Adsorption Potential, Speciation Transformation, and Risk Assessment of Hg-, Cd-, and Pb-Contaminated Soils Using Biochar in Combination with Potassium Dihydrogen Phosphate.

The objective of this study is to develop a remediation technology for composited heavy metal-contaminated soil. Biochars (BC300, BC400, and BC500) derived from corn were combined with potassium dihydrogen phosphate (KH2PO4) to immobilize and remove heavy metal ions, including mercury (Hg2+), cadmium (Cd2+), and lead (Pb2+). The adsorption kinetics of metal ions in aqueous solutions with different concentrations was tested, and the fitting effects of the two models were compared. The findings demonstrate that the joint application of biochar and KH2PO4 could markedly enhance the immobilization efficacy of Pb2+, whereas the utilization of KH2PO4 on its own exhibited a more pronounced immobilization impact on Cd2+. Furthermore, the present study underscores the shortcomings of various remediation techniques that must be taken into account when addressing heavy metal-contaminated soils. It also emphasizes the value of comprehensive remediation techniques that integrate multiple remediation agents. This study offers a novel approach and methodology for addressing the intricate and evolving challenges posed by heavy metal contamination in soil. Its practical value and potential for application are significant.

Reaction Process of Solid Waste Composite-Based Cementitious Materials for Immobilizing and Characterizing Heavy Metals in Lead and Zinc Tailings: Based on XRD, SEM-EDS and Compressive Strength Characterization.

This study investigates the synergistic effect and mechanism of gelling materials with blast furnace slag (BFS), steel slag (SS) and desulphurization gypsum (DG) as the main components on the hardening of heavy metal ions by lead and zinc tailings. It is found that lead and zinc tailing (LZT) is mainly composed of dolomite and quartz and contain small amounts of calcium, aluminum, iron, magnesium and other elements as well as heavy metals such as lead and zinc. By the mechanical activation method, it is found that the lead and zinc tailings powder has the largest specific surface area and the highest activity index when the ball milling time is 2 h. At a hardening timepoint of 28 d, the calcite crystals in the samples are intertwined with the amorphous C-S-H gel (C-S-H gels are mainly composed of 3CaO∙SiO2 and 2CaO∙SiO2), which enhances the structural strength of the samples. The chemical reaction analysis confirmed that the formation of calcite is a major driver for the hydration reaction of the steel slag-desulphurization gypsum (SSSDG) system. Overall, the slag, steel slag and desulphurization gypsum solid waste-based gelling materials have synergistic effects in hardening heavy metals by limiting the leaching of metal ions, adsorbing metal ions and hardening heavy metals, and facilitating the hydration process through the formation of compound salt precipitates.

Fine Structure Characterization of Representative Coal-Bearing Rocks of the Late Carboniferous Taiyuan Formation in Huainan Coalfield: Combined SEM, FESEM, and µCT Techniques.

Pores and fractures are important channels for coalbed methane (CBM) storage, seepage, and production, and accurate characterization of the microstructure of coal-bearing rock strata is of great significance for CBM exploration and development. Taking the coal-bearing rocks of the Late Carboniferous Taiyuan Formation in the Huainan coalfield as the research object, accurate characterization of the organic macerals, microstructure, and mineral distribution of sandstone, coal, and sandy mudstone was achieved using a multiscale combination of polarization microscopy (POM), X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), and X-ray computed tomography (µCT). The thin section identification results indicated that the organic matter in the coal measures rocks of the Taiyuan Formation was well developed and mainly composed of vitrinite, followed by fusinite and exinite, and in addition, there was a distribution of bituminite and sapropelite. The mineral composition of the rocks was dominated by quartz, calcite, siderite, and clay minerals, in addition to plagioclase and ankerite in the fine sandstone. In terms of pore and fracture development, all types of rocks were highly developed with nanoscale and micrometer-scale pores and of mostly irregular shapes, and all types of rocks had fracture development except for medium sandstone. The above-mentioned results show that the Late Carboniferous Taiyuan Formation in the Huainan coalfield has good space for CBM storage and transportation and has certain potential for CBM development. This study provides theoretical guidance for unconventional oil and gas exploration and development in the Huainan coalfield.

