ORCID Profile
0000-0002-0676-0882
Current Organisation
Hohai University
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Water Resources Engineering | Environmental Engineering | Environmental Engineering not elsewhere classified | Conservation and Biodiversity
Urban and Industrial Flora, Fauna and Biodiversity | Environmental and Natural Resource Evaluation not elsewhere classified | Remnant Vegetation and Protected Conservation Areas in Urban and Industrial Environments |
Publisher: Wiley
Date: 24-02-2014
DOI: 10.1111/GWAT.12172
Abstract: We introduce a simple correction to coastal heads for constant-density groundwater flow models that contain a coastal boundary, based on previous analytical solutions for interface flow. The results demonstrate that accurate discharge to the sea in confined aquifers can be obtained by direct application of Darcy's law (for constant-density flow) if the coastal heads are corrected to ((α + 1)/α)hs - B/2α, in which hs is the mean sea level above the aquifer base, B is the aquifer thickness, and α is the density factor. For unconfined aquifers, the coastal head should be assigned the value hs1+α/α. The accuracy of using these corrections is demonstrated by consistency between constant-density Darcy's solution and variable-density flow numerical simulations. The errors introduced by adopting two previous approaches (i.e., no correction and using the equivalent fresh water head at the middle position of the aquifer to represent the hydraulic head at the coastal boundary) are evaluated. Sensitivity analysis shows that errors in discharge to the sea could be larger than 100% for typical coastal aquifer parameter ranges. The location of observation wells relative to the toe is a key factor controlling the estimation error, as it determines the relative aquifer length of constant-density flow relative to variable-density flow. The coastal head correction method introduced in this study facilitates the rapid and accurate estimation of the fresh water flux from a given hydraulic head measurement and allows for an improved representation of the coastal boundary condition in regional constant-density groundwater flow models.
Publisher: Elsevier BV
Date: 07-2020
Publisher: Elsevier BV
Date: 10-2020
Publisher: Elsevier BV
Date: 05-2017
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.SCITOTENV.2019.03.309
Abstract: The transformation of dissolved organic nitrogen (DON) in the drinking water treatment plants could be closely associated with nitrogenous disinfection by-product (N-DBP) formation. In this study, we have assessed the molecular transformation of DON and its impact on N-DBP formation in a full scale drinking water treatment plant. Based on the result of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis, DON compounds with low molecular weight (<1 kDa) were classified as CHON, CHON
Publisher: Copernicus GmbH
Date: 23-12-2021
DOI: 10.5194/HESS-25-6591-2021
Abstract: Abstract. Seawater intrusion in island aquifers was considered analytically, specifically for annulus segment aquifers (ASAs), i.e., aquifers that (in plan) have the shape of an annulus segment. Based on the Ghijben–Herzberg and hillslope-storage Boussinesq equations, analytical solutions were derived for steady-state seawater intrusion in ASAs, with a focus on the freshwater–seawater interface and its corresponding watertable elevation. Predictions of the analytical solutions compared well with experimental data, and so they were employed to investigate the effects of aquifer geometry on seawater intrusion in island aquifers. Three different ASA geometries were compared: convergent (smaller side is facing the lagoon, larger side is the internal no-flow boundary and flow converges towards the lagoon), rectangular and ergent (smaller side is the internal no-flow boundary, larger side is facing the sea and flow erges towards the sea). Depending on the aquifer geometry, seawater intrusion was found to vary greatly, such that the assumption of a rectangular aquifer to model an ASA can lead to poor estimates of seawater intrusion. Other factors being equal, compared with rectangular aquifers, seawater intrusion is more extensive, and watertable elevation is lower in ergent aquifers, with the opposite tendency in convergent aquifers. Sensitivity analysis further indicated that the effects of aquifer geometry on seawater intrusion and watertable elevation vary with aquifer width and distance from the circle center to the inner arc (the lagoon boundary for convergent aquifers or the internal no-flow boundary for ergent aquifers). A larger aquifer width and distance from the circle center to the inner arc weaken the effects of aquifer geometry, and hence differences in predictions for the three geometries become less pronounced.
