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On 27 January 2021, at 21:00 (UTC + 8), a shallow loess landslide occurred in Heifangtai, Yongjing County, Gansu Province, northwest of the Chinese Loess Plateau. Fortunately, the independently developed global navigation satellite system predicted the landslide 7 h in advance. Although farmland and channels were buried and destroyed, no damage has been done to the lives and houses of residents. In order to explore the triggering factors and movement process of the landslide, based on the field investigation, we collected the precipitation and temperature data more than 1 year before the landslide and comprehensively used UAV photogrammetry, numerical simulation, and laboratory test for comprehensive research. It was found that as the temperature rose and freeze–thaw cycles, changes in mechanical properties of loess and unique stratum structure were the main factors triggering the landslide. The rise in temperature led to an increase in groundwater levels, and the strength of soil decreased gradually until shear liquefaction occurred. This landslide caused a substantial topographic change, which provided conditions for slope instability in the future. The process of landslide movement can be divided into three stages: start-up stage, severe sliding stage, and deceleration stage. Simulation results show that the maximum velocity was 22 m/s, and the maximum sliding distance was 393 m. The main movement period was 40 s, and the apparent friction angle was 5°. Finally, this study provides a reliable basis for studying the dynamic process and failure mechanism of loess landslides.

Internal erosion is a complex phenomenon that is one of the main risk factors to soil destruction. Its occurrence is mainly due to water infiltration and can cause slope instability. “Karst soil” is a type of loess with special soil and water sensitivity that makes it prone to landsliding. The processes of internal erosion include transport erosion and chemical dissolution, which strongly effect loess structure and strength. To reveal the internal processes and effects of the loess due to water infiltration, field investigations and indoor tests, including infiltration tests, undrained triaxial tests, particle analysis, chemical analysis, and scanning electron microscopy (SEM), were conducted. The results show that (1) the fine particles (clay and silt) and chemicals can move within the matrix of the macro-pores under seepage flow. The physical internal erosion is mainly due to fine particle migration out of the water and clay and silt particles, and the sample column settlement was 3.3 cm with a settlement ratio of 16.5%, which results in changes to the soil skeleton, increasing the porosity and infiltration rate of loess. (2) Chemical dissolution is also an important internal erosion process in loess, especially cations of Na, Mg, Ca, and K and anions of Cl, SO4, and CO3, which are mainly lost due to dissolution and flow out of with water and clay particles, resulting in altered physical characteristics of the soil. (3) Soil particles’ mitigation and chemical dissolution change the loess structure, leading to skeletal destruction and decreased peak strength and residual strength of the infiltrated sample to 7.75% and 8.13%, respectively. During internal erosion, physical fine particle migration and chemical dissolution are important for loess stability and loess slope susceptible to failure during water infiltration.

Ferrocene-based metal-organic framework with different transition metals (M-Fc-MOFs, M=Fe, Mn, Co) were synthesized by a simple hydrothermal method and used as a heterogeneous catalyst for persulfate activation. The samples were characterized by X-ray diffraction, transmission electron microscopy, X-ray electron spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Meanwhile, the influences of factors such as catalyst dosage, persulfate concentration and pH on the degradation of acid orange 7 (AO7) were studied in detail. The results showed that hollow cobalt-based ferrocenyl metal-organic framework microspheres (Co-Fc-MOFs) exhibited the best catalytic performance, which is closely related to the synergy of Fc/Fc+ and Co2+/Co3+ cycles in persulfate activation. Free radical quenching studies indicated that both sulfate and hydroxyl appeared to contribute to the degradation of AO7.

