| 1. |
- Liu, Zhenzhong, et al.
(författare)
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Geochemical and S isotopic studies of pollutant evolution in groundwater after acid in situ leaching in a uranium mine area in Xinjiang
- 2023
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Ingår i: Nuclear engineering and technology. - : Elsevier BV. - 1738-5733 .- 2234-358X. ; 55:4, s. 1476-1484
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory experiments and point monitoring of reservoir sediments have proven that stable sulfate reduction (SSR) can lower the concentrations of toxic metals and sulfate in acidic groundwater for a long time. Here, we hypothesize that SSR occurred during in situ leaching after uranium mining, which can impact the fate of acid groundwater in an entire region. To test this, we applied a sulfur isotope fractionation method to analyze the mechanism for natural attenuation of contaminated groundwater produced by acid in situ leaching of uranium (Xinjiang, China). The results showed that delta S-34 increased over time after the cessation of uranium mining, and natural attenuation caused considerable, area-scale immobilization of sulfur corresponding to retention levels of 5.3%-48.3% while simultaneously decreasing the concentration of uranium. Isotopic evidence for SSR in the area, together with evidence for changes of pollutant concentrations, suggest that area-scale SSR is most likely also important at other acid mining sites for uranium, where retention of acid groundwater may be strengthened through natural attenuation. To recapitulate, the sulfur isotope fractionation method constitutes a relatively accurate tool for quantification of spatiotemporal trends for groundwater during migration and transformation resulting from acid in situ leaching of uranium in northern China.
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| 2. |
- 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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| 3. |
- Guan, Yanlong, et al.
(författare)
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Elevation Regulates the Response of Climate Heterogeneity to Climate Change
- 2024
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Ingår i: GEOPHYSICAL RESEARCH LETTERS. - 0094-8276 .- 1944-8007. ; 51:12
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Tidskriftsartikel (refereegranskat)abstract
- Climate change represents a profound threat to the diversity and stability of global climate zones. However, the complex interplay between climate change and elevation in shaping climate heterogeneity is not yet fully understood. Here, we combine Shannon's diversity index (SHDI) with the K & ouml;ppen-Geiger climate classification to explore the altitudinal distributions of global climate heterogeneity; and their responses to climate change. The study reveals a distinctive pattern: SHDI, a proxy for climate heterogeneity tends to slow down or decline at lower elevations with increasing temperatures, while at higher elevations, it continues to rise due to continuing cold conditions. Examination of climate simulations, both with and without anthropogenic forcing, confirms that observed changes in climate heterogeneity are primarily attributable to anthropogenic climate change within these high-elevation regions. This study underscores the importance of high-elevation regions as not only custodians of diverse climate types but also potential refuges for species fleeing warmer climates. Climate change is threatening the diversity and stability of global climate patterns. But we're still not completely sure how climate change interacts with elevation to affect climate heterogeneity. In this study, we looked at how climate heterogeneity changes with altitude and responds to climate change. We found that as temperatures rise, the climate diversity tends to decrease at lower elevations, but it increases at higher elevations. We used climate simulations to show that these changes can be attributed to anthropogenic climate change. This study shows that high-elevation regions are important because they can sustain diverse climates and are likely to be a safe haven for plants and animals when climate diversity continues to decline at lower elevations. We employed a high-resolution climate data set to analyze changes in global climate heterogeneity With increasing temperatures, global climate heterogeneity amplifies at higher elevations, while diminishing at lower altitudes Anthropogenic climate change primarily drives alterations in climate heterogeneity at higher elevations
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| 4. |
- Liu, Yi, et al.
(författare)
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Impacts of anemometer changes, site relocations and processing methods on wind speed trends in China
- 2024
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Ingår i: Atmospheric Measurement Techniques. - 1867-1381 .- 1867-8548. ; 17, s. 1123-1131
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Tidskriftsartikel (refereegranskat)abstract
- In situ surface wind observation is a critical meteorological data source for various research fields. However, data quality is affected by factors such as surface friction changes, station relocations and anemometer updates. Previous methods to address discontinuities have been insufficient, and processing methods have not always adhered to World Meteorological Organization (WMO) World Climate Programme guidelines. We analyzed data discontinuity caused by anemometer changes and station relocations in China's daily in situ near-surface (1/410m) wind speed observations and the impact of the processing methods on wind speed trends. By comparing the wind speed discontinuities with the recorded location changes, we identified 90 stations that showed abnormally increasing wind speeds due to relocation. After removing those stations, we followed a standard quality control method recommended by the World Meteorological Organization to improve the data reliability and applied Thiessen polygons to calculate the area-weighted average wind speed. The result shows that China's recent reversal of wind speed was reduced by 41% after removing the problematic stations, with an increasing trend of 0.017ms-1yr-1 (R2Combining double low line0.64, P<0.05), emphasizing the importance of robust quality control and homogenization protocols in wind trend assessments.
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| 5. |
- Piao, Shilong, et al.
