Areas Of Southwestern China Research Articles

Non-lethal sampling of phalanges for heavy metal bioaccumulation in Pelophylax nigromaculatus from historical mercury mining areas in Southwestern China

The Wanshan mercury mining area (WMMA) in Guizhou Province, China, has been identified as a region at high ecological risk owing to heavy metal contamination. This study employed non-lethal sampling methods, using the phalanges of Pelophylax nigromaculatus in the WMMA as analytical material. Ten heavy metal (metalloid) elements were selected for analysis, including Hg, Cr, Mn, Ni, Cu, Zn, Cd, Pb, As, and Se. These elements were measured using inductively coupled plasma mass spectrometry (ICP-MS), while Hg was determined using atomic fluorescence spectrometry (AFS). The bioaccumulation characteristics of heavy metals in P. nigromaculatus were analyzed through the bioaccumulation factor (BAF), and the extent of heavy metal pollution along with potential ecological risk was assessed using the potential ecological risk index (RI). The scaled mass index (SMI) was utilized to evaluate the body condition of P. nigromaculatus. Additionally, a combination of Spearman correlation analysis and non-negative matrix factorization (NMF) was employed to identify the sources and contributions of heavy metal elements. The results indicated that the distribution characteristics of heavy metal elements in the phalanges of P. nigromaculatus varied. Except for Pb, the concentrations of essential trace elements were significantly higher than those of non-essential elements. The bioaccumulation potential of P. nigromaculatus for heavy metal elements in the soil was found to be low, whereas the exposure risk from heavy metals in the water was high. The presence of heavy metal elements poses a significant potential ecological risk to P. nigromaculatus, with Hg, Cd, and As identified as the primary contributors to this risk. The environmental sources of heavy metals were identified as follows: Hg, Pb, Zn, and Se mainly originated from mining pollution sources; As and Cd primarily came from atmospheric pollution sources; Cr and Cu were mainly from natural activities sources; and Mn and Ni had multiple composite sources. Although heavy metal pollution negatively impacted the physical condition of P. nigromaculatus, no significant differences in SMI were observed across different regions. We believe that this is primarily attributable to the high levels of Se, which effectively mitigate the toxicity of heavy metals. The study demonstrated that using frog phalanges for heavy metal bioaccumulation analysis and SMI for physical condition assessment are simple, safe, and non-lethal methods, which can serve as useful indicators of environmental pollution and help trace the sources of environmental pollutants.

Shale reservoir rock physics modeling and “sweet spot” prediction based on digital core

Abstract With the increasing advancement in shale exploration and development, the complex pore structure and organic-rich characteristics of shale have gradually become the focus of rock physics models. This study combined digital core technology to obtain detailed information on the shale mineral composition, content, pore and crack contents, and composition. The isotropic self-compatible approximation (SCA) model was used to couple the shale minerals and hard pores to construct a brittle mineral framework. The VRH model was used to mix kerogen and clay, and the SCA-DEM (differential equivalent medium) model was used to add organic pores to construct a clay organic matter mineral framework. The anisotropic SCA model treated the clay organic matter mineral framework as an inclusion added to the brittle mineral framework to construct the shale mineral framework. The Eshelby–Cheng model was used to add fracture to the mineral framework and establish a physical shale model. This model was used to optimize the selection of sensitive elastic parameters for physical properties such as brittle mineral and kerogen content, fracture density, and porosity, and the optimization results were combined to construct an explanatory quantity template. In addition, according to actual data from a study area in southwestern China, we combined to the interpretation chart established by the model to perform isotropic inversion. Then, we analyzed and interpreted the brittleness index and total organic carbon content of the reservoir and predicted the sweet spot area of the shale reservoir.