Ferrocene-based metal-organic framework with different transition metals (M-Fc-MOFs, M = Fe, Mn, Co) was synthesized by a simple hydrothermal method and used as a heterogeneous catalyst for persulfate activation. The samples were characterized by X-ray diffraction, transmission electron microscopy, X-ray electron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Meanwhile, the influences of factors such as catalyst dosage, persulfate concentration, and pH on the degradation of acid orange 7 (AO7) were studied in detail. The results showed that hollow cobalt-based ferrocenyl metal-organic framework microspheres (Co-Fc-MOFs) exhibited the best catalytic performance, which is closely related to the synergy of Fc/Fc

In this study, 14,544 loess landslides collected from the Loess Plateau of China are used to reveal their distribution and origins. Main factors considered include landslide density, regional tectonics, soil properties, geomorphic structure, rainfall distribution, seismic activity, and human activity. Based on these factors, the Loess Plateau is divided into eight zones with high possibilities of landslides that are classified into six genetic types. The first genetic type of clustering distribution of loess landslides is related to several main regional active faults. The second type is related to broken pieces of loess geomorphic structures. The third type is considered to be due to unloading of the geomorphic peripheral slope that can cause the internal structural plane to open and thus controls the prototype and scale of the loess landslide. Change of hydrogeological conditions in the slope softens the loess pedestal and the slippery layer, forming a softening zone and thus controlling the shear crack and slip model of the fourth type of loess landslides. The fifth type is due to seismic activities that can generate additional stress to the Earth's surface and landform slopes, causing the opening of joints and seismic liquefaction. The last type of landslides is caused by human activities by changing the geological structure, hydrogeological conditions, and the inner stress balance of slopes.

Gully Stabilization and Highland Protection (GSHP) techniques are useful in preventing gully erosion and have been widely utilized in the Loess Plateau. Rolling backfill is used to fill ditches in remolded loess, which is an important part of gully stabilization and highland protection, but destroys the original loess structure and changes the circulation of groundwater and surface water leading to a rise in groundwater. Groundwater rising is an important factor for filled loess slope instability and can induce landslides. A test device was designed to study the process of water infiltration into the filled project and the failure process of the filled loess slope due to groundwater rising. First, the groundwater was uniformly infiltrated with water, then preferential seepage with the deformation and cracks appeared in the slope. The pore-water pressure response to the groundwater infiltration and the pore-water pressure in the front of the slope body sharply increased, especially near the sliding surface, while the pore-water pressure at the back of the slope sharply decreased during slope failure. The failure process of the experimental slope can be divided into three stages: settlement deformation, collapse deformation, and slope toe slide-flow or regressive failure. In the first and second stages, the deformation is vertical displacement as slope settlement, and the third stage deformation is mainly horizontal displacement in the direction of the free surface of the slope body. The filled slope failure is due to groundwater infiltration with suffusion erosion, saturated softening, and infiltration dynamics.

The failure of landslide dams is a sudden geological disaster, and thus their formation and failure greatly threaten the security of people's lives and property. In this research, the influences of different flume gradients, dam heights, and downstream slope angles relative to the flume bed on the overtopping breaching process of noncohesive landslide dams are explored through 12 sets of model experiments. Based on these experimental results, the dam overtopping breaching can be divided into four stages: initiation, head cutting, acceleration, and riverbed rebalancing. The variation in the erosion rate (EAX and EBX) and the downstream slope angle relative to the horizontal line (Φ) exhibit clear differences in the different stages. The influences of the flume gradient, dam height, and downstream slope angle on the breaching process of landslide dams are different. In our experiments, accumulation bodies could only form in the middle and lower parts of the downstream dam face when the total height from the spillway to the flume bed was greater than 15 cm. In addition, the downstream slope angle relative to the horizontal line determined the breaching process and stage of the dam overtopping breaching. Since the dam breach evolution mode and dam overtopping breaching process were mainly affected by the dam height and downstream slope angle relative to the horizontal line, the evolution of the longitudinal section in the process of dam body failure can be divided into four modes based on our experimental results. The applicability of the widely used empirical equations for the erosion rate was assessed using the experimental data, which revealed obvious differences between the measured and calculated erosion rates. However, the erosion rate and the shear stress at the soil/water interface exhibited a good correlation in every test. Therefore, these widely used empirical equations need to be improved in future research. This preliminary research provides a basis for subsequent studies of dam breaching using models and a scientific reference for the prevention and mitigation of landslide dams.

