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Previous studies have shown that geostatistics-based transient hydraulic tomography (THT) is robust for subsurface heterogeneity characterization through the joint inverse modeling of multiple pumping tests. However, the hydraulic conductivity ( K ) and specific storage ( S s ) estimates can be smooth or even erroneous for areas where pumping/observation densities are low. This renders the imaging of interlayer and intralayer heterogeneity of highly contrasting materials including their unit boundaries difficult. In this study, we further test the performance of THT by utilizing existing and newly collected pumping test data of longer durations that showed drawdown responses in both aquifer and aquitard units at a field site underlain by a highly heterogeneous glaciofluvial deposit. The robust performance of the THT is highlighted through the comparison of different degrees of model parameterization including: (1) the effective parameter approach; (2) the geological zonation approach relying on borehole logs; and (3) the geostatistical inversion approach considering different prior information (with/without geological data). Results reveal that the simultaneous analysis of eight pumping tests with the geostatistical inverse model yields the best results in terms of model calibration and validation. We also find that the joint interpretation of long-term drawdown data from aquifer and aquitard units is necessary in mapping their full heterogeneous patterns including intralayer variabilities. Moreover, as geological data are included as prior information in the geostatistics-based THT analysis, the estimated K values increasingly reflect the vertical distribution patterns of permeameter-estimated K in both aquifer and aquitard units. Finally, the comparison of various THT approaches reveals that differences in the estimated K and S s tomograms result in significantly different transient drawdown predictions at observation ports. [ABSTRACT FROM AUTHOR]

Transient hydraulic tomography (THT) is a robust method of aquifer characterization to estimate the spatial distributions (or tomograms) of both hydraulic conductivity ( K ) and specific storage ( S s ). However, the highly-parameterized nature of the geostatistical inversion approach renders it computationally intensive for large-scale investigations. In addition, geostatistics-based THT may produce overly smooth tomograms when head data used to constrain the inversion is limited. Therefore, alternative model conceptualizations for THT need to be examined. To investigate this, we simultaneously calibrated different groundwater models with varying parameterizations and zonations using two cases of different pumping and monitoring data densities from a laboratory sandbox. Specifically, one effective parameter model, four geology-based zonation models with varying accuracy and resolution, and five geostatistical models with different prior information are calibrated. Model performance is quantitatively assessed by examining the calibration and validation results. Our study reveals that highly parameterized geostatistical models perform the best among the models compared, while the zonation model with excellent knowledge of stratigraphy also yields comparable results. When few pumping tests with sparse monitoring intervals are available, the incorporation of accurate or simplified geological information into geostatistical models reveals more details in heterogeneity and yields more robust validation results. However, results deteriorate when inaccurate geological information are incorporated. Finally, our study reveals that transient inversions are necessary to obtain reliable K and S s estimates for making accurate predictions of transient drawdown events. [ABSTRACT FROM AUTHOR]

• HPT surveys at a site with K spanning nearly-seven orders of magnitude. • HPT reveals both sharp and gradual changes in K values across layer boundaries. • Integration of HPT-inverted K into HT yields better matches with permeameter K. • HPT K can help HT refine layer boundaries and capture intralayer K variability. Hydraulic profiling tool (HPT) and hydraulic tomography (HT) have been developed as promising techniques for the high-resolution characterization of surficial aquifer systems. HPT surveys can be rapidly conducted at a resolution of 1.5-cm, but provide only one-dimensional vertical profiles and require site-specific formulae to relate HPT measurements to K. Geostatistics-based HT can estimate three-dimensional distributions of hydraulic parameters, but may fail to provide detailed information and can be smooth when pumping/observation data density is sparse and usually are constrained to the area enclosed by the pumping and observation network. In this study, HPT and HT surveys were conducted at the North Campus Research Site (NCRS) in Waterloo, Ontario, Canada to characterize a glaciofluvial multi-aquifer-aquitard system with permeameter K values spanning nearly seven orders of magnitude. We first performed the geostatistical analysis of K values derived from 11 HPT surveys using the power-law model developed for the NCRS by Zhao and Illman (2022b). Then, the benefits of incorporating HPT K profiles into HT were evaluated for the reconstruction of hydraulic parameter fields. Results showed that the arithmetic mean of 11 HPT K profiles was nearly one order of magnitude higher than that of the 544 permeameter test K measurements. The K fields interpolated by ordinary kriging captured the vertical alternating layering patterns of aquifer and aquitard layers, while they over-predicted the values by nearly one order of magnitude than permeameter K for the top part of the aquifer system. By incorporating the kriged K values as prior means for the geostatistics-based HT, improvements were found in capturing spatial heterogeneity of K fields for areas both inside and outside the well cluster and in drawdown predictions than the inversion case using only pressure head data. The inclusion of vertical variation information of K derived from HPT into HT was also helpful in refining the vertical locations of estimated layer boundaries and introducing intralayer variation patterns of K for both aquifer and aquitard layers. This study demonstrates the potential ability of HT and HPT and advocates the joint use of both techniques for the characterization of subsurface heterogeneity at highly heterogeneous sites such as the NCRS. [ABSTRACT FROM AUTHOR]

Hydraulic tomography (HT) has been shown to map subsurface heterogeneity accurately through the joint interpretation of multiple pumping tests. Previous research has shown that smooth hydraulic conductivity ( K ) estimates are obtained beyond where pumping/observation data are available using the geostatistical inversion approach, when the inversion begins with a homogeneous K and when data densities are not high. However, geological data are typically available through outcrops and borehole logs to provide geological variability. Therefore, we investigate the usefulness of geological data for HT analysis at a highly heterogeneous field site by: (1) comparing calibrated geological models of two different resolutions to two homogeneous and four highly parameterized geostatistical inverse models, in terms of both model calibration and validation performances as well as correspondence of estimated K values with permeameter-estimated K profiles along boreholes; and (2) using geological models as prior information for the geostatistical inversion approach. Results reveal that the simultaneous calibration of geological models to seven pumping test data yields K values that correctly reflect the general patterns of vertical distributions of permeameter-estimated K . We also find that the geostatistical inversion approach using a geological model as prior information performs better for both model calibration and validation than using a homogenous K as a prior, and more importantly, improves the correspondence of K estimates to permeameter test results along wells, as well as in preserving geological features where drawdown measurements are lacking. Overall, our results suggest the joint use of both geological and pumping test data for HT analysis when accurate geological data are available. [ABSTRACT FROM AUTHOR]