Influence of Mineral Composition on Rock Mechanics Properties and Brittleness Evaluation of Surrounding Rocks in Soft Coal Seams.

The structural fracture of the coal seam with its low permeability is the dominant reason for the "difficult gas out" of the broken soft coal seam. The brittleness of the roof and floor rock stratum of the broken soft coal seam has a significant effect on the fracture extension pressure of the surrounding rock after casing perforation and hydraulic fracturing of the horizontal well for coalbed methane (CBM). In this paper, 15 rock samples were scientifically collected from the roof and floor of the main mining coal seam of the Early Permian coal-bearing series in the Xinxie-1 well of the Huainan Coalfield in Anhui Province, China. On the basis of mineral composition analysis of these samples, the influence of mineral composition on the mechanics properties of the rock at the roof and floor of the coal seam was investigated. The correlation analysis and gray correlation analysis were adopted to construct an evaluation method for the brittleness of the rock at the roof and floor of the coal seam based on the mineral content. The results indicated that the most significant compositions of the minerals in the rock at the roof and floor of the broken soft coal seam were quartz and clay minerals. The most significant types of rock cementation are quartz agglomeration and rhodochrosite cementation. Pore destruction as a result of cementation was much greater than that of compaction. In comparison to clay minerals, the variation in the content of brittle minerals such as quartz, plagioclase, and siderite in the rock showed more sensitivity to the mechanics properties of the rock. The more sensitive minerals for compressive strength (CS), shear strength (SS), modulus of elasticity (E), softening coefficient (K), and Poisson's ratio (µ) are quartz, those for tensile strength (TS) are plagioclase and siderite, and those for Poisson's ratio are clay minerals. Based on the established mineral content weighting analysis method, it was calculated that the brittleness index (BI) of the rocks at the roof of the 13-1, 11-2, 9-2, and 4-2 coal seams was larger, which was advantageous for the formation of longer fracturing crack networks. This is theoretical guidance for the optimization of horizontal well fracturing design in the deep coal beds of the Huainan Coalfield.

To explore the remediation mechanism and effect of biochar and KH2PO4 on soils contaminated with heavy metal ions Hg2+, Cd2+ and Pb2.

In this study, wheat straw-derived biochar was prepared by setting a temperature of 400 °C under an oxygen-limited environment using the technique of "programmed temperature increase control". The results showed that the biochar had a strong adsorption capacity for Hg2+, Cd2+ and Pb2+ ions, and the adsorption pattern was Hg2+>Cd2+>Pb2+. There was a competitive adsorption effect during the coexistence of the ions. The results of the soil remediation tests showed that the effects of biochar on soil physicochemical properties and heavy metal distribution was generally greater than those of KH2PO4 in single or combined contaminated soil. The adsorption effect of heavy metal ions in soil was the best in the case of mixed additions. The results can provide a scientific basis for the treatment of heavy metal contaminated soil with wheat straw biochar in the future.

Evolutionary Analysis of Coal Molecular Structure under Different Metamorphism: An Attempt to Use Electron Paramagnetic Resonance.

The metamorphic process of coal is often affected by magma intrusion and stratigraphic tectonic movement. It is of great significance to analyze the evolution characteristics of coal structure under different metamorphisms in the study of coalification. Nineteen coal samples collected from Huainan coalfield (Zhangji coal mine, Panji-4 coal mine, and Xinji-2 coal mine) were tested by electron paramagnetic resonance (EPR) to clarify the average evolution information on organic molecular structure during coal metamorphism. The results showed that compared with deep burial metamorphism, magma intrusion and stratigraphic tectonic stress could deepen the metamorphic degree of coal. For coal samples under three kinds of metamorphism, the relationship between three EPR parameters (free radical concentration Ng, line width ΔH, and Lande factor g) and vitrinite reflectance Rmax0 approximately satisfied a quartic polynomial distribution. At the same time, with the increase of Rmax0, the changes of EPR parameters fluctuated, showing a phased and stepwise trend of change. Compared with related studies, the results showed that there were great differences in the Ng and ΔH distribution between high-rank and medium-rank coals during organic evolution. In this paper, the functional relationship between EPR parameters of coal and Rmax0 under different metamorphisms was constructed, and the internal relationship between them and its influencing factors was analyzed, which provides a reference for the study of molecular structure evolution characteristics of coal in Huainan coalfield.

