Cinnamic Acid: A Low-Toxicity Natural Bidentate Ligand for Uranium Decorporation.

Uranium accumulation in the kidneys and bones following internal contamination results in severe damage, emphasizing the pressing need for the discovery of actinide decorporation agents with efficient removal of uranium and low toxicity. In this work, cinnamic acid (3-phenyl-2-propenoic acid, CD), a natural aromatic carboxylic acid, is investigated as a potential uranium decorporation ligand. CD demonstrates markedly lower cytotoxicity than that of diethylenetriaminepentaacetic acid (DTPA), an actinide decorporation agent approved by the FDA, and effectively removes approximately 44.5% of uranyl from NRK-52E cells. More importantly, the results of the prompt administration of the CD solution remove 48.2 and 27.3% of uranyl from the kidneys and femurs of mice, respectively. Assessments of serum renal function reveal the potential of CD to ameliorate uranyl-induced renal injury. Furthermore, the single crystal of CD and uranyl compound (C9H7O2)2·UO2 (denoted as UO2-CD) reveals the formation of uranyl dimers as secondary building units. Thermodynamic analysis of the solution shows that CD coordinates with uranyl to form a 2:1 molar ratio complex at a physiological pH of 7.4. Density functional theory (DFT) calculations further show that CD exhibits a significant 7-fold heightened affinity for uranyl binding in comparison to DTPA.

The effect of extracellular polymeric substances on MICP solidifying rare earth slags and stabilizing Th and U.

Microbially induced carbonate precipitation (MICP) has been used to cure rare earth slags (RES) containing radionuclides (e.g. Th and U) and heavy metals with favorable results. However, the role of microbial extracellular polymeric substances (EPS) in MICP curing RES remains unclear. In this study, the EPS of Lysinibacillus sphaericus K-1 was extracted for the experiments of adsorption, inducing calcium carbonate (CaCO3) precipitation and curing of RES. The role of EPS in in MICP curing RES and stabilizing radionuclides and heavy metals was analyzed by evaluating the concentration and morphological distribution of radionuclides and heavy metals, and the compressive strength of the cured body. The results indicate that the adsorption efficiencies of EPS for Th (IV), U (VI), Cu2+, Pb2+, Zn2+, and Cd2+ were 44.83%, 45.83%, 53.7%, 61.3%, 42.1%, and 77.85%, respectively. The addition of EPS solution resulted in the formation of nanoscale spherical particles on the microorganism surface, which could act as an accumulating skeleton to facilitate the formation of CaCO3. After adding 20 mL of EPS solution during the curing process (Treat group), the maximum unconfined compressive strength (UCS) of the cured body reached 1.922 MPa, which was 12.13% higher than the CK group. The contents of exchangeable Th (IV) and U (VI) in the cured bodies of the Treat group decreased by 3.35% and 4.93%, respectively, compared with the CK group. Therefore, EPS enhances the effect of MICP curing RES and reduces the potential environmental problems that may be caused by radionuclides and heavy metals during the long-term sequestration of RES.

Microbial adaptations and biogeochemical cycling of uranium in polymetallic tailings.

Microorganisms inhabiting uranium (U)-rich environments have specific physiological and biochemical coping mechanisms to deal with U toxicity, and thereby play a crucial role in the U biogeochemical cycling as well as associated heavy metals. We investigated the diversity and functional capabilities of indigenous bacterial communities inhabiting historic U- and Rare-Earth-Elements-rich polymetallic tailings from the Mount Painter Inlier, Northern Flinders Ranges, South Australia. Bacterial diversity profiling identified Actinobacteria as the predominant phylum in all samples. GeoChip analyses revealed the presence of diverse functional genes associated with biogenic element cycling, metal homeostasis/resistance, stress response, and secondary metabolism. The high abundance of metal-resistance and stress-tolerance genes indicates the adaptation of bacterial communities to the "harsh" environmental (metal-rich and semi-arid) conditions of the Northern Flinders Ranges. Additionally, a viable bacterial consortium was enriched from polymetallic tailings. Laboratory experiments demonstrated that the consortium scrubbed uranyl from solution by precipitating a uranyl phosphate biomineral (chernikovite), thus contributing to U biogeochemical cycling. These specialised microbial communities reflect the high specificity of the mineralogy/geochemistry, and biogeography of these U-rich settings. This study provides the fundamental knowledge to develop future applications in securing long-term stability of polymetallic mine waste, and for reprocessing this "waste" to further extract critical minerals.