This paper investigates the importance of geological data in Hydraulic Tomography (HT) through sandbox experiments. In particular, four groundwater models with homogeneous geological units constructed with borehole data of varying accuracy are jointly calibrated with multiple pumping test data of two different pumping and observation densities. The results are compared to those from a geostatistical inverse model. Model calibration and validation performances are quantitatively assessed using drawdown scatterplots. We find that accurate and inaccurate geological models can be well calibrated, despite the estimated K values for the poor geological models being quite different from the actual values. Model validation results reveal that inaccurate geological models yield poor drawdown predictions, but using more calibration data improves its predictive capability. Moreover, model comparisons among a highly parameterized geostatistical and layer-based geological models show that, (1) as the number of pumping tests and monitoring locations are reduced, the performance gap between the approaches decreases, and (2) a simplified geological model with a fewer number of layers is more reliable than the one based on the wrong description of stratigraphy. Finally, using a geological model as prior information in geostatistical inverse models results in the preservation of geological features, especially in areas where drawdown data are not available. Overall, our sandbox results emphasize the importance of incorporating geological data in HT surveys when data from pumping tests is sparse. These findings have important implications for field applications of HT where well distances are large. [ABSTRACT FROM AUTHOR]

• A calibrated perfect-geological model yields better flow and transport predictions. • With HT-inverted K fields, the ADE can reasonably simulate tracer plumes and BTCs. • Fusing geology into geostatistics-based HT reveals inter- and intra-layer K changes. • High-resolution K fields with geological features reproduce plume fingering vividly. Hydraulic tomography (HT) has been developed over the last two decades to image subsurface heterogeneity at high resolution that is critically important to robust solute transport predictions. In this study, HT based on two concepts (i.e., geological zonation and geostatistical inversion models) was utilized to characterize the K distribution of a laboratory sandbox aquifer at different parameter resolutions. We compared the estimated K fields for predicting independent pumping tests and solute transport using the classical advection–dispersion equation (ADE). The impact of using geological zonation models of varying accuracy for HT analyses was investigated. Results revealed that, when being calibrated to datasets from multiple pumping tests, geological zonation models that faithfully represented the true stratigraphy predicted groundwater flow satisfactorily. The deterministic K field of the calibrated reliable geological zonation models satisfactorily reproduced the preferential migration path of the observed tracer plume, and the breakthrough curves (BTCs) at sampling ports. With further resolving the inter- and intra-layer heterogeneity, the reconstructed K fields by HT better predicted both migrating plumes and BTCs for two conservative tracer tests. The estimated dispersivity values for ADE only resulted in slight improvements in the fitting between observed and simulated solute tracer data. It also demonstrated the need of integrating reliable geological information into the geostatistical inversion approach to reproduce geological structures in K fields. Our study suggested the proper consideration of geological zonation between boreholes during field implementation of HT to yield improved solute transport results. [ABSTRACT FROM AUTHOR]

• Inverse modeling approach proposed to invert cm-scale K from HPT surveys. • Based on inverted K , a new power-law model was developed for HPT surveys at NCRS. • The site-specific model predicted K values that correspond well with permeameter K. • Integrating HPT-inverted K into SSHT better defined sharp boundaries of a K field. Direct-push based hydraulic profiling tool (HPT) and geostatistically-based hydraulic tomography (HT) are two promising techniques for the high-resolution estimation of hydraulic conductivity (K) for unconsolidated sediments. Although HPT surveys could be conducted rapidly, relating the 1.5-cm resolution injection logging profiles to K always involve the upscaling of centimeter-scale measurements to coarser intervals for the development of site-specific formulae. On the other hand, K fields reconstructed by HT could be smooth when pumping test data are sparse. In this study, an inverse modeling approach was firstly utilized to estimate K values directly from HPT survey data for the glaciofluvial deposits at the North Campus Research Site (NCRS) in Waterloo, Ontario, Canada. A site-specific power-law relationship was generated for the NCRS to relate HPT profiles to the vertical distributions of K. Then, the proposed inverse modeling approach was evaluated with a two-dimensional synthetic aquifer under controlled conditions, and the estimated K profiles from inverse analysis of synthetic HPT surveys were incorporated into the steady-state HT. Results of the field study showed that K estimates from the developed formula corresponded better with K values from permeameter tests, than those estimated from the empirical model of McCall and Christy (2010) for HPT surveys. Moreover, through synthetic experiments, we demonstrated that integration of K values inverted from HPT into steady-state HT analyses yielded K tomograms that were significantly better than the geostatistical inversion results relying on pumping test data alone. Overall, this study highlights the need in developing site-specific formulae for the HPT and the joint implementation of HPT and HT techniques for the more cost-effective high-resolution characterization of subsurface heterogeneity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Active site engineering in MOFs is first explored for photocatalytic N 2 fixation. • Acetic acid is added to expose and regulate the (1 0 0) facet with more active sites. • The FeIII/FeII ratio is controlled to improve active site reduction ability. • The photocatalytic NH 3 production rate of optimal MOFs reaches 164 μmol h−1 g−1. Photocatalytic ammonia synthesis from N 2 is a carbon neutral approach, its efficiency is yet impeded by the lack of abundant and efficient active sites on catalyst surface. Herein, we explore active site engineering strategy via employing MOF-235-based heterovalent metal organic frameworks (HMOFs) with FeIII/FeII clusters to break this dilemma. Acetic acid was added in solvothermal process, which was adsorbed on (1 0 1) facet of HMOF(FeIII/FeII) to restrain its further growth. The (1 0 0)/(1 0 1) facet ratio of HMOFs was regulated by the acetic acid content. Meanwhile, the FeIII/FeII ratio was regulated by the Fe3+/Fe2+ feeding ratio. It is found that the (1 0 0) facet of HMOFs exists more abundant Fe active sites, exposing (1 0 0) facet can increase the amount of active sites. On the other hand, the FeIII active site is favourable of N 2 adsorption, while the FeII active site is favourable for N 2 activation. The excellent balance between N 2 adsorption and N 2 activation can promote the reduction ability of active sites. At the optimal FeIII/FeII ratio of 1:1 and (1 0 0)/(1 0 1) facet ratio of 4.84, the photocatalytic activity of HMOF(FeIII/FeII)-10 reached 164 μmol g−1 h−1, more than 20 times compared to HMOF(FeIII/FeII)-0 without exposing the (1 0 0) facet. Our strategy may provide a reference in exploiting advanced photocatalysts based on organic framework-based materials. [ABSTRACT FROM AUTHOR]

