineral water and it can be consumed safely.