(författare)
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Evidence for a weakening relationship between interannual temperature variability and northern vegetation activity.
- 2014
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Satellite-derived Normalized Difference Vegetation Index (NDVI), a proxy of vegetation productivity, is known to be correlated with temperature in northern ecosystems. This relationship, however, may change over time following alternations in other environmental factors. Here we show that above 30°N, the strength of the relationship between the interannual variability of growing season NDVI and temperature (partial correlation coefficient RNDVI-GT) declined substantially between 1982 and 2011. This decrease in RNDVI-GT is mainly observed in temperate and arctic ecosystems, and is also partly reproduced by process-based ecosystem model results. In the temperate ecosystem, the decrease in RNDVI-GT coincides with an increase in drought. In the arctic ecosystem, it may be related to a nonlinear response of photosynthesis to temperature, increase of hot extreme days and shrub expansion over grass-dominated tundra. Our results caution the use of results from interannual time scales to constrain the decadal response of plants to ongoing warming.
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| 6. |
- Shao, Yue, et al.
(författare)
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Scalable Synthesis of Photoluminescent Single-Chain Nanoparticles by Electrostatic-Mediated Intramolecular Crosslinking
- 2022
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 61:27
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Tidskriftsartikel (refereegranskat)abstract
- We report the large-scale synthesis of photoluminescent single-chain nanoparticles (SCNPs) by electrostatic-mediated intramolecular crosslinking in a concentrated solution of 40 mg mL−1 by continuous addition of the free radical initiator. Poly(vinyl benzyl chloride) was charged by quaternization with vinyl-imidazolium for the intramolecular crosslinking by using 2,2-dimethoxy-2-phenylacetophenone (DMAP) as the radical initiator. Under the electrostatic repulsion thus interchain isolation, the intrachain crosslinking experiences the transition from coil through pearl-necklace to globular state. The SCNPs demonstrate strong photoluminescence in the visible range when the non-emissive units are confined thereby. Composition and microstructure of the SCNPs are tunable. The photoluminescent tadpole-like Janus SCNP can be used to selectively illuminate interfacial membranes while stabilizing the emulsions.
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| 7. |
- Wang, Xiaohong, et al.
(författare)
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Effects of tungsten and aluminum additions on the formation of molybdenum disilicide by mechanically-induced self-propagating reaction
- 2010
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 490:1, s. 388-392
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Tidskriftsartikel (refereegranskat)abstract
- The effects of tungsten and aluminum additions to Mo–Si system on the formation of MoSi2 by mechanically-induced self-propagating reaction in a high-energy ball mill were investigated by X-ray diffraction. The incubation time for mechanically-induced self-propagating reaction to form MoSi2 was 90 min in Mo–Si system. With the addition of tungsten to Mo–Si system, the incubation time of mechanically-induced self-propagating reaction of (Wx,Mo1−x)Si2 system was prolonged. It was due to the decrease of adiabatic temperature with increase in x, and the mechanically-induced self-propagating reaction was not observed until 150 min of high-energy milling in (Wx,Mo1−x)Si2 powder sample with x equals to 0.4. Conversely, the minor aluminum (y < 0.2 in Mo(Si1−y,Aly)2 system) substituting for silicon had shorten the incubation period and accelerated the reaction. When tungsten and aluminium were added simultaneously to Mo–Si system, the mechanically-induced self-propagating reaction was observed in (W0.1,Mo0.9)(Si0.9,Al0.1)2 sample, but it was not observed in (W0.2,Mo0.8)(Si0.8,Al0.2)2 and (W0.3,Mo0.7)(Si0.7,Al0.3)2 samples.
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| 8. |
- Wang, Xinchi, et al.
(författare)
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High-Resolution Mapping of Ice Cover Changes in Over 33,000 Lakes Across the North Temperate Zone
- 2021
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Ingår i: Geophysical Research Letters. - 0094-8276. ; 48:18
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Tidskriftsartikel (refereegranskat)abstract
- More than 50% of global lakes periodically freeze, and their lake ice phenology is sensitive to climate change. However, spatially detailed quantification of the changes in lake ice at the global scale is not available. Here, we map ice cover in >33,000 lakes throughout the North Temperate Zone (23.5°–66.5°N) using 0.55 million Landsat images from 1985 to 2020. Over this period, we found a remarkable reduction in median ice cover occurrence (ICO) (61% to 43%), which was strongly related to warming terrestrial mean surface temperatures (R2 = 0.94, p < 0.05). Lakes in Europe showed the most pronounced ice loss (median ICO decreased from 50% to 24%), and extensive lake ice losses were also detected in the northern US, and central and eastern Asia. An overall increase in ice cover was identified from P2 (1999–2006) to P3 (2007–2014) due to regional decreased temperatures associated with the “global warming hiatus.” Thehigh-resolution mapping of lake ice here provides essentialbaseline information whichcan be used to elucidate ice loss-induced environmental and societal impacts.
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