Uranium In Soils Research Articles

Uranium Speciation and Mobilization in Thawing Permafrost.

Uranium is a toxic and pervasive geogenic contaminant often associated with organic matter. Its abundance and speciation in organic-rich permafrost soils are unknown, thereby limiting our ability to assess risks associated with uranium mobilization during permafrost thaw. In this study, we assessed uranium speciation in permafrost soil and porewater liberated during thaw using active-layer and permafrost samples from a study area in Yukon, Canada where elevated uranium concentrations occur in bedrock and groundwater. Permafrost contained 1.1-28 wt % organic carbon and elevated uranium (range 7.6-1040 μg g-1, median 25 μg g-1) relative to local bedrock. The highest soil uranium concentrations were encountered in catchments hosting uranium-enriched bedrock and correlated positively with soil organic carbon. X-ray absorption spectroscopy, micro-X-ray fluorescence, and electron microscopy analyses revealed that solid-phase uranium predominantly occurs as uranium(VI) associated with soil organic matter. Extended X-ray absorption fine structure (EXAFS) analyses suggested the presence of uranium(VI) coordinated with carbon, consistent with bidentate-mononuclear uranyl complexation on carboxyl groups. Permafrost thaw produced circumneutral pH porewater (pH 6.2-7.5) with elevated dissolved uranium (0.5-203 μg L-1). Geochemical modeling indicated that calcium-uranyl-carbonate complexes dominated the dissolved uranium speciation. This study highlights that permafrost soil can mobilize uranium upon thaw and that uranium fate is linked to dynamic biogeochemical reactions involving organic carbon and groundwater chemistry.

Geochemical Distribution of Lanthanum, Thorium, and Uranium in Surface Soils. Case Study: Mitrovica Region, Republic of Kosovo

ABSTRACTThe aim of this study is to investigate the distribution of lanthanum, thorium, and uranium content in soils from the Mitrovica region in the Republic of Kosovo. For this purpose, 156 samples of topsoil (0–5 cm) were considered in a sampling network of 1.4 × 1.4 km2. The soil samples were prepared using the aqua regia digestion method and analyzed using inductively coupled plasma mass spectrometry. The contents of La, Th, and U in the soil of the study area were determined to be 19, 4.8, and 0.84 mg/kg, respectively. The enrichment factor values for La, Th, and U ranged from 3.8 to 7.9, 3.2 to 7.0, and 2.0 to 7.0, respectively, indicating moderate to substantial enrichment. The geo‐accumulation index values of all elements were less than zero, indicating uncontaminated levels. The spatial distribution patterns of La, Th, and U content showed that the values are elevated in the north‐eastern and western parts of the study area, where Miocene latites and quartz latites predominate (average contents of 35, 2.4, and 2.1 mg/kg, respectively). These areas are located in rural areas, suggesting that the high La, Th, and U contents in the soil are related to the lithology of the study area and there is no influence of possible anthropogenic sources. This study contributes to the database of La, Th, and U contents in the soils of the Mitrovica region and allows an assessment of the relationship between geochemistry and ecosystem health.

Target-triggered oxygen vacancy increase of Co3O4 nanoparticles with promoted peroxidase-like activity for specific turn-on colorimetric sensing of uranyl ions

As the most stable form of uranium in water and soil, uranyl ions (UO22+) possess strong biological toxicity and radioactivity, causing a great threat to human health. Therefore, it is of significance to develop reliable methods for monitoring uranyl ions in the environment. Here we propose a “light-up” colorimetric strategy based on target-accelerated peroxidase-mimicking activity of Co3O4 for the specific detection of uranyl ions. Original Co3O4 nanoparticles exhibit a certain peroxidase-like activity in catalyzing colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB with the participation of H2O2. When UO22+ is introduced, it interacts with the nanozyme rapidly and specifically and promotes the latter’s catalytic ability via increasing active oxygen vacancies on Co3O4 surface. According to such a phenomenon and mechanism, selective determination of UO22+ with favorable performance is achieved, with a linear measurement range of 0.2–10 μM and a detection limit of 0.08 μM. Reliability and practicability of the proposed method are demonstrated by analyzing the pollutant in several environmental water matrices. Our work not only offers a novel, efficient yet convenient approach for measuring UO22+, but may also inspire the exploration of new nanozyme-based sensing principles and strategies for other analytical applications.