Uranium mining effluents: What about the re-use of mining wastes to improve the bioproduction of industrially relevant bioactive compounds?

The shift towards a circular economy, where waste generation is minimized through waste re-use and the development of valorization strategies, is crucial for the establishment of a low carbon, sustainable, and resource-efficient economy. However, there is a lack of strategies for re-using and valorizing specific types of waste, particularly those containing naturally occurring radioactive materials (NORM), despite the prevalence of industrial activities that produce such waste due to their chemical and radiological hazards. Living organisms, including fungi, are valuable sources of bioactive compounds with various industrial applications. In this study, we assessed the growth and metabolic profile changes of three white rot fungi species in response to low concentrations of a uranium mine effluent containing NORM and metals to explore their potential for producing biotechnologically relevant bioactive compounds. The growth rate was assessed in three different culture media, with and without the uranium mine effluent (1% V/V)), and the metabolic profile was analyzed using FTIR-ATR spectroscopy. Results suggested an improvement in growth rates in media containing the uranium mine effluent, although not statistically significant. T. versicolor showed promise in terms of bioactive compound production. The production of droplets during growth experiments and significant metabolic changes, associated with the production of bioactive compounds like laccase, melanin, and oxalic acid, were observed in T. versicolor grown in mYEPDA with the uranium mine effluent. These findings present new research opportunities for utilizing waste to enhance the biotechnological production of industrially relevant bioactive compounds and promote the development of circular economy strategies for re-using and valorizing NORM-containing waste.

Effects and driving mechanisms of bioremediation on groundwater after the neutral in situ leaching of uranium.

The remediation of groundwater subject to in situ leaching (ISL) for uranium mining has raised extensive concerns in uranium mill and milling. This study conducted bioremediation through biostimulation and bioaugmentation to the groundwater in an area in northern China that was contaminated due to uranium mining using the CO2 + O2 neutral ISL (NISL) technology. It identified the dominant controlling factors and mechanisms driving bioremediation. Findings indicate that microorganisms can reduce the uranium concentration in groundwater subject to NISL uranium mining to its normal level. After 120 days of bioaugmentation, the uranium concentration in the contaminated groundwater fell to 0.36 mg/L, achieving a remediation efficiency of 91.26 %. Compared with biostimulation, bioaugmentation shortened the remediation timeframe by 30 to 60 days while maintaining roughly the same remediation efficiency. For groundwater remediation using indigenous microbial inoculants, initial uranium concentration and low temperatures (below 15 °C) emerge as the dominant factors influencing the bioremediation performance and duration. In settings with high carbonate concentrations, bioremediation involved the coupling of multiple processes including bioreduction, biotransformation, biomineralization, and biosorption, with bioreduction assuming a predominant role. Post-bioremediation, the relative abundances of reducing microbes Desulfosporosinus and Sulfurospirillum in groundwater increased significantly by 10.56 % and 6.91 %, respectively, offering a sustainable, stable biological foundation for further bioremediation of groundwater.

Enhanced microbial remediation of uranium tailings through red soil utilization.

