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Abstract Dispersion coefficients and the average solute transport velocity are pivotal for groundwater solute transport modeling. Accurately and efficiently determining these parameters is challenging due to difficulties in directly correlating them with pore‐space structure. To address this issue, we introduced the Physics‐enhanced Convolutional Neural Network‐Transformer (PhysenCT‐Net), an innovative model designed to concurrently estimate the longitudinal dispersion coefficient and average solute transport velocity in three‐dimensional porous media. PhysenCT‐Net exhibited excellent predictive performance on unseen testing datasets and significantly reduced computational demands. Comprehensive evaluations confirmed its robust generalization across various flow conditions and pore structures. Notably, the longitudinal dispersion coefficient predictions closely align with established empirical relationships involving Péclet number, affirming the model's physical interpretability and potential to aid in simulating transport phenomena in porous media.

The heavy metal pollutant Cr (VI) has high toxicity and strong mobility, posing a great threat to groundwater safety. The current relevant soil standards often overlook groundwater safety. It is urgent to establish a Cr(VI) soil environmental reference value based on groundwater safety in order to provide support for the supervision of contaminated sites. In order to determine the calculation method of soil environmental reference value for groundwater protection that is in line with China’s characteristics, research and derivation of soil environmental reference value based on groundwater safety at home and abroad, and draw reference from foreign methods for formulating environmental reference value of pollutants based on groundwater safety. Taking Zhejiang clay loam, Jiangsu loamy sandy soil and Jilin loamy clay as research objects, the distribution coefficients of Cr(VI) in the three soils were obtained through indoor static adsorption tests. The soil parameters and aquifer-related parameters of the three soils were obtained through literature research, The soil screening level (SSL) method proposed by the United States Environmental Protection Agency in the Soil Screening Guidelines was adopted，based on groundwater quality standards (GBT14848—2017), a soil environmental reference value aiming at groundwater protection is obtained.The results show that the baseline values of Cr(VI) soil environment based on groundwater safety were 0.944 0.690, 0.514 mg/kg, respectively. The results are close to the reference values of foreign countries for the purpose of protecting groundwater safety. However, the differences of soil properties in each study area make the final base values different. Therefore, when improving the soil environmental quality system, local regulatory agencies should build a database of soil and aquifer parameters to help soil pollution control. The research results can provide scientific basis for deducing the environmental reference value of heavy metal soil based on groundwater safety in various regions of China.

Abstract Background B7 homology 4 (B7-H4), a potential target for cancer therapy, has been demonstrated to inhibit T cell cytotoxicity in the early stages of breast cancer. However, B7-H4 manipulating breast tumor immune microenvironment (TIME) in the tumor progression remains unknown. Methods We engineered T cells with B7-H4-specific chimeric antigen receptors (CARs) and performed a T cell co-culture assay to characterize B7-H4 expression level in breast cancer cells escaping from T cell cytotoxicity. We generated B7-H4 knockout (KO) and overexpression (OE) breast cancer cells to determine the epithelial-to-mesenchymal transition (EMT) and stemness characteristics in vitro and in vivo, including tumor proliferation, migration, metastasis and chemoresistance. The Cancer Genome Atlas breast cancer database was accessed to investigate the correlation between B7-H4 expression levels and EMT characteristics in patients with breast cancer. Results Our result found that B7-H4 expression level was significantly reduced in a subset of breast cancer cells that escaped from the cytotoxicity of B7-H4 CAR-T cells. Compared with wild type cells, B7-H4 KO cells prompt EMT and stemness characteristics, including migration, invasion and metastasis, and OE cells vice versa. The increase in H3K27me3 in KO cells confirmed the epigenetic reprogramming of cancer stem cells. The IC50 of doxorubicin or oxaliplatin significantly increased in KO cells, which was in agreement with a decrease in OE cells. Moreover, a trend of downregulated B7-H4 from stage I to stage II breast cancer patients indicates that the low-expressing B7-H4 breast cancer cells escaping from TIME have spread to nearby breast lymph nodes in the cancer progression. Conclusions Our study illuminates the novel role of renouncing B7-H4 in breast cancer cells through immune escape, which contributes to EMT processes and provides new insights for breast cancer treatments.

The drilling methods and the partitioning inter-well tracer tests which are often used to characterize dense non-aqueous phase liquids (DNAPL) source zones cost a lot. Compared with common methods, the single- well “push-pull” partitioning tracer tests not only save money, but also reduce the disturbance to the contaminated site, which can be used to estimate the residual DNAPL. However, the accuracy of this method in estimating residue DNAPL has not been quantitatively verified. To solve the problem, this paper analyses the influence of several factors on estimating the accuracy of residual DNAPL based on the numerical method, including tracer type, the injection and pumping rate and contaminant source zone architectures. The results display that Hexanol with a smaller partition coefficient than DMP can be selected for tests, as the tracer are recovered more fully, which can result in the average accuracy of residue DNAPL estimated to increase by 35.11%. When the injection rate of the tests increases from 100 m³/d to 130 m³/d and the pumping rate increases from 120 m3/d to 150 m3/d, the tracer can expose to a larger contaminant source area so that the average accuracy of the homogeneous source zones increases from 42.45% to 60.26% while the average accuracy of the heterogeneous source zones increases from 27.69% to 48.72%. The increase of the complexity of the source zone architectures will hinder the tracer migration, and the average accuracy of the heterogeneous source zones is 13.15% lower than that of the homogeneous source zones. The single well “push-pull” partitioning tracer test is more suitable for the ganglia-dominated contaminant source zones, and the average accuracy of the ganglia-dominated contaminant source zones is 15.74% higher than that of the pool-dominated source zones. The single-well “push-pull” partitioning tracer tests combined with numerical analysis can effectively estimate the distribution of residual NAPL, and are recommended for use in the fine investigation of DNAPL contaminated sites, so as to provide a reference for the risk assessment and the site remediation.

