In situ resource utilization of lunar regolith provides a cost-effective way to construct the lunar base. The melting and solidifying of lunar soil, especially under the vacuum environment on the Moon, are the fundamentals to achieve this. In this paper, lunar regolith simulant was melted and solidified at different temperatures under a vacuum, and the solidified samples' morphology, structure, and mechanical properties were studied. The results indicated that the density, compressive strength, and Vickers hardness of the solidified samples increased with increasing melting temperature. Notably, the sample solidified at 1400 degrees C showed excellent nanohardness and thermal conductivity originating from the denser atomic structure. It was also observed that the melt migrated upward along the container wall under the vacuum and formed a coating layer on the substrate caused by the Marangoni effect. The above results proved the feasibility of employing the solidified lunar regolith as a primary building material for lunar base construction.

A novel iron-based phosphate cement (IPC), derived from iron-rich smelting slag (ISS), was developed as a sustainable and efficient binder for the stabilization/solidification of trivalent chromium (Cr3+). The mechanical properties, hydration behavior, microstructure, leaching toxicity, chromium chemical forms, and environmental safety of chromium-stabilized iron phosphate cement (CIPC) were thoroughly evaluated. The results showed that, with a mass ratio of ISS to ammonium dihydrogen phosphate (ADP) of 2.0, and even with the addition of 20 % chromium nitrate nonahydrate (CN), the compressive strength of CIPC reached 4.2 MPa after curing for 28 d. Furthermore, chromium leaching was well below 1 mg/L, significantly lower than the GB 5085.3-2007 standard limit of 15 mg/L, demonstrating the effective encapsulation of Cr3+ due to IPC's high early strength. In the IPC system, Cr3+ was primarily stabilized by forming CrPO4 and CrxFe1-x(OH)3 co-precipitates, which were further solidified through the physical encapsulation of IPC hydration products, such as (NH4)2Fe(PO3OH)2 center dot 4H2O, (NH4) (Mg,Ca)PO4 center dot H2O, and FePO4. This process resulted in a solidification efficiency of up to 99 %. BCR analysis confirmed that more than 98 % of the chromium in the CIPC remained in a stable residual form. Finally, the ecological risk index (PERT) was found to be 23.52, far below the safety threshold of 150, indicating the solidified material's long-term environmental safety. This study provides an innovative approach for the reutilization of ISS while effectively stabilizing/solidifying chromium.

Lakes are commonly accepted as a sensitive indicator of regional climate change, including the Tibetan Plateau (TP). This study took the Ranwu Lake, located in the southeastern TP, as the research object to investigate the relationship between the lake and regional hydroclimatological regimes. The well-known Budyko framework was utilized to explore the relationship and its causes. The results showed air temperature, evapotranspiration and potential evapotranspiration in the Ranwu Lake Basin generally increased, while precipitation, soil moisture, and glacier area decreased. The Budyko space indicated that the basin experienced an obviously drying phase first, and then a slightly wetting phase. An overall increase in lake area appears inconsistent with the drying phase of the basin climate. The inconsistency is attributable to the significant expansion of proglacial lakes due to glacial melting, possibly driven by the Atlantic Multidecadal Oscillation. Our findings should be helpful for understanding the complicated relationships between lakes and climate, and beneficial to water resources management under changing climates, especially in glacier basins.

The construction of a lunar base requires a huge amount of material, which cannot be entirely transported from Earth. Therefore, technologies are needed to build with locally available resources, such as the lunar regolith. One approach is to directly melt the lunar regolith on the surface and under the vacuum condition of the Moon, using laser radiation. In this article, a lunar regolith simulant is laser beam melted to two-dimensional singlelayer-structures using different ambient pressures from 0.05 mbar to 2000 mbar, laser process parameters from 60 W to 100 W laser power, and 1 mm s- 1 to 3 mm s- 1 feed rates. Additionally, the influence of the ambient gas was investigated using argon as an air alternative. The results show that the ambient pressure on the Moon is not negligible when studying the melting processes of lunar regolith on Earth. With decreasing ambient pressure, the appearance of the melted regolith simulant varies from a shiny to a matt surface. At the highest laser energy density, the thickness of a single-layer increases from 2.6 +/- 0.4 mm to 5.3 +/- 0.3 mm and the porosity of the melted regolith increases from 17.2 % to 52.2 % with decreasing ambient pressure. Additionally, mechanical properties are determined using 3-point bending tests. The maximum bending strength decreases by 60 % with the increased ambient pressure from 10 mbar to 2000 mbar. Consequently, the development of in-situ resource utilization technologies, which process the lunar regolith directly on the lunar surface, must consider the ambient pressure on the Moon. Otherwise, the processes will not work as expected from the experiments in Earth-based laboratories.