Heavy metal changes related to land use changes in a karst area: a case study in Changshun, Guizhou Province, China

Karst areas are often characterized by fragile ecological systems, and environmental pollution has increased the pressures on people living in such regions. This study aimed to investigate the status of pollution caused by heavy metals (Pb, Cd, Hg, As, and Cu) in soils based on different land uses in Changshun County, a karst area in southwestern China. Soil samples were collected from natural forestlands (NFLs), natural brush lands (NBLs), natural pasture lands (NPLs), artificial forestlands (AFLs), artificial brush lands (ABLs), and artificial pasture lands (APLs) for evaluation. The results suggest that the soil profile characteristics of the heavy metals studied herein vary significantly among different land uses. The heavy metal concentrations in all soil samples collected from NFLs were lower than those in samples from other land uses. Forest trees can protect soil from heavy metal pollution caused by atmospheric deposition; this is especially true for Hg. In cultivated forestlands and brush lands, special attention should be devoted to Cd pollution in the soil, which may be caused by the use of fertilizers. Changing both natural and artificial pastoral lands to forestlands could benefit the local ecosystems as it may reduce Hg contamination.

Cross-sectional study on the current status of county-level cancer prevention and treatment capabilities in the four southwestern provinces of China.

184 Background: Lung cancer (LC) stands out as the most prevalent form of cancer in China, and it is also the primary cause of cancer-related mortality. Notably, 42.3% of newly diagnosed cancer patients are identified at the grassroots level each year. In response, the Chinese government is actively promoting tiered diagnosis and treatment approaches. This study aims to evaluate the current state of county-level cancer prevention and treatment capabilities in China, offering suggestion for policy and the standardized pathway development. Methods: A cross-sectional study was conducted in 470 district and county (city) hospitals across four provinces in southwest China: Sichuan, Yunnan, Guangxi, and Guizhou, from December 2023 to March 2024. The study was initiated by 13 hospitals, and all participating physicians signed informed consent forms. All analyses were conducted by SPSS 22.0. Results: Of the 470 county-level hospitals in China, 151 have a permanent population of over 500,000. 146 counties (198 hospitals) have established cancer specialties. There are 74 medical linear accelerators and 33 cobalt-60 treatment machines. Among them, 63.6% are tertiary hospitals, and 94.9% are public hospitals. 37.4% of hospitals have linear accelerators, and 16.7% have cobalt-60 treatment machines. 89.8% perform TNM staging, 79.1% perform radical surgery, 96.4% perform chemotherapy, 83.2% perform endocrine therapy, 97.5% perform targeted therapy, 87.3% perform immunotherapy, 54.8% perform interventional therapy, and 34.0% perform radiotherapy. Additionally, 56.8% conduct multidisciplinary diagnosis and treatment (MDT), and 37.0% provide palliative care. 83% hospitals have pathology departments, and 46.0% have established cancer centers. 79% hospitals can perform routine pathological diagnosis, and 17.0% can perform genetic testing in-hospital. Imaging departments have conducted CT plain scans in 96.4% of cases, CT enhancements in 87.7%, MRI plain scans in 84.1%, and MRI enhancements in 72.3%. Fibro-bronchoscopy was carried out in 87.2% of cases, and gastrointestinal endoscopy in 84.2%. Morphine injection was accessible in 84.8% of cases, oxycodone in 64.5%, and tramadol in 86.8%. Non-steroidal analgesics were accessible in 88.3% of cases. Conclusions: In the southwestern areas of China, the penetration rate of oncology expertise is 31.1%. Most medical institutions offering oncology specialties are tertiary public hospitals. The average number of radiotherapy machines per county or district is 0.16. The development of surgery, oncology, and the imaging is well. Radiotherapy is still in developing, and the genetic testing capacity in-hospital is insufficient. The application of TNM staging is satisfactory. Accessibility to analgesic and anti-inflammatory drugs is well, but the construction of county cancer centers still needs improvement.

