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Dive into the research topics where Yuqiang Xia is active.

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Featured researches published by Yuqiang Xia.


Journal of Contaminant Hydrology | 2014

Numerical study of wave effects on groundwater flow and solute transport in a laboratory beach

Xiaolong Geng; Michel C. Boufadel; Yuqiang Xia; Hailong Li; Lin Zhao; Nancy L. Jackson; Richard S. Miller

A numerical study was undertaken to investigate the effects of waves on groundwater flow and associated inland-released solute transport based on tracer experiments in a laboratory beach. The MARUN model was used to simulate the density-dependent groundwater flow and subsurface solute transport in the saturated and unsaturated regions of the beach subjected to waves. The Computational Fluid Dynamics (CFD) software, Fluent, was used to simulate waves, which were the seaward boundary condition for MARUN. A no-wave case was also simulated for comparison. Simulation results matched the observed water table and concentration at numerous locations. The results revealed that waves generated seawater-groundwater circulations in the swash and surf zones of the beach, which induced a large seawater-groundwater exchange across the beach face. In comparison to the no-wave case, waves significantly increased the residence time and spreading of inland-applied solutes in the beach. Waves also altered solute pathways and shifted the solute discharge zone further seaward. Residence Time Maps (RTM) revealed that the wave-induced residence time of the inland-applied solutes was largest near the solute exit zone to the sea. Sensitivity analyses suggested that the change in the permeability in the beach altered solute transport properties in a nonlinear way. Due to the slow movement of solutes in the unsaturated zone, the mass of the solute in the unsaturated zone, which reached up to 10% of the total mass in some cases, constituted a continuous slow release of solutes to the saturated zone of the beach. This means of control was not addressed in prior studies.


Ground Water | 2010

A Falling-Head Method for Measuring Intertidal Sediment Hydraulic Conductivity

Hailong Li; Pingping Sun; Shi Chen; Yuqiang Xia; Shuang Liu

This paper presents an in situ falling-head method for measuring hydraulic conductivity of beach sediments in tidal environment. A polyvinyl chloride (PVC) standpipe was vertically pushed into the submerged beach sediments so that its lower part was filled by a sediment column. During the experiment, the sediments were submerged by sea water and the standpipe top was higher than the sea level. The pipe was fully filled with sea water at the beginning of the experiment. Then the water level time series inside and outside the standpipe were recorded. Analytical solutions were derived to describe the relation among the sediments hydraulic conductivity and the water levels inside and outside the standpipe and used to analyze the experiment data obtained from the intertidal zone of Puqian Bay, Haikou, Hainan Province, China. The water levels predicted by the analytical solution agreed very well with all the experiment data. Experiments for horizontal hydraulic conductivity estimation were also conducted using L-shaped standpipe which bends from vertical to horizontal in the beach sediments. The averaged hydraulic conductivity anisotropy ratio at the study area is about 2.9. After each in situ experiment, the sediments in the standpipe were stored in a plastic box and transported to university laboratory to measure the hydraulic conductivity using falling-head method. It is found that the in situ hydraulic conductivity averages one order of magnitude greater than the laboratory one, indicating that the original beach surface sediments were loose due to tidal and wave actions and that the samples were significantly compacted during the transportation to laboratory.


Journal of Hydrodynamics | 2010

A new perturbation solution of groundwater table fluctuations in tidal beaches

Yuqiang Xia; Hailong Li; Michel C. Boufadel

This paper modeled tide-induced groundwater flow in a vertical beach with a thin submarine outlet-capping. By implementing a perturbation method based on the Boussinesq’s equation, a new approximate solution was derived for the model. Then the solution was compared with previous analytical solutions derived from the linearized Boussinesq’s equation. The results showed that the error between the present and previous solutions increases with the value of the ratio of tidal amplitude to the aquifer’s depth below the mean sea level and the leakage of the submarine outlet-capping.


