Molecular Dynamics Simulation of the Interaction within the Carboxymethyl Cellulose-Modified Montmorillonite Lamellae at Aggressive CuCl2 Concentrations.

To elucidate the degradation mechanism of the CMC-modified MMT composite at aggressive Cu2+ concentrations, large scale molecular dynamics simulation was conducted for CuCl2 concentrations ranging from 0 to 800 mM. Both CMC and MMT followed the Langmuir isotherm for Cu2+ adsorption, and the adsorption capacity of CMC (8.75 mmol/g) was much higher than that of MMT (0.83 mmol/g). Despite the CMC mass ratio being only 4.1%, it adsorbed up to 34.3% of the total adsorbed Cu2+. The Cu2+ attraction ability hierarchy of oxygen-containing functional groups in the CMC is as follows: carboxylic oxygens > alcoholic oxygens > carbinolic oxygens > bridging oxygens > glucose oxygens. Carboxyls were the most effective in chelating and complexing with Cu2+, and they could be intentionally added in artificially synthesized polymer-MMT composites for Cu2+ containment. Formation of the Cu2+ cation bridge between CMC and MMT at aggressive CuCl2 concentrations contributed to the transition of CMC density distribution from unimodality to bimodality and enhanced resistance of polymer elution. As the CuCl2 concentration increased, the stoichiometric ratio between the chelated Cu2+ and carboxylic oxygens increased from 1:2 to 1:1, suggesting the evolution of the Cu2+ chelation mechanism.

Numerical investigation and optimal design of capillary barrier cover with passive gas collection pipes on the performance at limiting landfill gas emissions.

Relying solely on soil properties may not fully ensure the performance of capillary barrier covers at limiting landfill gas (LFG) emissions. This study proposed to install passive gas collection pipes in the coarse-grained soil layers of capillary barrier covers to enhance their performance at limiting LFG emissions. First, the LFG generation rate of municipal solid waste and its influencing factors were analyzed based on empirical formulas. This information provided necessary bottom boundary conditions for the analyses of LFG transport through capillary barrier covers with passive gas collection pipes (CBCPPs). Then, numerical simulations were conducted to investigate the LFG transport properties through CBCPPs and reveal relevant influencing factors. Finally, practical suggestions were proposed to optimize the design of CBCPPs. The results indicated that the maximum whole-site LFG generation rate occurred at the end of landfilling operation. The gas collection efficiency (E) of CBCPPs was mainly controlled by the ratio of the intrinsic permeability between the coarse- and fine-grained soil (K2/K1) and the laying spacing between gas collection pipes (D). E increased as K2/K1 increased but decreased as D increased. An empirical expression for estimating E based on K2/K1 and D was proposed. In practice, CBCPPs were supposed to be constructed once the landfilling operation finished. It is best to select the fine- and coarse-grained soils with K2/K1 exceeding 10,000 to construct CBCPPs.

Negative mixing enthalpy solid solutions deliver high strength and ductility.

Body-centred cubic refractory multi-principal element alloys (MPEAs), with several refractory metal elements as constituents and featuring a yield strength greater than one gigapascal, are promising materials to meet the demands of aggressive structural applications1-6. Their low-to-no tensile ductility at room temperature, however, limits their processability and scaled-up application7-10. Here we present a HfNbTiVAl10 alloy that shows remarkable tensile ductility (roughly 20%) and ultrahigh yield strength (roughly 1,390 megapascals). Notably, these are among the best synergies compared with other related alloys. Such superb synergies derive from the addition of aluminium to the HfNbTiV alloy, resulting in a negative mixing enthalpy solid solution, which promotes strength and favours the formation of hierarchical chemical fluctuations (HCFs). The HCFs span many length scales, ranging from submicrometre to atomic scale, and create a high density of diffusive boundaries that act as effective barriers for dislocation motion. Consequently, versatile dislocation configurations are sequentially stimulated, enabling the alloy to accommodate plastic deformation while fostering substantial interactions that give rise to two unusual strain-hardening rate upturns. Thus, plastic instability is significantly delayed, which expands the plastic regime as ultralarge tensile ductility. This study provides valuable insights into achieving a synergistic combination of ultrahigh strength and large tensile ductility in MPEAs.