• HPT pressure logs (P c) can be rapidly collected in unconsolidated deposits. • P c data provide information on sharp and gradually-varying layer boundaries. • Integrating HPT-derived hydrostratigraphy and HT yields a K field with sharp boundaries. • HPT K estimates require additional evaluations for highly heterogeneous deposits. Hydraulic tomography (HT) has been developed as a robust technique in characterizing subsurface heterogeneity over the last two decades. Hydraulic conductivity (K) and specific storage (S s) estimated by geostatistically-based HT inversion approaches are typically smooth and lack geological features when observation data density is sparse. Although integrating geological information can be helpful in adding structural features into parameter fields, costly efforts are required to obtain borehole logging through conventional coring and sampling. Also, identification of geological features such as layer boundaries from sampled materials can be a subjective process. In this study, corrected pressure (P c) logs collected during hydraulic profiling tool (HPT) surveys are utilized to derive the local hydrostratigraphic layers of the glaciofluvial deposit at the North Campus Research Site (NCRS) in Waterloo, Ontario, Canada. Site-specific geological models representing aquifer and aquitard layers are developed and calibrated to drawdown data of multiple pumping tests. Results show that estimated K fields correctly reflect the variation features of permeameter-estimated K profiles, as well as the spatial distribution of high and low K sediments. The calibrated geological models performed better than the geostatistically-based inversion approach in predicting independent pumping tests used for model validation. Moreover, by including K estimates of geological models as prior means, the estimated K fields reveal both intra- and interlayer heterogeneity, and the performances of drawdown prediction are further improved for the geostatistical inversion approach. Overall, our study suggests that, integration of stratigraphic information derived from HPT P c logs is useful for HT to capture the sharp boundaries in K fields, especially when the pumping test data is sparse. [ABSTRACT FROM AUTHOR]

• School climate was negatively associated with bullying victimization among a sample of Chinese adolescents. • Self-esteem mediated the relationship between school climate and bullying victimization. • Psychological suzhi moderated the first link of the mediational chain and the direct relationship between school climate and bullying victimization. • Gender moderated the relationship between self-esteem and bullying victimization, and the negative effect of self-esteem on bullying victimization was larger among boys than among girls. The present study constructed a moderated mediation model to investigate whether self-esteem mediated the relationships between school climate and bullying victimization and whether psychological suzhi and gender moderated the mediation of self-esteem. The participants were 3645 students (M age = 14.01 years, SD = 1.19) from 5 urban public secondary schools in Southwest China. The results indicated that school climate was negatively associated with bullying victimization and that self-esteem mediated the relationship between them. Furthermore, psychological suzhi moderated the first link of the mediational chain and the direct relationship between school climate and bullying victimization. More specifically, psychological suzhi increases the association between school climate and self-esteem and reduces the link between school climate and bullying victimization. The results further showed a gender difference in the association between self-esteem and bullying victimization. The negative effect of self-esteem on bullying victimization was larger among boys than girls. The findings provide implications for school decision makers and school professionals regarding the importance of fostering a positive school climate and improving psychological suzhi to prevent school bullying and promote positive development among Chinese adolescents. [ABSTRACT FROM AUTHOR]

Abstract: Environmental tracers (CFCs, stable isotopes 18O, 2H, and 3H) and major ions were employed to study river infiltration and groundwater recharge in the aquifer system in the basin of the Lower Heihe River, Northwest China. Three groups of waters have been recognized: (1) young groundwater, connected to the river, with large variation of CFC apparent ages ranging from <10a to 40a, and δ18O and δ2H values which are similar to the river water; (2) regional background water, unaffected by the river, having CFC apparent ages >40a, and being depleted in 18O and 2H compared with the river water; and (3) groundwater in Gurinai, a grassland located about 100km from the river, in which the predominant discharge is from the Badain Jaran desert, with CFC apparent ages ranging from 25 to >50a and being enriched in 18O and 2H compared to the river water. The groundwater along the river contains CFCs and 3H down to depths of about 120m, and the shallow groundwater exhibits CFC apparent ages in a wide range which are not dependent on the well depth. Groundwaters along the river show a similar trend of enrichment in 18O and 2H as the river water whereas groundwaters in depression cones are depleted in heavier isotopes, and have low CFC and 3H concentrations. The CFC apparent age of the groundwater increases with increasing distance downstream, indicating that the dominant part of the groundwater is from infiltration of river water in the upper reaches. Modifications of groundwater recharge are reflected in variations of stable isotope compositions, as well as CFC and 3H concentrations in the groundwater that was recharged from the river over the last decades. Despite recharging from river water, groundwater abstraction has induced a water balance deficit. The riparian ecosystem in the Ejina Oasis is constrained by both decreased river flow and increased groundwater abstraction. The vegetation degradation in the Ejina Oasis is controlled not only by natural aridification but also worsened by heavy groundwater abstraction and decreased river flow. [Copyright &y& Elsevier]