Abstract Molecular rotor‐based fluorophores (RBFs) activate fluorescence upon increase of micro‐viscosity, thus bearing a broad application promise in many fields. However, it remains a challenge to control how fluorescence of RBFs responds to viscosity changes. Herein, we demonstrate that the formation and regulation of intramolecular hydrogen bonds in the excited state of RBFs could modulate their rotational barrier, leading to a rational control of how their fluorescence can be activated by micro‐viscosity. Based on this strategy, a series of RBFs were developed based on 4‐hydroxybenzylidene‐imidazolinone (HBI) that span a wide range of viscosity sensitivity. Combined with the AggTag method that we previously reported, the varying viscosity sensitivity and emission spectra of these probes enabled a dual‐color imaging strategy that detects both protein oligomers and aggregates during the multistep aggregation process of proteins in live cells. In summary, our work indicates that installing intracellular excited state hydrogen bonds to RBFs allows for a rational control of rotational barrier, thus allow for a fine tune of their viscosity sensitivity. Beyond RBFs, we envision similar strategies can be applied to control the fluorogenic behavior of a large group of fluorophores whose emission is dependent on excited state rotational motion, including aggregation‐induced emission fluorophores.

Dense nonaqueous phase liquid (DNAPL) contamination is a growing problem. To assess the environmental risk of DNAPL-contaminated sites, the mass flux of the dissolved phase (mass flux) in the source zone of DNAPL contamination is often extrapolated using upscaling models. Due to the large number of parameters in the upscaling model and the high cost of investigation, the key parameters in the model need to be screened to guide the design of a reasonable observation data collection scheme for actual contaminated sites. In this paper, a global sensitivity analysis was first conducted on six parameters (mean groundwater velocity q, standardized concentration C0/Ceq, the mass ratio of ganglia GF0, the fraction of the mass flux attributable to the ganglia dissolution fg, and fitting parameters β1 and β2) in the upscaling model to identify the key parameters, and then a local sensitivity analysis was used to quantify the impact of changes in the key parameters on mass flux prediction. The results showed that the parameters q, C0/Ceq, GF0 and fg had a large impact on the mass flux prediction. The sensitivities of q and C0/Ceq were relatively high throughout the depletion process, while those of GF0 and fg increased continuously with the depletion process, reaching peaks in the middle and late stages of depletion, respectively. For source zones with different structures, the increase in mass flux was essentially constant when q or C0/Ceq increased. As the ganglia-to-pool (GTP) mass ratio increased in source zones, its effect on the mass flux prediction continued to increase or decrease when GF0 or fg increased. Therefore, the investigation needs to focus on q and C0/Ceq when predicting the mass flux, on GF0 when reasonably designing the remediation plan of the source zone, and on fg when predicting the lifetime of the source zone. For all structural source zones, q and C0/Ceq are the most important to investigate, and the investigation cost should be focused on GF0 for source zones with large GTP and fg for source zones with small GTP.

Contaminants in groundwater can spread downstream, causing risks to receptors along the path. The risk assessment of our current site groundwater contamination focuses mainly on human health risks. It rarely considers integrated risks of groundwater contamination, particularly neglecting risks to recepters at downstream locations. This study constructs a new index system and a tiered risk assessment approach for site groundwater contamination based on the “source-pathway-receptor” model considering risks to downstream receptors. For the construction of the index system, the source, pathway and receptor of site groundwater contamination are considered. For the risk assessment approach, a multi-tiered risk assessment are determined according to site groundwater contamination status. Based on the hypothetical case study of a chromium-contaminated site, four scenarios of groundwater contamination states are set. The spatio-temporal changes of groundwater contamination plumes are calculated by using the Wexler solute transport model, and risk assessment is carried out for different states of the groundwater contamination. The results show that in the two cases where the site groundwater contamination plumes have not reached the site boundary, the risk scores of the site groundwater are 4 and 6.2 points, respectively. The risk of the site groundwater at the two contamination states is low and medium, respectively. In the two cases where the site groundwater contamination plumes have arrived or exceeded the site boundary, the risk scores of the site groundwater are 7.0 and 8.8 points, respectively. The corresponding risk at the two contamination states is medium and high, respectively. It can be seen that this new method can comprehensively assess the potential level of harm of groundwater contamination to both human health and ecological environment, and therefore can provide technical support for the management of contaminated sites.

Research on combined phytotoxicity of perfluorooctanoic acid (PFOA) and nanoparticles is very important for the remediation of PFOA contaminated soil and further assessment for the potential of nano-enhanced phytoremediation. Here, joint effects of PFOA and CuO nanoparticles (nCuO) in plants were studied by exposing radish (Raphanus sativus L.) to PFOA (4 mg/kg) and nCuO (200 and 400 mg/kg) for 30 days, and measuring for contaminant accumulation, radish biomass, photosynthesis profiles and nutrient contents. Results showed that PFOA accumulated highly in radish organs but showed limited effects on radish biomass. nCuO could increase the transfer rate of PFOA from root to shoot and reduce PFOA accumulation in edible root part, but higher nCuO lead to decreased radish biomass. Reversely, PFOA alleviated the adverse effects of nCuO on leaf photosynthesis and root metabolism of vitamins and amino acids. These results provided basics for exploring possibility of nano-enhanced phytoremediation for PFOA soil pollution.

