The stable stabilization of uranium (U) in iron (Fe) containing environments is restricted by the reoxidation of UO₂. In the current study, based on air reoxidation tests, we propose a novel two steps accumulation method to enrich microbial consortia from paddy soil. The constructed microbial consortia, denoted as the Fe–U bacteria, can co-precipitate U and Fe to form stable Fe–U solids. Column experiments running for 4 months demonstrated the production of U(IV)–O–Fe(II) precipitates containing maximum of 39.51% uranium in the presence of Fe–U bacteria. The reoxidation experiments revealed the U(IV)–O–Fe(II) precipitates were more stable than UO₂. 16S rDNA high throughput sequencing analysis demonstrated that Acinetobacter and Stenotrophomonas were responsible for Fe and U precipitation, while, Caulobacteraceae and Aminobacter were crucial for the formation of U(VI)-PO₄ chemicals. The proposed two steps accumulation method has an extraordinary application potential in stable immobilization of uranium in iron containing environments.

Uranium, a radionuclide, is a predominant element utilized for speciality requirements in industrial applications, as fuels and catalyst. The radioactive properties and chemical toxicity of uranium causes a major threat to the ecosystem. The hazards associated with Uranium pollution includes the cancer in bones, liver, and lungs. The toxicological properties of Uranium are discussed in detail. Although there are many methods to eliminate those hazards, this research work is aimed to describe the application of bioremediation methods. Bioremediation methods involve elimination of the hazards of uranium, by transforming into low oxidation form using natural microbes and plants. This study deeply elucidates the methods as bioleaching, biosorption, bioreduction and phytoremediation. Bioleaching process involves bio-oxidation of tetravalent uranium when it gets in contact with acidophilic metal bacterial complex to obtain leach liquor. In biosorption, chitin/chitosan derived sorbents act as chelators and binds with uranium by electrostatic attraction. Bio reduction employs a bacterial transformation into enzymes which immobilize and reduce uranium. Phytoremediation includes phytoextraction and phytotranslocation of uranium through xylems from soil to roots and shoots of plants. The highest uranium removal and uptake reported using the different methods are listed as follows: bioleaching (100% uranium recovery), biosorption (167 g kg⁻¹ uranium uptake), bioreduction (98.9% uranium recovery), and phytoremediation (49,639 mg kg⁻¹ uranium uptake). Among all the techniques mentioned above, bioleaching has been proved to be the most efficient for uranium remediation.

The derivation of sediment quality guideline values (SQGVs) presents significant challenges. Arguably the most important challenge is to conduct toxicity tests using contaminated sediments with physico-chemistry that represents real-world scenarios. We used a novel metal spiking method for an experiment that ultimately aims to derive a uranium SQGV. Two pilot studies were conducted to inform the final spiking design, i.e. percolating a uranyl sulfate solution through natural wetland sediments. An initial pilot study that used extended mixing equilibration phases produced hardened sediments not representative of natural sediments. A subsequent percolation method produced sediment with similar texture to natural sediment and was used as the method for spiking the sediments. The range of total recoverable uranium (TR-U) concentrations achieved was 8–3200 mg/kg. This reflected the concentrations found in natural wetlands and water management ponds found on a uranium mine site and was above natural levels. Dilute-acid extractable uranium (AE-U) concentrations were >80% of total concentrations, indicating that much of the uranium in the spiked sediment was labile and potentially bioavailable. The portion of TR-U extractable as AE-U was similar at the start and end of the 4.5-month field-deployment. Porewater uranium (PW–U) analyses indicated that partition coefficients (Kd) were 2000–20,000 L/kg, and PW-U was greater in post- than pre-field-deployed samples when TR-U was ≤1500 mg/kg, indicating the binding became weaker during the field-deployment period. At higher spiked-U concentrations, the PW-U was lower post-field-deployment. Comparing the physico-chemical data of the spiked sediments with environmental monitoring data from sediments in the vicinity of a uranium mining operation indicated that they were representative of sediments contaminated by mining and that the U-spiked sediments had a clear U concentration gradient. This confirmed the suitability of the spiking procedure for preparing sediments that were suitable for deriving a SQGV for uranium.

Uranium (U) contamination often occurs in the topsoil (arable layer), and is a serious threat to crop growth. However, conventional microbial reduction methods are sensitive to oxygen and cannot be used to treat aerobic topsoils. In this study, phosphate-solubilizing microorganisms (PSM) were isolated from U-contaminated topsoil and used for soil remediation. Microbial metabolites and products were analyzed, and the pathways and mechanisms of PSM immobilization were revealed. The results showed that strain PSM8 had the highest phosphate-solubilizing capacity (dissolved P was 208 ± 5 mg/L) and the highest U removal rate (97.3 ± 0.1%). Multi-technical analyses indicated that bacterial surface functional groups adsorbed (UO₂)²⁺ ions on the cell surface, glycolysis produced 3–10 mg/L of lactic acid (pH 4.7–6.0), and lactic acid solubilized Ca₃(PO₄)₂ to form stable chernikovite (a type of uranyl phosphate) on the cell surface. The coupled application of Ca₃(PO₄)₂ and strain PSM8 significantly reduced the bioavailability of soil U (62 ± 11%), converting U from the exchangeable to the residual phase and P from the steady to the available form. In addition, pot experiments showed that soil remediation promoted crop growth and significantly reduced U uptake and toxicity to photosynthetic systems. These findings demonstrate that PSM and Ca₃(PO₄)₂ are good coupled fertilizers for U-contaminated agricultural soil.