Effects of Natural Vegetation Restoration on Soil Physicochemical Properties in Tropical Karst Areas, Southwestern China

Natural soil and vegetation recovery following human disturbance is the primary means of restoring degraded ecosystems globally. However, it remains unclear how vegetation recovery in the tropical karst areas of China affects the soil physicochemical properties. Here, we investigated the impacts of natural vegetation recovery on soil physicochemical properties at different soil depths in tropical karst areas in southwestern China, using a space–time substitution method. We found that with the natural vegetation recovery, soil bulk density (SBD) decreased. Soil pH initially decreased and then increased, reaching its lowest value during the shrubland stage. There was a significant increase in other soil physicochemical factors. In the soil profiles, SBD tended to increase with depth. The pH, total potassium (TK), total phosphorus (TP), and exchangeable calcium remained relatively stable across the different soil layers. TK, TP, available phosphorus, SBD, total nitrogen, pH, exchangeable magnesium, and available potassium significantly contributed to the soil physicochemical properties. Soil physicochemical properties were predominantly directly affected by litter and biological factors, albeit indirectly influenced by topographic factors. Our study provides crucial insights into karst soils and their relationship with vegetation recovery, which are pivotal for steering vegetation restoration and soil amelioration in karst areas.

Four new erythroneurine leafhopper species from karst areas in Southwestern China (Hemiptera, Cicadellidae, Typhlocybinae, Erythroneurini).

Four new erythroneurine leafhopper species, Empoascanaraaparaoides Wang & Song, sp. nov., Motagamengyangensis Wang & Song, sp. nov., Motagaacicularis Wang & Song, sp. nov., and Tautoneuraqingxiuensis Wang & Song, sp. nov. from karst areas in Southwestern China, are described and illustrated.

Uneven primary healthcare supply of rural doctors and medical equipment in remote China: community impact and the moderating effect of policy intervention

BackgroundUnequal access to primary healthcare (PHC) has become a critical issue in global health inequalities, requiring governments to implement policies tailored to communities’ needs and abilities. However, the place-based facility dimension of PHCs is oversimplified in current healthcare literature, and formulating the equity-oriented PHC spatial planning remains challenging without understanding the multiple impacts of community socio-spatial dynamics, particularly in remote areas. This study aims to push the boundary of PHC studies one step further by presenting a nuanced and dynamic understanding of the impact of community environments on the uneven primary healthcare supply.MethodsFocusing on Shuicheng, a remote rural area in southwestern China, multiple data are included in this village-based study, i.e., the facility-level healthcare statistics data (2016–2019), the statistical yearbooks, WorldPop, and Chinese GDP’s spatial distribution data. We evaluate villages’ PHC service capacity using the number of doctors and essential equipment per capita, which are the major components of China’s PHC delivery. The indicators describing community environments are selected based on extant literature and China’s planning paradigms, including town- and village-level factors. Gini coefficients and local spatial autocorrelation analysis are used to present the divergences of PHC capacity, and multilevel regression model and (heterogeneous) difference in difference model are used to examine the driving role of community environments and the dynamics under the policy intervention.ResultsDespite the general improvement, PHC inequalities remain significant in remote rural areas. The village’s location, aging, topography, ethnic autonomy, and economic conditions significantly influence village-level PHC capacity, while demographic characteristics and healthcare delivery at the town level are also important. Although it may improve the hardware setting in village clinics (coef. = 0.350), the recent equity-oriented policy attempts may accelerate the loss of rural doctors (coef. = − 0.517). Notably, the associations between PHC and community environments are affected inconsistently by this round of policy intervention. The town healthcare centers with higher inpatient service capacity (coef. = − 0.514) and more licensed doctors (coef. = − 0.587) and nurses (coef. = − 0.344) may indicate more detrimental policy effects that reduced the number of rural doctors, while the centers with more professional equipment (coef. = 0.504) and nurses (coef. = 0.184) are beneficial for the improvement of hardware setting in clinics.ConclusionsThe findings suggest that the PHC inequalities are increasingly a result of joint social, economic, and institutional forces in recent years, underlining the increased complexity of the PHC resource allocation mechanism. Therefore, we claim the necessity to incorporate a broader understanding of community orientation in PHC delivery, particularly the interdisciplinary knowledge of the spatial lens of community, to support its sustainable development. Our findings also provide timely policy insights for ongoing primary healthcare reform in China.

