Search

Saltmarshes are a blue carbon ecosystem accumulating large quantities of organic carbon in sediments. Some of this carbon can be transformed into dissolved inorganic carbon (DIC) and methane (CH4) that may eventually be exported to the ocean or atmosphere. Although extensive studies have quantified specific components of the carbon budget such as carbon burial, limited attention has been given to pore‐water‐derived carbon and total alkalinity (TA) exports to the ocean. Here, we quantified lateral exports to the ocean (outwelling) of 202 ± 160 and 78 ± 75 mmol m−2d−1of DIC and TA, respectively. The TA : DIC concentration ratio in the creek waters was ~ 1, implying TA production from anaerobic mineralization in sediments. The lateral TA exports were comparable to the local (94 ± 48 mmol m−2d−1) and national (~ 50 mmol m−2d−1) organic carbon burial. High TA exports could locally increase the ocean buffering capacity and contribute bicarbonate to the coastal ocean, acting as a long‐term carbon storage. Pore water traced by radon contributed 28–37% and 58–69% of DIC and TA exports. Separating the two major DIC components (i.e., CO2emissions and alkalinity exports) is essential to resolve the carbon sequestration potential from saltmarshes. Here, dissolved CO2emissions to the atmosphere accounted for 3–5% of total DIC outwelling. CH4emissions played a minor role offsetting around 0.3 to 6% of the carbon sequestration. Overall, we demonstrate that alkalinity export into the ocean can be an overlooked carbon sequestration pathway in saltmarshes at rates comparable to carbon burial.

Soil temperature regulates biogeochemical processes and is a key environmental factor affecting salt marsh ecosystems. Previous studies on soil temperature and heat transport in intertidal marshes predominantly focused on short‐term changes, leaving seasonal variations unclear. This study conducted a yearlong field and modeling investigation to examine temporal and spatial temperature variations in a creek‐marsh section under estuarine and meteorological influences. The results showed that inundating tidal water propagated the seasonal water temperature signal to marsh soils, especially at low elevations, thereby modulating air temperature‐induced soil temperature variations and distributions. The response of soil temperature to air and tidal water temperatures exhibited a damped and delayed pattern. In contrast, tide‐induced porewater circulations near the creek facilitated the temperature responses. A regression model incorporating a Gamma distribution function was developed to quantify the delayed and cumulative thermal effects of tidal water and air on shallow soil temperatures. The model coefficients varied along the creek‐marsh section, capturing the seasonal regulation of periodic tidal inundation on soil temperature in the low‐elevation marsh and near the creek. Sensitivity analyses indicated that relative sea level rise lowered yearly‐averaged temperatures for the marsh platform by enhancing latent heat export. Surface water warming increased the marsh temperatures at lower elevations. This study demonstrates that the creek‐marsh topography, warming, and relative sea level rise jointly affect soil temperature dynamics, advancing our understanding of temperature‐dependent biogeochemical processes in marsh ecosystems. Seasonal temperature distributions along a creek‐marsh section were identifiedShallow soil temperature dynamics were predominated by seasonal tidal water and air temperaturesRelative sea level rise decreased the yearly‐averaged temperature in the high‐elevation marsh Seasonal temperature distributions along a creek‐marsh section were identified Shallow soil temperature dynamics were predominated by seasonal tidal water and air temperatures Relative sea level rise decreased the yearly‐averaged temperature in the high‐elevation marsh

Surface-enhanced Raman spectroscopy (SERS) has been recognized as a promising analytical technique for its capability of providing molecular fingerprint information and avoiding interference of water. Nevertheless, direct SERS detection of complicated samples without pretreatment to achieve the high-efficiency identification and quantitation in a multiplexed way is still a challenge. In this study, a novel spectral extraction neural network (SENN) model was proposed for synchronous SERS detection of each component in mixed solutions using a demonstration sample containing diquat dibromide (DDM), methyl viologen dichloride (MVD), and tetramethylthiuram disulfide (TMTD). A SERS spectra dataset including 3600 spectra of DDM, MVD, TMTD, and their mixtures was first constructed to train the SENN model. After the training step, the cosine similarity of the SENN model can achieve 0.999, 0.997, and 0.994 for DDM, MVD, and TMTD, respectively, which means that the spectra extracted from the mixture are highly consistent with those collected by the SERS experiment of the corresponding pure samples. Furthermore, a convolutional neural network model for quantitative analysis is combined with the SENN, which can simultaneously and rapidly realize the qualitative and quantitative SERS analysis of mixture solutions with lower than 8.8% relative standard deviation. The result demonstrates that the proposed strategy has great potential in improving SERS analysis in environmental monitoring, food safety, and so on.

Objective: The specific objective of this study was to evaluate the effects of atmospheric pressure plasma (APP) in the treatment of experimental periodontitis in Beagle dogs. Methods: The APP jet was diagnosed using optical emission spectroscopy and laser-induced fluorescence spectroscopy. Six Beagles received stainless steel ligatures to establish experimental periodontitis model. The teeth in the control group were subjected to conventional root surface debridement (RSD) and chlorhexidine irrigation. The APP group also started with RSD and was then subjected to plasma irradiation. Clinical analyses including plaque index, modified sulcus bleeding index, pocket depth and attachment loss (AL), as well as cone-beam computed tomography (CBCT) analysis, were performed at baseline, 4th week, 8th week and 12th week after treatment. Results: The results showed that typical reactive oxygen and nitrogen species were found in the full spectrum and the gas temperature of APP was close to room temperature. The highest concentrations of hydroxide and oxygen were obtained at 5 mm away from the nozzle. In both groups, all values in clinical examinations were significantly lower (P<0.05) at 12th week after treatment than those at baseline. At the 12th week, the AL in clinical examinations and the bone loss in CBCT images in the APP group were significantly lower than those in the control group (P<0.05). The hematoxylin-eosin staining showed more renascent alveolar bone in the APP group than in the control group. Conclusion: These findings suggested that APP has profound potential for use as an adjunct approach for periodontitis treatment.