The Ensemble Kalman Filter (EnKF) has been widely applied for real-time simulation of groundwater flow and solute transport. The majority of previous studies tend to assume no bias in forecast models, therefore ignoring the model uncertainties. This assumption, however, may be invalid when a conceptual model is not accurately generalized. As a result, forecast bias will lead to incorrect estimation of the system parameters or states. In this work, a bias aware Ensemble Kalman Filter with Confirming Option (Bias-CEnKF) is proposed to take into account the forecast bias by the model during the filtering process. The proposed method is tested in a real-time groundwater simulation considering model uncertainties, by setting inaccurate boundary conditions, initial conditions and recharge items. The results show that the standard EnKF may lead to filter divergence and assimilation failure, if the forecast model is not accurately generalized. Instead, Bias-CEnKF not only achieves better performances, but also reduces the inconsistency caused by the nonlinear relationship among the parameters, variables and bias corrections. Four scenarios are investigated, with the results showing the aquifer hydraulic conductivities and heads obtained by Bias-CEnKF are close to the real values, and the prediction results are also more reliable. This study further improves the applicability of the EnKF under the uncertain condition of model generalization, and provides a reliable method for groundwater data assimilation under complex field conditions.

Groundwater resource is the basic power for the socio-economic development of arid-inland basins, and is also the major factor affecting the ecological environment of the Huangqihai Lake. As a typical study area of arid-inland basins, with the lowering of groundwater levels in recent years, the total area of the Huangqihai Lake decreases and even faces the risk of drying up. To quantitatively analyze the spatial-temporal evolution of groundwater resources in the Huangqihai Basin and the transformation relationship between lake water and groundwater, a numerical simulation model of groundwater flow in the Huangqihai Basin is established. The model is calibrated and validated by using long-term observation data from 2010 to 2016. The simulation results show that the accumulative deficit of groundwater storage in the Huangqihai Basin is 1.5×108 m3 from 2010 to 2016, and over-exploitation of groundwater is the critical reason for the negative water balance in this area. The Sobol method is used to identify the controlling factors affecting the changes of groundwater resources in this area. The sensitivity of eight main parameters affecting the groundwater system is evaluated by using four objective functions: lake stage, lake leakage, groundwater storage and groundwater discharge to lake. There are significant differences in sensitivity analysis results of model parameters under different objective functions. The first two functions are significantly affected by the horizontal permeability and lake leakage rate, while the last two are mainly affected by exploitation and recharge from precipitation and irrigation. It is proved that the influence of over-exploitation of groundwater is the main controlling factor of the depletion of water resources and shrinking of lake area in the Huangqihai Basin. The results of this study can provide technical support and scientific decision making for the sustainable utilization of groundwater resources and the protection of surrounding ecological environment in the Huangqihai Basin.

A physical unclonable function (PUF) is a technology designed to safeguard sensitive information and ensure data security. PUFs generate unique responses for each challenge by leveraging random deviations in the physical microstructures of integrated circuits (ICs), making it incredibly difficult to replicate them. However, traditional silicon PUFs are now susceptible to various attacks, such as modeling attacks using conventional machine learning techniques and reverse engineering strategies. As a result, PUFs based on new materials or methods are being developed to enhance their security. However, in the realm of survey papers, it has come to our attention that there is a notable scarcity of comprehensive summaries and introductions concerning these emerging PUFs. To fill this gap, this article surveys PUFs based on novel technologies in the literature. In particular, we first provide an insightful overview of four types of PUFs that are rooted in advanced technologies: bionic optical PUF, biological PUF, PUF based on printed electronics (PE), and PUF based on memristors. Based on the overview, we further discuss the evaluation results of their performance based on specific metrics and conduct a comparative analysis of their performance. Despite significant progress in areas such as limited entry and regional expertise, it is worth noting that these PUFs still have room for improvement. Therefore, we have identified their potential shortcomings and areas that require further development. Moreover, we outline various applications of PUFs and propose our own future prospects for this technology. To sum up, this article contributes to the understanding of PUFs based on novel technologies by providing an in-depth analysis of their characteristics, performance evaluation, and potential improvements. It also sheds light on the wide range of applications for PUFs and presents enticing prospects for future advancements in this field.

The infiltration process in the vadose zone is affected by many factors. A quantitative study of the influence of the layered heterogeneous lithological structure and infiltration rate on the process of water infiltration in the vadose zone is helpful in selecting a single-phase flow model or water-gas two-phase flow model for simulating the infiltration process in the vadose zone under different conditions. In this study, combined with stratum conditions of landfills and other sites and the infiltration characteristics of polluted or waste water, water infiltration single-phase flow and water-gas two-phase flow models are established under the “upper fine and lower coarse” and “upper coarse and lower fine” layered heterogeneous lithological structures of the vadose zone, in order to discuss the applicability of the models under different layered heterogeneous lithological structures. Based on the “upper coarse and lower fine” lithological structural model, the influence of infiltration rate on the results of water-gas two-phase migration is further explored. The results based on paper models show that (1) under the “upper fine and lower coarse” lithological structure condition of the vadose zone, the influence of the gas phase can be ignored and the single-phase flow model can be used to simulate water migration in the vadose zone. Under the settings of the “upper coarseness and lower fineness” lithological structure, the fixed bottom pressure and no precipitation infiltration before the leakage of sewage and wastewater in this model, gas phase has a significant impact on the water migration when the permeability ratio of the upper and lower media in the vadose zone is greater than about 16 times, and the lower the permeability of the underlying medium and the greater the permeability ratio of the upper and lower media, the greater the difference between the results of the single-phase flow and water-gas two-phase flow. It is necessary to use the water-gas two-phase flow model to simulate the water migration in the vadose zone. (2) Under the “upper coarseness and lower fineness” lithological structure condition of the adose zone, the greater the infiltration rate, the stronger the blocking effect of air on the water infiltration, and the water-gas two-phase flow model should be used to simulate the process of water migration in the vadose zone.