Tree Radial Growth Responses to Climate and Reservoir Impoundment in Valleys in Southwestern China

Southwestern China is a critical biodiversity hotspot area, and many large hydroelectric projects have been established in the valleys in the region. Tree growth in the valleys will be affected by both regional climate and reservoir impoundment. However, it remains unknown whether the radial growth of trees in the valleys has a common response pattern to the regional climate, and it is also unclear whether the response of radial growth to reservoir impoundment can be detected. In this study, we developed tree-ring width chronologies of Pinus yunnanensis Franch. collected at 11 sites with vertical and horizontal gradients to three hydroelectric reservoirs in three riverine valleys in southwestern China. We analyzed the radial growth responses to the regional climate from 1986 to 2017 by correlation with instrumental meteorological data. Tree growth responses to reservoir impoundment were investigated through spatial and temporal comparisons using the change in the Euclidean distance and difference test. We also distinguished their responses at tree-ring sites without influenced by reservoir impoundment including two sites in the valleys and seven sites at high elevations. The results showed that the climate conditions in May and the dry season before the growth season significantly limit the radial growth in the valleys, which is different to that at high-elevation areas in southwestern China. Growth variations in the valleys are related to elevations and the trees in similar slopes positions exhibit similar responses. For trees in the low slope positions, both variance and mean values of radial growth are affected by reservoir impoundment. Trees at relatively low sites (i.e., sites M2, R2, L2), rather than the trees close to the reservoirs (i.e., sites M1, R1, L1), respond more sensitively to reservoir impoundment.

Out-of-plane behavior of masonry infilled Chuan-dou timber frames

The masonry infilled Chuan-dou timber frame is a traditional structural system widely used for non-engineered residential buildings in southwestern areas of China, where earthquakes are common. And the masonry is prone to out of plane (OOP) collapse due to the lack of an effective connection between the timber frame and the masonry. This paper discusses the OOP seismic performance of masonry infilled wall Chuan-dou timber frame. Considering the slenderness ratio and the compressive strength of mortar, three full-scale single-story specimens were subjected to airbag loading to investigate the out-of-plane seismic behavior of the structural systems. Two typical failure modes of the structural systems including one-way bending and shearing slip were observed in the study. The results indicated that the slenderness ratio of the infilled masonry was inversely proportional to the bearing capacity of the structural systems. The columns have a limited effect on the constraint of infill wall while the beam can prevent the wall from falling out of the frames. And the OOP seismic behavior of the infill wall can be improved by strengthening the connection between the infilled wall and the frame. At the same time, the formulas for peak OOP load are presented based on a two-hinged arching/rocking pier mechanism.

Unraveling soil filling and transport in fissures on karst slopes using multiple tracers

The fragile ecological environment and unique surface–subsurface geological duality of karst regions have led to complex processes and rates of underground soil loss, which is subject to much controversy. However, to ensure the ecological sustainability of karst areas, it is imperative to address this issue systematically using innovative study methods. With focuses on ten fissures and fivecross-sections in a typical karst area in southwestern China, this study applied unmanned aerial vehicles for field surveys and indoor modeling techniques to investigate the distribution density of fissures in typical karst areas, which is crucial for calculating underground soil loss. By measuring magnetic susceptibility, organic carbon content, and particle size of fissure soils, the primary sources of soil in the fissures were identified. Additionally, the rate of soil loss passing through karst fissure was calculated using 137Cs tracing and 14C dating techniques. Results indicate that (1) the proportion of fissure area per square kilometer of land is 1.59 %; (2) the soil in the fissures is mainly filled with the topsoil outside the fissures, and (3) the average rate of soil filling into the fissures is 16.13 t km−2 yr−1, account for only 5.8 % of the total soil erosion modulus. The study shows that soil filling into fissures is the main process of underground soil loss on karst slopes, and the rate of soil loss through fissures is very small. This study offers valuable insights into soil movement processes and quantification of soil erosion in karst regions, thus aiding in the preservation and sustainable management of these unique ecosystems.