Publisher: Elsevier BV
Date: 07-2021
Publisher: American Chemical Society (ACS)
Date: 13-01-2020
Abstract: Dissolved organic nitrogen (DON) represents a unique challenge in prechlorinated raw water distribution systems (PRWDSs) because of its contribution to the formation of harmful nitrogen-disinfection byproducts, influence upon biogeochemical processes, and unclear molecular characteristics. Here, Fourier transform ion cyclotron resonance mass spectrometry in combination with high-throughput sequencing was applied to elucidate the molecular changes of DON and biofilm microbial communities in a PRWDS in Yixing, China. Our study revealed that dynamic characteristics of DON are significantly correlated with the biofilm. The accumulation of refractory lignin-like compounds and C
Publisher: American Geophysical Union (AGU)
Date: 02-2020
DOI: 10.1029/2019WR025750
Abstract: Freshwater lenses within riparian zones of some arid and semiarid settings assist in maintaining the health of riparian ecosystems. We propose an approach for expanding freshwater lenses in saline aquifers adjacent to gaining rivers through the addition of a vertical barrier of low‐hydraulic‐conductivity (low‐ K ) parallel to the river bank. Sharp‐interface analytical solutions for the lens shape and water table distribution are developed to examine the effectiveness of the proposed method and are verified using sand tank experiments and numerical simulations. The sensitivity analysis is used to apply the method to parameters typical of the Lower River Murray (South Australia) and its floodplain aquifers. The results show that the barrier can create significant freshwater lenses in head‐controlled systems, whereas the barrier may lead to lens shrinkage in flux‐controlled systems due to saline water table rise. That is, the effectiveness of the barrier is highly dependent on the inland boundary condition. The analytical solution presented herein can be used to efficiently predict the riparian freshwater lens extent in response to engineered barriers, adding to existing techniques for studying and modifying riparian freshwater lenses.
Publisher: Wiley
Date: 08-2022
DOI: 10.1002/HYP.14654
Abstract: Global‐change drivers that alter tidal litude or sea level could directly impact coastal aquifers' seawater–microbe interactions. The semidiurnal or diurnal tide can have consequences for chemical redistribution, because it deepens oxygen and nutrients penetration depth, thereby increasing O 2 depletion via microbial respiration in sediments during groundwater circulation. However, chemical and microbial distributions in tidal aquifers remain unclear, in deference to their link with depth and lateral location. By combining the microbes‐accumulated equation with the traditional groundwater flow model in coastal aquifers, we explicitly unravelled the heterotrophic zonation, the salinity zonation, and the oxic zonation of tidal aquifers. According to the model estimates, salt penetrates deeper than reactive chemicals, and the heterotrophic high biomass zone is presumably 2–3 m deep. Such depth of heterotrophic distribution is 2–3 orders of magnitude higher than phototrophic distribution. Additionally, heterotrophic biomass can exhibit faint oscillations, even under the tide forces, whereas dissolved chemicals fluctuate significantly with tidal pumps. Due to the transport of nutrients by tidal penetration, intertidal sediments have a higher respiration rate than subtidal sediments, converting more organic carbon from seawater to atmospheric CO 2 via microbes. We demonstrate that heterotrophic biomass may play the dominant role in the chemical reactions of nearshore sediments. Our results confirm the efficacy of unvegetated tidal sediments that rely on ubiquitous heterotrophs as a driver of oxygen consumption and DOC transformation. These steps above will allow for better field investigations of coastal aquifers within a framework of zonations and oscillations.
