The environmental threat, pollution and damage posed by heavy metals to air, water, and soil emphasize the critical need for effective remediation strategies. This review mainly focuses on microbial electrochemical technologies (MET) for treating heavy metal pollutants, specifically includes Chromium (Cr), Copper (Cu), Zinc (Zn), Cadmium (Cd), Lead (Pb), Nickel (Ni), and Cobalt (Co). First, it explores the mechanisms and current applications of MET in heavy metal treatments in detail. Second, it systematically summarizes the key microbial communities involved, analyzing their extracellular electron transfer (EET) processes and summarizing strategies to enhance the EET efficiencies. Next, the review also highlights the synergistic microbial interactions in bioelectrochemical systems (BES) during the recovery and removal (remediation) processes of heavy metals, underscoring the crucial role of microorganisms in the transfer of the electrons. Then, this paper discussed how factors including pH values, applied voltages, types and concentrations of electron donors, electrode materials, biofilm thickness and other factors affect the treatment efficiencies of some specific metals in BES. BES has shown its great superiority in treating heavy metals. For example, for the treatments of Cr6+, under low pH conditions, the recovery and removal rate of Cr-6(+) by double chambers microbial fuel cell (DCMFC) can generally reach 98-99%, with some cases even achieving 100% (Gangadharan & Nambi, 2015). For the treatments of heavy metal ions such as Cu2+, Zn2+ and Cd2+, BES can also achieve the rates of treatments of more than 90% under the corresponding conditions of appropriate pH values and applied voltages(Choi, Hu, & Lim, 2014; W. Teng, G. Liu, H. Luo, R. Zhang, & Y. Xiang, 2016; Y. N. Wu et al., 2019; Y. N. Wu et al., 2018). After that, the review outlines the future challenges and the research opportunities for understanding the mechanisms of BES and microbial EET in heavy metal treatments. Finally, the prospect of future BES researches are pointed out, including the combinations with existing wastewater treatment systems, the integrations with the wind energy and the solar energy, and the application of machine learning (ML) in future BES. This article has certain significance and value for readers to better understand the working principles of BES and better operate and control BES to deal with heavy metal pollutants.

Background: With growing concern during the COVID-19 pandemic, indoor environmental quality has received significant attention. Radon, a radioactive gas produced from the decay of radium found in soil, rocks, and building materials, can accumulate indoors, posing serious health risks such as lung cancer. University environments, where occupants spend significant time indoors, are particularly susceptible to prolonged radon exposure. Method: This study focused on the estimation of indoor radon concentrations from multiple university buildings in Shanghai. A field investigation was conducted between June 2020 and August 2022. Continuous radon measurements were conducted in the dormitories and classroom buildings. Environmental factors include indoor air temperature and relative humidity. Results: Radon concentrations were influenced by season, floor level, and measurement period, with the highest concentrations recorded during summer and on lower floors due to reduced ventilation. The mean radon concentration in dormitories was 14.8 +/- 9.2 Bq/m3, and in classrooms 12.6 +/- 6.7 Bq/m3, both below national safety limits and lower than those in the pre-pandemic era. Seasonal effect, floor level, and time of measurement were the significant factors for indoor radon concentrations. Conclusion: This study has identified the main factors that affect indoor radon concentration in university campus. The radon concentrations at the lower floor levels remain the highest in the building. The results provide evidence for conducting refined radon monitoring and risk assessment in campus environment, especially during the summer.

In this essay, by summarizing the research progress and achievements of various scholars at home and abroad in recent years on the material properties and corrosion resistance of magnesium phosphate cement (MPC), we review the factors influencing on the properties of MPC, and analyze the effects of raw materials, retarders, and admixtures on the properties of MPC. Two different hydration mechanisms of MPC are discussed, and finally the research progress of MPC in the field of anti-corrosion coatings for steel and ordinary concrete (OPC) is highlighted, and suggestions and prospects are given.