Periodic injection of liquefied kitchen and food waste in municipal solid waste: Effects on leachate and gas generation.

With continuous advancements in the zero-waste strategy in China, transportation of fresh municipal solid waste to landfills has ceased in most first-tier cities. Consequently, the production of landfill gas has sharply declined because the supply of organic matter has decreased, rendering power generation facilities idle. However, by incorporating liquefied kitchen and food waste (LKFW), sustainable methane production can be achieved while consuming organic wastewater. In this study, LKFW and water (as a control group) were periodically injected into high and low organic wastes, respectively. The biochemical characteristics of the resulting gas and leachate were analyzed. LKFW used in this research generated 19.5-37.6 L of methane per liter in the post-methane production phase, highlighting the effectiveness of LKFW injection in enhancing the methane-producing capacity of the system. The release of H2S was prominent during both the rapid and post-methane production phases, whereas that of NH3 was prominent in the post-methane production phase. As injection continued, the concentrations of chemical oxygen demand, 5-d biological oxygen demand, total organic carbon, ammonia nitrogen, total nitrogen, and oil in the output leachate decreased and eventually reached levels comparable to those in the water injection cases. After nine rounds of injections, the biologically degradable matter of the two LKFW-injected wastes decreased by 8.2 % and 15.1 %, respectively. This study sheds light on determining the organic load, controlling odor, and assessing the biochemical characteristics of leachate during LKFW injection.

CFD-DEM study on transport and retention behaviors of nZVI-clay colloids in porous media.

Transportation process of nano scale zero valent iron (nZVI) in clay-rich soils is complicated and crucial for in-situ remediation of contaminated sites. A coupled computational fluid dynamic and discrete element method (CFD-DEM) was used to investigate the interplays of repulsive and attractive forces and the injection velocity of this process. The screened Coulomb's law was used to represent the electrostatic interaction, and surface energy density was introduced to represent the effects of the van der Waals interaction. A phase diagram was constructed to describe the interplay between injection velocity and repulsive force (in terms of charge of colloids). Under the boundary and initial conditions in this study, clogging formed at low repulsive force (colloidal charge = -1 ×10-15 C), where increment of injection velocity (from 0.002 m/s to 0.02 m/s) cannot prevent clogging, as in the case of bare nZVI transportation with limited mobility; On the other hand, excessive repulsive force (charge = -4 ×10-14 C) is detrimental to nZVI-clay transportation due to repulsion from the concentrated colloids in pore throats, a phenomenon as in the overuse of stabilizers and was defined as the "membrane repulsion effect" in this study. At moderate charge (-1 ×10-14 C), injection velocity increment induced clogging due to aggregates formed at the windward of cylinder and accumulated at the pore throats.

Monitoring the remediation of groundwater polluted by MSW landfill leachates by activated carbon and zeolite with spectral induced polarization technique.

The municipal solid waste (MSW) landfill in Hangzhou, China utilized zeolite and activated carbon (AC) as permeable reactive barrier (PRB) fill materials to remediate groundwater contaminated with MSW leachates containing ammonium, chemical oxygen demand (COD), and heavy metals. The spectral induced polarization (SIP) technique was chosen for monitoring the PRB because of its sensitivity to pore fluid chemistry and mineral-fluid interface composition. During the experiment, authentic groundwater collected from the landfill site was used to permeate two columns filled with zeolite and AC, and the SIP responses were measured at the inlet and outlet over a frequency range of 0.01-1000 Hz. The results showed that zeolite had a higher adsorption capacity for COD (7.08 mg/g) and ammonium (9.15 mg/g) compared to AC (COD: 2.75 mg/g, ammonium: 1.68 mg/g). Cation exchange was found to be the mechanism of ammonium adsorption for both zeolite and AC, while FTIR results indicated that π-complexation, π-π interaction, and electrostatic attraction were the main mechanisms of COD adsorption. The Cole-Cole model was used to fit the SIP responses and determine the relaxation time (τ) and normalized chargeability (mn). The calculated characteristic diameters of zeolite and AC based on the Schwarz equation and relaxation time (τ) matched the pore sizes observed from SEM and MIP, providing valuable information on contaminant distribution. The mn of zeolite was positively linear with adsorbed ammonium (R2 = 0.9074) and COD (R2 = 0.8877), while the mn of AC was negatively linear with adsorbed ammonium (R2 = 0.8192) and COD (R2 = 0.7916), suggesting that mn could serve as a surrogate for contaminant saturation. The laboratory-based real-time non-invasive SIP results showed good performance in monitoring saturation and provide a strong foundation for future field PRB monitoring.

