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The Xiangxi UNESCO Global Geopark (XUGG) contained the largest karst red stone forest landscape and the Global Standard Stratotype-section and Points (GSSPs) in the Cambrian System. Those geoheritage contribute to a better understanding of Earth’s evolution. Therefore, it is of great significance to conduct geoscience research and geosciences popularization in the XUGG. In this study, we took the XUGG as the research object, and analyzed the situation of the strengths, weaknesses, opportunities and threats in the development process of geopark popular science tourism by using SWOT analysis method, in order to realize the sustainable development of geoparks in popular science tourism. The results show that: the XUGG continent possesses geoheritage, good facilities and unique advantages of popular science development. In the new era, we should optimize the development of popular science tourism in Geoparks, realize the two-way interactive participation of popular science, explore the community participation model of popular science tourism, and promote the development of rustic areas with unique geological resources. Then, it not only facilitates the broadcasting and popularization of earth sciences, but also contributes to the sustainable development of geotourism.

The Jilinbaolige Pb-Zn-Ag polymetallic deposit is located in the eastern part of Inner Mongolia and in the central-southern part of the Great Xing’an Range, in which several large-sized Pb-Zn-Ag deposits have been found. The Jilinbaolige deposit, which occurs mainly at the contact zone between Yanshanian granite intrusion and sedimentary strata, shows strong NE-to-NNE structural control. The deposit includes three ore-forming stages: (1) the arsenopyrite–pyrite–chalcopyrite–sphalerite stage, (2) the galena–sphalerite–quartz stage, and (3) the pyrite–calcite–quartz stage. In this study, we present a systematic study on the mineralogical and geochemical characteristics (including major elements, S isotopes, and Pb isotopes) of the main sulfide ore minerals in the Jilinbaolige Pb-Zn-Ag deposit in order to evaluate the metallogenic environment, ore-forming material source, and genesis of this polymetallic deposit. The sulfide typomorphic characteristics, ore fabric, and thermometry suggest that the genesis of sulfides in the deposit is closely related to magmatic-hydrothermal activity. The early stage of mineralization might have evolved from a high-temperature hydrothermal environment. The sulfur isotopic results show that the δ34S values in the Jilinbaolige deposit range from 2.3‰ to 6.1‰, with an average value of 3.98‰, indicating that the sulfur originated from magmas with both mantle and crustal components. The Pb isotopic compositions (206Pb/204Pb = 18.214–18.330, 207Pb/204Pb = 15.478–15.615, 208Pb/204Pb = 37.957–38.292, μ = 9.24–9.50, ω = 34.49–36.49) of the sulfide ores suggest that that the lead is of crust-mantle mixed origin. The comparison between the S and Pb isotopic compositions of the Jilinbaolige deposit and the polymetallic deposits from the central-southern parts of the Great Xing’an Range suggests that these deposits have a similar metallogenic source, which is closely related to the Yanshanian granite and medium-temperature hydrothermal fluids. These ore-bearing hydrothermal fluids that evolved from deep magmatic sources migrated along the contact and fracture zones and during the subsequent gradual decrease in temperature, and the metallogenic components were deposited in the relatively open fracture and fissure space. Our results provide insights for further mineral prospecting in the south-central part of the Great Xing’an Range.

Reasonable control of the leaching range is one of the critical indicators of the in-situ leaching uranium mining process. However, there is currently no mature control technology. To verify and improve the current control technology of the leaching range in the industry, this work proposes an injection control mode for a small flow around the well-site and establishes a hydrodynamic model of the leaching range under eight different pumping and injection conditions by using the groundwater modeling system (GMS). The model calculation, range prediction, comparative analysis, and on-site SO42− and S isotope verification tests were carried out. Results show that with the change of liquid injection ratio, the area ratios of fixed pumping injection ratio (total pumping flowrate is greater than 0.3% of the total injection flowrate) and model leaching range under four pumping injection equilibrium conditions were 99.10%, 99.99%, 98.30%, and 97.95%, respectively. The farthest migration distance ratios of the leaching solution were 99.37%, 100%, 98.02%, and 97.58%, respectively. It is considered that the operation mode with a fixed pumping injection ratio has no noticeable control effect on the leaching range; selecting a reasonable proportion to regulate the flowrate of injection wells at different positions can effectively reduce the area of the groundwater flow field and realize the effective control of the leaching range. The research results are conducive to saving a lot of evaporation pool construction, land acquisition, human and material resource investment, and environmental policy pressure.