Soil erosion is an important driver of land and ecological degradation, with hydraulic erosion in particular leading to widespread impacts and damage. As an important concept and indicator for characterizing the potential and pathways of sediment production and transportation within watersheds or on slopes, sediment connectivity has gained global attention and thus been analysed since its proposal in 2003. Sediment connectivity has become an effective metric for analysing the sources, processes, and potentials of soil erosion and sediment yield (SY) in watersheds, and it has been considered a popular research topic in the field of soil erosion over the past decade. Considering the lack of up-to-date systematic reviews of conceptual connotations, characterization indicators for sediment connectivity, and quantitative relationships between these indicators and erosion and SY, a bibliometric analysis of sediment connectivity was conducted via the CiteSpace tool, which is based on the Web of Science (WOS), Scopus (Elsevier) and China National Knowledge Infrastructure (CNKI) databases. In this research, the current state, popular topics, and trends in relevant studies were identified, and the conceptual connotations, influencing factors, and indicator algorithms of sediment connectivity and their quantitative relationships with soil erosion and SY were summarized. Furthermore, the contents and directions to be strengthened and improved in the future were determined. The results indicated that over the past 21 years, sediment connectivity has been analysed in 123 countries or regions. Researches have focused primarily on related concepts, indicators, scales, and influencing factors. This concept has been widely applied in various practices such as soil and water resource regulation, land use optimization, and soil erosion control. In previous studies, several linear (SY = a center dot IC + b) and exponential (SY = a center dot eb center dot IC) increasing relationships between sediment connectivity indicators (such as the index of connectivity (IC)) and SY at the slope or watershed scale have been established, facilitating the development of research on prediction and attribution analysis for the identification of sediment sources and changes. There is a consensus on what sediment connectivity is to date, but a unified and complete system has not been yet formed for sediment connectivity and several of its derived concepts. The Index of Connectivity (IC), as the primary means for quantitatively characterizing the status and distribution of sediment connectivity, has led to the creation of more than 20 different algorithms, whereas the included parameters mainly reflect the internal factors influencing topography and land use/cover. The effects of climatic factors and human activities have not been fully considered in previous studies, which has led to relatively backwards researching on functional connectivity indicators. Hence, the classification systems and theoretical frameworks for a series of concepts must be further refined on the basis of sediment connectivity, such as the objective openness, scale dependence, comprehensive impact, and distribution heterogeneity. Moreover, the amount of research on the influences of external drivers and the coupled effects of different factors on indicators of sediment connectivity should be increased. Nevertheless, it is still necessary to explore certain aspects, such as the parameter combinations and normalization methods of the upslope and downslope components of the IC algorithm, and to continuously improve the explanation of the dynamic changes in sediment while considering both hydrological connections along flow paths and off-site impacts on underlying surface variations. Moreover, there is a need to increase the spatiotemporal scale of research on sediment connectivity, explore its feedback mechanisms and close quantitative relationships with soil erosion and SY, focus on the integrated application of different indicators (methods), and validate and results via multisource information to promote relevant applications. The obtained results provide valuable reference for the refinement of theories and methods for sediment connectivity and enhance its support of studies of soil erosion and SY in watersheds.

To the aim of this paper is to study the structural and environmental deformation characteristics caused by the excavation of a very large deep foundation pit in the sandy soil area of Beijing. This paper is based on numerical simulation and field monitoring results and these results are compared with the deformation data of a soft soil foundation pit in the Shanghai area. The results show that the influence of the environment surrounding the super-large deep foundation pit project studied in this paper is obviously too great. With the progress of construction, the deformation rate and deformation amount of the column at the side of the foundation pit are obviously higher than that of the column in the middle area. Due to the hysteresis of stress transfer in the sand, the settlement of the roof of the north wall is delayed and the deformation range is smaller than that of the south wall. Compared with the conventional foundation pit, the influence area of the surrounding surface is larger, reaching 4 He (He is the depth of the foundation pit). Delta vmax (the maximum surface settlement) is between 0.2 similar to 2.3% He, and the relationship between delta vmax = 1.43% Vwm. Through orthogonal experiments and numerical simulation, it is concluded that the deformation of foundation pit structure and its surrounding environment is more sensitive to excavation unloading, precipitation amplitude, and column spacing. It is also concluded that the strong, medium, and weak influence areas of the bottom uplift after foundation pit construction are (0 similar to 0.07) x L, (0.07 similar to 0.14) x L, and (0.14 similar to 0.5) x L, respectively (L is the width of foundation pit). When the embedment ratio is between 1.8 similar to 2.4, the displacement mode of the parapet structure is T mode; when the embedment ratio is between 2.4 similar to 3.4, the displacement mode of the parapet structure is RB mode.

Covered sinkhole, due to its hidden, uncertain, and sudden characteristics, often becomes a key and difficult issue in the prevention and control of karst geological disasters. This paper takes the sinkhole in Yaoshan Huamu Farm, Guilin City as an engineering case, and uses field investigation, indoor and outdoor experiments, and theoretical analysis to systematically analyze the main patterns, influencing factors, and evolution laws of sinkhole. The results show that: (1) High-density resistivity tests show that there are many significant low-resistance anomalies at different locations and depths in the study area, indicating that karst fissures are developed in the study area. This is the basic condition for the occurrence of sinkhole. (2) Drilling results show that the groundwater level in the study area is shallow and groundwater is abundant. Groundwater changes the state and strength of the soil, or dissolves the mineral components of the soil layer and dissolves and transports the soil particle aggregates through subsurface erosion and seepage. Therefore, groundwater destroys the soil structure, resulting in the formation of soil caves or sinkholes. (3) Rainfall monitoring shows that the rainy season from May to July each year provides abundant groundwater for the karst area and changes the physical and mechanical properties of the rock and soil mass; while the small rainfall peak around November may trigger the occurrence of sinkhole through mechanisms such as groundwater level fluctuations and enhanced seepage. (4) The vibrations caused by long-term pumping irrigation, surface water leakage, and planting activities in the study area provide important external dynamic conditions for sinkhole. This study can provide theoretical basis and technical support for the prevention and control of collapse disasters in karst areas.

