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Strong earthquakes often bring amounts of loose material, disrupting the balance of material transportation within a watershed and severely impacting the restoration of the ecological environment and human safety downstream. Therefore, it is crucial to identify the frequency and scale of these debris flow events, as well as to explore their long-term development and impact on internal and external channels. Using multi-source remote sensing images from four perspectives, hillslope, channel, accumulation fan, and their relationship with the mainstream, we reconstructed a debris flow event dataset from 2008 to 2020, explored a method for identifying these events, and analyzed their impacts on channels and accumulation fans in Mozi Gully affected by the Wenchuan earthquake. Loose matter was predominantly found in areas proximate to the channel and at lower elevations during debris flow events. Alterations in channel width, accumulation fans downstream, and their potential to obstruct rivers proved to be vital for identifying the large scale of debris flow event. Finally, we encapsulated the evolution patterns and constraints of post-earthquake debris flows. Determination in frequency and scale could offer valuable supplementary data for scenario hypothesis parameters in post-earthquake disaster engineering prevention and control.

Phenology is a critical mirror reflecting vegetation growth and has a major impact on terrestrial ecosystems. The Loess Plateau (LP) is a paramount ecological zone in China that has experienced considerable vegetation changes. However, understanding the dynamics of vegetation phenology is limited by ambiguous vegetation interpretation and anthropogenic-induced forces. This study combined the multi-climatic and anthropogenic datasets to characterize the interactions between phenology shifts and environmental variables. The principal findings were as follows: (1) Phenological shifts exhibit spatial heterogeneity and an interannually increasing trend in greenness (R2 > 0.6, p < 0.05). Notably, SOS (the start of the growing season) advances while EOS (the end of the growing season) delays in both the southeastern and northwestern regions. (2) SOS and EOS, primarily in the range of 100–150 and 285–320 days, respectively. Phenological changes vary depending on vegetation types. The forest has an early SOS, within 80–112 days, and a delayed EOS, within 288–320 days. The SOS of shrub is mainly within 80–144 days. (3) EOS shows a strong response to the preseason of each climate variable. Precipitation (R = 0.76), soil moisture (R = −0.64), and temperature (R = 0.89) are the governing determinants in shaping vegetation phenology. In addition, agriculture and urbanization play a significant role in shaping the spatial variations of SOS. These findings provide a basis for a systematic understanding of the processes that affect vegetation growth, which is crucial for maintaining the health and sustainability of arid and semiarid ecosystems.

Study area: The Dawenhe River and Xiaoqinghe River Basins (116°21′–118°41′E, 35°43′–37°15′N) in the center of the North China Plain (NCP), China. Study focus: To quantitatively assess the influence of urbanization (two indicators including Impervious Surface Percentage (ISP) and Average Night Light Index (ANLI)) on baseflow hydrological behavior (nine baseflow signatures), this study selects the typical urbanized catchment (nine sub-catchments) within the central NCP, where the baseflow was estimated from the total daily streamflow from 2006 to 2016. New hydrological insights for the region: Findings show that: (i) Baseflow signatures had a notable spatial variability, in which the magnitude baseflow signatures (Qb10, Qb25, Qb50, Qb90), Baseflow Index (BFI), Concavity Index (CI), and Slope of the baseflow duration curve (SBDC) demonstrated greater values in the north versus the south. (ii) Both ISP and ANLI exhibited an upward trend over time with some fluctuations (R2 > 0.65, p

Abstract To solve the issue of hexavalent chromium (Cr(VI)) contamination in water bodies, blue coke powder (LC) was chemically changed using potassium hydroxide to create the modified material (GLC), which was then used to treat a Cr(VI)-containing wastewater solution. The differences between the modified and unmodified blue coke’s adsorption characteristics for Cr(VI) were studied, and the impact of pH, starting solution concentration, and adsorption period on the GLC's adsorption performance was investigated. The adsorption behavior of the GLC was analyzed using isothermal adsorption models, kinetic models, and adsorption thermodynamic analysis. The mechanism of Cr(VI) adsorption by the GLC was investigated using characterization techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FE-SEM), X-Ray Diffraction (XRD), and X-Ray Photoelectron Spectroscopy (XPS). With the biggest difference in removal rate at pH = 2, which was 2.42 times that of LC, batch adsorption experiments revealed that, under the same adsorption conditions, the GLC always performed better than LC. With a specific surface area that was three times that of LC and an average pore diameter that was 0.67 times that of LC, GLC had a more porous structure than LC. The alteration significantly increased the number of hydroxyls on the surface of GLC by altering the structural makeup of LC. The ideal pH for removing Cr(VI) was 2, and the ideal GLC adsorbent dosage was 2.0 g/L. Pseudo-second-order kinetic (PSO) model and Redlich-Peterson (RP) model can effectively describe the adsorption behavior of GLC for Cr(VI). Physical and chemical adsorption work together to remove Cr(VI) by GLC in a spontaneous, exothermic, and entropy-increasing process, with oxidation–reduction processes playing a key role. GLC is a potent adsorbent that can be used to remove Cr(VI) from aqueous solutions.