In the present paper, we focus on studying the bifurcations and the traveling wave solutions (TWSs) for the regularized Schamel equation. Based on the bifurcation method of a dynamical system, a complete phase portrait analysis is given in various parameter conditions and some novel TWSs with the same energy of the Hamiltonian system are discovered. Various significant results on exact expressions of TWSs, including solitary waves, periodic waves, cusp waves, weak kink waves, loop solitons, compactons in different conditions are obtained.

To construct a saliva-based caries risk assessment model, saliva samples from 176 severe early childhood caries (S-ECC) children and 178 healthy (H) children were screened by real-time PCR-based quantification of the selected species, including Streptococcus mutans, Prevotella pallens, Prevotella denticola and Lactobacillus fermentum. Host factors including caries status, dmft indices, age, gender, and geographic origin were assessed in their influence on abundance of the targeted species, which revealed host caries status as the dominant factor, followed by dmft indices (both P S. mutans and P. denticola in the S-ECC group were significantly higher than those in the healthy group (P S. mutans and P P. denticola). Interestingly, the co-occurrence network of these targeted species in the S-ECC group differed from that from the healthy group. Finally, based on the combined change pattern of S. mutans and P. pallens, we constructed an S-ECC diagnosis model with an accuracy of 72%. This saliva-based caries diagnosis model is of potential value for circumstances where sampling dental plague is difficult.

The petrogenesis of A-type granites with different occurrences in the Nanling Range remains unclear. In this study, a case study of the Jiuyishan complex massif and Xianghualing intrusive stocks was conducted to determine this problem. The Jiuyishan complex massif is composed of four units (Jinjiling, Pangxiemu, Shaziling and Xishan). These four units have similar zircon U-Pb ages of approximately 153 Ma, with high Zr + Nb + Ce + Y contents (>350 ppm), high 10,000 Ga/Al ratios (>2.6), and a high crystallization temperature, indicating A-type affinities. They show a gradual change in lithology and geochemistry, implying a fractional crystallization process. These units also have similar εNd(t) values (−8.2 to −5.8) and zircon εHf(t) values (−7.5 to −2.2) except for the Shaziling MMEs (mafic microgranular enclaves) (−14.2 to 4.8), demonstrating their lower crustal source. However, the Shaziling unit may have contributed mantle-derived magma based on the geochemical data of its hosted MMEs. In comparison, the two Xianghualing intrusive stocks have similar geochemical features but exhibit highly evolved features (high Rb, U, Y, Ta and Nb contents and low Eu, Ba, Sr, P, Ti, Ca, Mg and Fe contents, with V-shaped REE distribution patterns). They have different zircon U-Pb ages of approximately 160 Ma and 155 Ma. The two stocks also have similar whole-rock εNd(t) values (−6.5 to −5.7) and zircon εHf(t) values (−7.6 to −2.7) and equally illustrate a lower crustal source region. Combining with their vertical zonation, they may have experienced remarkable fractional crystallization with possible assimilation processes. We propose that the Jiuyishan complex and Xianghualing stocks have two distinct fractional crystallization mechanisms during their formation. The Jiuyishan complex was formed by in situ crystal mush fractionation, while the Xianghualing stocks were formed by flowage differentiation during magma ascent or gravitational settling during magma solidification after emplacement. However, more than one mechanism affected the fractional crystallization processes of these granitic rocks.

Acid in situ leaching (AISL) is a subsurface mining approach suitable for low-grade ores which does not generate tailings, and has been adopted widely in uranium mining. However, this technique causes an extremely high concentration of contaminants at post-mining sites and in the surroundings soon after the mining ceases. As a potential AISL remediation strategy, natural attenuation has not been studied in detail. To address this problem, groundwater collected from 26 wells located within, adjacent, upgradient, and downgradient of a post-mining site were chosen to analyze the fate of U(VI), SO

