Microbial Induced Calcium Carbonate Precipitation (MICP), recognized as a low-carbon and environmentally sustainable consolidation technique, faces challenges related to inhomogeneous consolidation. To mitigate this issue, this study introduces activated carbon into uranium tailings. The porous structure and adsorption capacity of activated carbon enhance bacterial retention time, increase the solidification rate, and promote the growth and distribution of calcium carbonate, resulting in more uniform consolidation and improved mechanical properties of the tailings. Additionally, a novel independently developed grouting method significantly enhances the mechanical strength of the tailing sand samples. To perform a micro-scale analysis of the samples, distinct activated carbon-tailings DEM models are constructed based on varying activated carbon dosages. Physical experiments and parameter calibration are employed to investigate the micro-mechanical properties, such as velocity field and force chain distribution. Experimental and simulation results demonstrate that incorporating activated carbon increases the calcium carbonate production during the MICP process. As the activated carbon content increases, the peak stress of the tailings initially rises and then declines, reaching its maximum at 1.5 % activated carbon content. At 100 kPa confining pressure, the peak stress is 2976.91 kPa, 1.23-1.59 times that of samples without activated carbon and 6.08-7.86 times that of unconsolidated samples. Micro-scale motion analysis reveals that particle movement is predominantly axial at the ends and radial near the central axis. The initial direction of the primary force chains aligns with the loading direction. Following failure, some primary force chains dissipate, while new chains form, predominantly along the axial direction and secondarily in the horizontal direction. Compared with samples without activated carbon, those containing activated carbon exhibit more uniform force chain distribution, higher stress levels, and greater peak stress. This study offers a novel approach to enhance the stabilization and solidification efficiency of MICP and establishes a DEM model that provides valuable insights into the structural deformation and micro-mechanical characteristics of MICPcemented materials.

Uranium/cadmium (U/Cd) pollution poses a significant global environmental challenge, and phytoremediation offers a sustainable solution for heavy metal contamination. However, the mechanisms by which plants survive U/Cd stress remain unclear. Here, we conducted soil culture experiments of moso bamboo seedlings under U/Cd stress (U, Cd and U + Cd) to examine the effects of it on plant growth, mineral metabolism, and rhizosphere micro-environment. Our findings reveal that U/Cd stress inhibits seedling growth, enhances reactive oxygen species damage, and bolsters the antioxidant system. Additionally, Partial Least Squares Path Modeling (PLS-PM) was employed to uncover potential tolerance mechanisms in moso bamboo under U/Cd stress. U/Cd is mainly distributed in the root cell walls and also exists predominantly in the residual state within the roots. Correspondingly, U and Cd significantly disrupt mineral metabolism in plant. Metabolomic analyses indicate that U/ Cd markedly suppress amino acid metabolism pathways, while they stimulate carbon metabolism to mitigate toxicity. Furthermore, U/Cd stress disrupts the rhizosphere microbial community structure, and the competitive interaction of nitrogen functions exists between rhizosphere microorganism and bamboo roots. PLS-PM reveal the U/Cd stress impacts the interaction of the soil-rhizosphere-plant system. Together, these findings offer new insights into the response mechanism of bamboo plants to heavy metal stress, and provide a theoretical foundation for screening heavy metal tolerant plants and managing mining areas.