Publisher: Elsevier BV
Date: 03-2015
Publisher: American Geophysical Union (AGU)
Date: 05-2016
DOI: 10.1002/2016WR018724
Publisher: Wiley
Date: 25-02-2022
Publisher: American Geophysical Union (AGU)
Date: 04-2019
DOI: 10.1029/2018WR024665
Publisher: American Geophysical Union (AGU)
Date: 06-2023
DOI: 10.1029/2022WR032931
Abstract: Unsaturated flow influences both the seawater extent under steady‐state conditions and the propagation of tides in coastal aquifers. However, its effects on salt distributions in tidally influenced coastal aquifers are little investigated. The present study used numerical simulations and data from laboratory experiments to analyze the effects of unsaturated flow on density‐dependent solute transport in coastal unconfined aquifers. The effects of the inland boundary condition (i.e., constant‐head or constant‐flux) were tested. Compared to a stable sea level, the results show that unsaturated flow has a more pronounced influence on salt distributions in coastal unconfined aquifers when tides are considered, regardless of the type of inland boundary condition. Neglect of unsaturated flow effects leads to expansion of the upper saline plume (USP), shrinkage of the saltwater wedge (seaward movement of saltwater wedge), and overestimation of water and salt exchange across the aquifer‐ocean interface. This is caused by a lower head in the nearshore area during high‐tide periods with the unsaturated zone effects removed. Thus, without the unsaturated zone, stronger head gradients within the nearshore aquifer occur at high tide, leading to stronger tidally driven seawater infiltration and hence a larger USP. Counterintuitively, ignoring unsaturated flow effects leads to greater average inland head over a tidal period, which shifts the saltwater wedge seaward. It is concluded that unsaturated zone effects should not be neglected for modeling tide‐affected seawater intrusion, especially if quantification of near‐shore conditions is important.
Publisher: Elsevier BV
Date: 09-2020
Publisher: American Geophysical Union (AGU)
Date: 10-2015
DOI: 10.1002/2015WR017019
Publisher: Elsevier BV
Date: 10-2016
Publisher: American Geophysical Union (AGU)
Date: 03-2023
DOI: 10.1029/2022WR033309
Abstract: The freshwater lenses (“lenses” hereafter) within saline floodplain aquifers are sensitive to river flooding events. However, the effects of extensive floodplain inundation on saline aquifers are rarely considered and have not been examined previously under controlled laboratory conditions. We conducted laboratory experiments within a two‐dimensional (cross‐section) sand tank (i.e., representing a saline floodplain aquifer) and built both laboratory‐ and field‐scale numerical models to examine lens responses to flood events. Three sets of experiments were performed to explore different lateral extents of floodplain inundation. The temporal behavior of experimental lenses was quantified and compared to variable‐density numerical models that adopted calibrated laboratory parameters, showing good agreement. Results show that more extensive floodplain inundation leads to larger lenses (as expected). The sensitivity analysis was performed based on field‐scale numerical models, demonstrating that the floodplain inundation extent, hydraulic conductivity, and dispersivity are key factors controlling the post‐flood recession in lens extent and volume. In field‐scale simulations of floodplain inundation, the entire lens was significantly salinized during flood recession due to enhanced dispersion accompanying higher groundwater velocities, which may further split into several isolated freshwater bodies before eventually returning to steady‐state conditions. Importantly, field‐scale numerical results indicated that the salt load to the adjacent river increased immediately following the flood event, consistent with reporting of the River Murray (South Australia). These results provide critical new insights into relationships between flood events and the behavior of lenses, highlighting the significance of flooding events on both intermediate and long‐term conditions of saline floodplains.
Publisher: American Geophysical Union (AGU)
Date: 03-2021
DOI: 10.1029/2020WR028386
Abstract: Freshwater lenses are of great importance in supporting both the vulnerable ecosystems of small‐to‐medium oceanic islands and the lives of local inhabitants. Recently, an engineering approach that embeds a low‐permeability, fully penetrating barrier along the shoreline was proposed and demonstrated under controlled conditions to be effective in enhancing island lens size. The current study extends that work by investigating the effect of partially penetrating barriers placed at the shoreline on both circular and strip island lenses, using: (1) sharp‐interface analytical solutions, (2) dispersive numerical modeling, and (3) sand tank experimentation. Analytical, experimental, and numerical results are in reasonable agreement in terms of the freshwater‐seawater interface. The findings indicate that partially penetrating barriers of sufficient depth (i.e., the freshwater depth in barrier from the fully penetrating barrier case) produce comparable results to fully penetrating barriers, and therefore, the former is more cost‐effectiveness. Moreover, the minimum barrier depth (i.e., the “critical depth”) required to obtain approximately the same lens as that achieved using the fully penetrating barrier is estimable from the analytical solution, as verified by laboratory experiments and numerical simulations. The sensitivity analysis based on the analytical solution indicates that a lower barrier permeability and a greater barrier thickness, which lead to a higher freshwater storage (as expected), require a larger critical depth. The guidance on the design of partially penetrating shoreline barriers arising from this research adds to existing engineering techniques for enhancing freshwater resources on circular and strip islands.