Uranium resource distribution and accurate reserve evaluation are important references for mineral investment and production. Eight kinds of interpolation methods in the Groundwater Modeling System (GMS), including ordinary kriging (OK), are used in this study to predict the spatial distribution of reserve-related parameters, such as uranium grade, ore thickness and uranium content per square meter. The present study draws the following conclusions: (1) Cross-validation found that the uranium grade value using the spherical method is the closest to the actual value. The spherical method has the best interpolation effect. (2) The relative error, which is +3.62%, between the uranium reserves that is calculated by the spherical interpolation method and that by the traditional calculation value is the smallest. (3) The setting of the number of interpolation grids is related to the actual number of boreholes. The ratio between the two will affect the accuracy of reserve estimation, and different interpolation methods have different degrees of influence on reserve estimation. This method is applicable to all in-situ leaching sandstone uranium mines. Further study needs to be carried out toward heterogeneity of three-dimensional space, which will make the estimation more accurate.

Pore structure characteristics have significant effects on the flow distribution, seepage characteristics, and reaction mechanism of the leachate as well as the uranium leaching efficiency in‐situ leaching (ISL) of uranium. In this study, a series of experiments including mercury injection and uranium leaching were conducted to study the characteristics of the pore structure and their effects on uranium leaching. The following conclusions can be drawn: The distribution of uranium‐bearing sandstone particle size shows the double fractal characteristic, and the particle size can be divided into coarse particles (r > 0.6 mm) and fine particles (r ≤ 0.6 mm). Furthermore, the pore volume and specific surface area of uranium sandstone both have dual fractal features corresponding to an intergranular‐dominant region and intragranular‐dominant region from mercury injection results. Fractures in the uranium‐bearing sandstone may be the main factors that lead to the abnormal fractal dimensions of pore structure. The uranium leaching efficiency of the sandstone increase with the leaching time and reach the maximum value (above 90%) at the 112th hour, and the whole leaching process can be divided into two phases taking the 60th hour as the demarcation point. Through correlation analysis, fractal dimension of the particle size, pore volume, and specific surface area was significantly correlated with the leaching efficiency of uranium at different dissolution phase. Corresponding measures such as adjusting solutions concentration and adding hydrofluoric acid can be taken to avoid the negative effect of pore structure. Those observations can provide a theoretical reference for the optimization of the leaching period and site design parameters of uranium‐bearing sandstone.

Radon in the household water (especially groundwater) which is an important source of indoor radon, has become a potential health hazard to residents. In this study, radon concentrations in groundwater sampled from five villages near Dongpo W-polymetallic metallogenic region were measured using RAD-7 detector with RAD H2O accessory, and the effect of regional geology and mineralization on radon concentration in groundwater was studied. In addition, we also estimated the radiation doses received by people via ingestion of radon in water and inhalation of the radon from the indoor air while using water. The results show that the radon concentration in groundwater samples varies from 1.29 Bq L−1 to 31.31 Bq L−1 with 10.47 Bq L−1 on average, and about 31.3% of the groundwater samples analyzed have a higher radon concentration than the maximum contaminant level of 11.1 Bq L−1 recommended by United States Environmental Protection Agency (USEPA). The relatively high radon level in groundwater can be attributed to a relatively high uranium background produced by the magmatic activity and magmatic-hydrothermal system. The values of annual effective dose (AEDing) due to ingestion of radon in groundwater range from 0.002 mSv y−1 to 0.055 mSv y−1, 0.005 mSv y−1 to 0.11 mSv y−1 and 0.008 mSv y−1 to 0.188 mSv y−1 for adult, child and infant respectively. The values of annual effective dose due to the inhalation of radon released from water are 63.6, 15.4 and 3.8 times of those through the ingestion of radon in groundwater by the adults, children and infants, respectively. In addition, the values of estimated total annual effective doses are 0.020–0.480 mSv y−1, 0.017–0.406 mSv y−1 and 0.020–0.484 mSv y−1 for adult, child and infant, respectively. These values are much lower than the reference dose level of 1 mSv y−1 recommended by World Health Organization (WHO) and United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR).