Although disinfection is key to infection control, the colonization patterns and resistomes of hospital-environment microbes remain underexplored. We report the first extensive genomic characterization of microbiomes, pathogens and antibiotic resistance cassettes in a tertiary-care hospital, from repeated sampling (up to 1.5 years apart) of 179 sites associated with 45 beds. Deep shotgun metagenomics unveiled distinct ecological niches of microbes and antibiotic resistance genes characterized by biofilm-forming and human-microbiome-influenced environments with corresponding patterns of spatiotemporal divergence. Quasi-metagenomics with nanopore sequencing provided thousands of high-contiguity genomes, phage and plasmid sequences (>60% novel), enabling characterization of resistome and mobilome diversity and dynamic architectures in hospital environments. Phylogenetics identified multidrug-resistant strains as being widely distributed and stably colonizing across sites. Comparisons with clinical isolates indicated that such microbes can persist in hospitals for extended periods (>8 years), to opportunistically infect patients. These findings highlight the importance of characterizing antibiotic resistance reservoirs in hospitals and establish the feasibility of systematic surveys to target resources for preventing infections.

Due to the inherent working mode of rotating detonation engine (RDE), the detonation flow field has the characteristics of pressure oscillation and axial kinetic energy loss, which makes it difficult to design nozzle and improve propulsion performance. Therefore, in order to improve the characteristics of detonation flow field, the three-dimensional numerical simulation of annular chamber and hollow chamber is carried out with premixed hydrogen/air as fuel in this paper, and then tries to combine the two chambers to weaken the oscillation characteristics of detonation flow field through the interaction of detonation flow field, which is a new method to regulate the detonation flow field. The results show that there are four states of velocity vectors at the outlet of annular chamber and hollow chamber, which makes RDE be affected by rolling moment and results in the loss of axial kinetic energy. In the external flow field of combined chamber, the phenomenon of cyclic reflection of expansion wave and compression wave on the free boundary is observed, which results in Mach disk structure. Moreover, the pressure monitoring points are set at the external flow field. The pressure signal shows that the high-frequency pressure oscillation at the external flow field of the combined chamber has been greatly weakened. Compared to the annular chamber, the relative standard deviation (RSD) has been reduced from 14.6% to 5.6%. The results thus demonstrate that this method is feasible to adjust the pressure oscillation characteristics of the detonation flow field, and is of great significance to promote the potential of RDE and nozzle design.

Tides and seasonally varying inland freshwater input, with different fluctuation periods, are important factors affecting flow and salt transport in coastal unconfined aquifers. These processes affect submarine groundwater discharge (SGD) and associated chemical transport to the sea. While the individual effects of these forcings have previously been studied, here we conducted physical experiments and numerical simulations to evaluate the interactions between varying inland freshwater input and tidal oscillations. Varying inland freshwater input was shown to induce significant water exchange across the aquifer‐sea interface as the saltwater wedge shifted landward and seaward over the fluctuation cycle. Tidal oscillations led to seawater circulations through the intertidal zone that also enhanced the density‐driven circulation, resulting in a significant increase in the total SGD. The combination of the tide and varying inland freshwater input, however, decreased the SGD components driven by the separate forcings (e.g., tides and density). Tides restricted the landward and seaward movement of the saltwater wedge in response to the varying inland freshwater input in addition to reducing the time delay between the varying freshwater input signal and landward‐seaward movement in the saltwater wedge interface. This study revealed the nonlinear interaction between tidal fluctuations and varying inland freshwater input will help to improve our understanding of SGD, seawater intrusion, and chemical transport in coastal unconfined aquifers. The lower and upper part of the saltwater‐freshwater interface are, respectively, affected by varying inland freshwater input and tidesInteraction between tidal fluctuations and varying inland freshwater input is nonlinearTide reduces the time lags in the response of the saltwater wedge and submarine groundwater discharge to the varying inland freshwater input

Salt flats are bare soil surfaces with elevated salinity levels which inhibit vegetation. They are commonly found in areas of coastal wetlands where salt in surface soil accumulates due to evaporation from the shallow saline water table. The expansion of these vegetation‐free zones may severely affect the bio‐ecological function of these coastal wetland systems. In this study, sand flume experiments and numerical modeling were carried out to investigate the mechanisms underpinning the development of salt flats in the elevated areas of coastal wetlands. We found that salt precipitation occurred on the soil surface where water content is low, but the hydraulic connection to the saline groundwater table is maintained. This connection is required for evaporation to promote upward porewater flow and bring salt to the surface. However, the surface salinity level decreases with increasing surface saturation due to the density‐driven removal of salt. As a result, salt efflorescence is absent on the surface with higher water saturations, despite strong evaporation. Density‐driven flows can be triggered by the evaporation‐induced upward salinity gradient and transfer salt from the surface back to the water table. Numerical simulations confirmed this salt removal process and suggested the intensity of the density‐driven flow is mainly dictated by the soil permeability in the unsaturated zone. The findings from this study increase understanding of the processes involved in the formation and evolution of salt flats. Salt precipitated on the soil surface with continuous evaporation and low water saturationEvaporation‐induced upward salinity gradient can trigger salt fingersSalt fingers tended to form near the soil surface with higher water saturation and inhibited surface salt accumulation Salt precipitated on the soil surface with continuous evaporation and low water saturation Evaporation‐induced upward salinity gradient can trigger salt fingers Salt fingers tended to form near the soil surface with higher water saturation and inhibited surface salt accumulation