A STUDY OF THE RELATIONSHIP BETWEEN PERFECTIONISM AND LONELINESS AMONG YOUNG TEACHERS IN UNIVERSITIES


 
 
 
 The FMPS and UCLA scales measured 100 young university teachers from ethnic areas in southwestern China. The results showed that perfectionism and loneliness differed significantly on the demographic variables of origin, age, discipline, gender, ethnicity, and being an only child. The perfectionism dimensions of fear of making mistakes and organization were predictive of loneliness, and all the perfectionism dimensions, except family expectations, personal standards, and doubts about action, affected loneliness.
 
 
 

Experimental and Numerical Investigation of Rock Failure Process under Hydromechanical Coupling Action

Abstract In order to study the initiation mechanism of rocks under hydromechanical coupling, hydromechanical coupling triaxial tests and acoustic emission tests were carried out on basalt in the Xiluodu hydropower station dam site area in southwestern China. The test results indicate that the basalt displays typical hard brittle behavior, and its peak strength increases as confining pressure rises. Conversely, the peak strength decreases gradually as the initial water pressure increases, which leads to decreased hardness. Meanwhile, tensile failure is the main crack initiation mode under hydromechanical coupling action. During the stable crack growth stage, tensile failure is predominant, complemented by shear failure, with failures mainly occurring in the rock middle position. Contrary to this, during the unstable stage, the rock failure is mainly due to shear failure. The critical pore water pressure failure criterion of rock crack initiation under hydromechanical coupling conditions is derived based on the test results and introduced into the numerical simulation. The hydromechanical coupling failure process and pore water pressure distribution law of basalt are analyzed, and the rationality of the critical pore water pressure failure criterion is verified. These findings are significant for understanding the rock failure process under hydromechanical coupling action and provide a valuable reference for future research.

The effect of instrumental and vocal musical experience on tone categorical perception in individuals in a Chinese dialect area

IntroductionPrevious studies have shown that music training modulates adults’ categorical perception of Mandarin tones. However, the effect of music training on tone categorical perception ability in individuals in Chinese dialect areas remains unclear.MethodsWe recruited three groups of college students majoring in music in Chongqing, a dialect area in southwestern China. These groups included an instrumental music group (n = 31), a vocal music group (n = 32), and an instrumental-vocalist music group (n = 30). Additionally, we recruited a group of college students who did not receive any music training (n = 32). The accuracy and reaction time of the four groups were measured using the oddball task and compared to explore the differences in their tone categorical perception ability.ResultsConsidering both between-tone category and within-tone category, the three music groups showed both greater accuracy and shorter reaction times than the non-music group. Regarding the three music groups, no significant differences in accuracy and reaction time were detected between the instrumental and vocal groups. However, the instrumental vocalist group outperformed both the instrumental and vocal groups in terms of accuracy and reaction time.DiscussionResults showed that music training seems to have a positive effect on the categorical perception of Mandarin tone categories in Chinese dialect areas, and demonstrated that the combination of instrumental and vocal music training can further enhance tone categorical perception. To some extent, these findings provide a theoretical basis for the improvement of individual tone perception ability in dialect areas, and provided theoretical support for music and language education.

Changing trend analysis on early detection of rifampicin resistant tuberculosis patients in southwestern area of China, 2016-2020.