Early childhood caries (ECC) is one of the most prevalent chronic diseases affecting children worldwide, and thus its etiology, diagnosis, and prognosis are of particular clinical significance. This study aims to test the ability of salivary microbiome and electrolytes in diagnosing ECC, and their interplays within the same population. We here simultaneously profiled salivary microbiome and biochemical components of 331 children (166 caries-free (H group) and 165 caries-active children (C group)) aged 4-6 years. We identified both salivary microbial and biochemical dysbiosis associated with ECC. Remarkably, K+, Cl-, NH4+, Na+, SO42-, Ca2+, Mg2+, and Br- were enriched while pH and NO3- were depleted in ECC. Moreover, the dmft index (ECC severity) positively correlated with Cl-, NH4+, Ca2+, Mg2+, Br-, while negatively with pH and NO3-. Furthermore, machine-learning classification models were constructed based on these biomarkers from saliva microbiota, or electrolytes (and pH). Unexpectedly, the electrolyte-based classifier (AUROC = 0.94) outperformed microbiome-based (AUROC = 0.70) one and the composite-based one (with both microbial and biochemical data; AUC = 0.89) in predicting ECC. Collectively, these findings indicate ECC-associated alterations and interplays in the oral microbiota, electrolytes and pH, underscoring the necessity of developing diagnostic models with predictors from salivary electrolytes.

The microbial composition of dental caries may depend on age, diet, and geography, yet the effect of geography on these microbiomes is largely underexplored. Here, we profiled and compared saliva microbiota from 130 individuals aged 6 to 8 years old, representing both healthy children (H) and children with severe caries (C) from two geographical regions of China: Qingdao Guangzhou. First, the saliva microbiota exhibited profound differences in diversity and composition between the C and H groups. The caries microbiota featured a lower alpha diversity and more variable community structure than the healthy microbiota. Furthermore, the relative abundance of several genera (e.g., Lactobacillus, Gemella and Cryptobacterium) was significantly higher in the C group than in the H group. Next, geography dominated over disease status in shaping salivary microbiota, and a wide array of salivary bacteria was highly predictive of the individuals’ city of origin. Finally, we built a universal diagnostic model based on 14 bacterial species, which can diagnose caries with 87% and 85% accuracy within each city and 83% accuracy across cities. These findings demonstrated that despite the large effect size of geography, a universal model based on salivary microbiota has the potential to diagnose caries across human populations.

In the process of acid in situ leaching of sandstone uranium ore, pyrite, which is a common associated mineral of pitchblende, would inevitably participate in the reaction. Therefore, it is important to study the influence of pyrite on the leaching kinetics of pitchblende. In this study, we compared the difference leaching rates of pitchblende in the systems of sulfuric acid–hydrogen peroxide, sulfuric acid–hydrogen peroxide–pyrite and sulfuric acid–pyrite and studied the influence of temperature and pyrite quantity on the leaching rate of pitchblende. The results show that the leaching process of pitchblende follows the shrinking particle model controlled by a chemical reaction, and the apparent activation energy Ea of the leaching reaction is (3.74 ± 0.40) × 10 kJ/mol. Pyrite itself cannot promote the dissolution of pitchblende; however, it can promote the leaching of pitchblende in the presence of an oxidizer. Increasing the quantity of pyrite in a certain range can increase the leaching rate of pitchblende, and the reaction order of pyrite is 0.36.

Based on the uranium chemical fractions, combined with laboratory experiments and field monitoring data, a prediction model of uranium concentration for in situ leaching pregnant solution was established. It was demonstrated that the kinetics of in situ leaching of uranium is affected by four chemical fractions from exchangeable to oxidizable after the acidification stage, meanwhile the variation of uranium concentration with time displays two trends as high → low and low → high → low, moreover, it is basically consistent with the fourth-order polynomial relationship. The prediction model equation is yi,x= aix4+ bix3+ cix2+ dix + ei, among which the parameters can be obtained by the regression of uranium chemical fractions of ores.

Radon generated in porous media such as soils and rocks migrates into indoor and outdoor air mainly by diffusion, possessing significant hazards to human health. In order to reduce these hazards of radon, it is of great importance to study the diffusion behavior of radon. In this study, we systematically measured the radon diffusion coefficient of laterite with the density ranging from 0.917 g cm−3 to 2.238 g cm−3, and studied the effect of laterite density on the radon diffusion. The results show that the radon diffusion coefficient of the laterite generally decreases with the increasing laterite density. In addition, three possible relationships between the radon diffusion coefficient and the laterite density are found out as follows: (1) the linear correlation with a slope of −4.48 × 10−6 for laterite with density ranging from 0.917 to 1.095 g cm−3, (2) the exponential correlation for laterite with density from 1.095 to 1.63 g cm−3, (3) linear correlation with a slope of −3.1 × 10−7 for laterite with density from 1.63 to 2.238 g cm−3. The complex relationship between the radon diffusion coefficient and density is caused by the change of porosity and tortuosity of the laterite. Therefore, we suggest that a suitable density should be adopted while using the laterite to effectively cover uranium tailings or economically produce building materials that can curb the radon exhalation.