When uranium heap leaching tailings (UHLT) are used as filling aggregates, their discontinuous and non-uniform grading characteristics can easily cause segregation, settlement of the filling slurry, and deterioration of cemented body mechanical properties, seriously affecting the safety of the filling system and filling quality. To address the bimodal distribution defects of UHLT, characterized by excessively high proportions of coarse and fine particles with a lack of intermediate particle sizes, this study simulated its particle size characteristics using inert materials such as loess, fine sand, sand, and gravel. The study systematically verified the impact of grading defects on flow stability and mechanical properties. The filling slurry exhibited a spread of 222.5 mm with obvious segregation, and the uniaxial compressive strength at 28 days was 9.09 MPa. To overcome this bottleneck, this research innovatively proposed optimization strategies of qualitative reconstruction (QLR) and quantitative reconstruction (QTR). QLR involves adding medium-sized particles in stages and replacing equal amounts of coarse and fine particles, reducing the spread to 202.7 mm under an optimized quantity of 50 g, with a uniaxial compressive strength of 6.84 MPa at 3 days. However, slurry segregation still occurred. QTR established a multi-particle-size independent calculation model based on the extended Talbot gradation theory, and through the staged quantitative reconstruction of UHLT with aggregate having a grading index of 0.4, the spread decreased to 168.4 mm without segregation, achieving a uniaxial compressive strength of 5.58 MPa at 3 days and 9.11 MPa at 28 days. The study shows that both QLR and QTR can effectively improve the grading of UHLT, with QLR being simple and QTR offering precise control. The research provides new approaches for regulating filling slurries with similar discontinuous and non-uniform graded aggregates, and its innovative methodology can be extended to multiple fields such as concrete aggregate optimization.

The application of uranium (U) in the nuclear energy and defense industry has driven U mining activities, leading to subsequent U contamination. Understanding the toxicity and detoxification mechanism of U in plants is crucial for enhancing the efficiency of phytoremediation efforts in U-contaminated soils. The present study investigated the toxicity of uranium (U) in radish and its impact on physiological and molecular responses. The application of U (5-25 mu M) for 3 days significantly inhibited the elongation of radish lateral roots, and the lateral root length decreased by 35.6%-60.7% compared with the control. Under U stress, radish root tip meristem cells suffered DNA damage, fortunately the cells remained viable. To repair damaged DNA, the expression of genes involved in DNA repair (e.g. RAD2, XPC, BLM) was up-regulated, and the expression of genes involved in cell cycle was down-regulated (e.g. CYCB, CDKB). Under U stress, the expression of respiratory burst oxidase homologs (RBOHs) genes in radish roots up-regulated, which caused ROS burst, and then enhanced autophagy by promoting the expression of autophagy related genes (ATGs). Simultaneously, the glutathione (GSH) content increased, and the gene expression levels and activities of antioxidant enzymes (e.g. catalase) were increased, which enhanced the antioxidant capacity of root cells. Moreover, ubiquitin-proteasome system (UPS) (e.g. E3 ligase genes NEDD4) was involved in the activation of DNA repair, GSH synthesis and autophagy. In summary, DNA repair, autophagy, and antioxidant systems were activated in radish roots, which promoted the survival of apical meristem cells under U stress.

Uranyl ions (UO22+) are the form of uranium usually dissolved in water and are radioactive and can cause serious damage to the environment. Adsorption of uranyl ions is a critical method for removing and safely storing radioactive materials that harm the environment. It is also an important tool for combating water and soil contamination, managing nuclear waste and environmental sustainability. Polymer-based composites were developed for this purpose. Polymer-based composites enable the efficient removal of harmful and radioactive uranium compounds from water and soil. Through the incorporation of polymers and fillers (such as zeolite), materials with specific properties capable of adsorbing uranyl ions with high efficiency can be designed. The ratio of the components constituting the composites can be adjusted to optimize the adsorption capacity, as well as the chemical and thermal behaviors. Two composites were created: P(MA-Z50), consisting of ethylene glycol dimethacrylate (EGDM), methacrylic acid (MA), and zeolite, and P(MA-Z75), which contained a higher amount of zeolite. These composites were synthesized at room temperature and analyzed using various techniques such as Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). The study investigated the effects of adsorbent quantity, adsorbate concentration, temperature, time, and pH on adsorption efficiency and capacity. The Langmuir adsorption isotherm provided the best fit for uranium (VI) adsorption. The results showed that rapid adsorption occurred within the first 100 min, with the rate slowing down until equilibrium was reached after 360 min. The pseudo-second-order kinetic model best described the adsorption process.