There were no data about prevention and control status of RR-TB in a poor area with high burden of TB in China. In order to develop evidence-based RR-TB response strategies and improve enrollment of RR-TB patients in Yunnan province, China, this study was aimed at analyzing the changing trends in the detection and enrollment of RR-TB patients and examining the factors that may have implication on enrollment in treatment. Data, which includes demographics, screening and testing, and treatment enrollment, was collected from the TB Management Information System. Retrospective data analysis and factors analysis were applied. Descriptive statistics, Chi-square test, Rank sum test and logistic regression analysis were used. From 2016 and 2018, the province had been challenged by low levels of screening, detection and enrollment of RR-TB. During the period between 2019 and 2020, a comprehensive model of RR-TB prevention and control was established in Yunnan, characterized by a robust patient-centered approach for RR-TB care and multiple, targeted interventions through the cascade of care from detection to treatment. In 2020, 93.8% of the bacteriologically positive TB patients were screened for RR-TB, which had been significantly increased by 146.9% from 38.0% in 2016. The interval from initial consultation at RR-TB facility to diagnosis (inter-quartile range) was reduced from 29.5 (1-118) days in 2016 to 0 (0-7) days in 2020. Despite the increasing rates of enrollment of RR-TB patients over the years, non-enrollment of those detected was still high (32.3%) in 2020. The main reasons for non-enrollment identified were refusal of treatment due to financial difficulties, loss to follow-up or death before starting treatment. Multivariate analysis showed that the elderly patients aged 65 or above (OR = 2.7, CI: 1.997-3.614), new patients (OR = 0.7, CI: 0.607-0.867), conventional DST used for confirmatory diagnosis of RR-TB (OR = 1.9, CI: 1.620-2.344) and diagnosis of RR-TB being conducted by the RR-TB care facilities at the prefecture and municipal level (OR = 4.4, CI: 3.608-5.250) have implications on RR-TB non-enrollment. As a comprehensive RR-TB model was implemented in Yunnan with scaled up use of molecular test for rapid detection of RR-TB, initial screening of RR-TB were decentralized to the county- and district-level to strengthen rapid, early detection of RR-TB, achieving a higher coverage of screening in the end. However, there remains a major gap in enrollment of RR-TB. The main barriers include: limited knowledge and awareness of RR-TB and financial burdens among patients, delayed diagnosis, loss to follow-up, difficulties in self care and travel for elderly patients, and limited capacity of clinical management at the lower-level RR-TB care facilities. The situation of the RR-TB epidemic in Yunnan could be improved and contained as soon as possible by continuous strengthening of the comprehensive, patient-centered model with targeted interventions coordinated through multi-sectoral engagement to improve enrollment of RR-TB patients.

Deformation Monitoring and Dynamic Analysis of Long-Runout Bedding Landslide Based on InSAR and Particle Flow Code

Long-runout landslides occur frequently in the sandstone and mudstone mountainous areas in southwestern China under heavy rainfall conditions. This has been a key issue in the field of disaster prevention and reduction. Considering the Niuerwan landslide in Wulong, Chongqing, on 13 July 2020, as an example, we employed technical methodologies, including unmanned aerial vehicle (UAV) images, field investigation, geological condition analysis (including geomorphology and topography, stratigraphic structure and formation lithology, etc.), interferometric synthetic aperture radar (InSAR) monitoring and Particle Flow Code 3D (PFC3D) simulations to study failure mechanism and a long-runout motion model of flow-like landslides induced by the heavy rainfall. The results showed that (1) the large differences between the upper and lower strata are the root cause of the instability and long-runout fluidization movement; (2) heavy rainfall is the key driving factor of slope instability and deep-seated landslides, leading to long-distance movement of the upper saturated residual soil; (3) the long-runout fluidization model of bedding landslides is mainly divided into the overall sliding in the lower layer, the mixing of coarse and fine particles in the middle layer, and saturation fluidization in the upper layer; and (4) the long-runout fluidization process of bedding landslides is composed of three stages: overall instability, mixed acceleration, and fluidization accumulation. In view of these findings, in the risk evaluation and prediction of long-runout fluidization landslides in sandstone and mudstone mountainous areas, this particular disaster model can be used to provide quantitative references for disaster prevention and mitigation.