In recent years, prestressed pipe piles have been widely used in the reinforcement of soft soil foundation, and there will be obvious soil squeezing effect in the construction of pipe piles. However, the research on the soil squeezing effect of pipe piles under various influencing factors is not clear, and it is difficult to guide the actual construction on site. In this paper, the evolution mechanism of soil squeezing effect, pile-soil deformation characteristics and bearing characteristics in the process of pile sinking are analyzed in depth by means of field monitoring and laboratory test. Combined with visual model test, the distribution law of soil displacement field is clarified, and the effects of various influencing factors such as changing pile spacing and pile sinking sequence are revealed. The results show that the soil deformation caused by pile sinking increases first and then decreases in depth, and the soil deformation decreases exponentially in the horizontal direction. The width of the shear strain zone does not change with the increase of penetration, that is, the influence of the squeezing effect on the adjacent pile is mainly rotation and translation. For double piles, the expansion trend of the inner side of the two piles is smaller than that of the outer side of the pile. The squeezing effect will cause the adjacent pile to move and rotate. When the subsequent pile penetration is completed, the displacement field is no longer a basically symmetrical state, and the influence range in the depth area increases. When the pile spacing is set to more than 4 times the pile diameter, the synergistic bearing capacity of the pile group can be better played; The construction sequence from near to far is preferentially selected during construction, which can effectively reduce the impact on adjacent structures. The research results of this paper can provide a reference for further solving the disposal problem of composite foundation reinforced by pipe pile group.

For slope instability caused by rainfall, there are some differences between ideal rainfall conditions and actual rainfall conditions. In order to study the stability of slopes under heavy rainfall, this paper therefore takes the 7.20 special rainstorm in Zhengzhou as an example. Four factors, namely average annual rainfall q, soil permeability coefficient anisotropy kr, water table height h(w), and suction friction angle phi(b), were selected as variables. The finite element method was used to analyze the variation rule of initial pore water pressure (IPWP) at the top and bottom of the slope under various factors during the rainfall process, the limit equilibrium method was used to calculate the safety factor (F-s) after the rainfall, and the grey correlation analysis method was used to analyze the sensitivity of factors affecting slope stability under heavy rainfall. The result shows that the pore water pressure at the top of the slope varies more than that at the bottom of the slope during rainfall. The lower the initial pore water pressure, the lower the safety factor of the slope at the end of rainfall. The sensitivity of each factor to the slope safety factor is in the following order: phi(b)>k(r)>h(w)>IPWP.

Artificial ground freezing technology is the most important construction method of complex water-bearing soft clay rock. The thermodynamic properties of soft clay rock are important evidence for the design and construction of space resources development, and the variable hydrothermal parameter can directly affect the uncertain thermodynamic properties of soft clay rock. In this work, an array of field experiments on the soft clay rock are carried out, and the anisotropic spatial variations of hydrothermal parameters of soft clay rock are obtained. The statistical variability characteristics of variable hydrothermal parameters are estimated. A stochastic coupling model of soft clay rock with heat conduction and porous flow is proposed, and the uncertain thermodynamic properties of soft clay rock are computed by the self-compiled program. Model validation with the experimental and numerical temperatures is also presented. According to the relationship between anisotropic spatial variations and statistical variability characteristics for the different random field correlation models, the effects of the autocorrelation function, coefficient of variation, and autocorrelation distance of variable hydrothermal parameters on the uncertain thermodynamic properties of soft clay rock are analyzed. The results show that the proposed stochastic analysis model for the thermal characteristics of soft clay rock, considering the spatial variability of frozen soil layers, is scientifically reasonable. The maximum standard deviation of average thickness is 2.33 m, and the maximum average temperature is 2.25 degrees C. For the autocorrelation function, the most significant impact comes from DBIN. For the coefficient of variation, the most significant impact comes from thermal conductivity. Different variations of hydrothermal parameters have different effects on the standard deviation of soft clay rock temperature. The biggest influence is the thermal conductivity, while the lowest influence is the specific heat capacity.

To alleviate problems in urban living environments, an increasing number of shield tunnels have been built that go through rivers or underwater areas. Most of these tunnels experience leakage after a long period of operation, which can impact the safety of the tunnel and induce dangerous accidents, resulting in a loss of life and property. This paper reports the leakage characteristics during operation of a double-line ultralarge-diameter underwater shield tunnel that crosses the Yangtze River. After detailed geological surveys and field inspections of the prototype tunnel, the leakage characteristics and patterns of the tunnel were summarized based on long-term monitoring data. The distribution of leak-related defects was described in-depth with sketches and field photographs. Factors influencing the leakage of the prototype tunnel (i.e., the groundwater table, longitudinal settlement, and soil conditions) were interpreted based on field measurements. The mechanisms that triggered two typical leakage accidents that occurred during tunnel operation were systematically analyzed. The leakage mechanisms of the prototype tunnel were subsequently categorized into three patterns: joint leakage, bolt hole leakage and concrete crack leakage. Four countermeasures against leakage were proposed considering the leakage-associated damage to the prototype tunnel: backfill grouting, joint grouting, installation of a bolt hole sealing cover, and caulking gasket addition. The proposed mitigation measures were validated through laboratory tests and field applications. This unique tunnel prototype engineering case can provide a reference for water leakage prevention and control in the design, construction, and operation stages of similar underwater shield tunnel projects.