Editorial for the Special Issue: "Spatial Structure of Minerals".

The spatial structure of minerals is a fundamental factor in determining the morphology, physical properties, and genesis of minerals [...].

Preparation of Bamboo-Based Activated Carbon via Steam Activation for Efficient Methylene Blue Dye Adsorption: Modeling and Mechanism Studies.

Dye pollution has long been an ecological and human health issue. Activated carbon is considered to be the most promising material for dye adsorption. In this study, bamboo was used as a biomass precursor to produce activated carbon with a high specific surface area by the steam activation method. The physical activation reaction between water vapor and bamboo promotes the carbonization product to have a rich porous structure. The prepared activated carbon was investigated from the perspectives of surface morphology, elemental change, surface porosity, and surface functional groups using a variety of techniques. According to the Brunauer-Emmett-Teller analysis, the activated carbon has a high surface area (1273 m2/g) and a mesoporous structure (average pore size 3.1 nm). On this basis, the effect of activated carbon on the removal of methylene blue (MB) dye from aqueous environments was evaluated and optimized by response surface methodology (RSM). Key adsorption parameters include initial MB concentration (150-200 mg/L), adsorption time (5-120 min), adsorbent dosage (30-50 mg), adsorption temperature (5-50 °C), and solution pH (3-11). Box-Behnken design (BBD) was used for modeling and analysis. Kinetic and isotherm model studies show that pseudo-second-order model kinetics and Langmuir isotherm can better describe the process of MB dye adsorption. This study will provide new ideas for the preparation of bamboo-activated carbon and provide a model prediction basis for dye adsorption research.

Polygenic Risk Score, Lifestyles, and Type 2 Diabetes Risk: A Prospective Chinese Cohort Study.

The aim of this study was to generate a polygenic risk score (PRS) for type 2 diabetes (T2D) and test whether it could be used in identifying high-risk individuals for lifestyle intervention in a Chinese cohort. We genotyped 80 genetic variants among 5024 participants without non-communicable diseases at baseline in the Wuxi Non-Communicable Diseases cohort (Wuxi NCDs cohort). During the follow-up period of 14 years, 440 cases of T2D were newly diagnosed. Using Cox regression, we found that the PRS of 46 SNPs identified by the East Asians was relevant to the future T2D. Participants with a high PRS (top quintile) had a two-fold higher risk of T2D than the bottom quintile (hazard ratio: 2.06, 95% confidence interval: 1.42-2.97). Lifestyle factors were considered, including cigarette smoking, alcohol consumption, physical exercise, diet, body mass index (BMI), and waist circumference (WC). Among high-PRS individuals, the 10-year incidence of T2D slumped from 6.77% to 3.28% for participants having ideal lifestyles (4-6 healthy lifestyle factors) compared with poor lifestyles (0-2 healthy lifestyle factors). When integrating the high PRS, the 10-year T2D risk of low-clinical-risk individuals exceeded that of high-clinical-risk individuals with a low PRS (3.34% vs. 2.91%). These findings suggest that the PRS of 46 SNPs could be used in identifying high-risk individuals and improve the risk stratification defined by traditional clinical risk factors for T2D. Healthy lifestyles can reduce the risk of a high PRS, which indicates the potential utility in early screening and precise prevention.

A two-dimensional Te/ReS2 van der Waals heterostructure photodetector with high photoresponsivity and fast photoresponse.