Abstract: This study describes biomimetic calcium phosphate (Ca-P) coatings formation under simulated physiological conditions on Ti surfaces that go through nitric acid treatment (NT). In the present study, nitric acid treatment was used to treat Ti specimens so that Ti specimens could have the ability to induce Ca-P formation. After careful selection of the NT parameters, Ca-P coatings success fully formed on the nitric-acid-treated Ti surfaces in a supersaturated calcium phosphate solution (SCPS) and in the simulated body fluid (SBF). Before NT, the Ti specimen should go through mixed acid etching to increase its surface roughness because rough surfaces lead to good adherence between coatings and substrates. Amorphous Ca-P coatings were formed on the Ti surfaces by immersing the NT Ti specimens in SBF, while octacalcium phosphate (OCP) coatings were formed in the SCPS after 3 days of immersion. The study firstly proved that nitric acid treatment is not only just for surface passivation but also is another bioactive treatment as an alternative to the alkaline treatment and two-step method. The experimental results also confirmed that the conventional nitric acid treatment of a titanium surface does not increase the titanium oxide on the Ti surfaces. However, extending the nitric acid treatment time and enhancing the nitric acid treatment temperature help to increase Ti surface ability of Ca-P induction in simulated physiological environments. Ti specimens that had 600 min of NT at 60 °C had the best Ca-P induction ability under biomimetic conditions. [Copyright &y& Elsevier]

Abstract: Cathodic deposition of calcium phosphate (Ca–P) on titanium was studied under controlled atmospheres. Electrochemical deposition was conducted in a sealed electrochemical cell with a controlled flow of nitrogen, carbon dioxide or compressed air. The Ca–P phases of the depositions on titanium were examined by X-ray diffraction, Fourier transform–infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. Experimental results showed that hydroxyapatite (HA) deposition occurs under a pure nitrogen atmosphere, while octacalcium phosphate (OCP) deposition occurs under a carbon dioxide atmosphere. The atmosphere in the electrochemical cell effectively maintained constant levels of pH value in the electrolyte during the deposition process. A HA/OCP layered structure on titanium was obtained by controlling the atmosphere. The electrochemical deposition process of Ca–P can be explained by the thermodynamic and kinetics theory of the Ca–P precipitation from an aqueous supersaturated solution. [Copyright &y& Elsevier]

• THT analysis treating S s to be homogeneous yields less accurate results. • S s heterogeneity should be considered in THT for improved mapping of K and S s fields. • Reliable geological data helps THT to improve not only K , but also S s estimates. Over the last two decades, various studies on Transient Hydraulic Tomography (THT) have shown that it is an effective approach to characterize subsurface heterogeneity. Typically, high-resolution hydraulic conductivity (K) distributions were recovered, while the spatial variability of specific storage (S s) was found to be smooth. In some studies, S s heterogeneity has been intentionally ignored due to the belief that S s is less variable than K. Therefore, one may question the importance of considering S s heterogeneity during THT and its impact on the reliability of estimated hydraulic parameters. To investigate these issues, three modeling approaches (i.e., effective parameters, geological, and geostatistics-based) were used to obtain K and S s estimates of varying spatial resolutions. The reliability of K and S s estimates were evaluated by comparing their drawdown prediction performances. The values of using different prior K and S s information for THT analyses were investigated. Our results revealed that: (1) the K distribution estimated from the geostatistics-based steady-state HT analysis accurately predicted the late time drawdowns, while further improvements in transient drawdowns were obtained only after jointly treating the S s field as heterogeneous; (2) S s heterogeneity should be considered in addition to K for THT inversions, even when the estimated S s field is smooth; and (3) using K and S s estimates from the calibrated geological model as initial mean distributions for the geostatistical inversion approach were helpful in capturing both interlayer and intralayer heterogeneity of K and S s. These findings suggested that S s heterogeneity should be properly considered during the implementation of THT. [ABSTRACT FROM AUTHOR]

• Nitrogenase-inspired MIL-53(FeII/FeIII) is first synthesized for N 2 photo fixation. • Mixed-valence FeII/FeIII clusters mimic the active center in nitrogenase. • FeII are in-situ formed by ethylene glycol reductant in solvothermal process. • FeII/FeIII ratio is vital to coordinate catalytic activity and framework stability. • MIL-53(FeII/FeIII) stably yields 306 μmol h−1 g−1 NH 3 under visible light. Biological nitrogenases exhibit superior nitrogen fixation efficiency owing to their unique multi-iron metallocluster (Fe2+ 3 Fe3+ 4 M3+, M = Mo, V, Fe) coordinated by organic polypeptide. Herein, we design a kind of metal organic framework (MOF) photocatalyst, MIL-53(FeII/FeIII) (MIL = Material from Institute Lavoisier), in which the FeII and FeIII constitute the mixed-valence metalloclusters to mimic the Fe2+ active sites and high-valence metal ions in nitrogenases, respectively. Both the FeII and FeIII are coordinated by organic ligands (terephthalic acid), which afford the electron transfer chains as well as the support of monodispersed FeII active sites. The FeIII in MIL-53(FeII/FeIII) is partly in-situ reduced into FeII by ethylene glycol (EG) via one-step solvothermal method, and the FeII/FeIII ratio is regulated from 0.18:1 to 1.21:1 by varying the EG content. Our results show that the FeII/FeIII ratio can significantly affect the photocatalytic activity and structure stability, and MIL-53(FeII/FeIII)-1 with optimal FeII/FeIII ratio (1.06:1) achieves the highest ammonia evolution rate up to 306 μmol h−1 g−1, nearly 10-fold higher than that of other framework-based materials, while remaining stable after 24 h irradiation. Such nitrogenase-like design in MIL-53(FeII/FeIII) endows the efficient electron transfer, exposed active sites, and in particular rational synergy between the catalytic function and non-catalytic function. This work may open a new avenue to the rational design of nitrogen fixation photocatalysts based on framework materials. [ABSTRACT FROM AUTHOR]