AbstractA methodology for simulating groundwater flow in three-dimensional (3D) stochastic fracture rocks based on a commonly used finite-difference method is presented in this paper. Different realizations of fracture networks are generated by the fracture continuum method (FCM), in which appropriate 3D cuboids are used to describe the geometry of fractures. Then, the effects of different parameter distributions on the fracture networks indicated that the length, orientation, and density of fractures all play significant roles in the connectivity of fractures in this methodology. Greater length and density and wider orientation range of fractures lead to greater connectivity. The proper contrast in hydraulic conductivities between the fractures and matrix is found to be approximately 105 due to the contribution of fluid flow in the matrix which can be ignored. It is shown that the fracture density plays a key role in stabilizing the equivalent hydraulic conductivity (Ke) of the fracture networks. Furthermore, the greater length and closer orientation of fractures to the general flow direction, the larger Ke of the generated fracture networks possess. The findings of this study can help for a better understanding of the mechanism of FCM and the influence of geometry characteristics on the hydraulic conductivity of FCM models.

Gaussian Process Regression (GPR) is a supervised learning algorithm based on Bayesian theory, which is widely used in model structural uncertainty analysis based on data-driven method (DDM). In this study, it is usually assumed that the physical parameters and hyperparameters are independent and identified jointly, which will lead to parameter compensation. In this paper, a two-stage based DDM method is proposed to quantify the model structural errors, and two case studies are used to compare and analyze the results of parameter identification and model prediction with considering the model structural errors (joint calibration based DDM and two-stage based DDM) and without considering the model structural errors. The results show that when the parameters are identified directly without considering the model structural errors, the parameters will be overfitted and compensate the model structural errors, thereby affecting the model prediction performance. When considering the model structure deviation based on DDM, the independence assumption of physical parameters and hyperparameters will affect the parameter estimation results. The proposed two-stage based DDM method does not assume that the physical parameters and hyperparameters are independent, and can reduce parameter overfitting caused by the independence assumption of physical parameters and hyperparameters, portraying more accurate structural errors and effectively improving the model prediction performance.

Seawater intrusion (SI) has become a global concern for groundwater environment. SI not only seriously threatens freshwater resources in coastal aquifers, but also undermines the balance of coastal ecosystem and further restricts the socioeconomic development. This paper simulates the SI process in a 2D synthetic aquifer constructed from sandbox experiment using the simulator SEAWAT-2000. The transport phenomenon of the brackish water interface is investigated by altering the location and injection rate of a recharge well and the layout of the physical barrier. The results show that when the recharge well is located near the toe of the salt water wedge of 40 cm from the coastline and 5 cm from the surface, the optimal performance of the recharge scheme is achieved with the repulsion rate up to 21.5%. When the physical barrier is located 10 cm from the coastline and the penetration depth is 35 cm, the toe of saltwater wedge is effectively driven to the coastline with the repulsion rate up to 81.8%. Moreover, we simulate the variable-density groundwater flow and transport in a typical two-dimensional section of coastal aquifer in the Longkou District of Shandong Province. The SI model is established to evaluate the influences of different management schemes (i.e., physical barrier and recharge well) on the prevention of seawater intrusion. The results show that when the physical barrier is located 600 m from the coastline and the penetration depth is 18 m, the toe of salt water wedge is effectively driven back to the coastline with the repulsion rate up to 28.4%. The results reveal the influence of hydraulic and physical barriers under different settings on the migration rule of the brackish water interface. The findings may provide insights into the optimization suggestions for coastal groundwater management under site conditions.

The inconsistency between continuous feedrate scheduling and discrete interpolation of Non-Uniform Rational B-Splines (NURBS) curves as toolpath interpolation affects the interpolation accuracy and motion smoothness of computer numerical control (CNC) machining. The S-shaped series feedrate scheduling method of the NURBS curve is presented to meet the consistency between feedrate scheduling and interpolation, and the needs of the motor to receive accurate discrete pulses to avoid chatter. The acceleration and deceleration margin factor models are respectively established in the acceleration and deceleration stages to compensate for the velocity loss in the discrete process, so that the feedrate scheduling can be accurately reached in each acceleration and deceleration stage. Based on this, 17 kinds of acceleration and deceleration situations are summarized according to the comparison of displacement, start and end velocity, and the number of interpolation cycles. The butterfly three-segment trajectories are selected for simulation in Matlab. The experimental platform is built based on the Codesys platform programing, and the series feedrate scheduling of the proposed method for a NURBS toolpath is carried out. Both simulations and experiments have verified the effectiveness of the algorithm.