Both heavy metals and radiation could affect the proliferation and dissemination of emerging antibiotic resistance pollutants. As an environmental medium rich in radioactive metals, the profile of antibiotic resistance in uranium mine remains largely unknown. A uranium mine in Guangdong province, China was selected to investigate the distribution and influencing factors of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) including intracellular ARGs (iARGs), adsorbed-extracellular ARGs (aeARGs), and free extracellular ARGs (feARGs). The result indicated that sulfonamide and tetracycline ARB could be generally detected in mining area with the absolute concentrations of 7.70 × 10²–5.18 × 10⁵ colony forming unit/g. The abundances of aeARGs in mine soil were significantly higher than those of iARGs (p < 0.05), highlighting the critical contribution of aeARGs to ARGs spread. The feARGs in mine drainage and its receiving river were abundant (3.38 × 10⁴–1.86 × 10⁷ copies/mL). ARB, aeARGs, and iARGs may correlate with nitrogen species and heavy metals (e.g., U and Mn), and feARGs presented a significant correlation with chemical oxygen demand (p < 0.05). These findings demonstrate the occurrence of ARB and ARGs in uranium mine for the first time, thereby contributing to the assessment and control of the ecological risk of antibiotic resistance in radioactive environments.

The adverse health effects associated with the inhalation and ingestion of naturally occurring radon gas produced during the uranium decay chain mean that there is a need to identify high-risk areas. This study detected radon-prone areas using a geographic information system (GIS)-based probabilistic and machine learning methods, including the frequency ratio (FR) model and a convolutional neural network (CNN). Ten influencing factors, namely elevation, slope, the topographic wetness index (TWI), valley depth, fault density, lithology, and the average soil copper (Cu), calcium oxide (Cao), ferric oxide (Fe₂O₃), and lead (Pb) concentrations, were analyzed. In total, 27 rock samples with high activity concentration index values were divided randomly into training and validation datasets (70:30 ratio) to train the models. Areas were categorized as very high, high, moderate, low, and very low radon areas. According to the models, approximately 40% of the study area was classified as very high or high risk. Finally, the radon potential maps were validated using the area under the receiver operating characteristic curve (AUC) analysis. This showed that the CNN algorithm was superior to the FR method; for the former, AUC values of 0.844 and 0.840 were obtained using the training and validation datasets, respectively. However, both algorithms had high predictive power. Slope, lithology, and TWI were the best predictors of radon-affected areas. These results provide new information regarding the spatial distribution of radon, and could inform the development of new residential areas. Radon screening is important to reduce public exposure to high levels of naturally occurring radiation.

Ants can influence ecological processes, such as the transfer of elements or radionuclides, in several ways. For example, they redistribute materials while foraging and maintaining their nests and have an important role in terrestrial food webs. Quantitative data of the transfer of elements into ants is needed, e.g., for developing improved radioecological models. In this study, samples of red wood ants (genus Formica), nest material, litter and soil were collected from a former uranium mining site in Eastern Finland. Concentrations of 33 elements were analyzed by Inductively Coupled Plasma-Mass Spectroscopy/Optical Emission Spectroscopy. Estimated element concentrations in spruce needles were used as a proxy for studying the transfer of elements into ants via aphids because spruces host the most important aphid farms in boreal forests. Empirically determined organism/medium concentration ratios (CRs) are commonly used in radioecological models. Ant/soil CRs were calculated and the validity of the fundamental assumption behind the of use of CRs (linear transfer) was evaluated. Elements that accumulated in ants in comparison to other compartments were cadmium, potassium, phosphorus, sulfur, and zinc. Ant uranium concentrations were low in comparison to soil, litter, or nest material but slightly elevated in comparison to spruce needles. Ant element concentrations were quite constant regardless of the soil concentrations. Non-linear transfer models could therefore describe the soil-to-ant transfer better than conventional CRs.