Seepage of uranium tailings has become a focus of attention in the uranium mining and metallurgy industry, and in-situ microbial remediation is considered an effective way to treat uranium pollution. However, this method has the drawbacks of easy biomass loss and unstable remediation effect. To overcome these issues, spare red soil around the uranium mine was used to enhance the efficiency and stability of bioremediation. Furthermore, the bioremediation mechanism was revealed by employing XRD, FTIR, XPS, and 16S rRNA. The results showed that red soil, as a barrier material, had the adsorption potential of 8.21-148.00 mg U/kg soil, but the adsorption is accompanied by the release of certain acidic and oxidative substances. During the dynamic microbial remediation, red soil was used as a cover material to neutralize acidity, provide a higher reduction potential (<-200 mV), and increase the retention rate of microbial agent (19.06 mL/d) compared to the remediation group without red soil. In the presence of red soil, the anaerobic system could maintain the uranium concentration in the solution below 0.3 mg/L for more than 70 days. Moreover, the generation of new clay minerals driven by microorganisms was more conducive to the stability of uranium tailings. Through alcohol and amino acid metabolism of microorganisms, a reducing environment with reduced valence states of multiple elements (such as S2-, Fe2+, and U4+) was formed. At the same time, the relative abundance of functional microbial communities in uranium tailings improved in presence of red soil and Desulfovirobo, Desulfocapsa, Desulfosporosinus, and other active microbial communities reconstructed the anaerobic environment. The study provides a new two-in-one solution for treatment of uranium tailings and resource utilization of red soil through in-situ microbial remediation.

Long-term tracking of the microbiology of uranium-amended water-saturated bentonite microcosms: A mechanistic characterization of U speciation.

Deep geological repositories (DGRs) stand out as one of the optimal options for managing high-level radioactive waste (HLW) such as uranium (U) in the near future. Here, we provide novel insights into microbial behavior in the DGR bentonite barrier, addressing potential worst-case scenarios such as waste leakage (e.g., U) and groundwater infiltration of electron rich donors in the bentonite. After a three-year anaerobic incubation, Illumina sequencing results revealed a bacterial diversity dominated by anaerobic and spore-forming microorganisms mainly from the phylum Firmicutes. Highly U tolerant and viable bacterial isolates from the genera Peribacillus, Bacillus, and some SRB such as Desulfovibrio and Desulfosporosinus, were enriched from U-amended bentonite. The results obtained by XPS and XRD showed that U was present as U(VI) and as U(IV) species. Regarding U(VI), we have identified biogenic U(VI) phosphates, U(UO2)·(PO4)2, located in the inner part of the bacterial cell membranes in addition to U(VI)-adsorbed to clays such as montmorillonite. Biogenic U(IV) species as uraninite may be produced as result of bacterial enzymatic U(VI) reduction. These findings suggest that under electron donor-rich water-saturation conditions, bentonite microbial community can control U speciation, immobilizing it, and thus enhancing future DGR safety if container rupture and waste leakage occurs.

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.

Organophosphorus mineralizing-Streptomyces species underpins uranate immobilization and phosphorus availability in uranium tailings.

Phosphate-solubilizing bacteria (PSB) are important but often overlooked regulators of uranium (U) cycling in soil. However, the impact of PSB on uranate fixation coupled with the decomposition of recalcitrant phosphorus (P) in mining land remains poorly understood. Here, we combined gene amplicon sequencing, metagenome and metatranscriptome sequencing analysis and strain isolation to explore the effects of PSB on the stabilization of uranate and P availability in U mining areas. We found that the content of available phosphorus (AP), carbonate-U and Fe-Mn-U oxides in tailings was significantly (P < 0.05) higher than their adjacent soils. Also, organic phosphate mineralizing (PhoD) bacteria (e.g., Streptomyces) and inorganic phosphate solubilizing (gcd) bacteria (e.g., Rhodococcus) were enriched in tailings and soils, but only organic phosphate mineralizing-bacteria substantially contributed to the AP. Notably, most genes involved in organophosphorus mineralization and uranate resistance were widely present in tailings rather than soil. Comparative genomics analyses supported that organophosphorus mineralizing-Streptomyces species could increase soil AP content and immobilize U(VI) through organophosphorus mineralization (e.g., PhoD, ugpBAEC) and U resistance related genes (e.g., petA). We further demonstrated that the isolated Streptomyces sp. PSBY1 could enhance the U(VI) immobilization mediated by the NADH-dependent ubiquinol-cytochrome c reductase (petA) through decomposing organophosphorous compounds. This study advances our understanding of the roles of PSB in regulating the fixation of uranate and P availability in U tailings.