Understanding the fate and transport of polystyrene nanoparticles (PSNPs) in porous media under various conditions is necessary for evaluating and predicting environmental risks caused by microplastics. The transport kinetics of PSNPs are investigated by column experiment and numerical model. The surface of DLVO interaction energy is calculated to analyze and predict the adsorption and aggregation of PSNPs in porous media, which the critical ionic strength of PSNPs can be accurately investigated. The results of the DLVO energy surface suggest that when the concentration of Na+ increases from 1 mM to 50 mM, the DLVO energy barrier of PSNPs-silica sand (SS) decreases from 78.37 kT to 5.46 kT. As a result, PSNPs are easily adsorbed on the surface of SS and the mobility of PSNPs is reduced under the condition of a high concentration of Na+ (PSNPs recovery rate decreases from 62.16% to 3.65%). When the concentration of Ca2+ increases from 0.1 mM to 5 mM, the DLVO energy barrier of PSNPs-SS decreases from 12.10 kT to 1.90 kT, and PSNPs recovery rate decreases from 82.46% to 4.27%. Experimental and model results showed that PSNPs mobility is enhanced by increasing initial concentration, flow velocity and grain size of SS, while the mobility of PSNPs with larger particle diameter is lower. Regression analysis suggests that kinetic parameters related to PSNPs mobility are correlated with DLVO energy barriers. The environmental behavior and mechanism of PSNPs transport in porous media are further investigated in this study, which provides a scientific basis for the systematic and comprehensive evaluation of the environmental risk and ecological safety of nano-plastic particles in the groundwater system.

Investigation of extreme precipitation events in arid and semiarid regions, especially for occurrence time and the associated circulation mechanisms, is vital to support the forecasting of and the advanced response to resultant disasters. In this study, the spatiotemporal pattern of occurrence time of extreme precipitation and atmospheric circulation mechanisms in the Arid Region of Northwest China (ARNC) were analyzed using two indicators (precipitation concentration degree and period) and the climate diagnosis method. Results showed that the significant scattered pattern of extreme precipitation occurrence time (EPOT) in Northern Xinjiang and the postponed pattern of maximum extreme precipitation occurrence (MEPO) from southern to northern Xinjiang are consistent with the input pathway of the Arctic air mass. During the anomaly dispersion year of EPOT and the anomaly delay year of MEPO, the Arctic air mass carried sufficient water vapor is transported to ARNC for triggering extreme precipitation events. Meanwhile, the pattern of concentration–dispersion–concentration in eastern ARNC demonstrates interaction between the westerlies and the summer monsoon. Sufficient water vapor is transported to southwestern ARNC by the southwest monsoon during the anomaly delay year of MEPO and the anomaly concentration year of EPOT. The findings of this study suggest that invasion of the Arctic air mass and the summer monsoon could influence extreme precipitation in ARNC.

In order to investigate the distribution characteristics of pollutants at contaminated sites, it is necessary to collect soil and groundwater samples by drilling and test them by the standard procedure. In the preliminary and detailed investigation, a large amount of data of soil and groundwater pollution will be obtained. These data are often characterized by large sample size, multiple monitoring indicators and complex data structures, and how to extract valuable information from the big data has become an important research issue. This study takes an organic contaminated site as an example, and carries out big data analytics by using self-organizing map (SOM) and k-means algorithm to explore the correlation between each organic pollution indicator of groundwater and soil. The results show that (1) the big data analytics based on self-organizing map can rapidly mine the complicated multi-dimensional monitoring data of contaminated site, and extract key information effectively. (2) The pollution indicators in groundwater are characterized by significant clustering, and the indicators in the same cluster are of similar spatial distribution characteristics. In view of this, a screening strategy may classify the indicators first and then rank them, and can be adopted at contaminated site to reduce the number of pollution indicators detected and finally save the cost of site detection. (3) The pollution indicators in soil and groundwater also have strong spatial correlation, which is mainly due to the slow seepage velocity of groundwater. According to the correlation of the spatial distribution of pollution indicators in soil and groundwater, it is helpful to trace the pollution sources at contaminated sites.

AbstractThe hydrogeochemical analysis and numerical simulation were conducted to explore the impact of land reclamation on submarine groundwater discharge and groundwater evolution in the seawater intrusion-retreat processes in eastern Jiangsu, China. The hydrogeochemical results indicated that the origin of salt in most groundwater is saltwater mixing, and weathering-dissolution of minerals enriches the salt in fresh groundwater. The evolution path of coastal groundwater in Jiangsu is Ca-Na-HCO3-Cl → Ca-Na-Cl-HCO3 → Na-Ca-Cl-HCO3 → Na-Mg-HCO3 → Na-Mg-HCO3-Cl → Na-Cl-HCO3 → Na-Cl, and the difference in groundwater evolution in different regions is obvious. The numerical simulation revealed that the land reclamation has blocked groundwater exchange and restrained the seawater intrusion. The sensitive analysis indicated that the permeability and the slope of the land reclamation have dominated the salinity distribution. And the aquifer heterogeneity promotes groundwater evolution and leads to the irregular salinity distribution of the groundwater. Moreover, the groundwater evolution in the shallow aquifer with the land reclamation shows that the residual seawater is gradually desalinating and discharged into the sea. The land reclamation is salinized by saltwater discharge and seawater intrusion together and then subsides into a stable saltwater wedge. The groundwater salinity distribution in Jiangsu is not fit seawater intrusion, which is caused by the coastline changes due to anthropogenic land reclamation and natural activities.