In order to overcome the obstacles of poor wear resistance and complex preparation process of the traditional tillage soil-engaging parts, this study presents a powder laying-feeding multi-material additive manufacturing method based on selective laser melting (SLM), to fabricate the heterogeneous material tillage parts with 316 L stainless steel (316 L) as the part-body and high entropy alloys (HEAs)-diamond composites as the part-blade. The microstructures including SLM forming quality, interfacial bonding of heterogeneous material, graphitization of diamond and interfacial behavior of diamond/HEAs matrix are systematically investigated. The results indicate that, adopting medium laser energy density 79.4 J/mm(3) of the composites during same-layer deposition, the overlapping area of 316 L/composites exhibits metallurgical bonding with high relative density of the composites section. Only slight graphitization of diamond happens and similar to 2 mu m width diffusion zone forms between diamond and HEAs matrix, without harmful carbide formation. Moreover, compared with commercial 65Mn steel, the wear resistance (wear mass loss rate) and corrosion resistance (corrosion current density) of HEAs-diamond composites have been decreased by 28 times and 230 times, respectively. The hetero-material 316L-composites exhibits good interfacial bonding strength of 432.3 MPa with elongation of 11.2 %. This study not only results in a novel solution of tillage wear-resisting parts, but also provides a multi-material additive manufacturing technology for metallic heterogeneous components.

Antimony smelting activities damage the soil and vegetation surroundings while generating economic value. However, no standardized methods are available to diagnose the extent of soil degradation at antimony smelting sites. This study developed a standardized framework for assessing soil quality by considering microbial-induced resilience and heavy metal contamination at Xikuangshan antimony smelting site. The soil resilience index (SRI) and soil contamination index (SCI) were calculated by Minimum Data Set and geo-accumulation model, respectively. After standardized by a multi-criteria quantitative procedure of modified Nemerow's pollution index (NPI), the integrated assessment of soil quality index (SQI), which is the minimum of SRINPI and SCINPI, was achieved. The results showed that Sb and As were the prominent metal(loid) pollutants, and significant correlations between SQI and SRI indicated that the poor soil quality was mainly caused by the low level of soil resilience. The primary limiting factors of SRI were Fungi in high and middle contaminated areas, and Skermanella in low contaminated area, suggesting that the weak soil resilience was caused by low specific microbial abundances. Microbial regulation and phytoremediation are greatly required to improve the soil quality at antimony smelting sites from the perspectives of pollution control and resilience improvement. This study improves our understanding of ecological effects of antimony smelting sites and provides a theoretical basis for ecological restoration and sustainable development of mining areas. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

In order to explore the frost heave and thaw settlement characteristics of soil layers in the Sanya Estuary Channel Project, the frost heave rate and thaw settlement coefficient of gravel sand, fine sand, silty clay, and clay are obtained. The most unfavorable soil layers are then compared and analyzed. The variation law of frost heave and thaw settlement performance of the most unfavorable soil layer under different water content is studied. The results are as follows: (1) The freezing stage of the passage through the typical soil layer is divided into four stages: frost shrinkage, rapid frost heave, slow frost heave, and frost heave stability. The melting stage is divided into three stages: slow thaw settlement, rapid thaw settlement, and thaw settlement stability. (2) The most unfavorable soil layer in the typical soil layer of the Sanya Estuary Channel Project is silty clay, with a frost heave rate and thaw settlement coefficient of 4.51% and 5.88% at -28 degrees C. (3) The frost heave and thaw settlement performance of the most unfavorable soil layer is linearly related to water content. The larger the water content, the greater the frost heave rate and thaw settlement coefficient, and the more prone to damage.