Macropores created by crab burrowing are commonly found in vegetated coastal wetlands. However, their impact on surface water‐groundwater interactions and salt transport is insufficiently understood. In this study, we used numerical models to quantify the impact of crab burrows with random spatial distribution, morphology, and openings on groundwater flow and salt transport in creek‐marsh systems. Results showed that these burrows can lead to a more complex network of preferential flow paths and burrow flushing capabilities than those with a single pipeline. The velocity magnitude varied over seven orders in the burrowed mud layer. Local increases in the hydraulic gradient occurred in the burrows, leading to faster water circulation and salt transport as well as turnover of soil aeration. The salinity front in the burrowed marsh reached two‐m deeper than in the unburrowed marsh. Burrow flushing depth and intensity is significantly enhanced in burrows with multiple openings. This study emphasized the complexity of tortuous burrows regulating groundwater flow and solute transport through modeling realistic crab burrows. This work supports fiddler crabs as ubiquitous “ecoengineers” who can produce more significant impact on local hydrological cycle and ecosystem‐scale geochemical processes than previously indicated. Fiddler crabs are commonly regarded as “ecoengineers” for salt marshes, as their burrowing activity has great impact on ecological and environmental processes. This study provides innovative approaches for numerical simulations that can quantitatively evaluate the potential impact of crab burrows on groundwater flow and salt transport by considering burrow morphology. Our results showed that crab burrows can form complex preferential flow path networks, which in turn accelerates groundwater and salt circulation and enhances porewater exchange between burrows and the sediment matrix. Further, the burrow flushing depth and intensity were primarily controlled by the morphology (burrow shape, branch, and entrance) of crab burrow. For burrows with only one entrance, local circulation developed, limiting the burrow flushing to a relatively shallow depth and delaying the downward migration of salt. For burrows with multiple entrances, a more complex network of preferential flow paths will form, enhancing the bidirectional exchange between surface water and groundwater through the burrows. This study highlights the importance of biological disturbance on hydrology, which affects behavior and function of salt marshes. Local circulation within burrows enhances porewater exchange between crab burrows and the sediment matrixCrab burrows facilitate soil aeration and alter flow paths/rate depending on burrow morphologiesCrab burrows have the potential to enhance terrigenous groundwater discharge in the creek‐marsh system Local circulation within burrows enhances porewater exchange between crab burrows and the sediment matrix Crab burrows facilitate soil aeration and alter flow paths/rate depending on burrow morphologies Crab burrows have the potential to enhance terrigenous groundwater discharge in the creek‐marsh system

Salt is a key solute in salt marshes and under the influence of evapotranspiration can accumulate to a high concentration level in the marsh soil and precipitate in the solid form to become a significant stressor for plants, affecting marsh plant productivity and ecological zonation. Numerical simulations of coupled pore water flow and salt transport were conducted to examine how spring‐neap tides and evaporation combine to influence salt dynamics and distribution patterns in marshes. The salt pan formation was simulated with a sandy loam marsh soil subjected to a medium rate of potential evaporation. The critical condition for the salt pan formation was underpinned by hydraulic connection between the marsh surface and water table to sustain evaporation in the supratidal zone. Both low soil permeability and overly high potential evaporation were found to break the hydraulic connection. In this case, the surface soil salinity increased gradually over the intertidal zone to a maximum around the spring high tide mark followed by a rapid decrease to a lower constant level across the supratidal zone. This salinity distribution pattern has also been observed in the field. In both salt marshes with and without salt pans, excessive salt accumulated on the marsh surface due to evaporation was removed by tidally induced circulating flow and/or flow driven by density gradients associated with the accumulated salt. The salt dynamics and distribution patterns revealed here, especially the salt pan formation simulated for the first time, have important implications for studies of marsh plant growth and overall eco‐functions. Salt pan formation is simulated under the combined influence of spring‐neap tides and evaporationSalt pans are more likely to form in sandy soil marshes subjected to a moderate rate of potential evaporationSalinity gradients due to evaporation modify tide‐driven circulation in the intertidal zone and drive pore water flow in the supratidal zone

Shallow groundwater interacts strongly with surface water across a quarter of global land area, affecting significantly the terrestrial eco‐hydrology and biogeochemistry. We examined groundwater behavior subjected to unimodal impulse and irregular surface water fluctuations, combining physical experiments, numerical simulations, and functional data analysis. Both the experiments and numerical simulations demonstrated a damped and delayed response of groundwater table to surface water fluctuations. To quantify this hysteretic shallow groundwater behavior, we developed a regression model with the Gamma distribution functions adopted to account for the dependence of groundwater behavior on antecedent surface water conditions. The regression model fits and predicts well the groundwater table oscillations resulting from propagation of irregular surface water fluctuations in both laboratory and large‐scale aquifers. The coefficients of the Gamma distribution function vary spatially, reflecting the hysteresis effect associated with increased amplitude damping and delay as the fluctuation propagates. The regression model, in a relatively simple functional form, has demonstrated its capacity of reproducing high‐order nonlinear effects that underpin the surface water and groundwater interactions. The finding has important implications for understanding and predicting shallow groundwater behavior and associated biogeochemical processes, and will contribute broadly to studies of groundwater‐dependent ecology and biogeochemistry. Groundwater behaviors depend on antecedent surface water conditionsA regression model is developed to quantify the effect of antecedent surface water conditionsHysteretic shallow groundwater behavior is distance‐dependent