• NM@NHM hetero-framework photocatalysts are designed and constructed. • The optimal photocatalyst exhibits a H 2 evolution rate of 2.25 mmol g−1 h−1 under visible light. • Both dual-ligand push-pull effect and heterojunction structure promote the electron transfer. • This study provides a new strategy to intensify the electron transfer in photocatalysis. The efficient transfer of photogenerated carriers is essential to the photocatalytic H 2 evolution. Herein, we designed and synthesized a kind of novel NH 2 -MIL-125@NH 2 /H-MIL-125 hetero-frameworks with nanopore structure to drive efficient charge transfer for photocatalytic H 2 evolution. Single-ligand NH 2 -MIL-125 (NM) and dual-ligand NH 2 /H-MIL-125 (NHM), which have similar composition, structure and well-matched energy band, were selected as the core and shell to prepare the NM@NHM hetero-framework as a proof-of-principle system. The hetero-framework strategy is proposed to intensify the charge transfer and thus enhance the photocatalytic activity. The H 2 evolution rate of optimal NM@NHM hetero-framework can reach 2.25 mmol g−1 h−1 under visible light, much higher than pristine NM (0.726 mmol g−1 h−1) and NHM (1.27 mmol g−1 h−1). Such high performance can be attributed to the hetero-framework structure consisting of NM and NHM with similar composition and structure, which reduces the interfacial resistance in the charge transfer, thus facilitating the photocatalytic H 2 evolution. Our work may provide a new strategy for the rational design of high-performance photocatalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

The concept of chaotic advection is a novel approach that has the potential to overcome some of the challenges associated with mixing of reagents that commonly occur when injection based in situ treatment techniques are used. The rotated potential mixing (RPM) flow system is one configuration which has been theorized to achieve chaotic advection in porous media, and enhance reagent mixing by periodically re-oriented dipole pumping at a series of radial wells. Prior to field implementation of chaotic advection, the selection of an RPM flow protocol will likely require a numerical model that can adequately represent groundwater flow within the zone of interest. As expected, the hydraulic conductivity (K) field is the most critical input requirement for the selected groundwater flow model. Hydraulic tomography (HT) is an innovative characterization approach that has shown potential to provide information on a K field. In this investigation, we explored whether the same well system required to invoke chaotic advection can also be applied in a HT analysis, and evaluated the use of the generated K tomogram for the selection of RPM flow parameters that can enhance reagent mixing. A series of dipole pumping tests were conducted within an area of interest as defined by the limits of the circular network of eight injection/extraction wells used to invoke chaotic advection. Hydraulic head data collected from independent dipole pumping tests were used in an inverse model to perform steady-state hydraulic tomography (SSHT) analysis to generate a K tomogram. Both the K tomogram and an effective parameter approach (i.e., a single K value assigned across the entire spatial domain as determined by single well pumping and slug tests) produced estimates of hydraulic head that closely resembled those observed due to the relative homogeneous nature of the aquifer and the small spatial scale of the area of interest. In contrast, particle tracking results showed that incorporating a heterogeneous K field significantly enhanced the spatial distribution of particle trajectories indicative of reagent mixing. These findings support the hypothesis that the same well system used to invoke chaotic advection can be combined with SSHT analysis as a viable site characterization tool for delineating the spatial variability of K. Incorporating this K tomogram in a groundwater flow model with a particle tracking engine can be used as a design tool to aid in the selection of a site-specific RPM flow protocol to achieve enhanced reagent mixing. • The same well system for chaotic advection can be combined with K tomography to delineate the K field of a TTZ. • Use of a K tomogram led to enhanced spatial distribution of particle trajectories compared to a homogeneous K. • A design tool to aid in the selection of chaotic advection system parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] • A metal doping strategy is proposed for N 2 activation. • Ca2+-doped UiO-66 is synthesized. • The Ca2+ doping fortifies the electron transfer from active sites to N 2. • The diamino ligand incorporating fortifies the electron generation and separation. • Photocatalytic NH 3 yield reaches 759.3 μmol h−1 g−1 under full spectrum. Photocatalytic NH 3 synthesis from N 2 is a clean and sustainable approach, however, the efficiency of this process is low due to the difficult activation of N N triple bonds. Herein, we propose a metal-doping strategy to facilitate the interfacial charge transfer for promoting the photocatalytic NH 3 yield. Ca2+ with low electronegativity was doped in UiO-66-NH 2 , a kind of Zr-based MOFs, to increase the electron donor capacity of Zr active sites. The X-ray photoelectron spectroscopy (XPS) spectra and density functional theory (DFT) calculations show that the Ca2+ doping enhances the electron density of Zr active sites. Moreover, the diamino ligand is incorporated to tune the bandgap structure of MOFs to expand its light absorption range. By adjusting the ratio of metals and organic ligands, the optimal photocatalyst UN(Zr-0.30Ca)-4 reaches a high NH 3 evolution rate of 759.3 μmol g−1 h−1 under full spectrum. This study may provide some inspiration for the design of advanced photocatalysts for diverse chemical reduction reactions. [ABSTRACT FROM AUTHOR]