Radon-222 is a naturally occurring gas produced by the natural radioactive decay of Uranium, which is present in soil and rock. readily emanates from the soil and passes into the air, where it decays and emits alpha particles and produces a series of short-lived particles (Polonium-218, Polonium-214, and Polonium-210) that also decay by emitting alpha particles. People inhale the short-lived particles, these can cause significant damage to the inner cells of the bronchioles and may also lead to the development of lung cancer. For reasons stated above, it is of utmost importance to measure and evaluate the levels of exposure due to Radon. In this research work, concentration of Radon-222 is determined in 26 workplaces located in basements belonging to 10 buildings in the city of Lima, Peru. the measurements, LR-115 Type 2 detectors are used, which are placed on the walls of the basements under study at three levels, 100 cm and 160 cm high, measured from the floor. The detectors are then recorded and read following the protocol used in the Laboratory of the Nuclear Fingerprint Technique Research Group of the PUCP (GITHUNU-PUCP). The statistical results show that 12 workplaces presented concentration levels greater than 150 Bq/m3, in different measurement periods, and this was due to limitations in ventilation in these environments. In addition, using the Pearson coefficient, it was possible to evaluate the correlation of the concentration of radon-222 relative humidity and temperature, in 20 work environments. Of these, only one environment shows a significant positive linear correlation between concentration and temperature; and only one environment shows a significant negative linear correlation between concentration relative humidity. From this we conclude that meteorological variables of humidity and temperature probably do not significantly influence the concentration of radon-222 in this type of enclosure.

Uranium (U) resources play a crucial role in energy utilization; however, uranium contamination in wastewater and soil has caused severe damage to the ecosystem and human health. Addressing this challenge requires the development of cost-effective and environmentally sustainable remediation materials. This review highlights the environmental merits of biochar-based materials in uranium decontamination, focusing on the diverse applications of modification techniques for enhancing the properties of pristine biochar. By analyzing over 110 relevant studies, the review demonstrates that biochar derived from various biomass sources, with proper modification, could exhibit high adsorption capacities for immobilising uranium in aqueous and soil environments. The primary removal mechanisms identified include physical adsorption and chemical reduction. These works indicate that biochar, produced from green feedstocks and featuring superior reusability, represents a cost-effective, sustainable solution for uranium remediation. Moreover, its application aligns with carbon sequestration and waste valorization, supporting sustainable development goals. Looking ahead, the engineering performance-oriented biochar materials with tailored physicochemical properties hold significant promise for addressing uranium contamination challenges. This review provides a comprehensive evaluation of biochar-based materials as a green alternative for uranium remediation and offers valuable insights into advanced material modification strategies to enhance reactivity and effectiveness.