An ensemble deep-learning framework for landslide susceptibility assessment using multiple blocks: a case study of Wenchuan area, China

The improvement of the landslide susceptibility mapping (LSM) is a long-standing problem, as it provides basics for hazard mitigation. Recently, hybrid ensemble deep learning (DL) techniques have witnessed the potential for this purpose. In this paper, we proposed a novel ensemble DL model, namely GL-ResNet, which employs the conventional ResNet blocks for landslide feature extraction, long-short term memory (LSTM) structures for information storage, and a proposed GoogLeNet block (GBlk) to broaden model perception ability. To validate the model performance, a landslide inventory containing 1147 historical landslide polygons and the data of 12 landslide factors in the Wenchuan area in southwestern China, was presented and separated into training and validating dataset using a 7:3 randomly sampling ratio strategy. Based on AUC and Accuracy, GL-ResNet (0.96 and 0.909) outperformed logistic regression (0.92 and 0.851), support vector machines (0.94 and 0.884), deep belief networks (0.95 and 0.884), gated recurrent unit (0.94 and 0.884) and ResNet (0.95 and 0.894). We also explored the robustness of GL-ResNet for LSM. The results suggested that although GL-ResNet is sensitive to initial training conditions, it showed good robustness to model training method and sample ratios. In detail, GL-ResNet outperformed the conventional models in terms of fitting power and prediction performance by 0.03-0.04 and 0.02 respectively in most cases, with even greater differences in the limited training dataset.

Soil nutrients, enzyme activities, and bacterial communities in varied plant communities in karst rocky desertification regions in Wushan County, Southwest China.

Vegetation restoration has become a common practice in karst rocky desertification (KRD) areas of southwestern China. The bacteria, which have made a connection between soil and plants, have been an important role in regulating the succession and restoration of karst vegetation. However, it is still unclear how soil bacterial communities and soil properties respond to natural vegetation restoration processes in karst areas. To address this gap, we investigated the soil nutrients, enzyme activity, and soil bacterial community among various plant communities, including farmland (FL), land with herbs only (SSI), herb-and-shrub land (SSII), woody thickets (SSIII), coniferous forest (SSIV), coniferous and broad-leaved mixed forest (SSV), and evergreen broad-leaved forest (SSVI). Our results found that SSII had the highest levels of soil organic matter, total nitrogen, available phosphorus, available nitrogen, sucrase, and β-glucosidase among all the plant communities. These results indicated that herb-and-shrub land have contributed to the rapid restoration of vegetation in KRD regions. FL exhibited the lowest levels of soil nutrients and enzyme activities, while showing the highest bacterial richness and diversity among all the plant communities. This suggested that appropriate human intervention can increase bacterial diversity and richness in the area. The predominant bacterial phylum also varied among the different plant communities, with Actinobacteria being the most abundant in SSI, SSII, SSIII, and SSIV, while Proteobacteria were the most abundant in SSV and SSVI. Furthermore, PCoA analysis demonstrated significant changes in the soil bacterial community structure, with SSI, SSII, SSIII, and SSIV had shared similar structures, while SSV and SSVI had comparable structures. As for soil characteristics, total phosphorus (TP) and total potassium (TK) were the primary factors affecting the soil bacterial community. SSV and SSVI had the most complex bacterial networks and were more stable than other groups. The genera Ktedonobacter, norank_f_Anaerolineaceae, and Vicinamibacter had the highest betweenness centrality scores and were identified as keystone genera in the co-occurrence network in KRD areas. In summary, our results have demonstrated that herb-and-shrub can promote community succession and increase soil nutrient levels in KRD regions.

Dynamic Response Law and Failure Mechanism of Slope with Weak Interlayer under Combined Action of Reservoir Water and Seismic Force