The intense pulsed current superimposed on direct current arc discharges can promote arc spot splitting and reduce macroparticle ejection. In this study, the effects of different arc parameters including peak current, magnetic fields, pulse frequency and duty cycle on spot splitting characteristics for the pulsed cathodic arc discharge, as well as mechanisms involved in microspot formation, are investigated. The results show that under the effect of periodic micro-explosive emissions, the micro-spot splitting at the peak of the pulse displays a multi-stage annular expansion phenomenon, and its expansion radius increases with the increaseing peak current; the increasing transverse component of the arc source magnetic field gradually changes the microspot splitting pattern from annular expansion to arc-shaped expansion; the plasma motion after the micro-explosion requires a period of time to "accumulate force." In addition, an increase in pulse frequency leads to a gradual reduction in the range of the microspot splitting, in which the microspots are in a relative aggregation state; an increase in duty cycle, leads to an instability in the continuous motion of the microspots after the splitting in the peak period. This causes some of the microspots to merge, exhibiting a trend similar to the direct current arc. • This work aims to explore the dynamic evolution of the internal structure and motion of the pulsed cathodic arc spot under different discharge parameters, and the effects of different parameters on the characteristics of the arc spot formation and splitting motion are analyzed. • In this study, the effects of different arc parameters including peak current, magnetic fields, pulse frequency and duty cycle on spot splitting characteristics for the pulsed cathodic arc discharge, as well as mechanisms involved in microspot formation, are investigated. • The innovation we proposed looks to investigate the cathode arc spot's internal structure and splitting mechanism. We used the coupling theory of thermal field emission and electron explosive emission to analyze the phenomenon of microspot pulsed splitting observed at the microscopic level. [ABSTRACT FROM AUTHOR]

[Display omitted] • A multi-ligand strategy was proposed to design high-efficient MOF photocatalysts. • The three-ligand MOFs, EY/NH 2 /H-MIL-125, were synthesized to verify our strategy. • The optimal three-ligand MOF can yield H 2 of 2.15 mmol g−1 h−1 under visible light. • Electron transfer is enhanced by a push–pull effect induced by the NH 2 -H 2 BDC and H 2 BDC ligands. • The third ligand EY facilitates the electron photoexcitation under visible light. The design and construction of high-performance photocatalysts with both strong visible light harvesting and effective electron transfer are highly desired in the photocatalysis field. Herein, a multi-ligand strategy based on the MOF materials is proposed. A three-ligand Ti-MOF EY/NH 2 /H-MIL-125 (ENHM) was prepared via a facile hydrothermal method, in which 2-aminoterephthalic acid (NH 2 -H 2 BDC), terephthalic acid (H 2 BDC) and Eosin Y (EY) were employed as three ligands. The push–pull effect induced by different substituent groups (–NH 2 and –H) on the skeleton of NH 2 -H 2 BDC and H 2 BDC promotes the efficient transfer of photogenerated electrons from organic ligands to metal nodes; while the third ligand EY increases the number of photoexcited electrons by enhancing the visible light absorption ability. Among the three-ligand MOF photocatalytic materials, ENHM-2 performs the optimal H 2 production activity of 2.15 mmol g−1 h−1, much higher than dual-ligand NH 2 /H-MIL-125 and EY/NH 2 -MIL-125 and single-ligand NH 2 -MIL-125. A probable mechanism was also proposed for the three-ligand MOFs. This multi-ligand strategy may open up a new direction toward the preparation of MOF-based photocatalytic materials with excellent photocatalytic performances. [ABSTRACT FROM AUTHOR]

Optical fiber sensors should be encapsulated to prevent the possible damage in practical applications. Moreover, the encapsulation should be optimized to increase the sensitivity of the sensor as much as possible. Herein three different Helmholtz resonators are designed to encapsulate the singlemode-multimode-singlemode (SMS) fiber vibration sensor. Finite element analyses exhibit the acoustic pressure distributions in the resonators. The SMS fiber structures are fixed in the resonators with different schemes. Experiments demonstrate that the encapsulations increase the sensitivity of the sensors, which are determined by the fixing schemes, the acoustic pressure distributions, and the structures of the resonators. The combined resonator with two coaxially attached cavities renders the sensor a response range from 20 to 1000 Hz, which possesses a higher sensitivity and wider frequency response range than the sensor with a single cavity of resonator. The sensitivity of the encapsulated sensor with the combined resonator is 2.11 times of the sensitivity of the un-encapsulated sensor at 120 Hz. The SMS sensor encapsulated by the combined resonator exhibits a higher sensitivity than a commercial microphone, which indicates a favorable practicability of the Helmholtz resonator to the encapsulation of various kinds of fiber vibration sensors. [ABSTRACT FROM AUTHOR]

• Porous cPTA/CNT/CNU nanorod is prepared by using PTA as both template and adhesive. • A g-C 3 N 4 isotype heterojunction forms on the cPTA nanorod surface in cPTA/CNT/CNU. • Optimal cPTA/CNT/CNU nanorod can degrade 95% RhB within 1 h under visible light. • A multistep electron transfer path from CNU, CNT to cPTA forms in cPTA/CNT/CNU. • Porous cPTA nanorod increases light harvesting, active sites and molecule channels. Graphite carbon nitride (g-C 3 N 4) has a huge application potential in the photocatalysis field due to its unique conjugated structure. Inspired by the mussel adhesion protein, the cPTA/CNT/CNU (cPTA, carbonized poly(tannic acid); CNT, g-C 3 N 4 prepared by thiourea); CNU, g-C 3 N 4 prepared by urea) nanorod was synthesized by using PTA as the adhesive and template, and thiourea and urea as g-C 3 N 4 precursors. The CNT/CNU isotype heterojunction is assembled on the surface of porous cPTA nanorod, which effectively solves the problem of high photogenerated electron-hole recombination of pure g-C 3 N 4. The optimal cPTA/CNT/CNU photocatalyst can degrade 95% of rhodamine B (RhB) within 1 h under visible light, which is much higher than CNT, CNU and CNT/CNU. With the conduction band potential difference of cPTA, CNT and CNU, a multistep electron transfer path forms in the cPTA/CNT/CNU, which can accelerate the electron transfer through the interface, thereby increasing the photocatalytic activity. [ABSTRACT FROM AUTHOR]