Time headway is an important index used in characterizing dangerous driving behaviors. This research focuses on the decreasing tendency of time headway and investigates its association with crash occurrence. An autoregressive (AR) time-series model is improved and adopted to describe the dynamic variations of average daily time headway. Based on the model, a simple approach for dangerous driving behavior recognition is proposed with the aim of significantly decreasing headway. The effectivity of the proposed approach is validated by means of empirical data collected from a medium-sized city in northern China. Finally, a practical early-warning strategy focused on both the remaining life and low headway is proposed to remind drivers to pay attention to their driving behaviors and the possible occurrence of crash-related risks. [ABSTRACT FROM AUTHOR]

Numerical simulations were conducted to examine the effect of episodic rainfall on nearshore groundwater dynamics in a tidally influenced unconfined coastal aquifer, with a focus on both long‐term (yearly) and short‐term (daily) behavior of submarine groundwater discharge (SGD) and seawater intrusion (SWI). The results showed nonlinear interactions among the processes driven by rainfall, tides, and density gradients. Rainfall‐induced infiltration increased the yearly averaged fresh groundwater discharge to the ocean but reduced the extents of the saltwater wedge and upper saline plume as well as the total rate of seawater circulation through both zones. Overall, the net effect of the interactions led to an increase of the SGD. The nearshore groundwater responded to individual rainfall events in a delayed and cumulative fashion, as evident in the variations of daily averaged SGD and salt stored in the saltwater wedge (quantifying the extent of SWI). A generalized linear model (GLM) along with a Gamma distribution function was developed to describe the delayed and prolonged effect of rainfall events on short‐term groundwater behavior. This model validated with results of daily averaged SGD and SWI from the simulations of groundwater and solute transport using independent rainfall data sets, performed well in predicting the behavior of the nearshore groundwater system under the combined influence of episodic rainfall, tides, and density gradients. The findings and developed GLM form a basis for evaluating and predicting SGD, SWI, and associated mass fluxes from unconfined coastal aquifers under natural conditions, including episodic rainfall. SGD and SWI responded to rainfall events in a delayed and prolonged fashionEffect of episodic rainfall on SGD and SWI was quantified using the Gamma distribution functionRainfall‐induced SGD and SWI were predictable

In this study, we compare the performances of well injection and pond infiltration in controlling seawater intrusion in an unconfined coastal aquifer through two scenario groups: (1) a single injection well versus an elliptic infiltration pond and (2) an injection‐extraction well pair system versus an elliptic infiltration pond‐extraction well system. Comparison is based on quantitative indicators that include the interface toe location, saltwater volume, and maximum net extraction rate (for scenario 2). We introduce a method to determine the maximum net extraction rate for cases where the locations of stagnation points cannot be easily derived. Analytical analysis shows that the performances of injection and infiltration are the same, provided that the pond shape is circular. The examination of scenario group 1 suggests that the shape of the infiltration pond has a minor effect on the interface toe location as well as the reduction in the saltwater volume, given the same total recharge rate. The investigation of scenario group 2 indicates, by contrast, that the maximum net extraction rate increases significantly with the increasing ratio of bto a, where aand bare semiaxes of the ellipse parallel and perpendicular to the coastline, respectively. Specifically, for a typical aquifer assumed, an increase of 40% is obtained for the maximum net extraction when b/aincreases from 1/200 to 200. Despite that the study is based on a simplified model, the results provide initial guidance for practitioners when planning to use an aquifer recharge strategy to restore a salinized unconfined coastal aquifer. The performance of a circular pond is the same as that of an injection wellA method is introduced to derive the maximum net extractionThe maximum net extraction rate depends on the pond shape

Macropores such as crab burrows are a common feature of salt marsh sediment and are recognized as an important factor influencing pore‐water flow in salt marshes. In this study, we examined the effect of macropores on saline water evaporation and pore‐water salinity based on laboratory experiments and numerical simulations. Soil columns with and without an artificial macropore were packed with clay‐loam and were set with different hydraulic heads fixed at the bottom. The results showed that increase in pore‐water salinity significantly reduced evaporation rates. The preferential flow induced by macropores recharged the soil surrounding macropores and maintained higher evaporation rates in comparison with homogeneous soil without macropores. As macropores induced lateral flow, the pore‐water salinity in shallow soil around the macropores was reduced but that in the area away from the macropores was increased. These impacts were more remarkable on the soil layers with higher hydraulic heads. A sensitivity analysis showed that with a higher initial pore‐water salinity, the macropore's impact on soil evaporation rates was more remarkable for both clay‐loam and silt‐loam. These results revealed the effect of macropores on soil evaporation processes and soil conditions, and also shed light on associated biogeochemical processes in salt marshes. Macropores increased evaporation from marsh soil with high hydraulic headsMacropores altered pore‐water flow and salinity distributionsMacropores' impacts were more remarkable on soil with high hydraulic heads Macropores increased evaporation from marsh soil with high hydraulic heads Macropores altered pore‐water flow and salinity distributions Macropores' impacts were more remarkable on soil with high hydraulic heads