Adsorption rate of uranium and thorium isotopes in soil and plants grown in a high background radiation area

ABSTRACT An important method for measuring radionuclide activity is alpha spectrometry. Ten soil samples were collected from the studied area. The activity concentrations of 238U and 234U in the collected soil samples ranged between 135 and 218 Bq kg–1 and between 117 and 183 Bq kg–1, respectively. 232Th, 230Th and 228Th activity concentrations ranged between 101 and 339, between 122 and 234 and between 106 and 385 Bq kg–1, respectively. When calculating the amount of radionuclide transport across the food chain, assessment models usually employ a transfer factor. Through root uptake, U and Th are transferred from the soil to food plants. To monitor the movement of radionuclides from the uranium series in diverse environments, it may be possible to use the ratios of uranium and thorium isotopes. Uranium mobility in soil depends on different physicochemical, organic and enzymatic factors and mechanisms. The high mobility of uranium is the main reason for the accumulation of uranium in the soil at root level and the possibility of its transfer to plants. A group of plants were selected that are grown in this area and the population relies on them mainly to meet their food needs. The concentration and transfer factor values of uranium isotopes were the highest in roots as compared with leaves and stems. Uranium in plants accumulates in roots and is then transferred to leaves. The mobility of uranium in plant tissues is constrained because it frequently adsorbs cell wall components. As a result, concentrations are frequently higher in tissues located in lower parts of the plant, with root surfaces having the highest concentrations.

Study on the migration pattern of uranium in soil by Deino-ure, a genetically engineered bacterium of Deinococcus radiodurans

Study on the migration pattern of uranium in soil by Deino-ure, a genetically engineered bacterium of Deinococcus radiodurans

Radon Concentration Level in Selected offices at Bells University of Technology, Ota, Ogun State

Radon, a radioactive gas that emanates naturally from the earth crust is accountable for about 50% of the effective dose of ionizing radiation received by humans. Most radon susceptiveness occurs in homes and work places, it comes from the natural disintegration of uranium in soil, rock and water and escalate to the air that we breath, hence it is important to monitor the actual level of exposure in most buildings. This work analysed the indoor radon concentration in air at twenty different offices of different building at Bells University of Technology using Rad7 detector. The mean measured radon concentration ranges from 0-56.7 Bq/m3 for all the study locations. The mean absorbed dose, equivalent dose and effective dose were calculated with the radon concentration which are 0.152 mGy/y, 3.045 mSv/y and 0.365 mSv/y respectively. The results obtained are below the world set limit as recommended by International Commission on radiological protection, except for office 7 which slightly exceed the recommended limit. Thus, the study concluded that good ventilation is very important in the reduction of radon concentration level in our work places.

Preliminary construction of a microecological evaluation model for uranium-contaminated soil.

With the extensive development of nuclear energy, soil uranium contamination has become an increasingly prominent problem. The development of evaluation systems for various uranium contamination levels and soil microhabitats is critical. In this study, the effects of uranium contamination on the carbon source metabolic capacity and microbial community structure of soil microbial communities were investigated using Biolog microplate technology and high-throughput sequencing, and the responses of soil biochemical properties to uranium were also analyzed. Then, ten key biological indicators as reliable input variables, including arylsulfatase, biomass nitrogen, metabolic entropy, microbial entropy, Simpson, Shannon, McIntosh, Nocardioides, Lysobacter, and Mycoleptodisus, were screened by random forest (RF), Boruta, and grey relational analysis (GRA). The optimal uranium-contaminated soil microbiological evaluation model was obtained by comparing the performance of three evaluation methods: partial least squares regression (PLS), support vector regression (SVR), and improved particle algorithm (IPSO-SVR). Consequently, partial least squares regression (PLS) has a higher R2 (0.932) and a lower RMSE value (0.214) compared to the other. This research provides a new evaluation method to describe the relationship between soil ecological effects and biological indicators under nuclear contamination.

Enhanced adsorption of uranium onto humicacid modified goethite from aqueous solution: An soil environmental perspective

Uranium (U) pollution in soil resulted by human activities is a critical environmental issue. Goethite and humic acid (HA), as predominant soil constituents, significantly influence the migration and transformation of uranium in soil, but effects of combining them together on the sequestration and immobilization of U at different mineralization condition are still rare. To simulate the ability of different combinations of HA and goethite to limit the migration of uranium (VI) in the soil environment, the humic acid-modified goethite (OPHG, TSHG) were synthesized by one-pot and two steps synthesis methods in this study. After modified by HA, the specific surface area of materials increased from 29.67 m2/g to 121.53 m2/g and 39.89 m2/g respectively. The effects of dosage, contact time, pH, initial concentration and temperature on the removal of U(VI) by goethite and modified goethite were investigated. The results showed the maximum difference of them reached 41.59% and 15.69 mg/g for reaction 60 min at pH=4.5. The equilibrium adsorption data fit to the pseudo-second-order kinetics and Langmuir models, and the maximum adsorption capacities increased from 64.63 mg/g to 92.04 mg/g. The analyses results indicated that OPHG remove U(VI) mainly through the formation of ≡FeOUO2OH between Fe−O and uranyl ions, as well as the complexation of carboxyl and hydroxyl groups on HA molecules with uranium to form the HA-Goethite-U(VI) ternary complexes FeOHAUO2. These results are benefited for understanding the effects of HA and goethite on immobilization uranium in soil and would be used to predict and remediate the polluted soil.