Successful treatment of peritoneal dialysis for two patients with refractory nephrotic syndrome and acute kidney injury: a case report.

Two patients with refractory nephrotic syndrome were treated with peritoneal dialysis (PD) for diuretic resistance, anasarca and acute kidney injury. Following PD, their fluid overload was promptly alleviated, accompanied by an increase in urine volume and an improvement in renal function. PD as an adjuvant approach enabled them to resume corticosteroids and immunosuppressive agents. Eventually, both patients could be withdrawn from PD and achieved remission of proteinuria.

Biochemical, hydrological and mechanical behaviors of high food waste content MSW landfill: Numerical simulation analysis of a large-scale experiment.

The complex process of thermal-hydro-mechanical-biochemical (THMBC) coupled degradation in high food waste content (HFWC) municipal solid waste (MSW) is the main cause of intense heat, gas, and leachate generation in the landfills, which could lead to environmental disasters. A large-scale indoor experiment on HFWC MSW has been done with operations of loading, heated mature leachate recharging to study the rules of degradation. A THMBC coupled degradation model is used to analyze the results in the first 400 days drawn from the experiments, to explain how recharge of heated mature leachate accelerated degradation process and how was the portion of settlement led by intraparticle water release. The numerical simulation also calculated the landfill gas that was not collected in the experiment due to operational defects. The results show that recharging the heated mature leachate allows the stabilization process to occur at least six months earlier and settlement due to intraparticle water release accounts for half of the settlement in the first 60 days. The research indicates highly coupled THMBC model can be used to analyze the complex process in MSW degradation, make up for the shortcomings of physical experiments, and provide theoretical support for the design, construction, and management of landfills.

Comparison between the influence of roxadustat and recombinant human erythropoietin treatment on blood pressure and cardio-cerebrovascular complications in patients undergoing peritoneal dialysis.

Introduction: Roxadustat treatment in PD patients is equivalent to ESAs in increasing hemoglobin (Hb). But blood pressure, cardiovascular parameters, cardio-cerebrovascular complications and prognosis in the two groups before and after treatment has not been sufficiently discussed. Methods: Sixty PD patients who were treated with roxadustat for renal anemia in our PD center recruited from June 2019 to April 2020 as roxadustat group. PD patients treated with rHuEPO were enrolled at a 1:1 ratio as rHuEPO group using the method of propensity score matching. Hb, blood pressure, cardiovascular parameters, cardio-cerebrovascular complications and prognosis were compared between the two group. All patients were followed up for at least 24 months. Results: There were no significant differences in baseline clinical data or laboratory values between roxadustat group and rHuEPO group. After 24 months of follow-up, there was no significant difference in Hb levels (p > 0.05). There were no significant changes in blood pressure, or the incidence of nocturnal hypertension before and after treatment in roxadustat group (p > 0.05), while blood pressure significantly increased in rHuEPO group after treatment (p < 0.05). Compared with roxadustat group after follow-up, rHuEPO group had a higher incidence of hypertension, the levels of cardiovascular parameters were worse and cardio-cerebrovascular complications had a higher incidence (p < 0.05). Cox regression analysis showed age, systolic blood pressure, fasting blood glucose, and rHuEPO use before baseline were risk factors for cardio-cerebrovascular complications in PD patients, while treatment with roxadustat was a protective factor for cardiovascular and cerebrovascular complications. Conclusion: Compared with rHuEPO, roxadustat had less influence on blood pressure or cardiovascular parameters, and it was associated with a lower risk of cardio-cerebrovascular complications in patients undergoing PD. Roxadustat has a cardio-cerebrovascular protective advantage in PD patients with renal anemia.

A Deep Learning-Based Unbalanced Force Identification of the Hypergravity Centrifuge.