Two-dimensional (2D) semiconductors are the building blocks for high-performance optoelectronic devices. However, the performance of photoconductive photodetectors based on 2D semiconductors is hampered by low photoresponsivity and large dark current. Herein, a van der Waals heterostructure (vdWH) composed of rhenium disulfide (ReS2) and tellurium (Te) is fabricated. The Te/ReS2 vdWH photodetector exhibits a sensitive and broadband photoresponse and has high photoresponse on/off ratios under ultraviolet and visible light illumination, especially over 102 in visible light. The Te/ReS2 vdWH photodetector achieves the responsivity of 7.9 A W-1 at 365 nm, 3.02 A W-1 at 450 nm, 2.37 A W-1 at 532 nm, and 2.45 A W-1 at 660 nm. In addition, the device achieves a high specific detectivity of 1011 Jones and a fast photoresponse speed of 11.9 µs. Such high responsivity could be attributed to the efficient absorption of phonons by the Te/ReS2 vdWH and the high-quality heterostructure interfaces with a small amount of trap states. The highly crystalline structure of Te/ReS2 with a low density of defects reduces the grain boundary scattering, leading to the rapid diffusion of charge carriers. Moreover, the Te/ReS2 vdWH device exhibits a photovoltaic effect and can be employed as a self-powered photodetector (SPPD), which is sensitive to visible light of 450 nm, 532 nm, and 660 nm. Our findings demonstrate that the Te/ReS2 vdWH photodetector is an ideal building block for the next-generation electronic and optoelectronic devices in practical applications.

Characterization of the Physical Chemistry Properties of Iron-Tailing-Based Ceramsite.

In order to deal with the problems of resource waste and environmental pollution caused by solid waste, iron tailings (mainly SiO2, Al2O3 and Fe2O3) were used as the main raw material to create a type of lightweight and high-strength ceramsite. Iron tailings, dolomite (industrial grade, purity 98%) and a small amount of clay were combined in a N2 atmosphere at 1150 °C. X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and a themogravimetric analysis (TGA) were performed and the specific surface area was analyzed to determine the strength and adsorption of the ceramsite. The results of the XRF showed that SiO2, CaO and Al2O3 were the main components of the ceramsite, with MgO and Fe2O3 also included. The results of the XRD and SEM-EDS showed that the ceramsite contained several kinds of minerals and was mainly composed of akermanite, gehlenite and diopside, and that the morphology of the internal structure of the ceramsite was mainly massive and contained a small number of particles. The ceramsite could be used in engineering practice to improve the mechanical properties of materials and meet the requirements of actual engineering for the strength of materials. The results of the specific surface area analysis showed that the inner structure of the ceramsite was compact and that there were no large voids. The voids were mainly medium and large, with a high stability and strong adsorption ability. The TGA results showed that the quality of the ceramsite samples will continue to increase within a certain range. According to the XRD experimental results and experimental conditions, it was speculated that in the part of the ore phase containing Al, Mg or Ca in the ceramsite, the elements underwent relatively complex chemical reactions with each other, resulting in the formation of an ore phase with a higher molecular weight. This research provides the basis of characterization and analysis for the preparation of high-adsorption ceramsite from iron tailings and promotes the high-value utilization of iron tailings for waste pollution control.

Internet search data with spatiotemporal analysis in infectious disease surveillance: Challenges and perspectives.

With the rapid development of the internet, the application of internet search data has been seen as a novel data source to offer timely infectious disease surveillance intelligence. Moreover, the advancements in internet search data, which include rich information at both space and time scales, enable investigators to sufficiently consider the spatiotemporal uncertainty, which can benefit researchers to better monitor infectious diseases and epidemics. In the present study, we present the necessary groundwork and critical appraisal of the use of internet search data and spatiotemporal analysis approaches in infectious disease surveillance by updating the current stage of knowledge on them. The study also provides future directions for researchers to investigate the combination of internet search data with the spatiotemporal analysis in infectious disease surveillance. Internet search data demonstrate a promising potential to offer timely epidemic intelligence, which can be seen as the prerequisite for improving infectious disease surveillance.