Salt marshes are among the most important coastal wetlands and provide critical ecological services, including climate regulation, biodiversity maintenance, and blue carbon sequestration. However, most salt marshes worldwide are shrinking, owing to the effects of natural and human factors, such as climate change and artificial reclamation. Therefore, it is essential to understand the decline in the morphological processes of salt marshes, and accordingly, the likely evolution of these marshes, in order to enable measures to be taken to mitigate this decline. To this end, this study presented an extensive systematic review of the current state of morphological models and their application to salt marshes. The emergence of process-based (PB) and data-driven (DD) models has contributed to the development of morphological models. In morphodynamic simulations in PB models, multiple physical and biological factors (e.g., the hydrodynamics of water bodies, sediment erosion, sediment deposition, and vegetation type) have been considered. The systematic review revealed that PB models have been extended to a broader interdisciplinary field. Further, most DD models are based on remote sensing database for the prediction of morphological characteristics with latent uncertainty. Compared to DD models, PB models are more transparent but can be complex and require a lot of computational power. Therefore, to make up for the shortcomings of each model, future studies could couple PB with DD models that consider vegetation, microorganisms, and benthic animals together to simulate or predict the biogeomorphology of the salt marsh system. Nevertheless, this review found that there is a lack of unified metrics to evaluate model performance, so it is important to define clear objectives, use multiple metrics, compare multiple models, incorporate uncertainty, and involve experts in the field to provide guidance in the further study.

Fresh submarine groundwater discharge (FSGD), as an important natural and renewable water resource, occurs along much of the global coast but finally gets lost into the sea. Exploiting FSGD, however, could induce seawater intrusion in coastal aquifers. Here, we show that decreasing groundwater temperature (by extracting fresh groundwater from and recharging cooled and more viscous water back into coastal aquifers) can relieve seawater intrusion and lead to safe exploitation of FSGD, based on laboratory experiments and numerical simulations. The performance of groundwater cooling can be approximately quantified by an analytical solution which shows its dependence on the FSGD extraction ratio and temperature contrast. The seawater retreat ratio (ratio of the seawater retreat distance to the length of seawater intrusion prior to water extraction) can reach 47.4% with groundwater cooling and without fresh groundwater exploitation. Furthermore, without incurring further seawater intrusion, groundwater cooling can lead to 35.7% FSGD exploitation.

Sloping coastal aquifers in reality are ubiquitous and well documented. Steady state sharp‐interface analytical solutions for describing seawater intrusion in sloping confined and unconfined coastal aquifers are developed based on the Dupuit‐Forchheimer approximation. Specifically, analytical solutions based on the constant‐flux inland boundary condition are derived by solving the discharge equation for the interface zone with the continuity conditions of the head and flux applied at the interface between the freshwater zone and the interface zone. Analytical solutions for the constant‐head inland boundary are then obtained by developing the relationship between the inland freshwater flux and hydraulic head and combining this relationship with the solutions of the constant‐flux inland boundary. It is found that for the constant‐flux inland boundary, the shape of the saltwater interface is independent of the geometry of the bottom confining layer for both aquifer types, despite that the geometry of the bottom confining layer determines the location of the interface tip. This is attributed to that the hydraulic head at the interface is identical to that of the coastal boundary, so the shape of the bed below the interface is irrelevant to the interface position. Moreover, developed analytical solutions with an empirical factor on the density factor are in good agreement with the results of variable‐density flow numerical modeling. Analytical solutions developed in this study provide a powerful tool for assessment of seawater intrusion in sloping coastal aquifers as well as in coastal aquifers with a known freshwater flux but an arbitrary geometry of the bottom confining layer. Analytical solutions of seawater intrusion in a sloping coastal aquiferBoth confined and unconfined coastal aquifers are consideredBoth constant‐flux and constant‐head inland boundary conditions are examined

Using the Schwartz‐Christoffel conformal mapping method together with the complex variable techniques, we derive steady state analytical solutions for pumping in a rectangular aquifer with four different combinations of impermeable and constant‐head boundaries. These four scenarios include: (1) one constant‐head boundary and three impermeable boundaries, (2) two pairs of orthogonal impermeable and constant‐head boundaries, (3) three constant‐head boundaries and one impermeable boundary, and (4) four constant‐head boundaries. For these scenarios, the impermeable and constant‐head boundaries can be combined after applying the mapping functions, and hence only three image wells exist in the transformed plane, despite an infinite number of image wells in the real plane. The closed‐form solutions reflect the advantage of the conformal mapping method, though the method is applicable for the aspect ratio of the rectangle between 1/10.9 and 10.9/1 due to the limitation in the numerical computation of the conformal transformation from a half plane onto an elongated region (i.e., so‐called “crowding”phenomenon). By contrast, for an additional scenario with two parallel constant‐head boundaries and two parallel impermeable boundaries, an infinite series of image wells is necessary to express the solution, since it is impossible to combine these two kinds of boundaries through the conformal transformation. The usefulness of the results derived is demonstrated by an application to pumping in a finite coastal aquifer. Steady state analytical solutions for pumping in a rectangular aquifer are developedThe conformal mapping method together with the complex variable techniques is appliedThe conformal mapping method outperforms the direct image‐well method

The uncertainty and sensitivity of predicted positions and thicknesses of seawater-freshwater mixing zones with respect to uncertainties of saturated hydraulic conductivity, porosity, molecular diffusivity, longitudinal and transverse dispersivities were investigated in both head-control and flux-control inland boundary systems. It shows that uncertainties and sensitivities of predicted results vary in different boundary systems. With the same designed matrix of uncertain factors in simulation experiments, the variance of predicted positions and thickness in the flux-control system is much larger than that predicted in the head-control system. In a head-control system, the most sensitive factors for the predicted position of the mixing zone are inland freshwater head and transverse dispersivity. However, the predicted position of the mixing zone is more sensitive to saturated hydraulic conductivity in a flux-control system. In a head-control system, the most sensitive factors for the predicted thickness of the mixing zone include transverse dispersivity, molecular diffusivity, porosity, and longitudinal dispersivity, but the predicted thickness is more sensitive to the saturated hydraulic conductivity in a flux-control system. These findings improve our understandings for the development of seawater-freshwater mixing zone during seawater intrusion processes, and give technical support for groundwater resource management in coastal aquifers.