In situ leaching (ISL) uranium mining technology is an in situ mining technology in which the chemical solution is injected into the ore-bearing strata through drilling wells, and the solution moves along the ore bed by controlling the hydraulic gradient of the flow field and reacts with the ore to form uranium-bearing solution. To reduce leaching dead angle in the process of leaching, each pumping and injection unit should achieve uniform leaching at the end of production, and appropriate pumping and injection mode should be adopted for pumping and injection wells of each unit in the mining area. In this paper, on the basis of the actual production data of a sandstone uranium mine, we established the unit flow model of ISL uranium mining area by using GMS software. The unit flow balance of 72 boreholes in the whole mining area was analyzed and optimized through the model. The concept of flow microbalance of pumping and injection unit in the mining area is put forward for the first time, and the calculation equation of supply and receive the flow of pumping and injection well is determined. The calculation and analysis process of flow microbalance of pumping and injection unit in mining area is established. The simulation results showed that the application effect of the model was good, and the correlation coefficient of the solute transport model reached 0.8.

Radon diffusion and transport through different media is a complex process affected by many factors. In this study, the fractal theories and field covering experiments were used to study the fractal characteristics of particle size distribution (PSD) of six kinds of geotechnical materials (e.g., waste rock, sand, laterite, kaolin, mixture of sand and laterite, and mixture of waste rock and laterite) and their effects on radon diffusion. In addition, the radon diffusion coefficient and diffusion length were calculated. Moreover, new formulas for estimating diffusion coefficient and diffusion length functional of fractal dimension d of PSD were proposed. These results demonstrate the following points: (1) the fractal dimension d of the PSD can be used to characterize the property of soils and rocks in the studies of radon diffusion behavior; (2) the diffusion coefficient and diffusion length decrease with increasing fractal dimension of PSD; and (3) the effectiveness of final covers in reducing radon exhalation of uranium tailings impoundments can be evaluated on the basis of the fractal dimension of PSD of materials.

The Jilinbaolige polymetallic deposit, located in the Dong Ujimqin Banner in Inner Mongolia, China, belongs to the Daxinganling and Nangebi-Dongwu Banner polymetallic metallogenic belts. In recent years, many medium to large Ag-Pb-Zn deposits have been discovered, but due to their deep burial and the Quaternary soils cover, mineral exploration is difficult. In order to investigate the relationship among the mineralization, rock body and tectonic structures in the study region, we implemented 5.57 km2 magnetic exploration and four audio-magnetotelluric survey lines with 184 exploration points. Through comprehensive geophysical and geological inference and interpretation, we identified two types of granite which were formed at different stages in the early Yanshanian period, and inferred the NNE F4, NW F5 and NW F6 faults as the ore-conducting and ore-hosting structures of the Ag-Pb-Zn deposits. We determined that the faults' intersections provide the main metallogenic spaces while also locating concealed rock bodies interspersed as small stocks or veins within the upper Devonian Anguinwula formation. Apparently the Ag-Pb-Zn deposits are closely related to subsequently intrusive monzonitic granites of the early Yanshanian period. As confirmed by drilling, many Ag-Pb-Zn ore veins are found at 550–600 m depths and monzonitic granite porphyries at 750 m depth. Our geophysical exploration results reveal the coupling relationship between the concealed rock bodies and metallogenic structures, which can provide direction and effective geophysical methods to prospect for potentially similar deposits in the surrounding area.