As one of the widely used pavement materials and structures, the multilayer asphalt concrete pavement (MACP) presents evident heat absorption and hydrothermal accumulation behaviors, which is prone to severe frost and thaw damages in cold regions. A full-scale field experiment was performed to reveal the hydrothermal process within the MACP in Inner Mongolia of China. Based on the continuous three years’ monitoring data, the freezing-thawing process, moisture features, and hydrothermal interactions of the MACP were analyzed. The results indicate that: (1) the MACP generates an important heat absorption and storage effect. A high heat flux accumulation zone forms at the central part of the MACP. Compared to the natural surface, the thawing freezing ratio at the bottom of the embankment enlarges 1.65 times armed with the MACP, meaning a dominant thawing process over a year cycle. (2) Under the influence of the thermal effect, moisture migration is considerably active within the MACP. The liquid water content of the MACP varies sharply with the decrease of the temperature. Then the cement stabilized base (CSB) and asphalt treated base (ATB) undergo the maximum and minimum liquid water contents, respectively. Furthermore, a core-shaped moisture accumulation area develops, coinciding with the features of the yearly distribution of the temperature. (3) The heat and mass transfer theory in the unsaturated porous medium was used to separate liquid water flux drove by the temperature gradient within the MACP. The temperature gradient driving effect mainly occurs in cold seasons. Under the impact of the temperature gradient, the ATB layer presents only downwards liquid water movement, while the CSB layer presents upwards and downwards liquid water movements.

Qinglong Graben is located in southeastern Yuncheng Basin, China flanked by two north-east trending normal faults, where the geological condition is favourable for generating earth fissures. Since 1978, five earth fissures have formed in Qinglong Gaben. In the present work, a series of geological investigation consisting of site investigation, geological drilling and trench excavation was used to characterise and determine the reasons for the formation of the earth fissures. The site investigation indicated that the trend of the five earth fissures are parallel to the general strike of the normal fault, i.e., geological drilling and trench studies revealed that syn-sedimentary fault is the key reason for the formation of the earth fissures. Additionally, over-exploitation of groundwater and erosion process are important factors in the development and expansion of the earth fissures in Qinglong Graben. The earth fissures forming process in Qinglong Graben can be divided into three stages: the regional extension first caused normal faults under the surface, and then the pumping action of excessive groundwater induced the normal faults propagate to the surface, and finally the erosion promoted the formation of the current earth fissure.

Polyhydroquinone, an immobilized quinone, was synthesized by oxidative polymerization of hydroquinone. The polymers obtained were characterized by Fourier-transform infrared spectra and cyclic voltammetry. Polyhydroquinone is a redox-active polymer with quinone/hydroquinone redox active units in the main chain. The influence of polyhydroquinone in the Fe3O4/persulfate system was examined. It was found that the addition of polyhydroquinone in Fe3O4/persulfate system increased the oxidation rate of Rhodamine B (RhB), which was ascribed to their role as an electron shuttle. The presence of polyhydroquinone successfully builds up two cycles, one semiquinone/quinone cycle, another cycle of Fe(III)/Fe(II) induced by quinone. The presence of phenolic and quinonoid moieties in the structure of polyhydroquinone provide for their ability to reduce Fe(III), thereby assisting the redox cycling of Fe and increasing degradation of the target substrate.

The ground fissures in Gaoliying, Beijing, has caused panic among local people, and also caused severe damage to buildings and public facilities in its affected area. This paper takes the ground fissures as the research prototype and reveals its development and activities characteristics by field investigation and trenching exploration; The Flac3D finite difference method has also been used to simulate and calculate the deformation and failure characteristics of model strata under different fault dislocations and varying descend amounts of groundwater level. The results show that the ground fissure in Gaoliying are linearly distributed and cause the destruction mainly by vertical dislocation and horizontal tension in the shallow strata; Moreover, the differential settlement of the upper and lower strata of the model near the fault increases with the increase of fault dislocation. Vertical displacement and stress of soils on both sides of the fault are quite different, and the difference increases with the decrease of groundwater level.

In this study, the polyhydroquinone/Fe3O4 (PHQ/Fe3O4) was synthesized as a heterogeneous catalyst to activate persulfate to effectively degrade Rhodamine B (RhB). The synthetic PHQ/Fe3O4 nanopartic...