Under a persistent warming climate and increasing human activities, permafrost in the Source Area of the Yellow River (SAYR) has been degrading regionally, resulting in many eco-environmental problems. This paper reviews the changes in air temperature and precipitation over the past 60 years and presents the distribution and degradation of alpine permafrost in the SAYR. The review is focused on the permafrost degradation–induced changes in hydrology, wetlands, thermokarst lakes, ponds, and vegetation. Mean annual air temperatures have been rising at an average rate of 0.4°C/10a over the past 60 years, while precipitation has increased only slightly (16 mm/10a). Borehole temperature monitoring at the depth of 15 m shows the permafrost warming rates of 0.01–0.21°C/10a in the Headwater Aera of the Yellow River. As a result of permafrost thaw, the amount of surface waters has declined while groundwater storage has increased. Due to permafrost degradation, the supra-permafrost water table lowers gradually, resulting in a reduction in areal extents of wetlands and lakes in the SAYR. We further renamed the concept of the burial depth of the ecologically-safe supra-permafrost water table, the minimum depth of the groundwater table for sustaining the normal growth of alpine grassland vegetation, for the SAYR to describe the relationship between the lowering permafrost table and succeeding alpine vegetation. Furthermore, we recommended more studies focusing on snow cover and carbon stock and emissions related to permafrost degradation under a warming climate. We also advised to timely establish the long-term monitoring networks for the rapidly changing mountain cryosphere, alpine ecology, alpine hydrology, eco-hydrology, cryo-hydrogeology, and carbon fluxes. Moreover, process-based models should be developed and improved to better simulate and predict the responses of alpine ecosystem changes to the interacting cryospheric and other environmental variables and their ecological and ecohydrological impacts in the SAYR and downstream Yellow River basins. This study can help better manage the ecological and hydrological environments in the Upper Yellow River that are sensitive to changes in the alpine climate and cryosphere.

In this study, a pore-scale simulation method is applied to quantitatively study the variation of solute dilution through porous media with different cementation degrees and explore the corresponding mechanisms. The study results indicated that the cementation degrees of the solid grains had a significant effect on the solute dilution process and that the influence was very complicated. The complexity was manifested in that the effect of rising cementation degree on the solute dilution process would be different or even completely opposite in the porous media in which the solid grains cement slightly with that in porous media with a higher cementation degree. For example, for the porous media in which the solid grains were slightly cemented (the percentage of the cemented solid grains Pc is less than 40%), the dilution effects became enhanced with the increase of cementation degree. Then, after Pc increased to about 55%, the dilution effect was obviously weakened, and the solute was in an incomplete dilution state for a long period of time. In addition, this study found that the properties of the flow fields may vary greatly in porous media with different cementation degrees and that those differences in the flow fields resulted in the distinct behavior of the solute dilution. It is interesting to note that a more heterogeneous flow field had not necessarily led to the enhancement of the dilution process.

Polyamide (PA) and bisphenol A (BPA) are selected as typical microplastic and endocrine-disrupting chemicals in this study. The adsorption of BPA on the surface of PA and the effect of PA on the transport behavior of BPA in groundwater are systematically investigated using a combination of batch experiments, column experiments and numerical models. The results of scanning electron microscope (SEM) and Fourier transform infrared spectra (FTIR) show that the surface of PA particles is changed significantly after adsorption of BPA. The isothermal adsorption process of BPA can be simulated by the Langmuir model and the Freundlich model. Kinetic adsorption, on the other hand, can be fitted by a quasi-first-order adsorption model, and the adsorption results indicate that the maximum adsorption of BPA on PA reaches 13 mg·g−1. The results of the column experiments suggest that the mass recovery rate of BPA decreases with PA content, and increases with flow velocity, while initial concentration has no apparent influence on BPA transport. In addition, due to the hydrolysis of BPA, the mass recovery rate of BPA does not change with pH under conditions of pH < 10.2 and increases substantially to 94% when pH > 10.2. Moreover, Ca2+ has a significant inhibitory effect on the transport of BPA, while Na+ has no apparent influence on the transport of BPA. The transport process of BPA in porous media is simulated using a single-point kinetic model, and the fitted mathematical relationships for the variation of kinetic parameters with environmental factors are obtained by regression analysis.

Column experiments were conducted to investigate the effects of ion type, ion strength, humic acid (HA), and nanometer alumina (NA) particles on the transport of hexavalent chromium (HC) in saturated porous media. A one-dimensional model is developed to simulate the migration of HC affected by NA particles. The results show that nano-alumina particles would enhance the mobility of HC in saturated porous media. However, the influence of NA on the migration of HC in porous media is complex. When the concentration of NA reaches 30 mg/L, HC has minimum retention parameter and best mobility. The transport of HC also is affected by ion strength and ion type. Higher ionic strength would decrease the retention of HC and enhance its mobility. Compared with sodium ion, calcium ion has larger effects on the transport of HC. Moreover, HA can improve the mobility of HC in saturated porous media, but the corresponding promoting effect decreases with the increase of HA concentration. As nanometer contaminants and HC come into the subsurface environment, findings from this study elucidate the key factors and processes controlling the transport of HC in porous media, which can promote the prediction and assessment of HC in the groundwater system.