Spatial Distribution, Ecological Risk Assessment and Source Analysis of Heavy Metals Pollution in Urban Lake Sediments of Huaihe River Basin.

Heavy metals in freshwater lake sediments often exist in various chemical forms. However, the investigation and evaluation of heavy-metal elements in the sediments of the study area have not been reported, and there is a lack of objective understanding of the concentration level of heavy-metal elements. Therefore, this study is the first to report the concentrations, sources, and potential ecological risks of heavy metals in the sediments of Chengdong Lake and Chengxi Lake in Huoqiu County, Anhui Province, China. The spatial distribution, pollution characteristics, potential pollution sources, and ecological risks of heavy metals in the sediments of Chengxi Lake and Chengdong Lake of Huoqiu City in the middle section of Huaihe River in Anhui Province, China have not been reported. In this study, the sediment samples of the two Lakes were collected systematically, and the concentrations of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) were determined. The potential sources of heavy-metal elements in sediments were quantitatively analyzed according to the principal component analysis-absolute principal component fraction-multiple linear regression (PCA-APCS-MLR) receptor model. Descriptive statistics data showed that the enrichment degree of heavy metals in Chengxi Lake was higher than that in Chengdong Lake. The geo-accumulation index (Igeo) and pollution load index (PLI) indicated that there was moderate pollution for Cu, As, Hg, Ni, and Zn. The calculation results of the potential ecological risk index (Er) of the two lakes indicated that Cd (Er,max = 92.22, n = 60) and Hg (Er,max = 64.39, n = 60) showed a certain potential ecological risk in a small amount of sediment, while other heavy metals were classified as low risk. The mean sediment quality guideline quotient indicated that there was a moderate degree of potential adverse biological toxicity in lake sediments. Spatially, the seriously polluted contamination zones were the central position of Chengxi Lake and the northeast end of Chengdong Lake. The PCA-APCS-MLR receptor model revealed that Cr, Ni, Cu, and Zn were mainly from natural sources while Cd, As, Hg, and Pb elements were mainly from industrial sources and pesticide sources.

Developing spatio-temporal approach to predict economic dynamics based on online news.

Economic forecasting is a scientific decision-making tool, and it is one of the important basis for the government to formulate economic plans, predict the implementation of the plan, and guide the implementation of the plan. Current knowledge about the use of online news in the prediction of economic patterns in China is limited, especially considering the spatio-temporal dynamics over time. This study explored the spatio-temporal patterns of economic output values in Yinzhou, Ningbo, China between 2018 and 2021, and proposed generalized linear model (GLM) and Geographically weighted regression (GWR) model to predict the dynamics using online news data. The results indicated that there were spatio-temporal variations in the economic dynamics in the study area. The online news showed a great potential to predict economic dynamics, with better performance in the GWR model. The findings suggested online news combining with spatio-temporal approach can better forecast economic dynamics, which can be seen as a pre-requisite for developing an online news-based surveillance system The advanced spatio-temporal analysis enables governments to garner insights about the patterns of economic dynamics over time, which may enhance the ability of government to formulate economic plans and to predict the implementation of the plan. The proposed model may be extended to greater geographic area to validate such approach.

Experimental Study on the Mechanical Properties and Microstructure of Metakaolin-Based Geopolymer Modified Clay.