Colloids facilitate transport of cadmium and uranium in arable soils, which is undetected by suction cups in the field

AbstractColloids can facilitate the transport of trace elements in soil, but earlier studies fell short either because of sampling artefacts or because no contrasting soils were used; both factors hamper a better understanding of where this occurs. Here, leaching in undisturbed and unsaturated soil columns was observed to identify colloidal transport of cadmium (Cd) and uranium (U) in soils with contrasting properties. Crucially, it was examined how such column data relate to more traditional in situ data obtained with porous suction cups. Soils were collected from three agricultural fields in Switzerland (soil pH 5.1–7.3), leached during 36 days (0.6 pore volumes, ~1.6 mm day−1), and elements trapped in the PTFE suction plates were recovered and were ascribed to colloids. Of the total mobile mass (sum percolate and plate), 18%–53% (Cd) or 8–89% (U) was retained by plates, the range depending on the field where soil was sampled and that fraction depends on soil pH and for U also on dissolved inorganic carbon. The total mobile Cd or U mass divided by the percolated volume indicates the metal concentration in the average leachate and was logically highest for Cd in the most acidic soil and for U in the most alkaline soil. The concentrations of Cd and U in these column leachates were >10‐fold higher than corresponding concentrations in the suction cups in the field for those soils and elements where colloids dominated leaching. In contrast, they were within a factor of two where colloids are <20% of the mobile mass. Flow Field‐Flow Fractionation (FlFFF) analyses showed an association of colloidal U with oxyhydroxides, clays and organic matter and, for colloidal Cd, an association with organic matter. These data show that suction cups or filtered percolates can underestimate the leaching of Cd and U by up to an order of magnitude.

Effects of biochar pyrolysis temperature on uranium immobilization in soil remediation: Revealed by 16S rDNA and metabolomic analyses

Uranium-stressed soil caused by nuclear industry development and energy acquisition have attracted extensive attentions for a long time. This study investigated the effects of biochar application with different pyrolysis temperatures (300 ℃, 500 ℃ and 700 ℃) on remediation of uranium-stressed soil. The results showed that higher pyrolysis temperature (700 ℃) was benefit for ryegrass growing and caused a lower uranium accumulation in plants. At the same time, uranium immobilization was more effective at higher biochar pyrolysis temperature. Careful investigations indicated that activities of soil urease and sucrase were promoted, and bacterial diversity was strengthened in C700 group, which may contribute to uranium immobilization. The biochar application could activate metabolic of lipids and amino acids, organic acids and derivatives, and organic oxygen compounds. Nicotinate and nicotinamide metabolism, and Benzoxazinoid biosynthesis were unique metabolic pathways in the C700 group, which could enhance the uranium tolerance from different perspectives. Based on these results, we recommend to use biochar with 700 °C pyrolysis temperature when processing remediation of uranium-stressed soil. This study will facilitate the implementation of biochar screening and provide theoretical helps for remediation of uranium-stressed soil.

Occurrence and Spatial Distribution of Lead, Arsenic, Cadmium, and Uranium in Soils of Southern Louisiana

Occurrence and Spatial Distribution of Lead, Arsenic, Cadmium, and Uranium in Soils of Southern Louisiana

Uranium bioavailability in soil pore water: A long-term investigation in a contaminated soil mesocosm