Publisher: American Geophysical Union (AGU)
Date: 08-04-2015
DOI: 10.1002/2015GL063643
Publisher: American Geophysical Union (AGU)
Date: 08-2022
DOI: 10.1029/2021WR031445
Abstract: Aquifer storage and recovery (ASR) involves the injection of freshwater into an aquifer for temporary water storage and later use. Previous studies have shown that density‐driven convection may render part of the injectant unrecoverable when ASR is implemented in a saline aquifer. Where heterogeneity creates a significant proportion of immobile groundwater, dual‐domain (immobile and mobile porosities) effects also lead to reductions in the efficiency of ASR schemes. Presuming constant total porosity (sum of the mobile and immobile porosities), the combined effects of dual‐domain properties and water density on ASR are investigated for the first time in the present study, using numerical modeling of otherwise similar conceptual models to previous ASR analyses. Results show that the interactions between the density effect and dual‐domain mass transfer lead to complex controlling patterns of the density contrast, the ratio of immobile‐mobile porosities, the parameterization of immobile‐mobile solute exchange, and the number of cycles. The influence of these factors on mixing processes and the recovery efficiency (proportion of freshwater injectant recovered by extraction) during ASR are shown. Dual‐domain effects, where they occur in aquifers, must be included explicitly in models to reproduce recovery efficiencies, especially during early cycles, unless the immobile porosity is very small or the conductance between mobile and immobile regions is at extremes. Otherwise, a single‐domain model can be utilized. The findings of this research illustrate the influence of both density effects and dual‐domain processes on ASR and the need to account for both in assessing ASR feasibility in complex hydrogeological settings.
Publisher: Elsevier BV
Date: 08-2018
Publisher: American Geophysical Union (AGU)
Date: 03-2018
DOI: 10.1002/2017WR021761
Publisher: American Geophysical Union (AGU)
Date: 05-2022
DOI: 10.1029/2021WR031306
Abstract: Aquifer storage and recovery (ASR) involves the injection, and later extraction, of freshwater into aquifers, which often contain saline groundwater. Mixing between the fresh injectant and native saltwater often leads to part of the injectant becoming unrecoverable, thereby impacting ASR performance. This study explores freshwater‐saltwater mixing within ASR operations arising from aquifer heterogeneity using Monte Carlo analysis of 2D‐axisymmetric, density‐dependent flow and transport models. Logarithmic hydraulic conductivity (ln K ) distributions are generated using either two‐point statistics or higher‐order connectivity features. Results show that higher variance in ln K leads to stronger freshwater‐saltwater mixing, which lowers the recovery efficiency (RE i.e., ratio of extracted to injected freshwater). On average, the lowest RE values were obtained from ln K fields with connected high‐ K features, across all ASR cycles. In contrast, RE values from ln K fields with connected low‐ K features were typically the highest, at least where buoyancy was considered. The impact of aquifer heterogeneity on RE reduces with subsequent ASR cycles. Buoyancy was a major factor in lowering RE regardless of the adopted heterogeneity model. Heterogeneity tended to mitigate the adverse impacts of buoyancy, leading to some heterogeneous cases having higher RE values than the corresponding homogeneous case. These results highlight the importance of understanding buoyancy effects and subsurface heterogeneity (including the connectivity of geological structures), and interrelationships thereof when assessing the feasibility of multi‐cycle ASR in heterogeneous saline aquifers.