The sensing of surrounding medium is a research focus, which is highly dependent on the nanotechnology that exhibits typical features of technical difficulty and high price. In this work, a surrounding medium sensor based on gold nanoparticles (Au NPs) is fabricated. The formation of Au NP aggregates is deposited on quartz glass by alternately immerses the glass sheet in positive charged cationic polymer polyethyleneimine and negative charged citrate coated Au NPs. The formation of Au NP aggregates with different numbers of NPs is fabricated controlling numbers of deposition and deposition time. The formation of aggregates contains less NPs exhibit ability of refractive index sensing by monitoring the surface plasmon resonance (SPR) of Au NPs. The formation of Au NP aggregates can be used as a substitute of Au NPs array for the application of SPR sensing for the merits of easy fabrication and low cost. • A surrounding medium sensor based on gold nanoparticles with ability of refractive index sensing for SPR is fabricated. [ABSTRACT FROM AUTHOR]

• Pyrimidine-modified g-C 3 N 4 (Pym-CN) was prepared through a supermolecular assembly. • Curled Pym-CN nanosheet was formed due to the restrained structure growth of g-C 3 N 4. • Pyrimidine modification promotes charge separation and enhances light absorption. • The optimal sample shows a photocatalytic H 2 evolution rate of 1046 μmol g−1 h−1. • Pym-CN has the broad prospects due to high activity, stability and reusability. Designing visible-light-driven, high-efficiency, robust photocatalysts with practical potential is an important direction in the photocatalysis field. Herein, pyrimidine-modified g-C 3 N 4 (Pym-CN) photocatalysts with curled nanosheet morphology were prepared through a facile supramolecular assembly method. Pyrimidine has only two N atoms, thus leading to the deficiency formation in the supramolecular assembly of cyanuric acid with melamine. Upon calcination, the deficiency decreases the polycondensation degree of g-C 3 N 4 , thereby further affecting its morphology and optoelectronic property. The pyrimidine modification can enhance the absorption capacity toward visible light and facilitates the separation of photo-generated carriers. By changing the adding amount of pyrimidine, the optimal Pym-CN photocatalyst exhibits a H 2 evolution rate of 1046 μmol g−1 h−1 under visible light, which is almost 30 times higher than that of pristine g-C 3 N 4. This work may afford a novel approach to modifying organic polymer semiconductor photocatalysts with small organic molecules of nonplanar structure. [Display omitted] [ABSTRACT FROM AUTHOR]

Summary: Environmental tracers CFCs, 18O, 2H and tritium were used to determine the natural groundwater recharge and the impact of irrigation activity on the groundwater system in the semi-arid Zhangye Basin of China. Groundwaters in the irrigated areas have been identified as mixtures containing fractions recharged in different periods of time. The CFC and 3H data show that the oldest fraction in the groundwater was recharged before 1950, whereas the younger fractions were recharged in different periods of time since 1950. Stable isotope (18O, 2H), CFC and electrical conductivity data show that most of the samples can be regarded as binary mixtures with the river/irrigation water presents the younger fraction and the regional groundwater presents the older fraction. Binary mixing model is used to estimate the age and fraction of the younger component. Most of the younger fraction was recharged after 1980s, in response to the increasing irrigation activities. Compared to local precipitation surface water plays a major role in recharging the aquifer in the irrigated area. The irrigation activity had more impact on the aquifer under thin unsaturated zone (<10m), due to short travel times and high amounts of recharge, whereas it had less impact on the aquifer under thick unsaturated zone (tens of meters). CFCs are useful in identifying regions of different impact of irrigation return flow. The positive correlation between nitrate and CFC data show that contaminants are transported to the saturated zone by irrigation water. This study shows that in this semi-arid basin due to strong evaporation of infiltrating surface water and regional groundwater, δ18O and EC values, in contrast to CFCs, do not show simple relationship with concentration in groundwater. Combined with a proper mixing model, however, they can provide evidences that the CFCs found in groundwater were introduced by infiltrating irrigation return flow and, therefore, reveal that human activities can produce a much localized water circulation and influence groundwater vulnerability. [Copyright &y& Elsevier]

[Display omitted] • Porous cPTA/CN nanorod was prepared by using PTA as both template and adhesive. • In such a nanocomposite, the CN nanolayer forms on the surface of cPTA nanorods. • cPTA/CN degrades 97% RhB in 80 min and 78% tetracycline in 3 h under visible light. • cPTA facilitates the photoinduced carrier separation and afford more active sites. • This study offers a generic method for making nanorod photocatalysts. Solar energy-driven photocatalysis has become a promising green technology to degrade organic pollutants discharged into water environment in recent years. In this study, a kind of novel cPTA/CN nanorod photocatalysts were prepared by using poly(tannic acid) as both template and adhesive, in which the g-C 3 N 4 (CN) nanolayer formed on the surface of carbonized poly(tannic acid) (cPTA) nanorods, similar to the adhesion of marine mussel foot silk protein on the solid surface. The porous cPTA/CN nanorods with about 400 nm in width and 2–4 μm in length can degrade 97% Rhodamine B within 80 min and 78% tetracycline within 3 h under visible light irradiation. Porous cPTA nanorods play an important role for promoting the photocatalytic activity, which can not only accelerate the separation of photogenerated carriers, but also afford more active sites and molecule diffusion channels. This kind of nanocomposite photocatalysts may find broad application potential in the treatment of organic pollutants in aqueous solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogenase-inspired modular synthesis is designed to construct bimetallic UiO-66. • Zr-Hf clusters are constructed to coordinate the electron transfer and utilization. • U(0.5Hf)-2SH with TPA-2SH as the ligand can absorb and utilize the visible light. • A tandem ligand-to-metal-to-metal charge transfer mechanism (LMMCT) is proposed. • The resultant bimetallic UiO-66 yields 116.1 μmol h−1 g−1 NH 3 under visible light. Inspired by nitrogenase, we designed a kind of metal-organic framework (MOF) photocatalysts, U(Zr-Hf)-X, composed of bimetallic Zr-Hf nodes and different functional ligands. In the Zr-Hf bimetallic cluster, the Zr species serves as the active site of nitrogen fixation, while the Hf species acts as electron buffer tank to optimize electron transfer and utilization. In the organic ligands, the light absorption and utilization of MOFs is improved via introducing target functional groups to efficiently generate electrons. Notably, the organic ligand containing two thiol groups (-SH) can extend the absorption edge to the visible region. The optimal U(0.5Hf)-2SH (metal nodes: 0.5Zr: 0.5Hf; linkers: TPA-2SH) photocatalyst exhibits nitrogen fixation rate up to 116.1 μmol g−1 h−1 under visible-light, attributed to the ligand-to-metal-to-metal electron transfer (LMMET) pathway and Zr-based π-backbonding mechanism. Our nitrogenase-inspired strategy establishes a novel paradigm for rational design of visible-light-driven nitrogen fixation catalysts. [ABSTRACT FROM AUTHOR]