This study used the daily temperature and precipitation data from 27 stations in southeast Xizang during 1960-2017 to study the characteristics of climate change in China， by using the linear trend test， Mann-Kendall test， wavelet analysis， and extreme climate index methods.The results demonstrate that： （1） the annual mean， maximum and minimum temperature show obviously rising trends， with the increasing rate of 0.29~0.43 ℃·（10a）-1.The temperature increase in winter is the most obvious.The annual precipitation shows an increasing trend as a whole， with a linear trend of 6.66 mm·（10a）-1， in which it decreases in summer and autumn， and increases in winter and spring.（2） The temperature and precipitation have multi-period changes； and both have a variation period， 28 a， on a large time scale.（3） The times of the abrupt change of average temperature， maximum temperature and minimum temperature were in 1994， 2001 and 1992 respectively， and the precipitation changed from less to more in 1979.（4） The indexes of extreme high temperature， such as TXx， TNn， TNx， TXn， all increase.The frequency indexes of high temperature events， such as TX90p， TN90p， show an increasing trend， while the frequency indexes of low temperature events， such as TX10p， TN10p， show a decreasing trend.The persistence index of high temperature events （WSDI） shows an increasing trend， and the persistence index of low temperature events （CSDI） shows a decreasing trend.（5） Except that the CWD and CDD show a decreasing trend， the other extreme precipitation indexes show an increasing trend.According to the change results of mean and extreme climate， the southeastern Xizang is generally warm and humid， and it is also a sensitive area and an amplifier in Qinghai-Tibet Plateau and even China.

Abstract Snow avalanches can repeatedly occur along the same track under different snowpack and meteorological conditions during the snow season in areas of snow avalanche activity. The snowfall, air temperature, and snow cover can change dramatically in a warming climate, causing significant changes in the snow avalanche risk. But how the risk of snow avalanche activity during the snow season will change under a warming climate remains an open question. Based on the observed meteorological and snowpack data from 1968 to 2021 and the snow avalanche activity data during the 2011–2021 snow seasons along a transportation corridor in the central Tianshan Mountains that has a typical continental snow climate, we analyzed the temporal distribution of the snow avalanche activity and the impacts of climate change on it. The results indicate that the frequency of the snow avalanche activity is characterized by a Gaussian bimodal distribution, resulting from interactions between the snowfall, air temperature, and snowpack evolution. In addition, the active period of wet snow avalanches triggered by temperature surges and high solar radiation has gradually moved forward from the second half to the first half of March with climate warming. The frequency and size of snowfall-triggered snow avalanches showed only a slight and insignificant increase. These findings are important for rationally arranging snow avalanche relief resources to improve the risk management of snow avalanche disasters, and highlight the necessity to immediately design risk mitigation strategies and disaster risk policies to improve our adaptation to climate change.

This study primarily focused on the efficient transformation of low-priced blue coke powder into a high-capacity adsorbent and aimed to address the pollution issue of hexavalent chromium (Cr (VI))-laden wastewater and to facilitate the effective utilization of blue coke powder. A two-step method was utilized to fabricate a blue coke-based nitric acid-modified material (LCN), and the impact of nitric acid modification on the material’s structure and its efficacy in treating Cr (VI)-contaminated wastewater was evaluated. Our experimental results illustrated that, under identical conditions, LCN exhibited superior performance for Cr (VI) treatment compared to the method employing only potassium hydroxide (LCK). The specific surface area and pore volume of LCN were 1.39 and 1.36 times greater than those of LCK, respectively. Further chemical composition analysis revealed that the functional group structure on the LCN surface was more conducive to Cr (VI) adsorption. The highest amount of Cr (VI) that LCN could bind was measured at 181.962 mg/g at 318 K. This was mostly due to chemisorption, which is dominated by redox reactions. The Cr (VI) removal process by LCN was identified to be a spontaneous, exothermic, and entropy-increasing process. Several tests on recycling and reuse showed that LCN is a stable and effective chromium-containing wastewater adsorbent, showing that it could be used in many situations.