A landslide occurred on the morning of December 16, 2013, in Liujiabao village, Tianshui City, Gansu Province, China. The 260,000 m3 of landslide material traveled a distance of 190 m downslope and damaged a village road and several farmhouses before it stopped on the middle of the slope. These landslide materials are still threatening the lives and property of people in the downslope residential areas. A field survey revealed that this landslide was strongly affected by the geological setting. Six normal faults that extend from east to west developed in the Neogene mudstone of this region; these faults form a fault fracture zone with a width of 80 m. The authors performed a detailed investigation of the geological features of these six normal faults, and their spatial and faulting relationships to the landslide were examined. Finally, the evolutionary progress of the loess-mudstone landslide controlled by the fault fracture zone is discussed.

Wei River Basin (WRB) is the origin of the ancient and new Silk Road, and it is located in Southern Fen Wei Graben System, China. Since 1950s, hundreds of ground fissures have formed in this affluent basin, and these ground fissures have become the main geohazard in WRB. This paper used a series of geological investigations, such as site investigation, trench excavation, geological drilling and geophysical survey to understand the distribution and mechanism of formation of the ground fissures in WRB. The results are: (1) 212 ground fissures in WRB were located in Xi’an, Xianyang, Weinan city, and they have clear orientations, mainly distributed from NEE to SWW, NW to SE, and E to W. Moreover, the ground fissures are accompanied by active faults along the same directions. (2) Ground fissures in WRB can be divided into two types—some ground fissures display obvious horizontal and vertical separations on the earth surface, whereas others only display obvious horizontal separations on the earth surface. (3) Ground fissures in WRB are triggered by four factors, viz. basin structure, active fault, human activities and loess erosion. (4) The mechanism for the formation of ground fissures has also been proposed: tectonic faulting is the fundamental cause of ground fissures in the Wei River basin, and imbalances in the man-land caused by human actives accelerated the ground fissures activities. (5) Many effective measures have also been proposed to mitigate the hazards of ground fissures in WRB, such as planning, engineering measures, controlling the exploitation of groundwater and monitoring. This research will be helpful in safeguarding the sustainable development of the Silk Road economic belt.

In this work, graphene is suggested as an adsorbent to remove Sb(III) from aqueous solution. Graphene was obtained using a modified Hummers’ method and then investigated its ability to remove Sb(III) in solutions. The graphene was characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area and Zeta potential measurement. The adsorption of Sb(III) onto graphene was carried out under various conditions, that is, the initial concentration, the contact time, the solution pH and temperature. The adsorption data were successfully modeled using Langmuir ( R = 0.977) and Freundlich ( R = 0.985) isotherms. The kinetics of adsorption was also investigated. The experimental data showed a good compliance with the pseudo-second-order kinetic model, indicating the process was controlled by the chemical process. The calculated adsorption capacity q e (8.056 mg/g) is in accordance with the experimental data (7.463 mg/g). In addition, graphene showed excellent reusability with 0.1 mol/L of EDTA solution as desorbing agent and could be used as a potential adsorbent in wastewater treatment.

Increasing attention has been paid to pyrite due to its ability to generate hydroxyl radicals in air-saturated solutions. In this study, the mineral pyrite was studied as a catalyst to activate molecular oxygen to degrade Acid Orange 7 (AO7) in aqueous solution. A complete set of control experiments were conducted to optimize the reaction conditions, including the dosage of pyrite, the AO7 concentration, as well as the initial pH value. The role of reactive oxygen species (ROS) generated by pyrite in the process was elucidated by free radical quenching reactions. Furthermore, the concentrations of Fe(II) and total Fe formed were also measured. The mechanism for the production of ROS in the pyrite/H2O/O2 system was that H2O2 was formed by hydrogen ion and superoxide anion (O2(·-)) which was produced by the reaction of pyrite activating O2 and then reacted with Fe(II) dissolved from pyrite to produce (·)OH through Fenton reaction. The findings suggest that pyrite/H2O/O2 system is potentially practical in pollution treatment. Moreover, the results provide a new insight into the understanding of the mechanism for degradation of organic pollutants by pyrite.