Copper smelting slag (CSS) are waste slag obtained from smelters after reusing sulphur smelting slag. This study explores the potential of CSS to serve as a resource in cement mortar construction. Specifically, the study investigates the use of mechanical and chemical methods to enhance the volcanic ash activity of CSS, enabling them to replace up to 30 % of the cement content in cement mortar. The modified CSS was analyzed in terms of particle size and (Toxicity Characteristic Leaching Procedure) TCLP testing, while cement mortar specimens were subjected to a battery of tests including compressive strength, Freeze-thaw experiment, TCLP testing and cement stability testing. The results showed that compared with the unmodified CSS material, the copper smelting slag cement material with CaCO3 3 meets the requirements of GB/T 1596-2017 on the standard compressive strength of OPC 42.5 grade, with a compressive strength of 38.88 MPa at 10 % CaCO3 3 admixture, among which the CSS cement material with 10 % CaCO3 3 is the best and meets the leaching toxicity standard. Moreover, the modified CSS reduced energy consumption by 7.15 %, CO2 2 emissions by 27.41 %, and cost by 19.84 %. XRD, FTIR and SEM analysis showed that the mechanical activation of CaCO3 3 doping more drastically damaged the crystal structure of CSS, and local lattice distortion occurred, which induced the transformation of CSS from crystalline phase to amorphous phase and destroyed the ordered structure of minerals, resulting in the volcanic ash activity increased. Overall, this study demonstrates that CSS can serve as a viable raw material in cement mortar samples, reducing environmental impact and achieving resourceful use of slag.

The soil freezing-thawing characteristic curve (FTCC) can reflect the physical and mechanical properties of soil-water system during freezing-thawing (FT) process, which is of guiding significance to the study of soil moisture, heat and matter transport in cold regions. In this study, firstly, according to the evolution law of freezing-thawing hysteresis with freezing-thawing process, revealing the hysteresis mechanisms at different stages based on ice-water transformation theory. The freezing-thawing hysteresis can be divided into four stages as temperature decreasing. The hysteresis of the first three stages are due to nucleation and electrolyte effects, capillarity and pore clogging effects, structural damage effect, respectively; and the last stage is extremely weak and can be ignored. Secondly, evaluating freezing-thawing curves of soil-water system with three pore structures (cylindrical, spherical, and sphere-cylinder binary pore) based on the thermodynamic theory, quantitatively. The upper and lower boundaries of the freezing/thawing characteristic curve with natural pores are those with idealized cylindrical and spherical pores, respectively. Finally, the evaluation index (i.e., hysteresis degree) was introduced to quantitatively describe the variation of unfrozen water hysteresis degree with freezing-thawing process. The relationship between the unfrozen water hysteresis degree and temperature can be divided into four stages. The maximum hysteresis degree was found in the second stage, indicating that hysteresis was most significant in the second stage, followed by the first, third, and fourth stages. Our results provide theoretical support for studying hydrothermal characteristics and water, heat, and solute transport of geotechnical materials in seasonally frozen regions.

To investigate the presence of pressure melting during the compression of frozen gravel soil, we conducted unconfined compression tests and resistance tests on gravel soil samples with varying water (ice) contents and freezing temperatures. The unfrozen water content in saturated gravel soil samples was quantified using nuclear magnetic resonance (NMR) spectroscopy. The results indicate that: (1) During compression, the resistance of gravel soil initially decreased rapidly, subsequently slowing down, with only the dry sample exhibiting an increase in resistance post-peak stress. (2) In the rapid reduction stage, the resistance reduction rate of dry samples was lower compared to saturated frozen samples. Specifically, the resistance reduction rate of - 4 degree celsius saturated samples was 26.8%, which was fourfold that of dry samples at the same temperature. (3) As the freezing temperature decreased, the rate of resistance reduction initially increased and subsequently decreased during the rapid reduction stage. (4) Upon temperature reduction, the relative contents of both free water and capillary water underwent rapid declines, whereas the relative content of adsorbed water initially increased marginally before gradually decreasing. Analysis reveals that the compression of frozen gravel soil elicits a pressure melting effect, resulting in an increase in unfrozen water content within the high-stress regions of the sample during loading. This meltwater subsequently migrates through the unfrozen water film into the pore spaces of low-stress areas, where it re-freezes, altering the pore structure. Notably, the pressure melting effect is most pronounced within the temperature range of -2 degree celsius to -4 degree celsius .