The southwestern region of China is close to the Eurasian earthquake zone. Many engineering areas in southwestern China are affected by earthquakes and are close to the epicenter of earthquakes that occur in this region. During earthquakes, slopes with weak interlayers are more likely to cause large-scale landslides. In response to the low stability of slopes with weak interlayers in reservoir dam areas, the dynamic response law and failure mechanism of weak interlayered slopes under the combined action of reservoir water and seismic forces were studied through shaking table model tests and finite element numerical simulation software. The height of the water level and the size of the seismic waves were changed during these tests. The research results indicate that seismic waves are influenced by weak interlayers and are repeatedly superimposed between the weak interlayers and the slope surface, resulting in an acceleration amplification effect that increases by approximately 1.8 times compared to homogeneous slopes. Vertical earthquakes have a significant impact on the dynamic response of slopes, and their peak acceleration amplification coefficient can reach 0.83 times the horizontal peak acceleration. The stability of weak interlayers during earthquakes is the worst within the range of the direct action of reservoir water. The failure mode of a slope is as follows: earthquake action causes cracking in the upper part of the slope, and as the earthquake increases in intensity, and the infiltration of reservoir water intensifies, the cracks expand. The soft and muddy interlayer in the front section of the slope forms a sliding surface, and ultimately, the sliding failure forms an accumulation body at the foot of the slope. In reservoir dam areas, the stability of a slope is closely related to the engineering safety of the reservoir dam. Therefore, when a strong earthquake and the water level in a reservoir jointly affect a weak-interlayer slope, the slope is in the stage of plastic deformation and instability. The stability of the slope may be overestimated, and the slope is likely vulnerable to sliding instability, which needs to be monitored and treated.

Wildfire risks under a changing climate: Synthesized assessments of wildfire risks over southwestern China

Wildfire events in southwestern China resulted in catastrophic loss of property and human life, and the localized wildfire risks show differentiated trends under global warming scenarios. In the case of quantitating climate impacts and localizing wildfire risks, synthesized assessments of wildfire risks of high-incident areas in southwestern China are established and mapped in this article, constituted by three essential elements: hazard, vulnerability, and disaster prevention/mitigation capacity. The hazard group includes vegetation ignitability and fire spreading related to climate and topography factors. Public and economic characteristic elements belong to the vulnerability and disaster prevention/mitigation capacity group based on their functions and influences on wildfire events. Each aspect and group are rated by the historical wildfire site records and weighted by the entropy weight method and analytic hierarchy process. Assessments indicate that most very high wildfire risk girds are distributed in the west of 103°E and the north of 28°N, covering an area of over 26,500 km2, mainly in low-altitude suburban regions in basins and valleys with high climate hazards. The highly localized wildfire risk maps specified both stresses of fire prevention/mitigation in each grid cell and general spatial patterns of wildfire risks, thereby enhancing the understanding of both current and future patterns of wildfire risks and thus helping improve suppression and prevention policies.

Identification of sources and their potential health risk of potential toxic elements in soils from a mercury‑thallium polymetallic mining area in Southwest China: Insight from mercury isotopes and PMF model

Identification of potential toxic element (PTE) sources and their specific human health risk is critical to the management of PTEs in soils. In this study, multi-medium were collected from a mercury‑thallium polymetallic mining area in Southwestern China. Hg isotope technique together with positive matrix factorization (PMF) model was used to identify PTE sources and assess their source-oriented health risk. Results showed that among the studied PTEs, this study area presented high pollution of Hg, Tl and As, with higher concentrations than their corresponding background values of Guizhou province, yet their average concentrations in covering soils were significantly lower than those in the natural soils. The Tl in coix grains should also be paid more attention due to its high concentration. Both natural and covering soils had different Hg isotope composition with tailings, while sediments have similar Hg isotope fractionation with covering soils. According to the PMF model, three sources in both natural and covering soils were apportioned and Hg, Tl and As were mainly influenced by the historical mining activities, which also confirmed by their Hg isotope signatures. The contributions of historical mining activities accounted for 40 % and 20 % of the PTEs in natural and covering soils, respectively. The assessment of source-specific health risks suggested that the non-carcinogenic risk of Hg, Tl and As was much higher than other elements. Historical mining activities were regarded as the major contributor to health risks (79 % and 76 % for natural soils and 50 % and 59 % for covering soils, respectively). This indicated that the restoration of coveing soils indeed decreased the health risk in this study area. These findings thus highlight the importance of ongoing monitoring of covering soils in the polymetallic mining area, which is imperative for preferably assessing the health risk of PTEs in similar mining area worldwide.