The Sichuan–Tibet Railway crosses through the largest maritime glacier region in China. A large number of moraines formed after the rapid glacial retreat caused by climate warming. Moraines could induce frequent geological hazards that seriously threatened the safe construction and operation of the railway. Accordingly, moraines in this maritime glacier region have become a new challenging research topic with respect to the formation of geological hazards. Using remote-sensing image interpretations, field investigations, and dating tests, moraines and their topographic information were systematically obtained. After analyzing the geometrical distribution characteristics of the moraine accumulations, the geometrical characteristics of three typical moraine accumulation forms were generalized into corresponding mathematical models. Consequently, a method to quickly and quantitatively estimate the moraine reserves is proposed. The moraine distribution is primarily affected by the elevation, slope, river–valley morphology, and climate conditions. Old moraines that formed in the Pleistocene epoch (the Guxiang and Baiyu glacial periods) are primarily distributed below 3,500 m above sea level, while most of the new moraines that formed in the Holocene epoch (Neoglaciation and Little Ice Age) are primarily distributed above 4,000 m above sea level. Both the new and old moraines are primarily distributed within a slope range of 10–30°. Furthermore, the main river–valley morphology has a significant impact on the distribution of the old moraines, which are primarily distributed in the Zhongba–Guxiang section of the river valley where the longitudinal slope is relatively gentle. The difference in glaciation is the main reason why the new moraines distributed on the south banks in the study area are different from those on the north banks and why those distributed upstream are different from those distributed downstream. In addition, moraines are the main source of glacial debris flows. According to the presented method, the loose moraine reserves can be accurately calculated by analyzing the position, consolidation, and supply capability of the new and old moraines in each debris flow gully. It is anticipated that the presented results can be used to better understand the formation mechanisms of glacier-related hazards and improve risk assessments.

Earthquakes–induced landslides generally provide abundant loose materials at hillslopes, possibly triggering morphological reshaping processes at river channels and riverbeds during the large flash flood hydrograph and bringing huge risk downstream. Therefore, in a Wenchuan earthquake-affected catchment, the collected hydro-meteorological data and high-precision small Unmanned Aerial Vehicle (sUAV) data were used to quantitatively analyze channel evolution by a large flash flood event on 25 and 26 June 2018. It was found that the stable riverbed structure formed by the armour layer appeared in the tenth year after the Wenchuan earthquake. In a confined channel, the layer can protect the channel and resist the drastic change after the flash flood event with only a small bed elevation from 0.2 m to 2 m. Without the protection of the armour, the change could reach 6 m in the unconfined channel. Meanwhile, more materials with a deposition volume of about 7450 m3 from tributaries were generally taken to the main channel, and more intense erosion with a volume of 105 m3 mostly occurred downstream of tributaries. It was noted that, in the cross-section, the increased channel width could lead to a significant change with the large volume of 35 m3. Additionally, a conceptual diagram of the generalized channel response to large flash floods was provided during multi-stage periods after the Wenchuan earthquake. It determined the rebalance processes of channel evolution in the tenth year after the earthquake. This study will contribute to understanding the post-earthquake long-term channel evolutions and could provide decision-makers of assessing the mitigation strategies for higher-magnitude flood disasters triggered by channel change in earthquake-affected watersheds.

Climate change is a significant force influencing catchment hydrological processes, such as baseflow, i.e., the contribution of delayed pathways to streamflow in drought periods and is associated with catchment drought propagation. The Weihe River Basin is a typical arid and semi-arid catchment on the Loess Plateau in northwest China. Baseflow plays a fundamental role in the provision of water and environmental functions at the catchment scale. However, the baseflow variability in the projected climate change is not well understood. In this study, forcing meteorological data were derived from two climate scenarios (RCP4.5 and RCP8.5) of three representative general circulation models (CSIRO-Mk3-6-0, MIROC5, and FGOALSg2) in CMIP5 and then were used as inputs in the Soil and Water Assessment Tool (SWAT) hydrological model to simulate future streamflow. Finally, a well-revised baseflow separation method was implemented to estimate the baseflow to investigate long-term (historical (1960–2012) and future (2010–2054) periods) baseflow variability patterns. We found (1) that baseflow showed a decreasing trend in some simulations of future climatic conditions but not in all scenarios (p < 0.05), (2) that the contribution of baseflow to streamflow (i.e., baseflow index) amounted to approximately 45%, with a slightly increasing trend (p ≤ 0.001), and (3) an increased frequency of severe hydrological drought events in the future (2041–2053) due to baseflows much lower than current annual averages. This study benefits the scientific management of water resources in regional development and provides references for the semi-arid or water-limited catchments.