Previous studies have revealed hysteretic behavior in subterranean estuaries in response to intensified wave conditions caused by offshore storm events, showing dependence of submarine groundwater discharge (SGD) and subsurface salt distribution on historic wave conditions. Although most shorelines worldwide are also exposed to tidal fluctuations, it is unclear how tides moderate wave‐induced SGD and salinity distribution in subterranean estuaries. This study presents numerical simulations that explore the combined influence of intensified wave conditions and tides on groundwater flow and salt transport in a subterranean estuary. The results show that tides weaken the hysteretic wave effect on SGD, suggesting that a tidally influenced subterranean estuary is less sensitive to intensified wave conditions with respect to the water fluxes across the aquifer‐sea interface. However, due to enhancement of salt‐freshwater mixing, tides strengthen the hysteretic wave effect on the salt fluxes across the aquifer‐sea interface, prolonging the recovery of salt distribution in the subterranean estuary to the prestorm state. These findings reveal the nonlinear, coupling nature of processes driven by oceanic oscillations at different time scales in subterranean estuaries. SGD is subjected to the nonlinear interaction of waves and tidesThe hysteretic effect of waves on SGD is reduced by tidesSalt distribution in a tidally influenced aquifer is more sensitive to a storm

Coastal tidal flats have received considerable attention in recent years, as they provide a direct channel for the discharge of terrestrial microplastics into the ocean. Land reclamation is occurring increasingly frequently in coastal tidal-flats; however, the environmental impacts of these activities remain unclear. Therefore, this pioneering study assessed the microplastic emission characteristics of reclamation geotextiles and performed a risk assessment accordingly. Morphological characterization of geotextile samples collected from five sites in Dongtai, China, provided evidence of sedimentary weathering. Based on several assumptions, the average abundance of microplastics in soil covered by geotextiles was estimated to reach 349±137 particles/kg dry weight, with the total microplastic load in the reclaimed area estimated to be 20.67±8.06 t. Compared with previous studies, this research demonstrates that coastal reclamation areas store a high concentration of microplastics, aggravating marine microplastic pollution. Moreover, conditional fragmentation model results revealed that the weathering and distribution characteristics of soil microplastics in coastal tidal-flat areas exhibit spatial heterogeneity, being more easily affected by natural factors (such as tides) than those in inland areas. As a result of tides, the annual discharge of geotextile-originating microplastics from the studied areas into the ocean was approximately 2465.52±960.77 t. These findings prove that the risks posed by engineering-microplastics are significant, indicating that further investigations are required on the precise laws of transfer and migration, as well as the toxicity mechanisms, in order to improve analytical techniques and policies in this field.

Tidal wetland ecosystems are sensitive to porewater salinity dynamics. However, it is unclear how salts move and distribute in these wetlands, particularly how the salts accumulated by evaporation get removed from the wetland soil, so that the salinity levels may stabilize to accommodate vegetation. We conducted a combined field and modeling study to identify the porewater flow and salinity patterns in a subtropical wetland subjected to tidal inundation and evaporation. Measured and simulated salinity contours indicated the formation of hypersaline porewater plumes in the upper intertidal zone and the fresher porewater zones with salinity close to that of seawater near the creek and in the supratidal zone. Simulations indicated the discharge of the hypersaline upper intertidal porewater to the creek with a discharge pathway developed under the fresher near‐creek porewater zone, and this was further confirmed by the field‐observed significant salinity gradient under the creek. Our model suggested that both water and salt discharge from the wetland soil occurred predominantly at the creek bank and creek bed. The porewater discharge is more intensive through the creek bank than the creek bed, while the salt discharge across both the creek bank and creek bed was comparable due to the much higher salinity level under the creek bed. Salt discharge driven by density gradients and tidal‐induced porewater circulation provides a mechanism for removing salts accumulated in the upper intertidal zone due to evaporation and could prevent salt flat formation and marsh plants dieback. Hypersaline porewater plumes formed in the upper intertidal wetland soil by evaporation with the highest salinity more than 150 pptDownward migration of hypersaline porewater contributed to deep aquifer salinizationSalt discharged to the creek through its bank and bed; the groundwater adjacent to the creek bed showed salinity stratification Hypersaline porewater plumes formed in the upper intertidal wetland soil by evaporation with the highest salinity more than 150 ppt Downward migration of hypersaline porewater contributed to deep aquifer salinization Salt discharged to the creek through its bank and bed; the groundwater adjacent to the creek bed showed salinity stratification

Water extracts of leaves from fourteen (14) mulberry varieties growing in China were investigated for their antioxidant activity by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. DPPH scavenging activities ranged from 34.60% to 61.70%. Total phenolic content of mulberry leaf (based on the Folin-Ciocalteu method) varied from 14.00 to 43.67 mg gallic acid equivalent/g leaf, and flavonoid content (based on the colorimetric aluminum nitrate method) varied from 4.02 to 28.32 mg rutin equivalent/g leaf. There was a significant linear relationship between the total phenolic and/or flavonoid content and the antioxidant activity in mulberry leaf extracts.

