| 1. |
- Liu, Zhenzhong, et al.
(författare)
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Study of natural attenuation after acid in situ leaching of uranium mines using isotope fractionation and geochemical data
- 2023
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 865, s. 161033-
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Tidskriftsartikel (refereegranskat)abstract
- Acid in situ leaching (AISL) is a subsurface mining approach suitable for low-grade ores which does not generate tail-ings, and has been adopted widely in uranium mining. However, this technique causes an extremely high concentra-tion 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), SO42-, delta 34S, and delta 238U, to reveal the main mechanisms governing the migration and atten-uation of the dominant contaminants and the spatio-temporal evolutions of contaminants in the confined aquifer of the post-mining site. The delta 238U values vary from -0.07 %o to 0.09 %o in the post-mining site and from -1.43 %o to 0.03 %o around the post-mining site. The delta 34S values were found to vary from 3.3 %o to 6.2 %o in the post-mining site and from 6.0 %o to 11.0 %o around the post-mining site. Detailed analysis suggests that there are large differences between the range of isotopic composition variation and the range of pollutants concentration distribution, and the es-timated Rayleigh isotope fractionation factor is 0.9994-0.9997 for uranium and 1.0032-1.0061 for sulfur. The isotope ratio of uranium and sulfur can be used to deduce the migration history of the contaminants and the irreversibility of the natural attenuation process in the anoxic confined aquifer. Combining the isotopic fractionation data for U and S with the concentrations of uranium and sulfate improved the accuracy of understanding of reducing conditions along the flow path. The study also indicated that as long as the geological conditions are favorable for redox reactions, natural attenuation could be used as a cost-effective remediation scheme.
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| 2. |
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| 3. |
- Kong, Xiangrui, et al.
(författare)
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Impact of SO2 and light on chemical morphology and hygroscopicity of natural salt aerosols
- 2024
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Ingår i: Atmospheric Environment. - 1352-2310 .- 1873-2844. ; 322
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between SO2 and natural salt aerosol particles represent complex and crucial dynamics within atmospheric processes and the broader climate system. This study investigated the SO2 uptake, hygroscopicity, morphology and mixing states of natural salt particles, which are generated from brines sampled from the Chaka salt lake located in the Qinghai-Tibet plateau. A comparison with atomized pure NaCl particles is included as reference. The results show that NaCl particles exhibit the lowest SO2 uptake, while Chaka salt particles demonstrate higher uptake due to their complex composition. The hygroscopicity of salt particles is influenced by several factors, including chemical complexity, SO2 exposure and light conditions. In comparison to pure NaCl, Chaka salt displays higher hygroscopicity, which is further enhanced in the presence of SO2. However, when exposed to light, mass growth is suppressed, suggesting the formation of species with lower hygroscopicity, such as Na2SO4. Analysis of particle morphology and mixing states reveals notable distinctions between NaCl crystals and Chaka salt particles, where the Chaka salt particles exhibit rounded shapes with a structure composed of cubic NaCl cores surrounded by sulfate materials as a coating. In addition, the chemical morphology analysis also reveals that the particles show morphological and spectral changes before and after the exposure to SO2, light and high RH. Therefore, this research highlights the intricate interactions between SO2 and natural salt aerosol particles in diverse environmental settings, underscoring their multifaceted impacts on atmospheric processes.
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| 4. |
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| 5. |
- Kong, Xiangrui, et al.
(författare)
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Surface solvation of Martian salt analogues at low relative humidities
- 2022
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Ingår i: Environmental Science: Atmospheres. - : Royal Society of Chemistry (RSC). - 2634-3606. ; 2:2, s. 137-145
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Tidskriftsartikel (refereegranskat)abstract
- Salt aerosols play important roles in many processes related to atmospheric chemistry and the climate systems on both Earth and Mars. Complicated and still poorly understood processes occur on the salt surfaces when interacting with water vapor. In this study, ambient pressure X-ray photoelectron spectroscopy (APXPS) is used to characterize the surface chemical environment of Martian salt analogues originating from saline lakes and playas, as well as their responses to varying relative humidities. Generally, APXPS shows similar ionic compositions to those observed by ion chromatography (IC). However, XPS is a surface-sensitive method while IC is bulk-sensitive and differences are observed for species that preferentially partition to the surface or the bulk. Element-selective surface enhancement of Cl− is observed, likely caused by the presence of SO42−. In addition, Mg2+ is concentrated on the surface while Na+ is relatively depleted in the surface layer. Hence, the cations (Na+ and Mg2+) and the anions (Cl− and SO42−) show competitive correlations. At elevated relative humidity (RH), no major spectral changes were observed in the XPS results, except for the growth of an oxygen component originating from condensed H2O. Near-edge X-ray absorption fine structure (NEXAFS) measurements show that the magnesium and sodium spectra are sensitive to the presence of water, and the results imply that the surface is fully solvated already at RH = 5%. The surface solvation is also fully reversible as the RH is reduced. No major differences are observed between sample types and sample locations, indicating that the salts originated from saline lakes commonly have solvated surfaces under the environmental conditions on Earth.
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| 6. |
- Li, Cong, et al.