In recent years, exploring efficacious visible-light photocatalysis has been one of core concerns owing to potential applications for energy utilization and environmental remediation. Among all nanostructured photocatalysts, the nano-hierarchical material composed of two-dimensional (2D) nanosheets is terrific owing to abundant 2D coupling interfaces that can decrease the diffusion distance of photogenerated carriers and facilitate the interfacial electronic transfer. Herein, utilizing the biomimetic adhesion, 2D/2D graphitic carbon nitride nanosheet/carbonized polydopamine (CNNS/CPDA) nanocomposites were fabricated via the dopamine (DA) self-polymerization on the surface of graphitic carbon nitride (GCN) followed by carbonization and delamination. Wherein CPDA acts a crucial role for the reinforcement of photocatalytic degradation activity in CNNS/CPDA nanocomposites. On the one hand, CPDA has strong adsorption capacity that can accelerate the adsorption and degradation of rhodamine B (RhB) molecules. On the other hand, as one of carbon materials, CPDA has high conductivity and contacts with CNNS tightly, which is conducive to the transfer of photo-induced carriers. Hence, for the optimal CNNS/CPDA nanocomposite (CNNS/CPDA-2), the RhB degradation rate (0.0466 min−1) is 5.1 times as high as that of pure GCN. This kind of 2D/2D nanocomposites based on one-pot biomimetic strategy may hold significant promise in practical applications of water treatment. Image 1 • A facile bioinspired-adhesion method is used to prepare CNNS/CPDA nanocomposites. • As-prepared samples possess distinct 2D/2D hierarchical nanosheet structure. • CPDA improves light harvesting, exciton separation and stability of samples. • Built-in electric field plays a key role for promoting photocatalytic activity. • Optimal sample exhibits 5.1-fold increase than bulk GCN for RhB degradation. [ABSTRACT FROM AUTHOR]

• CNNS/PDA/CdS is prepared via bioinspired adhesion and metal chelation of PDA. • CdS nanoparticles about 5−10 nm in size are in-situ anchored on the CNNS surface. • CNNS/PDA/CdS can degrade 97 % RhB within 80 min under visible light irradiation. • CNNS constructs type II heterostructure with CdS to improve energy band matching. • PDA layer facilitates the visible-light absorption and interfacial charge transfer. By utilizing the bioinspired adhesion and metal chelation of polydopamine (PDA), a kind of ternary nanocomposites that consist of the graphitic carbon nitride nanosheet (CNNS), PDA layer and cadmium sulfide (CdS) nanocrystals were synthesized. In the resultant CNNS/PDA/CdS nanocomposites, CdS nanocrystals about 5−10 nm in diameter are scattered on the CNNS surface in the presence of the PDA layer. Due to the energy band matching, CNNS constructs a type II heterostructure with CdS nanoparticles via the mediation of the electroconductive PDA layer, thus enhancing the photocatalytic activity. Compared with pristine CdS and CNNS, the CNNS/PDA/CdS nanocomposite conspicuously shows superior photocatalytic performance under visible light above 420 nm, which can degrade 97 % Rhodamine B (RhB) molecules within 80 min. The introduction of a PDA layer between CNNS and CdS not only promotes the photon energy absorption but also facilitates the separation of photoinduced electron-hole pairs. [ABSTRACT FROM AUTHOR]

• Highlights: Porous N-deficient g-C3N4 was fabricated with acetic acid-treated melamine as precursor. • Acetic acid plays a key role in the formation of porous structure and N deficiency. • PNCN can degrade almost 100 % RhB within 2.0 h and generate 257.5 μmol g−1 h−1 H2. • DFT calculation indicates that N deficiency can lead to bandgap narrowing and activity elevating. • This study affords a facile and scalable strategy to fabricate efficient g-C3N4 photocatalysts. Porous nitrogen-deficient graphic carbon nitride (PNCN) was fabricated by using acetic acid (HAc)-treated melamine as precursor via one-pot method. The as-prepared PNCN photocatalysts possess a loose porous structure with nitrogen deficiencies due to the decomposition of HAc during calcination process. The PNCN photocatalyst exhibits the rate constant of RhB degradation (1.92 h−1) and H 2 evolution rate (257.5 μmol g−1 h−1) for ∼4.6 and ∼2.5 times of pristine g-C 3 N 4 under visible light irradiation, respectively. The mesoporous structure can increase the specific surface area of PNCN (19.24 m2 g-1), thereby rendering ample active sites and facilitating visible-light utilization. The moderate nitrogen deficiencies can not only substantially enhance photocurrent density and interfacial charge transfer, but also restrain the recombination of photo-generated carriers. In addition, the density functional theory (DFT) calculation further provides insight into the photocatalytic mechanism over PNCN. This study may present a facile and scalable method to fabricate PNCN with superior photocatalytic performance, which may hold great promise in practical applications. [ABSTRACT FROM AUTHOR]