Despite early hydrological studies of 234U/238U in groundwaters, their utilization as a paleoclimatic proxy in stalagmites has remained sporadic. This study explores uranium isotope ratios in 235 datings (230Th) from six stalagmites in Ejulve cave, northeastern Iberia, covering the last 260 ka. The observed 234U enrichment is attributed to selective leaching of 234U from damaged lattice sites, linked to the number of microfractures in the drip route and wetness frequency, which under certain conditions, may result in the accumulation of 234U recoils. This selective leaching process diminishes with enhanced bedrock dissolution, leading to low S234U. Temperature variations significantly influence bedrock dissolution intensity. During stadial periods and glacial maxima, lower temperatures likely reduced vegetation and respiration rates, thereby decreasing soil CO2 and overall rock dissolution rates. This reduction could enhance the preferential leaching of 234U from bedrock surfaces due to lower bulk rock dissolution. Additionally, the temperature regime during cold periods may have facilitated more frequent freeze-thaw cycles, resulting in microfracturing and exposure of fresh surfaces. Conversely, warmer temperatures increased soil respiration rates and soil CO2, accelerating rock dissolution rates during interstadials and interglacials, when low S 234 U is consistent with high bedrock dissolution rates. The contribution of a number of variables sensitive to bedrock dissolution and wetness frequency processes successfully explains 57% and 74% of the variability observed in the S 234 U in Andromeda stalagmite during MIS 3-4 and MIS 5b-5e, respectively. Among these variables, the growth rate has emerged as crucial to explain S 234 U variability, highlighting the fundamental role of soil respiration and soil CO2 in S 234 U through bedrock dissolution. I-STAL simulations provides the potential for a combination of Prior Calcite Precipitation (PCP) indicators like Mg/Ca with PCP- insensitive indicators of bedrock dissolution such as S234U, along with growth rate data, may be useful to diagnose when PCP variations reflect predominantly changes in drip intervals and when changes in bedrock dissolution intensity contribute. The relationship between stalagmite S234U, bedrock dissolution, and initial dripwater oversaturation suggests two significant advancements in paleoclimate proxies. First, S 234 U could serve as a valuable complement to S13C since it is significantly influenced by soil respiration and soil CO2, thereby reflecting soil and vegetation productivity sensitive to both humidity and temperature. Secondly, since PCP does not fractionate uranium isotopes, S 234 U could be used in combination with Mg/Ca or S44Ca to deconvolve PCP variations due to changing drip rates from those due to changes in initial saturation state. This study emphasizes the overriding climatic control on S234U, regardless of the absolute 234U/238U activity ratios among samples and their proximity or distance from secular equilibrium, and advocates for its application in other cave sites.

Uranium (U) contamination of rice is an urgent ecological and agricultural problem whose effective alleviation is in great demand. Sphingopyxis genus has been shown to remediate heavy metal-contaminated soils. Rare research delves into the mitigation of uranium (U) toxicity to rice by Sphingopyxis genus. In this study, we exposed rice seedlings for 7 days at U concentrations of 0, 10, 20, 40, and 80 mg L- 1 with or without the Sphingopyxis sp. YF1 in the rice nutrient solution. Here, we firstly found YF1 colonized on the root of rice seedlings, significantly mitigated the growth inhibition, and counteracted the chlorophyll content reduction in leaves induced by U. When treated with 1.1 x 107 7 CFU mL- 1 YF1 with the amendment of 10 mg L- 1 U, the decrease of U accumulation in rice seedling roots and shoots was the largest among all treatments; reduced by 39.3% and 32.1%, respectively. This was associated with the redistribution of the U proportions in different organelle parts, leading to the alleviation of the U damage to the morphology and structure of rice root. Interestingly, we found YF1 significantly weakens the expression of antioxidant enzymes genes ( CuZnSOD, CATA, POD ), promotes the up- regulation of metal-transporters genes ( OsHMA3 and OsHMA2) , ) , and reduces the lipid peroxidation damage induced by U in rice seedlings. In summary, YF1 is a plant-probiotic with potential applications for U-contaminated rice, benefiting producers and consumers.

Compacted soil layers effectively prevent the migration of radon gas from uranium tailings impoundments to the nearby environment. However, surface damage caused by wet and dry cycles (WDCs) weakens this phenomenon. In order to study the effect of crack network on radon exhalation under WDCs, a homemade uranium tailing pond model was developed to carry out radon exhalation tests under five WDCs. Based on image processing and morphological methods, the area, length, mean width and fractal dimension of the drying cracks were quantitatively analyzed, and multiple linear regression was used to establish the relationship between the geometric characteristics of the cracks and the radon exhalation rate under multiple WDCs. The results suggested that the radon release rate and crack network of the uranium tailings pond gradually stabilized as the water content decreased, following rapid development in a single WDC process. The radon release rate increased continuously after each cycle, with a cumulative increase of 25.9% over 5 cycles. The radon release rate and average crack width remained consistent in size, and a binary linear regression considering width and fractal dimension could explain the changes in radon release rate after multiple WDCs.