Archive | 2013

Hydrogeology and Hydrochemistry Along Two Transects in Mangrove Tidal Marshes at Dongzhaigang National Nature Reserve, Hainan, China

Hailong Li; Yuqiang Xia; Xiaolong Geng

Dongzhaigang National Nature Reserve is the largest mangrove forest nature reserve in China, holds the most abundant mangrove species, and has been giving the best preservation. However, bald mud beaches were found among the mangrove marshes in the reserve. In order to investigate the environmental characteristics behind this phenomenon, the intertidal zones of a mangrove transect and a bald beach transect with similar topography and tidal actions were selected for comparison study. Several monitoring wells were installed along the two transects for in-situ measurements of pH, ORP, salinity and temperature of groundwater. Groundwater samples were collected for lab analysis as well. The results showed that pH values of the mangrove transect were higher than that of the bald beach transect, ORP measurements indicated that the mangrove transect had an oxidizing environment and the bald beach transect has a reducing environment. Lab analysis showed that the concentrations of anions (Cl−, SO4 2−, Br−) and cations (K+, Na+, Ca2+, Mg2+) of water sampled from the bald each transect were much higher than that of the mangrove beach transect. Along both transects, observed water table variations were significant in the high and low intertidal zones and negligible in the middle intertidal zones. The observed groundwater salinity was significantly smaller along the mangrove transect than along the bald beach transect. Previously published analysis concluded that the two transects have a mud-sand two-layered structure: a surface zone of low-permeability mud and an underlying high-permeability zone that outcrops at the high and low tide lines. The freshwater recharge from inland is considerable along the mangrove transect but negligible along the bald beach transect, this may explain the lower concentrations of salt and regular ions along the mangrove transect than along the bald beach transect. This comparative study of hydrogeology and hydrochemistry along the two transects would provide ecological implications on the restoration, protection and management of mangrove ecosystems.


Hydrological Sciences Journal-journal Des Sciences Hydrologiques | 2012

The enhancing effect on tidal signals of a submarine spring connected to a semi-infinite confined aquifer

Yuqiang Xia; Hailong Li; Ying Yang; Wei Huang

Abstract Submarine springs play an important role in submarine groundwater discharge (SGD). To investigate the effects of these springs on the propagation of tidal signals in coastal confined aquifers, this paper considers a general coastal aquifer system with a submarine spring on the seabed where the length of the aquifers offshore extent is finite and its submarine outlet is covered by an impermeable outlet-capping. An approximate analytical solution is obtained for describing the tidal head fluctuations in the aquifer. Solution analyses indicate that the error of the approximate analytical solution is negligible when both distances from the spring hole to the coastline and to the submarine outlet-capping are much greater than the radius of the spring hole. Sensitivity tests are conducted to investigate the effects of hydraulic properties, tidal and spring geometric configuration parameters on the tidal signal propagation in the inland aquifer. For aquifers with infinite offshore length, or without submarine springs, existing solutions in the literature are obtained. The comparison of groundwater head fluctuations for the cases with and without a submarine spring demonstrate the enhancing effect of the submarine spring on tidal signal propagation in the inland aquifer. Three situations that fit our model assumptions are given for future potential applications. A hypothetical example is used to show the possibility of identifying a springs location using the present analytical solution together with tidal signals observed from inland wells. Editor D. Koutsoyiannis; Associate editor Y. Guttmann Citation Xia, Y.Q., Li, H.L., Yang, Y., and Huang, W., 2012. Enhancing effect on tidal signals of a submarine spring related to a semi-infinite confined aquifer. Hydrological Sciences Journal, 57 (6), 1231–1248.


Water Resources Research | 2010

Hydrodynamic factors affecting the persistence of the Exxon Valdez oil in a shallow bedrock beach

Yuqiang Xia; Hailong Li; Michel C. Boufadel; Youness Sharifi


Journal of Hydrology | 2007

Tidal wave propagation in a coastal aquifer: Effects of leakages through its submarine outlet-capping and offshore roof

Yuqiang Xia; Hailong Li; Michel C. Boufadel; Qiaona Guo; Guohui Li


Environmental Modelling and Software | 2011

Modeling solute transport and transient seepage in a laboratory beach under tidal influence

Michel C. Boufadel; Yuqiang Xia; Hailong Li


Advances in Water Resources | 2007

Tide-induced groundwater head fluctuation in coastal multi-layered aquifer systems with a submarine outlet-capping

Qiaona Guo; Hailong Li; Michel C. Boufadel; Yuqiang Xia; Guohui Li


Hydrology and Earth System Sciences | 2011

A combined field and modeling study of groundwater flow in a tidal marsh

Yuqiang Xia; Hailong Li

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Hailong Li

China University of Geosciences

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Michel C. Boufadel

New Jersey Institute of Technology

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Guohui Li

China University of Geosciences

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Xiaolong Geng

New Jersey Institute of Technology

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Chaoyue Wang

China University of Geosciences

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Kai Xiao

China University of Geosciences

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Li Wan

China University of Geosciences

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Pingping Sun

China University of Geosciences

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