The lithospheric mantle beneath the South China Block (SCB) underwent a dramatic transformation from depleted to enriched during late Mesozoic. With a view to deeply understand this process, here we investigate the Mesozoic basalts and their melt inclusions from the Daoxian and Ningyuan regions within the central SCB. The geochemical features of the melt inclusions in these basalts suggest that these rocks originated from the lithospheric mantle enriched through interaction with K-rich aqueous fluids released from subducted Palaeo-Pacific oceanic sediments, whereas the Ningyuan basalts were mainly derived from the asthenospheric mantle source. Geochemical modelling indicates that the Daoxian basalts were generated from 15%-25% of partial melting of garnet lherzolite, whereas the Ningyuan basalts originated from 10%-20% of partial melting of garnet pyroxenites. Our data, combined with those from other Jurassic basalts suggest a temporal evolution of the SCB mantle sources during the Late Mesozoic. Diverse crust–mantle interactions through mixing of the asthenospheric melts with variable proportions of subducted Palaeo-Pacific oceanic sediments might account for the spatial heterogeneity of mantle sources observed beneath the SCB. The transition from Tethyan tectonic realm to the Palaeo-Pacific tectonic regime might have played a significant role in the transformation of the lithospheric mantle beneath the SCB.

Immobilization of U(VI) by naturally ubiquitous ferrous ions (Fe(II)) has been considered as an efficient and ecofriendly method to retard the migration of aqueous U(VI) at many nuclear sites and surface environments. In this study, we conducted Fe-U coprecipitation experiments to investigate the mechanism and stability of uranium (U) precipitation induced by a small quantity of Fe(II) under oxygen-rich conditions. The experimental results suggest that the sedimentation rates of U(VI) by Fe(II) under neutral oxygen-rich conditions are more than 96%, which are about 36% higher than those without Fe(II) and 16% higher than those under oxygen-free conditions. The Fe-U coprecipitates were observed to remain stable under slightly acidic to neutral and oxygen-rich conditions. Fe(II) primarily settles down as low-crystalline iron oxide hydroxide. U(VI) mainly precipitates as three forms: 16–20% of U forms uranyl hydroxide and metaschoepite, which is absorbed on the surface of the solids; 52–56% of U is absorbed as discrete uranyl phases at the internal pores of iron oxide hydroxide; and 27–29% of U is probably incorporated into the FeO(OH) structure as U(V) and U(VI). The U(V) generated via one-electron reduction is somewhat resistant to the oxidation of O2 and the acid dissolution. In addition, nearly 70% of U and only about 15% of Fe could be extracted in 24 h by a hydrochloric acid solution with the H+ concentration ([H+]) of 0.01 M, revealing that U(VI) immobilization by low concentration of Fe(II) combined with O2 has potential applications in the separation and recycling of aqueous uranium.

In order to study the fractal dynamic properties of uranium leach mining and discuss the influence of ore crushing on the dynamics of leach mining, uranium mine ore rocks in southern China were selected as the research object and an acid leaching experiment was performed on the ore samples with different fractal dimensions of 1.1, 1.4, 1.7, 2.0, 2.3 and 2.6. In the column leaching experiment, a PVC pipe with an inner diameter of 112 mm and a height of 1500 mm was used. The uranium content was determined by using titanium trioxide that was placed into a 0.1 mg ml−1 standard uranium solution, and a sampling rate of once daily with a 5 ml volume of leaching solution was adopted after 8 h drenching time. The results show that the flow rate of the leaching solution depends on the distribution of the ore's particle size, that is, a larger fractal dimension results in a smaller flow rate. The concentration of the uranium leaching solution reaches a maximum value which subsequently decreases with time on the third day of the experiment, and it seems that the changes in the uranium concentration tend to be stable at around 15 days. Moreover, the concentration seems to increase with the increasing fractal dimension, and the fractal dimension of the ore particle size has a significant impact on the leaching kinetics. When the fractal dimension is between 1.1 and 2.6, the uranium dissolution rate, K, increases with the increasing fractal dimension. The kinetic reaction of the uranium leaching is a liquid–solid one, which is controlled by chemical reactions in the earlier phase. While the middle reaction phase is mainly chemical-diffusion reaction coupling, and the latter part of the reaction is controlled by diffusion. As the fractal dimension increases, the liquid–solid reaction controlled by diffusion appears at earlier phases. When the fractal dimension is greater than 2.0, with an increase in the fractal dimension, the time of entering the diffusion control phase only changed very little. At last, a fractal dimension of 2.0 is suggested for the acid leaching of uranium ore crushing.