Groundwater samples from Kapurthala (45), Jalandhar (70), and Hoshiarpur (70) districts from northern Punjab, India, were studied for seasonal variation (pre-monsoon and post-monsoon) of uranium distribution and physicochemical parameters, quality and suitability for drinking purposes, source apportionment, and health risks. The average uranium concentration (in μg L⁻¹) in Kapurthala, Jalandhar, and Hoshiarpur districts was 12.7, 18.8, and 7.0, respectively, in pre-monsoon and 8.0, 17.3, and 5.6, respectively, in post-monsoon. In both seasons, uranium concentration was below WHO limit (30 μg L⁻¹) in more than 90% of groundwater samples, and it was found to exhibit positive correlation majorly with TDS, EC, and total alkalinity. Principal component analysis revealed dissolution of rocks/minerals contributing to mineralization of associated aquifers in addition to some anthropogenic activities such as excessive application of fertilizers/pesticides and dumping of domestic waste followed by their seepage into the groundwater table. All groundwater samples fall in very good to good drinking groundwater quality and its quality is more improved in post-monsoon season owing to dilution of various inorganic salts during groundwater recharge in monsoon season. Average Hazard Index (HI) values due to ingestion of U, F⁻, and NO₃⁻ via drinking water for both adults and children were found to be marginally greater than safe limit of 1 with major contribution from F⁻. It is advisable to local government/public that regular monitoring of groundwater and proper management policies or strategies should be adopted followed by their implementation to control groundwater pollution in three districts.

Uranium tailing ponds are a potential major source of radioactive pollution. Solidification treatment can control the diffusion and migration of radioactive elements in uranium tailings to safeguard the surrounding ecological environment. A literature review and field investigation were conducted in this study prior to fabricating 11 solidified uranium tailing samples with different proportions of PVA fiber, basalt fiber, metakaolin, and fly ash, and the weight percentage of uranium tailings in the solidified body is 61.11%. The pore structure, volume resistivity, compressive strength, radon exhalation rate variations, and U(VI) leaching performance of the samples were analyzed. The pore size of the solidified samples is mainly between 1 and 50 nm, the pore volume is between 2.461 and 5.852 × 10⁻² cm³/g, the volume resistivity is between 1020.00 and 1937.33 Ω·m, and the compressive strength is between 20.61 and 36.91 MPa. The radon exhalation rate is between 0.0397 and 0.0853 Bq·m⁻²·s⁻¹. The cumulative leaching fraction of U(VI) is between 2.095 and 2.869 × 10⁻² cm, and the uranium immobilization rate is between 83.46 and 85.97%. Based on a comprehensive analysis of the physical and mechanical properties, radon exhalation rates, and U(VI) leaching performance of the solidified samples, the basalt fiber is found to outperform PVA fiber overall. The solidification effect is optimal when 0.6% basalt fiber is added.

Associations between environmental metals and chemicals and adverse human health effects have emerged recently, but the links among environmental metals and respiratory diseases are less studied. The aim of this study was to assess 14 urinary metals (cadmium, barium, cobalt, molybdenum, mercury, cesium, manganese, antimony, lead, tin, strontium, tungsten, thallium, and uranium), seven species of arsenic (arsenous acid, arsenic acid, arsenobetaine, arsenocholine, dimethylarsinic acid, monomethylarsonic acid, and total arsenic) and seven polycyclic aromatic hydrocarbon (PAH) (1-hydroxynaphthalene, 2-hydroxynaphthalene, 3-hydroxyfluorene, 2-hydroxyfluorene, 1-hydroxyphenanthrene, 1-hydroxypyrene, 2 & 3-hydroxyphenanthrene) compounds’ concentrations in urine and the correlation with chronic obstructive pulmonary disease (COPD) in the adult US population. A cross-sectional analysis using the 2013–2014 and 2015–2016 National Health and Nutrition Examination Survey (NHANES) dataset was conducted. Self-questionnaires related to COPD criteria were used to identify the COPD cases. The correlation between urinary metals and PAH compounds and COPD was calculated. The total study population analyzed included 2885 adults aged 20 years and older. Seven types of urinary PAHs including 1-hydroxynaphthalene [odds ratio (OR): 1.832, 95% confidence interval (CI): 1.210, 2.775], 2-hydroxynaphthalene [OR: 3.361, 95% CI: 1.519, 7.440], 3-hydroxyfluorene [OR: 2.641, 95% CI: 1.381, 5.053], 2-hydroxyfluorene [OR: 3.628, 95% CI: 1.754, 7.506], 1-hydroxyphenanthrene [OR: 2.864, 95% CI: 1.307, 6.277], 1-hydroxypyrene [OR: 4.949, 95% CI: 2.540, 9.643] and 2 & 3-hydroxyphenanthrene [OR: 3.487, 95% CI: 1.382, 8.795] were positively associated with COPD. Urinary cadmium [OR: 12.382, 95% CI: 4.459, 34.383] and tin [OR: 1.743, 95% CI: 1.189, 2.555] showed positive associations with increased odds of COPD. The other types of urinary metals were not associated with COPD. The study observed that urinary PAHs, cadmium, and tin are significantly associated with COPD.