Using the First principles calculations, the crystal structure, band gap, total and partial density of states (DOS) of anatase TiO2 and anatase TiO2 doped with Yttrium were calculated by a plane-wave pseudopotential (PWPP) method based on density functional theory (DFT). The generalized gradient approximation (GGA) based on exchange-correlation energy optimization was employed to calculate them. From the calculation results, the band gap of anatase TiO2 and Y3+ doped TiO2 are about 2.15eV and 0.86eV. The calculated results demonstrated that the mixing of Yttrium (Y) dopants induces states with original titanium 3d and oxygen 2p valence band attributes to the band gap narrowing. This can enhance the photocatalytic activity of anatase TiO2.

Using first-principle calculations based on density function theory (DFT), the geometry , band structure and electronic density of states of Co-doped anatase titanium dioxide (Co/TiO2) have been studied at plane wave ultra-soft pseudo-potential (PWPP). The states of the valence bands and conduction bands of pure and Co doped TiO2 with anatase structure were calculated. The density of states of pure anataseTiO2 and Co-doped TiO2 is analyzed in detail based on the calculations using the first-principles. From the calculated results, the band gaps of anataseTiO2 and Co doped TiO2 are about 2.15 and 0.78eV, respectively. It shows that Co doped anatase titanium dioxide may lead to the narrowing of the band gap in Co/TiO2. The Co doped anataseTiO2 could be a potential candidate for photocatalyst because it can enhance the photocatalytic activity of anatase TiO2.

Pure TiO2, Nd3+doped TiO2 and Nd 3+-CTAB co-doped TiO2 nanometer thin films were prepared by the sol-gel technique with tetrabutyl titanate and neodymium nitrate as raw materials and surfactant cetyltrimethylammonium bromide (CTAB) as template. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Visible absorbance spectroscopy (UV-Vis). The photocatalytic activity was evaluated by photocatalytic degradation of methyl orange. The results show that the all samples calcined at 500oC are all anatase, and there are slight red shifts of the Nd3+doped TiO2 and Nd3+-CTAB co-doped TiO2 films compared with pure TiO2 films and the red shift of Nd 3+-CTAB co-doped TiO2 is more obvious than that of Nd 3+ doped TiO2, which is beneficial to improve the photocatalytic efficiency. The1.0% Nd3+-CTAB co-doped TiO2 nanometer film calcined at 500°C had excellent photocatalytic efficiencies and the degradation rate of the film is more than 90% after 120 min.

A new governing equation of watertable dynamics was derived.A new analytical solution for watertable fluctuations was derived.The effect of finite unsaturated zone thickness was examined. Parlange and Brutsaert (1987) derived a modified Boussinesq equation to account for the capillary effect on water table dynamics in unconfined aquifers. Barry et al. (1996) solved this equation subject to a periodic boundary condition. Their solution shows significant influence of capillarity on water table fluctuations, which evolve to finite‐amplitude standing waves at the high frequency limit. Here we propose a new governing equation for the water table, which considers both horizontal and vertical flows in an unsaturated zone of finite thickness. An approximate analytical solution for periodic water table fluctuations based on the new equation was derived. In agreement with previous results, the analytical solution shows that the unsaturated zone's storage capacity permits water table fluctuations to propagate more readily than predicted by the Boussinesq equation. Furthermore, the new solution reveals a capping effect of the unsaturated zone on both the amplitude and phase of the water table fluctuations as well as the water table overheight. Due to the finite thickness of the unsaturated zone, the capillary effect on water table fluctuations is modified mainly with reduced amplitude damping and phase shift.

In order to research the seismic property of masonry building constructed with the construction waste recycled bricks, a four stories building model with 1:3 scale is constructed and tested on the shaking table. Based on the test results, the cracks pattern, displacement response, acceleration response of the building are studied. The failure mechanism of the infill building is investigated. The results show that the construction waste recycled brick is a qualified building material to construct the low rise building.

Based on industrial CT technique, Meso-mechanical experiment was conducted on construction waste recycled brick to get the real-time CT image and stress-strain curve of brick during the loading process. Box counting method was used to calculate the fractal dimension of the inner pore transfixion and crack evolution. The results showed that lots of pore in the interfacial transition zone mainly resulted in the damage of the brick. With the increase of stress, the opening through-pore appeared and crack expanded, and the fractal dimension increased.

Abstract: Deriving analytical solutions for tide-induced groundwater fluctuations in unconfined aquifers confronts two problems: (1) As the Boussinesq equation itself contains nonlinear terms, the “secular term” would be generated in derivation, thus making perturbation solution unable to be deduced to higher order; (2) for aquifers with sloping beaches, the perturbation parameter in existing analytical solution integrating the beach slope and hydrogeological property would be sometimes larger than 1. So the application of perturbation solutions is relatively limited. Furthermore, as the beach slope decreases, the error of analytical solution would gradually increase. Given that water table over-height would increase the aquifer thickness and speed up wave propagation, this paper integrates over-height into the perturbation parameter and adjusts boundary conditions to settle the problem of “secular term” and to derive a new high-order analytical solution for nonlinear Boussinesq equation in terms of sloping beaches. Results show that the new analytical solution is more reasonable, and the analytical accuracy is obviously improved in comparison with the existing analytical solution for a gentle slope. The new analytical solution provides a theoretical basis for analyzing the propagation characteristics (e.g., wave length and over-height variation) of tide-induced groundwater wave in unconfined aquifers, particularly those with sloping beaches.