Biosorption is an effective and economic method to treat wastewater containing low concentrations of uranium pollutants. In this study, banyan leaves (BLs) were used as a biosorbent to adsorb uranium ions. The biosorption behavior, thermodynamics, and kinetics of this adsorption process, as well as its mechanism, were investigated. The results indicated that the optimal adsorption effect was achieved when the initial pH was 3.0, the initial uranium concentration was 100 mg L−1, the absorbent dosage was 5 g L−1, and the temperature was chosen to be 293 K. The biosorption rate could be described better by a pseudo-second-order model than a pseudo-first-order model, an Elovich kinetic model, and a double-constant speed kinetic model. The adsorption of uranium(VI) ions proceeded very rapidly in the first 30 min, which subsequently slowed down, and finally reached equilibrium after 50 min. The biosorption isotherm of uranium adsorbed onto BLs could be described better by Freundlich isotherm than Lang...

Tailings produced during mining and milling of uranium ores represent potentially large volumes of low level radioactive materials. A typical environmental problem associated with mill tailings is radon emanation. Covering tailings is widely applied to reduce radon exhalation rate. In this paper, the fractal theories and field covering tests are used to study the fractal characters of size distribution of six types of covering materials, including waste rock, sand, laterite, kaolin, mixture of sand and laterite, and mixture of waste rock and laterite, and their influences on radon exhalation. The size distributions of uranium tailings and the six aforementioned covering materials all exhibit a good fractal structure. The contents of fine grain increase with the increasing value of fractal dimension. The results of field radon measurement show that the radon emanation rate of tailings without covers is 14.7–18.6 Bq/m 2 s. Covering tests were carried out of the six abovementioned covering materials with thickness of 0.4 m, 0.8 m, 1.2 m, 1.6 m and 2.0 m. The results indicate that the application of these materials for cover layers can decrease the radon exhalation rate markedly. The effectiveness of a cover layer in reducing radon exhalation is related to its fractal texture of size distribution. Under the same thickness conditions, the attenuation coefficient of radon exhalation rate increases with the increasing fractal dimension of size distribution of covers. The empirical expressions of the attenuation coefficients in relation to fractal dimension D of size distribution and thickness x of covers is obtained for evaluating the effectiveness of final covers for uranium tailings impoundments.

A fundamental investigation on the removal of uranium from aqueous solutions by wheat straw was conducted in batch conditions. The influence of different experimental parameters such as modified methods, pH, contact time, adsorbent dose, initial concentration, and temperature, on the kinetics of uranium removal was studied. The results showed that the higher adsorption rate of uranium on wheat straw was modified by NaOH. At 303 K and pH was 3.0, the saturation adsorption was up to 1.20 mg/g at approximately 120 min. The uranium uptake was quantitatively evaluated using sorption isotherms and the correlation coefficients showed that the Freundlich model gave a better fit than the Langmuir equation. The process followed a pseudo-second-order kinetics. Scanning electron microscope coupled with Fourier transform infrared analysis for wheat straw, demonstrated that uranium-containing sites existed on the surface structure with hydroxyl, carbonyl, PO and SiO groups. © 2011 American Institute of Chemical Engineers Environ Prog, 2011

Three-dimensional thermoluminescence spectra are measured for different types of geological origin quartz from the Altay orogenic belt, northern Xinjiang, China. The results show striking differences which appear to be characteristic of their geological origin. Granitic quartz is dominated by emission bands at 420–430 nm, 550–560 nm, at a temperature of 170 °C. Pegmatite quartz is characterized by an intense 480 nm emission band at 170 °C. Volcanic quartz has exclusive UV (340–360 nm) and violet (410–430 nm) emission bands. Hydrothermal quartz exhibits very different TL spectral characteristics because of different hydrothermal activity and mineralization. Only one TL peaks at 485 nm/170 °C was observed in sedimentary quartz. An intense 730 nm emission band observed at 170 °C considered generally to be characteristics of feldspar was observed in quartz from granite and hydrothermal Au-bearing quartz. This TL peak is probably related to the centre of [FeO 4 ] 0 on an Si site. All samples show an intense 990–1000 nm emission band at 330 °C. Identical types of quartz formed in different regions or different geological and tectonic settings can also exhibit striking differences in TL spectra.