Accurate and quantitative identification of unbalanced force during operation is of utmost importance to reduce the impact of unbalanced force on a hypergravity centrifuge, guarantee the safe operation of a unit, and improve the accuracy of a hypergravity model test. Therefore, this paper proposes a deep learning-based unbalanced force identification model, then establishes a feature fusion framework incorporating the Residual Network (ResNet) with meaningful handcrafted features in this model, followed by loss function optimization for the imbalanced dataset. Finally, after an artificially added, unbalanced mass was used to build a shaft oscillation dataset based on the ZJU-400 hypergravity centrifuge, we used this dataset to train the unbalanced force identification model. The analysis showed that the proposed identification model performed considerably better than other benchmark models based on accuracy and stability, reducing the mean absolute error (MAE) by 15% to 51% and the root mean square error (RMSE) by 22% to 55% in the test dataset. Simultaneously, the proposed method showed high accuracy and strong stability in continuous identification during the speed-up process, surpassing the current traditional method by 75% in the MAE and by 85% in the median error, which provided guidance for counterweight and guaranteed the unit's stability.

Increased human risk caused by cascading hazards - A framework.

Cascading hazards occur frequently. Unexpected casualties and losses of properties, or even impacts on the society and the environment may ensue from failure to anticipate the amplified risks induced by cascading hazards. Current risk assessment methods pay relatively less attention to quantifying the increased human risk related to "cascading" events. An improved framework for quantifying the human risk caused by cascading hazards is proposed in this paper. The framework considers the interactions among the cascading hazards and among the vulnerabilities of elements to these hazards. Its kernel is to scientifically anticipate and gear up for any new intensified hazards, which may otherwise lead to serious social aftermath. The framework is illustrated with a multi-hazard example close to the epicenter of the Wenchuan earthquake, which involved a chain of hazards including slope failures, a large debris flow, river damming, and flooding.

Human health risk assessment for contaminated sites: A retrospective review.

Soil contamination is a serious global hazard as contaminants can migrate to the human body through the soil, water, air, and food, threatening human health. Human Health Risk Assessment (HHRA) is a commonly used method for estimating the magnitude and probability of adverse health effects in humans that may be exposed to contaminants in contaminated environmental media in the present or future. Such estimations have improved for decades with various risk assessment frameworks and well-established models. However, the existing literature does not provide a comprehensive overview of the methods and models of HHRA that are needed to grasp the current status of HHRA and future research directions. Thus, this paper aims to systematically review the HHRA approaches and models, particularly those related to contaminated sites from peer-reviewed literature and guidelines. The approaches and models focus on methods used in hazard identification, toxicity databases in dose-response assessment, approaches and fate and transport models in exposure assessment, risk characterization, and uncertainty characterization. The features and applicability of the most commonly used HHRA tools are also described. The future research trend for HHRA for contaminated sites is also forecasted. The transition from animal experiments to new methods in risk identification, the integration and update and sharing of existing toxicity databases, the integration of human biomonitoring into the risk assessment process, and the integration of migration and transformation models and risk assessment are the way forward for risk assessment in the future. This review provides readers with an overall understanding of HHRA and a grasp of its developmental direction.

Numerical model for static chamber measurement of multi-component landfill gas emissions and its application.

The quantitative assessment of landfill gas emissions is essential to assess the performance of the landfill cover and gas collection system. The relative error of the measured surface emission of landfill gas may be induced by the static flux chamber technique. This study aims to quantify effects of the size of the chamber, the insertion depth, pressure differential on the relative errors by using an integrated approach of in situ tests, and numerical modeling. A field experiment study of landfill gas emission is conducted by using a static chamber at one landfill site in Xi'an, Northwest China. Additionally, a two-dimensional axisymmetric numerical model for multi-component gas transport in the soil and the static chamber is developed based on the dusty-gas model (DGM). The proposed model is validated by the field data obtained in this study and a set of experimental data in the literature. The results show that DGM model has a better capacity to predict gas transport under a wider range of permeability compared to Blanc's method. This is due to the fact that DGM model can explain the interaction among gases (e.g., CH4, CO2, O2, and N2) and the Knudsen diffusion process while these mechanisms are not included in Blanc's model. Increasing the size and the insertion depth of static chambers can reduce the relative error for the flux of CH4 and CO2. For example, increasing the height of chambers from 0.55 to 1.1 m can decrease relative errors of CH4 and CO2 flux by 17% and 18%, respectively. Moreover, we find that gas emission fluxes for the case with positive pressure differential (∆Pin-out) are greater than that of the case without considering pressure fluctuations. The Monte Carlo method was adopted to carry out the statistical analysis for quantifying the range of relative errors. The agreement of the measured field data and predicted results demonstrated that the proposed model has the capacity to quantify the emission of landfill gas from the landfill cover systems.