(författare)
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Emergence of Weyl fermions by ferrimagnetism in a noncentrosymmetric magnetic Weyl semimetal
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Condensed matter physics has often provided a platform for investigating the interplay between particles and fields in cases that have not been observed in high-energy physics. Here, using angle-resolved photoemission spectroscopy, we provide an example of this by visualizing the electronic structure of a noncentrosymmetric magnetic Weyl semimetal candidate NdAlSi in both the paramagnetic and ferrimagnetic states. We observe surface Fermi arcs and bulk Weyl fermion dispersion as well as the emergence of new Weyl fermions in the ferrimagnetic state. Our results establish NdAlSi as a magnetic Weyl semimetal and provide an experimental observation of ferrimagnetic regulation of Weyl fermions in condensed matter.
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| 7. |
- Li, Jun, et al.
(författare)
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Hygroscopicity and Ice Nucleation Properties of Dust/Salt Mixtures Originating from the Source of East Asian Dust Storms
- 2022
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Ingår i: Frontiers in Environmental Science. - : Frontiers Media SA. - 2296-665X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Dust storms are common meteorological events that occur frequently in the late spring and early summer in arid and semi-arid areas. The resulting lofted dust and salt mixtures can impact atmospheric chemistry and climate systems through the many pathways represented by aerosol-cloud-climate interactions. In this study, dust/salt samples were collected from important sources of the East Asian dust storm, including the Badain Jaran Desert, the Tengger Desert and the Ulan Buh Desert in northwestern China. Ion chromatography (IC) measurements were performed to determine the concentrations of cations and anions. The ionic concentrations, pH and dissolvable fractions of sand samples show a positive correlation, indicating that the dissolved content is rich in alkaline ions. A positive matrix factorization (PMF) receptor model was employed to analyze the IC results, and from the PMF solutions non-obvious connections to local geography emerge. The results of hygroscopic experiments of sand samples which were measured by a vapor sorption analyzer indicate that the hygroscopicity may be related to the soluble content of samples, and the observed hygroscopic behavior can be well described by a thermodynamic model. The morphology of individual particles was chemically mapped by the synchrotron-based scanning transmission X-ray microscopy, and needle-shaped CaCO3 particles were observed to adhere to more irregular high K-containing particles. Moreover, a continuous flow diffusion chamber was used to investigate the ice nucleation abilities of typical salts, with both homogeneous freezing and deposition nucleation being observed. The results indicate that the salts primarily act as cloud condensation nuclei but can also act as ice nucleating particles at low temperatures.
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| 8. |
- Liu, Wanyu, et al.
(författare)
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Chemical and Hygroscopic Characterization of Surface Salts in the Qaidam Basin: Implications for Climate Impacts on Planet Earth and Mars
- 2021
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Ingår i: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 5:3, s. 651-662
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Tidskriftsartikel (refereegranskat)abstract
- Salt particles play important roles in many atmospheric processes due to their high hygroscopicity. Saline lakes and playas are sources of salt particles, which are normally mixed with mineral dust that can be transported over long distances. In this study, salt samples collected from four saline lakes and surrounding playas in the Qaidam Basin are studied for their physicochemical properties, focusing on the chemical compositions and hygroscopicity. The salt samples include brines, lakebed salts, crust salts, and crystallized brines. Thermodynamic models are used to explain the precipitating and hygroscopic behaviors based on ionic compositions of dissolved saline solutions. Regarding the ionic compositions, the crystallized brines are similar to the complex mineral compositions of brines, while the natural solid salts, including lakebed salts and crust salts, show very distinct composition differences. The main difference between brines and natural solid salts is the presence of Mg2+ and SO42–, which are primarily found in brines but not in the solid phases. Moreover, all the crust salts are dominated by NaCl regardless of the chemical compositions of the nearby saline lakes. Positive matrix factorization is applied to the ionic concentrations, and the results show that solid salts and brines are governed by different factors. The pH of brines correlates with Mg2+ concentrations and is potentially influenced by ambient CO2 uptake. The hygroscopicity experimental results and thermodynamic model outcomes show that the water uptake of different salt types is controlled by different salt components, that is, crystallized brines are controlled by MgCl2 and natural salts are governed by NaCl and KCl. The characterizations of saline lake and playa salts improve the understandings of the roles that surface salts potentially play in the climate systems of both Planet Earth and Mars.
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| 9. |
- Yue, Siyao, et al.
(författare)
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Brown carbon from biomass burning imposes strong circum-Arctic warming
- 2022
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Ingår i: ONE EARTH. - : Elsevier BV. - 2590-3330 .- 2590-3322. ; 5:3, s. 293-304
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Tidskriftsartikel (refereegranskat)abstract
- Rapid warming in the Arctic has a huge impact on the global environment. Atmospheric brown carbon (BrC) is one of the least understood and uncertain warming agents due to a scarcity of observations. Here, we performed direct observations of atmospheric BrC and quantified its light-absorbing properties during a 2 month circum-Arctic cruise in summer of 2017. Through observation-constrained modeling, we show that BrC, mainly originated from biomass burning in the mid-to high latitudes of the Northern Hemisphere (similar to 60%), can be a strong warming agent in the Arctic region, especially in the summer, with an average radiative forcing of-90 mW m(-2) (similar to 30% relative to black carbon). As climate change is projected to increase the frequency, intensity, and spread of wildfires, we expect BrC to play an increasing role in Arctic warming in the future.
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