Publisher: American Geophysical Union (AGU)
Date: 11-2020
DOI: 10.1029/2020WR027792
Publisher: American Geophysical Union (AGU)
Date: 11-2021
DOI: 10.1029/2021WR029728
Abstract: This study examines the occurrence of riparian lenses adjacent to partially penetrating, gaining rivers under the controlled conditions of a laboratory sand tank. Laboratory experiments and numerical modeling of the freshwater lens extent are used to provide physical verification (in light of limited ex les of well‐characterized field cases) of the analytical methodology, thereby evaluating the underlying assumptions. Parameter calibration and uncertainty analysis are applied to assess both the experimental conditions and the benefit of lens observations in applying the analytical approach. The experimental freshwater lens was reproduced by both analytical and numerical models, with the exception of small mismatches (between analytical results and measured data) in the lens thickness in the near‐river region. These are most likely due to vertical flow effects that arise from the partial river penetration and saltwater inflows to the river bottom, and that are only partly accounted for in the analytical approach. Uncertainty analysis highlighted that accurate lens predictions based on the analytical method requires calibration to direct lens measurements a similar finding from earlier studies of fully penetrating river conditions. Sensitivity analysis highlighted that the saltwater head boundary, freshwater and saltwater densities, and the aquifer depth below the riverbed (in descending order of sensitivity) are the most important factors in controlling freshwater lens occurrence and saltwater discharge. The results provide the first physical verification of the occurrence of stable riparian lenses adjacent to partially penetrating, gaining rivers, and verify a recent analytical solution for lens extent and saltwater discharge.
Publisher: American Geophysical Union (AGU)
Date: 30-09-2020
DOI: 10.1029/2020WR027786
Abstract: Previous studies of freshwater lenses in saline aquifers adjoining gaining rivers (“riparian lenses”) have so far considered only rivers that fully penetrate the aquifer, whereas in most cases, rivers are only partially penetrating. This paper presents a new methodology for obtaining the saltwater discharge and the shape of a steady‐state, non‐dispersive riparian lens, where the river is partially penetrating, combining two previous analytical solutions. The resulting analytical solution is compared to numerical modeling results to assess assumptions and the methodology adopted to approximate the “turning effect”, which is the change in groundwater flow direction (horizontal to vertical) near the partially penetrating river. Model parameters were taken from previous studies, representing simplified conditions in the River Murray floodplains (Australia). Consistency between analytical and numerical results and field observations highlights the capability of the proposed analytical solution to predict the riparian lens geometry and saltwater discharge into partially penetrating rivers. Sensitivity analysis indicates that larger riparian lenses are produced adjacent to the deeper and wider rivers, as expected. The change in width or depth of the river has more influence on the saltwater discharge and the horizontal extent of the riparian lens (and less effect on the vertical extent of the lens adjacent to the river) for shallower and narrower rivers. This research highlights the utility of the new method and demonstrates that the assumption of a fully penetrating river likely leads to significant overestimation of the saltwater discharge to the river and the riparian lens horizontal extent and vertical depth.
Publisher: Elsevier BV
Date: 04-2022
Publisher: Elsevier BV
Date: 2016
Publisher: American Geophysical Union (AGU)
Date: 06-2021
DOI: 10.1029/2020WR029028
Abstract: Previous studies of the effects of land reclamation on the extent of seawater in coastal aquifers have assumed that the reclaimed area penetrates to the impermeable base of aquifer, and that the seawater in the aquifer is entirely contained within reclaimed sediments. The current study extends previous research into the effects of reclamation on groundwater levels and seawater extent by developing new analytical expressions for the steady‐state heads and non‐dispersive freshwater‐seawater interface for situations where reclaimed soils overly permeable aquifer material. Situations involving reclaimed soils that are more permeable or less permeable than the original aquifer are explored. Sand‐tank experiments and associated numerical simulations (in 2D cross section) were undertaken to evaluate assumptions adopted in developing the solutions, which include an empirical correction to account for dispersion effects. Sand tank solute distributions are well matched to numerical modeling results, and provide validation of analytical solutions and the associated simplifications. Application of the new solution demonstrates that both the water level rise and the seaward shift of seawater extent caused by reclamation are modified with the inclusion of the underlying permeable layer, depending on permeability contrasts and the reclaimed area size. For ex le, if the reclaimed soil is less permeable than the original aquifer, water level rise and the seawater extent shift are reduced with the inclusion of an underlying permeable layer. The analytical solution developed in this study can provide rapid guidance on the changes to seawater extent and groundwater levels caused by land reclamation in otherwise permeable substrate.