Water accumulation in permafrost regions causes a heavy thermal impact on the frozen layer, thereby leading to its degeneration. First, based on the real heat transfer process, this study proposes relevant hypotheses and governing equations for heat calculation models involving completely melted water, ice-bearing water, water–soil interface, and soil under water. The models consider the water surface as a thermal boundary on account of the natural buoyancy convection mechanism in water and the phase transition process. Second, this study verifies the accuracy of the calculation models regarding the measured water and permafrost temperatures. The four seasonal vertical temperature changes in the water according to this model are found to be consistent with the actual temperature-change trend, and the permafrost temperature under water is also consistent with the actual temperature field. This study thus provides theoretical support for the thermal impact analysis of water in permafrost regions.

Aiming at the particularity on the transition surface, this paper carried out research on adaptive speed planning, local optimization of machining toolpaths to improve the surface quality of the transition surface, and visualization of motion parameters to predict the surface quality of the transition surface. Constant speed interval planning and trajectory optimization were carried out on the transition surface between the bottom of a Cola bottle and the curved surface with variable curvature, respectively, and the visualization maps before and after optimization were obtained. The comparison showed that the motion parameters of the optimized visualization map had better smoothness. Further, the effectiveness of the estimated surface quality was verified through the actual machining of the variable curvature transition surface and Wuzhi mountain parts. The consistency of the improvement of the processed surface quality and the quality of the visualization were verified.

The Qinghai-Tibet Plateau (QTP) is the largest mid-to low latitude and high-altitude permafrost. Open-pit coal mining and other activities have caused serious damage to the alpine ecological environment and have accelerated the degradation of permafrost on the QTP. In this study, the influence of open-pit coal mining on the time series ground surface deformation of the permafrost in the Muli region of the QTP was analyzed from 19 January 2018 to 22 December 2020 based on Landsat, Gaofen, and Sentinel remote sensing data. The primary methods include human-computer interactive visual interpretation and the small baseline subsets interferometric synthetic aperture radar (SBAS-InSAR) method. The results showed that the spatial distribution of displacement velocity exhibits a considerably different pattern in the Muli region. Alpine meadow is the main land use/land cover (LULC) in the Muli region, and the surface displacement was mainly subsidence. The surface subsidence trend in alpine marsh meadows was obvious, with a subsidence displacement velocity of 10–30 mm/a. Under the influence of changes in temperature, the permafrost surface displacement was characteristics of regular thaw subsidence and freeze uplift. Surface deformation of the mining area is relatively severe, with maximum uplift displacement velocity of 74.31 mm/a and maximum subsidence displacement velocity of 167.51 mm/a. Open-pit coal mining had resulted in the destruction of 48.73 km2 of natural landscape in the Muli region. Mining development in the Muli region had increased the soil moisture of the alpine marsh meadow around the mining area, resulting in considerable cumulative displacement near the mining area and the acceleration of permafrost degradation.

The coal mining has brought a series of ecological problems and environmental problems in permafrost regions. Taking Muli coal-mining area as an example, this article attempts to analyse the environmental harms caused by coal mining and its protection measures in permafrost regions of Qinghai–Tibet Plateau. This article analyses the influence of open mining on the surrounding permafrost around the open pit by using the numerical simulation. The results show that (1) based on the interrelation between coal mining and permafrost environment, these main environmental harm include the permafrost change and the natural environment change in cold regions; (2) once the surface temperature rises due to open mining, the permafrost will disappear with the increase of exploitation life. If considering the solar radiation, the climate conditions and the geological condition around the pit edge, the maximum thaw depth will be more than 2 m; (3) the protection measures are proposed to avoid the disadvantage impact on the permafrost environment caused by coal mining. It will provide a scientific basis for the resource development and environment protection in cold regions.

In the literature, the mean penetration depth (MPD) calculated by “walk on spheres” or “walk on cubes” was used to quickly estimate the intrinsic permeability of digitized porous media. However, these two methods encounter difficulties such as irregular boundaries and the determination of arrivals at a boundary. In this study, an MPD method that is based on a more flexible “random walk on grid” (WOG) is explored. Moreover, the accurate MPDs for the pores of simple shapes are derived with Green’s functions to validate the WOG-based MPD. The results suggested that MPDs based on Green’s functions and WOG are consistent with each other; the factor C in the permeability expression is slightly dependent on roundness of the cross sections and is approximately 1.125 on average, according to analytical and numerical results. In a synthetic complex pore, the permeability estimated by WOG is comparable to, but greater than, the estimate based on the pore-scale dynamics simulation in COMSOL.

The permafrost in the Qilian Mountains (QLMs), the northeastern margin of the Qinghai–Tibet Plateau, changed dramatically in the context of climate warming and increasing anthropogenic activities, which poses significant influences on the stability of the ecosystem, water resources, and greenhouse gas cycles. Yet, the characteristics of the frozen ground in the QLMs are largely unclear regarding the spatial distribution of active layer thickness (ALT), the maximum frozen soil depth (MFSD), and the temperature at the top of the permafrost or the bottom of the MFSD (TTOP). In this study, we simulated the dynamics of the ALT, TTOP, and MFSD in the QLMs in 2004–2019 in the Google Earth Engine (GEE) platform. The widely-adopted Stefan Equation and TTOP model were modified to integrate with the moderate-resolution imaging spectroradiometer (MODIS) land surface temperature (LST) in GEE. The N-factors, the ratio of near-surface air to ground surface freezing and thawing indices, were assigned to the freezing and thawing indices derived with MODIS LST in considerations of the fractional vegetation cover derived from MODIS normalized difference vegetation index (NDVI). The results showed that the GEE platform and remote sensing imagery stored in Google cloud could be quickly and effectively applied to obtain the spatial and temporal variation of permafrost distribution. The area with TTOP < 0 °C is 8.4 × 104 km2 (excluding glaciers and lakes) and accounts for 46.6% of the whole QLMs, the regional mean ALT is 2.43 ± 0.44 m, while the regional mean MFSD is 2.54 ± 0.45 m. The TTOP and ALT increase with the decrease of elevation from the sources of the sub-watersheds to middle and lower reaches. There is a strong correlation between TTOP and elevation (slope = −1.76 °C km−1, p < 0.001). During 2004–2019, the area of permafrost decreased by 20% at an average rate of 0.074 × 104 km2·yr−1. The regional mean MFSD decreased by 0.1 m at a rate of 0.63 cm·yr−1, while the regional mean ALT showed an exception of a decreasing trend from 2.61 ± 0.45 m during 2004–2005 to 2.49 ± 0.4 m during 2011–2015. Permafrost loss in the QLMs in 2004–2019 was accelerated in comparison with that in the past several decades. Compared with published permafrost maps, this study shows better calculation results of frozen ground in the QLMs.