Microbial reduction of soluble uranyl [U (VI)] to insoluble uraninite by sulfate reducing bacteria (SRB) is a promising remediation strategy for uranium-contaminated groundwater. Effects of environmental factors, including pH and coexisting ions, on U (VI) bioreduction processes (UBP) remain unknown. Anaerobic batch experiments were performed to evaluate impact on UBP. Kinetic investigations with varied pH demonstrated that U (VI) was reduced mostly within 48 h. The bioprecipitation yields depended strongly on pH, increasing from 12.9% to 99.4% at pH 2.0 and 6.0, respectively. Sulfate concentration ⩽4000 mg l−1 did not affect UBP; however, sulfate concentration ⩾5000 mg l−1 significantly slowed UBP. Biogenic H2S produced during sulfate reduction was not directly involved in UBP. At 20 mg l−1 Zn or 10 mg l−1 Cu, no UBP inhibition was observed and uraninite was detected in metal sulfide precipitate. However, 25 mg l−1 Zn or 15 mg l−1 Cu stopped UBP completely. Cu toxicity mechanism probably differed from Zn. The ability to reduce U (VI) was lost permanently with exposure to ⩾15 mg l−1 Cu, but not for Zn ⩾25 mg l−1. No uraninite could be detected before nitrate removal, suggesting nitrate strongly inhibited UBP, which may possibly be related to denitrification intermediates controlling the solution redox potential.

When a reactive fluid flows through a porous rock it can dissolve some minerals and increase the porosity and permeability. The positive feedback between fluid flow and mineral dissolution can lead to the complexity of the propagation of dissolution front and the formation of finger flow-focusing reaction area. As an example for in situ leaching Uranium mining, the simulation results indicate that the propagation of dissolution front is complex such as finger and more complicated reaction front morphologies. The nonlinearity of flow-reaction coupling and instability of dissolution front morphologies can lead to unleaching area and affect the rate of recovery of mineral resource.

A new powerful tool, chaotic theory, has been used to study mineralization through chaotic analysis for space series of gold grade in this paper. Both of the most important chaotic measures, Largest Lyapunov exponent (LLE) and fractal dimensional, for space series of gold grade in one gold deposit are computed. The positive LLE suggests that the space series of gold grade are chaotic series. When the phase space dimension approach 8~10, a chaotic attractor appears and their fractal dimension values vary from 1.94 to 3.99. It indicates that the evolution of ore-forming fluid and the enrichment and deposition of gold element are chaotic dynamic process.

The dissolution experiments of chalcopyrite in 2 mol/L NaCl solutions at 70°C show that the dissolution rate of chalcopyrite oscillates non-periodically with reaction time while in acid solutions (pH = 1.45–2.45) and far from Cu saturation concentration, and Cu concentration oscillates chaotically in solution of weak to intermediate acidity (pH = 3.66–7.0). In nonequilibrium and open systems, the nonlinear coupling between the dissolution of chalcopyrite and formation of cuprous chloride complexes and precipitation of hemitite caused by Cl−, H+ and O2 is the internal mechanism of oscillatory changes of dissolution rate, and the nonlinear coupling between the dissolution of chalcopyrite and precipitation of atacamite induced by Cl− and H+ has caused the chaotic oscillation of Cu concentration. There are consistence and difference between reaction rate oscillation and Cu concentration oscillation. However, both of them suggest that the dissolution of chalcopyrite in NaCl solution is a nonlinear reaction process.

This paper deals with the mechanism of dissolution reaction kinetics of minerals in aqueous solution based on the theory of surface chemistry. Surface chemical catalysis would lead to an obvious decrease in active energy of dissolution reaction of minerals. The dissolution rate of minerals is controlled by surface adsorption, surface exchange reaction and desorption, depending on pH of the solution and is directly proportional to $$a_{H^ + }^{n_\theta } $$ . When controlled by surface adsorption, i.e.,n θ= 1, the dissolution rate will decrease with increasing pH; when controlled by surface exchange reaction, i. e.,n θ= 0, the dissolution rate is independent of pH; when controlled by desorption,n θ is a positive decimal between 0 and 1 in acidic solution and a negative decimal between −1 and 0 in alkaline solution. Dissolution of many minerals is controlled by surface adsorption and/or surface exchange reactions under acid conditions and by desorption under alkaline conditions.