Publisher: American Geophysical Union (AGU)
Date: 09-2016
DOI: 10.1002/2016WR019101
Publisher: Wiley
Date: 16-02-2021
Publisher: Wiley
Date: 16-02-2021
Publisher: Elsevier BV
Date: 02-2022
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 05-2016
Publisher: American Geophysical Union (AGU)
Date: 06-2017
DOI: 10.1002/2016WR019625
Publisher: Wiley
Date: 31-08-2023
DOI: 10.1002/HYP.14964
Publisher: American Geophysical Union (AGU)
Date: 07-2017
DOI: 10.1002/2017WR020809
Publisher: Elsevier BV
Date: 06-2023
Publisher: Elsevier BV
Date: 07-2023
Publisher: American Geophysical Union (AGU)
Date: 06-2022
DOI: 10.1029/2022WR032164
Abstract: Submarine groundwater discharge via coastal aquifers is an important pathway for land‐derived chemicals to enter the oceans. While previous studies have mostly focused on natural coastal aquifers, little attention has been paid to those modified by land reclamation. This study used laboratory experiments and numerical simulations to investigate the effects of land reclamation on flow and mixing processes in a nearshore subterranean estuary. The results show that, regardless of the permeability, the addition of reclamation soil will shift the tide‐driven upper saline plume (USP) seaward and reduce the USP size. When the aquifer is reclaimed by low‐permeability soil, the seawater intrusion length is reduced for small tidal litudes but extended as tidal litude further increases. Depending on the tidal litude, high‐ and low‐permeability reclamation soils prolong or shorten the average particle travel time in the USP, the freshwater discharge zone, and the saltwater wedge. Compared to the case without reclamation, high‐/low‐permeability reclamation soil enhances/weakens the water discharge rate across the aquifer‐ocean interface, narrows/expands the freshwater discharge zone, and increases the tide‐/density‐driven recirculation percent. Findings from this study highlight the complexity of nearshore groundwater systems subject to human activities, and have significant implications for better understanding the fate of terrestrially sourced chemicals in subterranean estuaries before discharging into the coastal water.
Publisher: Copernicus GmbH
Date: 18-01-2022
Abstract: Abstract. Watertable fluctuations and seawater intrusion are characteristic features of coastal unconfined aquifers. The dynamic effective porosity due to watertable fluctuations is analyzed and then a modified (empirical) expression is proposed for the dynamic effective porosity based on a dimensionless parameter related to the watertable fluctuation frequency. After validation with both experimental data and numerical simulations, the new expression is implemented in existing Boussinesq equations and a numerical model, allowing for examination of the effects of the dynamic effective porosity on watertable fluctuations and seawater intrusion in coastal unconfined aquifers, respectively. Results show that the Boussinesq equation accounting for the vertical flow in the saturated zone and dynamic effective porosity can accurately predict experimental dispersion relations (that all existing theories fail to predict), highlighting the importance of the dynamic effective porosity in modeling watertable fluctuations in coastal unconfined aquifers. This in turn confirms the utility of the real-valued expression of the dynamic effective porosity. An outcome is that the phase lag between the total moisture (above the watertable) and watertable height measured in laboratory experiments using vertical soil columns (1D systems) can be ignored when predicting watertable fluctuations in coastal unconfined aquifers (2D systems). A dynamic effective porosity that is, by comparison, smaller than the soil porosity leads to a reduction in vertical water exchange between the saturated and vadose zones and hence watertable waves can propagate further landward. The dynamic effective porosity further plays a critical role in simulations of seawater intrusion, since it predicts a more landward seawater-freshwater interface and a higher position of the upper saline plume.
Start Date: 10-2015
End Date: 12-2020
Amount: $187,745.00
Funder: Australian Research Council
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