Water resource is an important part of human living and production. With the modernization of cities, the problem of groundwater contamination is becoming more and more serious. It is outstanding to effectively assess the risk of groundwater contamination to human health. This paper proposes a human health risk assessment method based on the simulation of contaminant transport process and parameter uncertainty analysis. The method combines health risk assessment with groundwater contaminant transport processes and applies the TOUGH2 program to simulate the temporal and spatial distribution of contaminant in groundwater. In order to improve the accuracy of the assessment results, the influence of the uncertainty of the transport model on human health risk assessment is taken into account. And the key parameter (e.g., the permeability) of the transport model is inversed by Markov chain Monte Carlo simulation method. Based on a sandbox experiment, the human health risk exposed to a typical dense non-aqueous phase liquids contaminant tetrachloroethylene (PCE) is evaluated by considering the parameter uncertainty of the PCE transport model, which confirmed that the method can provide decision-making information for the management and prevention of contaminated sites.

Solute transport through homogeneous media has long been assumed to be scale-independent and can be quantified by the second-order advection-dispersion equation (ADE). This study, however, observed the opposite in the laboratory, where transport of CuSO4 through relatively homogeneous silica-sand columns exhibits sub-diffusion growing with the spatial scale. Only at a very small travel distance (approximately 10 cm) and a relatively short temporal scale can the transport be approximated by normal diffusion. This is also the only spatiotemporal scale where the fundamental concept of the “representative element volume” (which defines the scale of homogeneous cells used by the ADE-based hydrologic models) is valid. The failure of the standard ADE motivated us to apply a tempered-stable, fractional advection-dispersion equation (TS-FADE) to capture the transient anomalous dispersion with exponentially truncated power-law late-time tails in CuSO4 breakthrough curves. Results show that the tempering parameter in the TS-FADE model generally decreases with an increase of the column length (probably due to the higher probability of long retention processes), while the time index (which is a non-local parameter) remains stable for the uniformly packed columns. Transport in sand columns filled with relatively homogeneous silica sand, therefore, is scale-dependent, and the resultant transient sub-diffusion can be quantified by the TS-FADE model.

Two new steroidal alkaloids, named hookerianine A (1) and hookerianine B (2) were isolated from the stems and roots of Sarcococca hookeriana Baill., along with two known compounds, sarcorucinine G (3) and epipachysamine D (4). On the basis of spectroscopic methods and by comparison with literature data, their structures were determined. As well as X-ray crystallography was performed to confirm compound 4. To identify novel antitumor inhibitors, all compounds were performed a CCK-8 assay against five human cancer cell lines SW480, SMMC-7721, PC3, MCF-7 and K562 in vitro. Compound 2 exhibited moderate cytotoxic activities to all cell lines with IC50 values in the range of 5.97⁻19.44 μM. Compound 3 was the most effective one against SW480 and K562 cell lines with IC50 values of 5.77 and 6.29 μM, respectively.

In hydrological statistics, the traditional assessment of goodness of fit test is interested in the testing precision to the sample generated from supposed PDF. However, the ability to reject the hypotheses when the supposed PDF is different from real PDF should be also emphasized. In addition, the sensitivity of test method to series length is important in hydrological analysis. Three methods of goodness of fit test that include Chi-Square (C-S), Kolmogorov-Smirnov (K-S), and Anderson-Darling (A-D) tests are applied in this study. The results of power test indicate that the most powerful tests for normal, uniform, P3, and Weibull distribution are K-S, C-S, and A-D tests, respectively. The test method with the best comprehensive power is C-S test, followed by K-S and A-D test.

We establish conditions for the extinction of solutions, in finite time, of the fast diffusion problem $u_t=Delta u^m+lambda u^p$, 0 less than $m$ less than 1, in a bounded domain of $R^N$ with $N$ greater than 2. More precisely, we show that if p greater than m, the solution with small initial data vanishes in finite time, and if $p$ less than $m$, the maximal solution is positive for all $t$ greater than $0$. If $p=m$, then first eigenvalue of the Dirichlet problem plays a role.

This paper uses Gumbel-Hougaard (G-H) copula, Clayton copula and Frank copula to construct joint distributions of hydrological variables of the two typical stations on the Yellow River Region, including the annual maximum flood magnitude (AMFM), the annual maximum flood occurrence date (AMFOD) and the annual runoffs (ARs). The results give the joint distribution between each pair of the variables. Also an isoline of the concurrence return periods between the AMFMs of the two stations was drawn up.