Degradation of azo dye Acid Orange 7 (AO7) by zero-valent aluminum (ZVAl) in combination with ultrasonic irradiation was investigated. The preliminary studies of optimal degradation methodology were conducted with sole ultrasonic, sole ZVAl/air system, ultrasonication + ZVAl/air system (US-ZVAl). In ZVAl/air system, the degradation of AO7 could almost not be observed within 30 min. The degradation of AO7 by ZVAl/air system was obviously enhanced under ultrasound irradiation, and the enhancement is mainly attributed to that the production of hydroxyl radicals in ultrasound-ZVAl process was much higher than that in sole ultrasonic or in sole ZVAl/air system. The variables considered for the effect of degradation were the power of ultrasound, the initial concentration of AO7, as well as the initial pH value and the dosage of zero-valent aluminum. The results showed that the decolorization rate increased with the increase of power density and the dosage of ZVAl, but decreased with the increase of initial pH value and initial concentration of AO7. More than 96% of AO7 removal was achieved within 30 min under optimum operational conditions (AO7: 20 mg/L, ZVAl: 2 g/L, pH: 2.5, ultrasound: 20 kHz, 300 W). This study demonstrates that ultrasound-ZVAl process can effectively decolorize the azo dye AO7 in wastewater.

Ammonium perfluorooctanoate (APFO) is an emerging environmental pollutant attracting significant attention due to its global distribution, high persistence, and bioaccumulation properties. The decomposition of APFO in aqueous solution with a combination of persulfate oxidant and ultrasonic irradiation was investigated. The effects of operating parameters, such as ultrasonic power, persulfate concentration, APFO concentration, and initial media pH on APFO degradation were discussed. In the absence of persulfate, 35.5% of initial APFO in 46.4 μmol/L solution under ultrasound irradiation, was decomposed rapidly after 120 min with the defluorination ratio reaching 6.73%. In contrast, when 10 mmol/L persulfate was used, 51.2% of initial APFO (46.4 μmol/L) was decomposed and the defluorination ratio reached 11.15% within 120 min reaction time. Enhancement of the decomposition of APFO can be explained by acceleration of substrate decarboxylation, induced by sulfate radical anions formed from the persulfate during ultrasonic irradiation. The SO4(-•)/APFO reactions at the bubble-water interface appear to be the primary pathway for the sonochemical degradation of the perfluorinated surfactants.

The removal of Rhodamine B (RhB) by Co(x)Fe(3-x)O(4) magnetic nanoparticles activated Oxone has been performed in this study. A series of Co(x)Fe(3-x)O(4) nanoparticles was synthesized using a hydrothermal method. The synthetic Co(x)Fe(3-x)O(4) nanoparticles were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that they were spinel structures and Co was introduced into their structures. The performances of Co(x)Fe(3-x)O(4) nanocatalysts on the activation of Oxone for removal of RhB were investigated and we found that the higher cobalt content in the catalyst, the better removal performance was resulted. A series experiments of reaction conditions were also performed, which confirmed that weak acidic, higher temperature, higher dosages of Co(x)Fe(3-x)O(4) nanocatalyst and Oxone and lower concentration of RhB were favored for the degradation of RhB. The pseudo-first order kinetics was observed to fit the Co(x)Fe(3-x)O(4)/Oxone process. Furthermore, the reaction mechanism was discussed and the scavenging effect was examined by using phenol and tert-butyl alcohol which indicated that sulfate radicals were the dominating reactive species responsible for the degradation process. Finally, the stability of Co(x)Fe(3-x)O(4) nanocatalyst was studied.

Degradation of the antibiotics amoxicillin in aqueous solution using sulphate radicals under ultrasound irradiation was investigated. The preliminary studies of optimal degradation methodology were conducted with only oxone (2KHSO(5) · KHSO(4) · K(2)SO(4)), cobalt activated oxone (oxone/Co(2+)), oxone+ultrasonication (oxone/US) and cobalt activated oxone+ultrasonication (oxone/Co(2+)/US). The chemical oxygen demand (COD) removal efficiency were in the order of oxone