Role of uranium toxicity and uranium-induced oxidative stress in advancing kidney injury and endothelial inflammation in rats.

OBJECTIVE: Uranium exposure may cause serious pathological injury to the body, which is attributed to oxidative stress and inflammation. However, the pathogenesis of uranium toxicity has not been clarified. Here, we evaluated the level of oxidative stress to determine the relationship between uranium exposure, nephrotoxic oxidative stress, and endothelial inflammation. METHODS: Forty male Sprague-Dawley rats were divided into three experimental groups (U-24h, U-48h, and U-72h) and one control group. The three experimental groups were intraperitoneally injected with 2.0 mg/kg uranyl acetate, and tissue and serum samples were collected after 24, 48, and 72 h, respectively, whereas the control group was intraperitoneally injected with 1.0 ml/kg normal saline and samples were collected after 24 h. Then, we observed changes in the uranium levels and oxidative stress parameters, including the total oxidative state (TOS), total antioxidant state (TAS), and oxidative stress index (OSI) in kidney tissue and serum. We also detected the markers of kidney injury, namely urea (Ure), creatine (Cre), cystatin C (CysC), and neutrophil gelatinase-associated lipocalin (NGAL). The endothelial inflammatory markers, namely C-reactive protein (CRP), lipoprotein phospholipase A2 (Lp-PLA2), and homocysteine (Hcy), were also quantified. Finally, we analyzed the relationship among these parameters. RESULTS: TOS (z = 3.949; P < 0.001), OSI (z = 5.576; P < 0.001), Ure (z = 3.559; P < 0.001), Cre (z = 3.476; P < 0.001), CysC (z = 4.052; P < 0.001), NGAL (z = 3.661; P < 0.001), and CRP (z = 5.286; P < 0.001) gradually increased after uranium exposure, whereas TAS (z = -3.823; P < 0.001), tissue U (z = -2.736; P = 0.001), Hcy (z = -2.794; P = 0.005), and Lp-PLA2 (z = -4.515; P < 0.001) gradually decreased. The serum U level showed a V-shape change (z = -1.655; P = 0.094). The uranium levels in the kidney tissue and serum were positively correlated with TOS (r = 0.440 and 0.424; P = 0.005 and 0.007) and OSI (r = 0.389 and 0.449; P = 0.013 and 0.004); however, serum U levels were negatively correlated with TAS (r = -0.349; P = 0.027). Partial correlation analysis revealed that NGAL was closely correlated to tissue U (rpartial = 0.455; P = 0.003), CysC was closely correlated to serum U (rpartial = 0.501; P = 0.001), and Lp-PLA2 was closely correlated to TOS (rpartial = 0.391; P = 0.014), TAS (rpartial = 0.569; P < 0.001), and OSI (rpartial = -0.494; P = 0.001). Pearson correlation analysis indicated that the Hcy levels were negatively correlated with tissue U (r = -0.344; P = 0.030) and positively correlated with TAS (r = 0.396; P = 0.011). CONCLUSION: The uranium-induced oxidative injury may be mainly reflected in enhanced endothelial inflammation, and the direct chemical toxicity of uranium plays an important role in the process of kidney injury, especially in renal tubular injury. In addition, CysC may be a sensitive marker reflecting the nephrotoxicity of uranium; however, Hcy is not suitable for evaluating short-term endothelial inflammation involving oxidative stress.

Análise de radioelementos, a níveis de traços, utilizando espectrometria de massa de íons secundários / Analysis of radioelements by levels of traits using mass spectrometry of secundary ions

A espectrometria de massa de íons secundários (SIMS) permite a detecção rápida de elementos estáveis ou radioativos, bem como o cálculo de seu percentual isotópico. Ademais, essa técnica possibilita a localização de radioisótipos, à níveis de traços, em amostras biológicas. Neste trabalho procurou-se estudar a utilização dessa metodologia na detecção de urânio natural à baixa concentração. Estudos sobre a preparação de amostras e limites de detecção foram também realizados.