The Effect of Sacubitril/Valsartan Treatment on Cardiac and Renal Functions of a Patient With Cardiorenal Syndrome Type 4 and Stage 5 CKD After More Than Three Years of Follow-Up.

It is difficult to treat cardiorenal syndrome (CRS) in clinical practice, which is the common reason for the death of patients. This report aimed to describe the effects of sacubitril/valsartan treatment on cardiac and renal functions of a patient with cardiorenal syndrome type 4 (CRS4) after more than 3 years of follow-up. A 77-year-old Chinese woman was admitted to our hospital because of CRS4 and stage 5 chronic kidney disease (CKD), who had a history of long-term proteinuria and renal failure. The patient's cardiothoracic ratio (CTR) measured by chest X-ray was 0.6. Cardiac ultrasonography showed that the left ventricular ejection fraction (LVEF) was 0.40. The patient had been treated for heart failure (HF) for 5 months, but there was no improvement in clinical manifestations, and the renal function gradually deteriorated. In our hospital, she received sacubitril/valsartan treatment for at least 40 months. The symptoms of HF relieved, and the indices of cardiac function improved. In addition, the patient's renal function was stable. During the treatment, the dosage of sacubitril/valsartan needed to be adjusted to achieve the optimal therapeutic effect. Follow-up results showed that she achieved cardiac function of New York Heart Association (NYHA) class II with an ejection fraction of 0.60 and E/A > 1 indicated by echocardiogram, and did not develop hyperkalemia. In summary, the improvement of cardiac and renal functions of the CRS4 patient was associated with the long-term sacubitril/valsartan treatment.

Measurement of contaminant adsorption on soils using cycling modified column tests.

An innovative cycled column test with supporting batch equilibrium and kinetic analysis for adsorption or desorption were developed for evaluation of adsorption behavior of soils. Non-equilibrium adsorption was observed in the cycled column tests as the traditional testing methods. The isotherm of local equilibrium of the soil was conducted based on the testing results within a relatively short duration with simple analysis. The concentration curves of influent and effluent of the cycled column tests were simulated by dual-porosity (DP) model with a modified inlet boundary. Based on the modeling results, the isotherm of local equilibrium is close to that of the mobile phase adsorption capacity, whereas the immobile phase of the soil is nearly inactive in the retardation of the contaminants. The testing results from cycled column tests are hardly interfered by desorption or the sorption rate according to the modeling for corresponding scenarios. The cycled column test can be used as an alternative or supplementary method to the traditional column test for the determination of local equilibrium isotherm, with advantages of shorter testing duration and easier data analysis.

The Migration and Deposition Behaviors of Montmorillonite and Kaolinite Particles in a Two-Dimensional Micromodel.

The pick-up, migration, deposition, and clogging behaviors of fine particles are ubiquitous in many engineering applications, including contaminant remediation. Deposition and clogging are detrimental to the efficiency of environmental remediation, and their mechanisms are yet to be elucidated. Two-dimensional microfluidic models were developed to simulate the pore structure of porous media with unified particle sizes in this study. Kaolin and bentonite suspensions were introduced to microfluidic chips to observe their particle deposition and clogging behaviors. Interactions between interparticle forces and particle velocity profiles were investigated via computational fluid dynamics and discrete element method simulations. The results showed that (1) only the velocity vector toward the micropillars and drag forces in the reverse direction were prone to deposition; (2) due to the negligible weight of particles, the Stokes number implied that inertia was not the controlling factor causing deposition; and (3) the salinity of the carrying fluid increased the bentonite deposition because of the shrinkage of the diffused electrical double layer and an increase in aggregation force, whereas it had little effect on kaolin deposition.

Soil heavy metal pollution of industrial legacies in China and health risk assessment.