Uranium in soil can exist in both (IV) and (VI) oxidation states, distributed among different soil fractions (exchangeable, carbonate, oxidizable, reducible, and residual). Following its release from these fractions, uranium enters the soil pore water, becoming bioavailable and potentially posing risks due to its radio and chemical toxicity. Given the significant health and environmental risks associated with uranium, it is crucial to understand its behaviour in contaminated soil pore water and how it changes over time, especially in response to seasonal variations. To address this issue, study was designed to investigate the temporal changes in uranium availability in soil pore water, with a special focus on effect of seasonal variations and biogeochemical reactions that govern the bioavailability of uranium in a contaminated soil mesocosm. This field investigation was carried out for two consecutive years, and revealed that, seasonal variation has a significant effect on the bioavailability of the uranium in the upper soil layers (<30 cm). The biogenic NO3− induced oxidative dissolution of uranium was found to be the predominant reaction causing the dissolution of uranium into soil pore water, followed by ion-exchange in upper layer, whereas at higher depths (30 cm < d < 70 cm) bioavailability is predominantly controlled by ion-exchange reaction. Furthermore, the study shows that at upper layers bioavailability is high during the summer, which is attributed to higher rate of biogenic denitrification and ion exchange reactions. Fast vertical migration of uranium in the soil column is attributed to formation of stable mobile species such as hydroxo‑carbonato ((UO2)xCO3(OH)y−), hydroxo (UO2)x(OH)y and carbonato (UO2CO3) complexes, identified by speciation modelling. For the first time, this study reports the process controlling uranium behaviour in soil pore water and the effect of seasonal variation on it in a contaminated soil. The findings are essential for assessing its potential radiological impact and remediation planning.

Determination of Uranium in Rock, Soil, and Fruits at Bodal Mines of Rajnandgaon District, Chhattisgarh, Using LED Fluorimetry

Determination of Uranium in Rock, Soil, and Fruits at Bodal Mines of Rajnandgaon District, Chhattisgarh, Using LED Fluorimetry

Existent forms and ecological risk assessment of uranium and heavy metals in soil at a uranium mining area in northern Guangdong, China

Existent forms and ecological risk assessment of uranium and heavy metals in soil at a uranium mining area in northern Guangdong, China

234U/238U disequilibrium and 235U/238U ratios measured using MC-ICP-MS in natural high background radiation area soils to understand the fate of uranium

The Chhatrapur-Gopalpur coastal area in Odisha, India is a well-known natural high background radiation (HBRA) area due to the abundance of monazite (a thorium bearing radioactive mineral) in beach sands and soils. Recent studies on Chhatrapur-Gopalpur HBRA groundwater have reported high concentrations of uranium and its decay products. Therefore, the soils of the Chhatrapur-Gopalpur HBRA are reasonably suspected as the sources of these high uranium concentrations in groundwater. In this report, first the uranium concentrations in soil samples were measured using inductively coupled plasma mass spectrometry (ICP-MS) and they were found to range from 0.61 ± 0.01 to 38.59 ± 0.16 mg kg−１. Next, the 234U/238U and 235U/238U isotope ratios were measured to establish a baseline for the first time in Chhatrapur-Gopalpur HBRA soil. Multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) was used for measurement of these isotope ratios. The 235U/238U ratio was observed to be the normal terrestrial value. The 234U/238U activity ratio, was calculated to understand the secular equilibrium between 234U and 238U in soil and it varied from 0.959 to 1.070. To understand the dynamics of uranium in HBRA soil, physico-chemical characteristics of soil were correlated with uranium isotope ratios and this correlation of 234U/238U activity ratio indicated the leaching of 234U from Odisha HBRA soil.

River water influenced by shale gas wastewater discharge for paddy irrigation has limited effects on soil properties and microbial communities

The processes of hydraulic fracturing to extract shale gas generate a large amount of wastewater, and the potential impacts of wastewater discharge after treatment are concerning. In this field study, we investigated the effects of the irrigation of paddy fields for 2 consecutive years by river water that has been influenced by shale gas wastewater discharge on soil physicochemical properties, microbial community structure and function, and rice grain quality. The results showed that conductivity, chloride and sulfate ions in paddy soils downstream of the outfall showed an accumulative trend after two years of irrigation, but these changes occurred on a small scale (<500 m). Two-year irrigation did not cause the accumulation of trace metals (barium, cadmium, chromium, copper, lead, strontium, zinc, nickel, and uranium) in soil and rice grains. Among all soil parameters, the accumulation of chloride ions was the most pronounced, with concentrations in the paddy soil at the discharge site 13.3 times higher than at the upstream control site. The use of influenced river water for paddy irrigation positively increased the soil microbial diversity, but these changes occurred after two years of irrigation and did not occur after one year of irrigation. Overall, the use of river water affected by shale gas wastewater discharge for agricultural irrigation has limited effects on agroecosystems over a short period. Nevertheless, the possible negative effects of contaminant accumulation in soil and rice caused by longer-term irrigation should be seriously considered.