Diesel engines are widely used in agricultural tractors. During field operations, the tractors operate at low speed and high load for a long time, the fuel efficiency is only about 15% to 35%, and the exhaust waste heat accounts for 38% to 45% of the energy released from the fuel. The use of tractor exhaust waste heat can effectively reduce fuel consumption and pollutant emissions, of which the organic Rankine cycle (ORC)-based waste heat recovery conversion efficiency is the highest. First, the diesel engine map is achieved through the test rig, a plate-fin evaporator is trial-produced based on the tractor size, and the thermodynamic and economic performance model of the ORC are established. Then, taking the thermal efficiency of ORC and the specific investment cost (SIC) as the objective function, the particle swarm optimization (PSO) algorithm and the technique for order of preference by similarity to ideal solution (TOPSIS) decision method were used to obtain the optimal operating parameter set under all working conditions. Finally, the results showed that the ORC thermal efficiency could reach a maximum of 12.76% and the corresponding SIC value was 8539.66 $/kW; the ORC net output power could be up to 8.31 kW compared with the system without ORC; and the maximum brake specific fuel consumption (BSFC) could be reduced by 8.3%. The improvement in the thermodynamic performance will lead to a sacrifice in economic performance, and at high speeds, the economic benefits and thermal efficiency reach a balance and show a better thermal economic performance. Recovering exhaust heat energy through ORC can reduce tractor fuel consumption and pollution emissions, which is one of the effective technical means to achieve “carbon neutrality” in agricultural production. At the same time, through the PSO algorithm, the optimal combination of ORC operating parameters is obtained, which ensures that the exhaust heat energy can be effectively recovered during the tractor field operation, and provides a basis for the adjustment of real-time work strategies for future research.

The increasing amount of coal gasification fine slag (CGFS) necessitates its resource utilization. CGFS, mainly composed of porous carbonaceous particles and partially fused spherical or agglomerated ash particles, is an inexpensive and high-quality raw material for preparing adsorbent materials. However, the challenge remains in developing a simple, low-cost, and environmentally friendly method to produce high-performance porous materials from CGFS. In this study, a one-step treatment method using 2 mol/L nitric acid under hydrothermal conditions was proposed for CGFS. The adsorbent material (CGFS-2 M) prepared under a solid–liquid ratio of 2:5 and an initial concentration of 200 mg/L methylene blue (MB) exhibited an equilibrium adsorption capacity as high as 210.20 mg/g. The excellent adsorption performance of CGFS-2 M can be attributed to several factors: acid leaching for mineral removal and pore formation, resulting in a specific surface area and total pore volume 2.2 and 1.6 times that of untreated CGFS, respectively, and an optimized mesoporous pore size distribution favorable for MB adsorption; optimal mineral removal and a well-defined carbon microcrystal structure providing more space for MB adsorption; nitric acid treatment increasing the surface oxygen content and hydrophilicity, enhancing its ability to remove MB. The synergistic effect of pore structure improvement and surface modification indicates a feasible research direction for enhancing the performance of CGFS-based adsorbent materials. These results provide theoretical support for the development of efficient CGFS-based adsorbents. [ABSTRACT FROM AUTHOR]

Glacier snouts respond to climate change by forming proglacial meltwater lakes, thereby influencing glacier mass balance and leading to advancements and surges. The positive feedback of climate change results in more frequent ice-dammed glacial lake outburst floods (GLOFs) in the Karakorum and surrounding regions, often facilitated by englacial conduits. However, the complex and multi-factor processes of conduit development are challenging to measure. Determining the lake depths that might trigger GLOFs and the numerical model specifications for breaching are still being determined. Empirical estimates of lake volumes, along with field-based monitoring of lake levels and depths and the assessment of GLOF risks, enable warnings and damage mitigation. Using historical data, remote sensing techniques, high-resolution imagery, cross-correlation feature-tracking, and field-based data, we identified the processes of lake formation, drainage timing, and triggering depth. We developed empirical approaches to determine lake volume and trigger water pressure leading to a GLOF. The correlation of glacier surge and lake volume reveals that glacier surge velocity plays a crucial role in lake formation and controlling the size and volume of the lake. Lake volume estimation involves geometric considerations of the lake basin shape. A GLOF becomes likely when the lake's non-dimensional depth (n') exceeds 0.60, correlating with a typical water pressure on the dam face of 510 kPa. Additionally, we identified the critical risk zone of lakes, where all lake outburst floods occur, as the point where the lake volume reaches or exceeds 60 % of its capacity. These field-based and empirical findings not only offer valuable insights for early warning procedures in the Karakorum but also suggest that similar approaches can be effectively applied to other mountain environments worldwide where GLOFs pose a hazard. [ABSTRACT FROM AUTHOR]