Under the high electric field, discharge sometimes occurs along the surface of solid in vacuum, gas or liquid dielectrics, which is called surface flashover.SiO2-B2O3-K2O-Li2O-Al2O3-ZnO-MgO-F system glass ceramics has great machinability and excellent dielectronic property.This paper tries to study different time of ion-exchanged samples and their microstructures，which affect surface flashover performance of this novel material under the systerm of high voltage in vacuum. Compared to traditional coating method on alumina ceramic, the ion exchange treatment on glass ceramic can produce a tremendous improvement of flashover characteristics. The results show that the 10 hours ion-exchanged glass ceramic enjoys the most prominent insulation strength.Based on the theory of SEEA (Secondary Electron Emission Avalanche), these phenomena can be reasonably explained by the charge carrier injection and transport behaviors.

Glass-ceramics are especially useful for the dental restorations because of their good biocompatibility, chemical stability, aesthetic, mechanical strength and wear resistance. The aim of this work was to obtain one mica glass-ceramic, which can be easily used for rapid machining into all-ceramic tooth with computer assisted design/computer assisted manufacture (CAD/CAM) devices. In the study, on the base of low melting machinable fluorosilicic mica glass ceramics, the effects of CeO2 and Fe2O3 in SiO2-B2O3-K2O-Na2O-Li2O-Al2O3-MgO-F system on color were studied. By orthogonal experimental design, the effects of crystallized parameters on the color, three point flexural strength and machinability of the glass ceramics were obtained, and the samples were analyzed by differential thermal analysis(DTA), X-ray diffraction (XRD) and scanning electron microscopy(SEM), respectively. Experimental results showed that the glass-ceramics with color close to the tooth can be obtained by adjusting the percentage of CeO2 and Fe2O3, and the glass-ceramics crystallized at 680°C for 2h have excellent mechanical properties and machinability.

The mechanical properties of two high manganese steels with manganese contents (15% and 25%) were investigated during tensile tests at room temperature. The results indicated that the strengths of steels were a little low and the elongations were improved greatly with increasing the manganese content. Stress fluctuations were found during tensile tests of the Fe-15Mn steels, and as the strain increased the range of stress fluctuations became wider. The strain hardening exponent n of samples changed with strain in a parabola model. The microstructures before and after deformation were investigated and the results showed that phase transformation of γ (fcc) →ε (hcp) and γ (fcc) →ε (hcp) →α (bcc) induced plasticity occurred in the Fe-15Mn steels. However, in the Fe-25Mn steels, at the beginning stage of the deformation, phase transformation induced plasticity played an important role, and with the increase of deformation, the main mechanism was twinning induced plasticity.

Salt marshes are highly productive intertidal wetlands providing important ecological services for maintaining coastal biodiversity, buffering against oceanic storms, and acting as efficient carbon sinks. However, about half of these wetlands have been lost globally due to human activities and climate change. Inundated periodically by tidal water, salt marshes are subjected to strong surface water and groundwater interactions, which affect marsh plant growth and biogeochemical exchange with coastal water. This paper reviews the state of knowledge and current approaches to quantifying marsh surface water and groundwater interactions with a focus on porewater flow and associated soil conditions in connection with plant zonation as well as carbon, nutrients, and greenhouse gas fluxes. Porewater flow and solute transport in salt marshes are primarily driven by tides with moderate regulation by rainfall, evapotranspiration and sea level rise. Tidal fluctuations play a key role in plant zonation through alteration of soil aeration and salt transport, and drive the export of significant fluxes of carbon and nutrients to coastal water. Despite recent progress, major knowledge gaps remain. Previous studies focused on flows in creek‐perpendicular marsh sections and overlooked multi‐scale 3D behaviors. Understanding of marsh ecological‐hydrological links under combined influences of different forcing factors and boundary disturbances is lacking. Variations of surface water and groundwater temperatures affect porewater flow, soil conditions and biogeochemical exchanges, but the extent and underlying mechanisms remain unknown. We need to fill these knowledge gaps to advance understanding of salt marshes and thus enhance our ability to protect and restore them. Salt marshes populated by salt‐tolerant plants are commonly found at the land‐ocean interface. As highly productive intertidal wetlands, salt marshes serve a variety of ecological functions. This review covers the current state of knowledge on surface water and groundwater interactions in salt marshes and their impacts on ecology and the environment. A global analysis is provided to understand the distribution, hydrological and ecological functions, status and potential challenges of salt marshes. Surface water and groundwater interactions under different driving forces and factors are discussed and linked to soil conditions and biogeochemical processes. Current approaches including field measurements, radionuclide analyses and numerical modeling provide a guide for applications targeted at specific questions in salt marsh science and management. Knowledge gaps identified by this review suggest needs for further investigations into the complex and dynamic surface water and groundwater interactions and associated biogeochemical processes that characterize salt marshes. Tides play a primary role in salt marsh surface water and groundwater interactionsSurface water and groundwater interactions affect plant zonation, and carbon and nutrient outwellingFuture research needs to couple hydrological processes to ecological and geochemical processes Tides play a primary role in salt marsh surface water and groundwater interactions Surface water and groundwater interactions affect plant zonation, and carbon and nutrient outwelling Future research needs to couple hydrological processes to ecological and geochemical processes