Clay is found in some countries all over the world. It usually has low compressive strength and cannot be used as a bearing material for subgrade soil. In this paper, the influence of basicity on a metakaolin-based polymer binder to improve clay was studied. The effects of the molar concentration of the alkali activator, different concentration of the metakaolin-based geopolymer and curing time on unconfined compressive strength were studied. The alkali activator-to-ash ratio was maintained at 0.7. The percentage of metakaolin added to the soil relative to metakaolin and soil mixture was 6%, 8%, 10% and 12%. The sodium hydroxide concentrations are 2M, 4M, 6M and 8M. Unconfined compressive strength (UCS) was tested on days 3, 7, 14 and 28, respectively. Compared with original clay, the results show that the unconfined compressive strength increases with the increase in metakaolin content and molar concentration of NaOH. The maximum compressive strength of the sample with NaOH concentration of 8M and percentage of 12% was 4109 kN on the 28th day, which is about 112% higher than that of the original clay. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results showed that the cementing compound covered the clay particles due to the reaction of the geopolymer with the clay, resulting in the formation of adhesive particles. The main purpose of this study is to verify the effectiveness and stability of metakaolin-based geopolymer binder polymerization under normal temperature and a strong alkali environment. The results can provide parameters for the application and promotion of metakaolin-based geopolymers in soil improvement engineering.

Bi-Directional Pollution Characteristics and Ecological Health Risk Assessment of Heavy Metals in Soil and Crops in Wanjiang Economic Zone, Anhui Province, China.

Understanding the extent of contamination, sources and various carcinogenic and non-carcinogenic risks associated with different heavy metals in soil-crop systems is crucial for the prevention of heavy metal pollution. A survey was undertaken to determine heavy metal concentrations and degree of pollution in soil-crop systems (rice, wheat, and corn) using various indices such as pollution factor (CF), geo-accumulation index (Igeo), enrichment coefficients and transfer coefficient, and to determine the source of heavy metals pollution in the Wanjiang Economic Zone, Anhui Province, China. A total of 308 pairs of soil-crop samples were collected in this study, comprising 245 pairs of soil-rice samples, 53 pairs of soil-wheat samples, and 10 pairs of soil-corn samples. The concentrations of cadmium (Cd) and nickel (Ni) in the soil of the study area exceeded the national limitation of heavy metals in the soil of China (GB 15618-2018, Soil Environmental Quality: Risk Control Standard for Soil Contamination of Agricultural Land. Ministry of Environmental Protection of China. Beijing. China). The concentrations of copper (Cu), zinc (Zn) and lead (Pb) were also above the national limits to a lesser extent. All eight heavy metals (Cd, Cu, Ni, Pb Zn, arsenic (As), chromium (Cr), and mercury (Hg)) exceeded the background values in the study area. The enrichment coefficients of rice, wheat and maize to Cd, Cu and Zn were higher than those to other elements. On the basis of Igeo, it can be indicated that the rhizosphere soil of rice was slightly polluted by Cd and Hg, while the concentrations of the other heavy metals were below the safety limits. The CF and pollution load index (PLI) indicated that the soil in the study area was heavily contaminated with heavy metals. A principal component analysis identified different sources of soil heavy metal pollution, that is, Cu, Pb, Zn and Cd from industrial sources, Cr and Ni from natural sources, and As and Hg from agricultural sources. The carcinogenic risk of heavy metals was related to the intake of crops. Residents in the study area ingest rice, wheat, and corn on a daily basis. On the basis this study, it is suggested that local governments should pay attention to the carcinogenic risk of heavy metals in rice.

Laser Shock Fabrication of Nitrogen Doped Inverse Spinel Fe3O4/Carbon Nanosheet Film Electrodes towards Hydrogen Evolution Reactions in Alkaline Media.

The reliable and cost-effective production of high-performance film electrodes for hydrogen evolution reactions remains a challenge for the laser surface modification community. In this study, prior to a thermal imidization reaction, a small number of Fe3O4 nanoparticles were vortexed into a poly(amic acid) (PAA) prepolymer, and the achieved flat composite film was then ablated by a 1064 nm fiber laser. After laser irradiation, the hierarchical architectures of carbon nanosheets decorated with Fe3O4 nanoparticles were generated. Although pure polyimide (PI) film and laser carbonized PI film, as well as bare Fe3O4, showcase poor intrinsic catalytic activity toward alkaline hydrogen evolution reactions, our laser-derived Fe3O4/carbon nanosheet hybrid film demonstrated enhanced electrocatalytic activity and stability in 1 M KOH electrolyte; the overpotential(η10) reached 247 mV when the current density was 10 mA cm-2 with a slight current decay in the chronoamperometric examination of 12 h. Finally, we proposed that the substitution of N to O in Fe-O sites of trans spinel structured magnetite would be able to modulate the free energy of hydrogen adsorption (ΔGH*) and accelerate water dissociation.