Numerical reproduction of the seasonal variation in dissolved uranium in Lake Biwa

The seasonal variation in dissolved uranium (DU) concentrations in the epilimnion of Lake Biwa, the largest lake in Japan, was successfully reproduced by geochemical calculations.The DU in Lake Biwa's epilimnion was calculated using an ion-exchange-equilibrium model. The model used the water-DU simple mixing based on monthly observations of water sources (river water, rainwater, evaporation, and groundwater) and thermocline depths from previous studies (Mochizuki et al. (2016)), the adsorbed uranium (AU) on the soil surface based on work by Saito et al. (2021), and the chemical equilibrium of major chemical species such as H, C, and Ca. The total uranium (TU = AU + DU), which determines the peak DU level in summer, and cation-exchange capacity of the soil surface (CECZp), which determines the DU decrease in winter, were optimized by reproducing the DU measurements.The DU value calculated by PHREEQC with the ion-exchange-equilibrium model can be expressed as the sum of three dissolved chemical species (DUeq), which constitute on average 97% of the DU calculated by PHREEQC. DUeq values were decomposed and the contribution of each factor was ranked by comparing their seasonal variabilities. The complexation equilibrium had the greatest variability and was proportional to the reciprocal of the cube of hydrogen ions. This indicates that the seasonal variation in DU is caused mainly by variation in pH.The peak in the DU observations lagged behind the peak in the pH observations by approximately 1 month. However, DUeq did not reproduce this peak delay. Therefore, we assumed that when DU fails to reach the ion-exchange equilibrium concentration and the peak delay occurs, it follows a first-order reaction, and the rate coefficient is determined by the reproducibility of the DU measurements. The DUlim, as the adsorption/desorption rate-limited DU, improved the reproducibility of the DU and the delay after the pH peak. This implies that the delay of the DU peak after the pH peak represents the lag from equilibrium to a first-order rate reaction caused by the soil uranium adsorption/desorption rate.

Gamma-radiation levels outdoors in Great Britain based on K, Th and U geochemical data

Gamma-rays from naturally occurring radionuclides are a major component of background radiation. They are an important tool for geology and are also important for radiation protection. In this paper we use over a quarter of a million geochemical measurements of concentrations of potassium, thorium and uranium in soils and in stream sediments to estimate outdoor gamma-ray dose rates across Great Britain. The soil concentrations are generally at a depth of 5–20 cm with some at 35–50 cm. Soil measurements will give spatially relatively precise estimates, but as soil data are not available for much of Scotland, stream sediment data are used there. Kriging methods are used to estimate surface concentrations of K, Th and U and dose rates are imputed from these concentrations. Our results are compared with measurement surveys of both outdoor and indoor gamma-ray dose rates. Recently there has been interest in exploring the carcinogenic risks of low dose radiation by investigating associations between childhood cancer rates and doses from natural background gamma radiation. To achieve adequate statistical power, such studies must be so large that it is impractical to assess exposures by direct measurements in the homes of study subjects. Instead the exposures must be modelled. The results presented here will be an important input to such work.

Radioecological studies of the main naturally occurring radionuclides in the area of Gela Phosphate Industry (Italy) through radioanalytical separation and measurement techniques

Radioecological studies have been carried out in area of Gela Phosphate Industry. As a part of the project, some achievements have been described in the paper, including: (1) determination of the activity concentrations of 210Po, 210Pb, uranium, and radium isotopes in phosphogypsum, phosphoric acid, soil, and marine sediment, (2) inventory estimation of the NORM in the residual product and by-product, and (3) the radioecological investigation and evaluation on the NORM contamination in the sea area of Gela. The obtained data showed that the 210Po, 210Pb, uranium, and radium isotope contamination due to discharge of phosphogypsum from 1960s to 1990s is not observable through sediment analyses.

A laboratory simulation to investigate effects of moistures on U distribution among solid phase components in army range soils

Uranium is a naturally occurring radioactive trace element found in rocks, soils, and coals. U may contaminate groundwater and soil from nuclear power plant operations, spent fuel reprocessing, high-level waste disposal, ore mining and processing, or manufacturing processes. Yuma Proving Ground in Arizona, USA has been used depleted uranium ballistics for 36 years where U has accumulated in this army testing site. The objective of this study is to develop a laboratory scheme on the effects of soil moisture regiments on the distribution and partitioning of U in army range soil among solid phase components to mimic U biogeochemical processes in the field. Three moisture regiments were saturated paste, field capacity, and wetting-drying cycle which covered major scenarios in fields from the wet summer season to the dry winter season. Uranium in soils with different forms of U (UO2, UO3, uranyl, and schoepite) was fractionated into 8 operationally defined solid components with sequential selective dissolution procedure. The essences of this new development were as following:•A scheme was developed for investigation of U distribution, partitioning and transformation among solid phase components in army weapon test range soils with various U forms under 3 soil moisture regimes.•Soil moisture was one of major environmental factors in controlling biogeochemical processes and fates of U in army weapon test site.