Rapid urbanization in China has brought about large-scale factory relocation. Severe environmental ecological and human health risks are caused by a large number of contaminated legacies left in the city. To comprehensively review the pollution and assess the health risk of industrial legacies in China, a total of 625 polluted industrial legacies were compiled by document retrieval. Legacies are mainly located in the southwest of China, the North China Plain, Yangtze River Basin, Yangtze River Delta, and Pearl River Delta with a mean operation time of 35 years, and legacies of chemical manufacturing take the biggest proportion of all sites. Health risk assessments considering the uncertainty of exposure and toxic factors reveal that the soil heavy metal pollution in China is serious, with Pb, Cd, Zn, Ni, and As as dominant pollutants. Legacies of chemical manufacturing, ferrous metal processing, non-ferrous metal processing, and mines should be priority controlled for their large number and serious risks. Children are the most vulnerable people with more serious non-carcinogenic and carcinogenic risks, while males are slightly surpassed by females. Insights for better risk management of legacies are provided based on the comprehensive assessment of pollution and human health risk in this study.

Evaluating iron remediation with limestone using spectral induced polarization and microscopic techniques.

Groundwater contamination with iron caused by mining and landfill activities has fueled the development of remediation strategies. Permeable reactive barriers (PRBs) are commonly applied in subsurface remediation because of their high removal effect and low costs. Spectral induced polarization (SIP) technique has been approved for its nondestructive ability to monitor the geochemical processes in porous media. In this study, SIP technique was applied for monitoring iron remediation by limestone at column scale. The chemical analysis showed the pH of the porous fluid increased - attributed to the dissolution of limestone, which promoted the precipitation of iron. The precipitate phases included both γ-FeOOH and Fe2O3 based on X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) results. The micro computed tomography (CT) technique investigated the uneven distribution of the precipitates in the column, which indicated the existence of preferential flow. SIP signals revealed the quantity of the accumulated iron precipitates, which was proved by the chemical measurement and calculation. SIP signals also derived the time evolution of both the average precipitate size and size distribution, which elucidated the processes of precipitate crystal growth and aggregation during Fe flow-through. Above results suggest that SIP holds the promise of monitoring the engineering barrier performance.

Datasets for liquefaction case studies of gravelly soils during the 2008 Wenchuan earthquake.

This Data in Brief article provides summarized information of the liquefaction case histories from the 12 May 2008 M w7.9 Wenchuan earthquake. According to the data processing procedures recommended in the related research article, all eighty-one case histories investigated by the present authors and seven other case histories from the literature are carefully compiled. All necessary information and the mean and standard deviation for some key parameters are given for these liquefaction case histories (i.e., site name, site location, site inclination angle, liquefaction manifestations, critical layer, soil sampling information, ground motion, total and effective stresses, shear-mass participation parameter, cyclic stress ratio (CSR) for M w=7.5, normalized shear wave velocity (V s1), data class and field testing time). These data may be used by colleagues to study the effect of gravel content on liquefaction behaviour of gravelly soils and develop the corresponding deterministic or probabilistic methods for liquefaction triggering evaluation.

Full-scale experimental study of methane emission in a loess-gravel capillary barrier cover under different seasons.

The methane emission in a loess-gravel capillary barrier cover (CBC) in winter and summer was investigated by constructing a full-scale testing facility (20 m × 30 m) with a slope angle of 14.5° at a landfill in Xi'an, China. Weather conditions, methane emission, gas concentration, temperature, and volumetric water content (VWC) in the CBC were measured. The temperature and moisture in the CBC showed a typical seasonal pattern of warm and dry in summer and cold and wet in winter. Accordingly, the maximum methane oxidation rate and methane emission were higher in summer. The mean methane influx and methane emission decreased significantly as the VWC increased beyond 40% (i.e., a degree of saturation 0.85) at a depth of 0.85 m, which was near the loess/gravel interface. At this depth, more water was presented in the loess layer in the downslope direction due to capillary barrier effects, which increased the upslope methane emission. More dominant methane emission in the middle- and upper-section of the CBC occurred in summer than in winter as there was less soil moisture to facilitate methane transfer. The LFG balance showed that a significant fraction of the loaded LFG was not accounted in the flux chamber measurements due to the preferential flow along the edges of the CBC. The maximum methane oxidation rate was 93.3 g CH4 m-2 d-1, indicating the loess-gravel CBC could mitigate methane emissions after landfill closure.