Aramid textile with near-infrared laser-induced graphene for efficient adsorption materials.

Porous carbon materials show great application potential in the field of adsorption. However, the preparation process of carbon adsorption materials relies on high temperature, high energy consumption, many steps, and long time. Most of them exist in the form of powder or block, and the practical application scenarios are limited and difficult to recycle. In this study, based on in-situ carbonization of polymer precursor, we directly generated laser-induced graphene (LIG) on the surface of commercial aramid textile using a low-energy near-infrared laser in air, and prospected the application prospect of the prepared aramid/graphene textile in the field of adsorption. Under a certain laser energy, the photothermal reaction promotes the breaking of the CO and CN bonds in the surface layer of the aramid fiber, and reorganizes into a graphene structure at an instantaneous high temperature, while the overall flexible structure of the textile was not destroyed. Further, adsorption materials based on the as-prepared aramid/graphene textiles were also designed, including VOC-adsorbing textile in air and dye-adsorbing textile in water. Using low-energy near-infrared laser to directly achieve LIG writing in commercial textiles under air condition will provide an efficient, environmentally friendly, and designable direction for the large-scale fabrication of textile adsorption products.

Mineral Composition and Graphitization Structure Characteristics of Contact Thermally Altered Coal.

Contact metamorphism in coal is usually characterized by a rapid, brief, and exotherm reaction that can change the geothermal gradient. In this process, coal adjacent to the intrusive body can form thermally altered coal-based graphite (TACG). In order to further study the structural changes of TACG at different distances from the intrusive body, four TACG samples were collected in the Zhuji coal mine in the Huainan Coalfield, North China, and their vitrinite reflectance and Raman spectra were measured using polarizing microscopy and Raman spectroscopy. The results showed that: (1) affected by the temperature and stress of magmatic hydrothermal intrusion, the clay minerals in the coal seams appeared distributed in strips; the occurrence of ankerite and pyrite in the coal seams near the magmatic intrusions could be due to a late magmatic hydrothermal mineralization; (2) the Rmax - Rmin correlation for the TACG samples under study showed that thermal metamorphism was the main factor leading to the graphitization of the TACG samples, without an obvious pressure effect; (3) with the increase of the graphitization process, the D- and G-band showed some similar changes, specifically, their peak positions shifted to lower wave numbers, and the full width at half maximum (FWG and FWD) gradually decreased; the difference was that the intensity of the G-band increased, while that of the D-band decreased; (4) the graphitization degree of the TACG samples increased with the increase of the transverse size of the crystals, while the FWG and FWD values of the G- and D-band decreased; (5) in comparison to natural graphite, the TACG still presented structural defects.

A case study on TBM cutterhead temperature monitoring and mud cake formation discrimination method.

The mud cake is easily formed during the tunnel boring machine (TBM) excavation in clay soils or rocks containing clay minerals. Mud cake will lead to soil disturbance of tunnel face, clogging cutterhead and even affect the construction efficiency and personnel safety. In this study, a discrimination method of mud cake formation based on cutterhead temperature was proposed. An online monitoring system was designed and installed on the slurry balance TBM. The results show that: (a) the cutterhead temperature data can be reliably detected and transmitted by the system; (b) in a tunneling cycle, the temperature at some positions of the cutterhead will increase first and then decrease; (c) during the field test, the temperature variation is around 2.5 °C under the normal condition, but the temperature variation will increase more than 50 °C due to the mud cake or geological change; (d) compared with the cooling rate, mud cake formation can be accurately discriminated.