Effects of hydrogeological properties on sea-derived benzene transport in unconfined coastal aquifers

This paper presents numerical investigations on quantifying the hydrodynamic effects of coastal environment factors, including tidal fluctuations, beach slopes, hydraulic conductivity, and hydraulic gradients on sea-derived benzene transport in unconfined coastal aquifers. A hydrologic transport and mixed geochemical kinetic/equilibrium reactions in saturated–unsaturated media model was used to simulate the spatial and temporal behaviors of the density flow and benzene transport for various hydrogeological conditions. Simulation results indicated that the tidal fluctuations lead to upper saline plumes (USPs) near the groundwater and seawater interfaces. Such local circulation zones trapped the seaward benzene plumes and carried them down in aquifers to the depth depending on the tide amplitudes and beach slopes across the coastal lines. Comparisons based on different tidal fluctuations, beach slopes, hydraulic conductivity, and hydraulic gradient were systematically conducted and quantified. The results indicated that areas with USPs increased with the tidal amplitude and decreased with the increasing beach slope. However, the variation of hydraulic conductivity and hydraulic gradient has relatively small influence on the patterns of flow fields in the study. The increase of the USP depths was linearly correlated with the increase of the tidal amplitudes. The benzene reactive transport simulations revealed that the plume migrations are mainly controlled by the local flow dynamics and constrained in the USP circulation zones. The self-cleaning process of a coastal aquifer is time-consuming, typically requiring double the time of the contamination process that the benzene plume reach the bottom of a USP circulation zone. The presented systematic analysis can provide useful information for rapidly evaluating seaward contaminants along a coastal line with available hydrogeological properties.

[1]  Bill X. Hu,et al.  Submarine Ground Water Discharge Driven by Tidal Pumping in a Heterogeneous Aquifer , 2009, Ground water.

[2]  W. Reay,et al.  Field Observations of Tidal and Seasonal Variations in Ground Water Discharge to Tidal Estuarine Surface Water , 1998 .

[3]  Hailong Li,et al.  Long-term persistence of oil from the Exxon Valdez spill in two-layer beaches , 2010 .

[4]  D. A. Barry,et al.  Tidal influence on behaviour of a coastal aquifer adjacent to a low-relief estuary , 2006 .

[5]  Geoffrey R. Tick,et al.  The extent of saltwater intrusion in southern Baldwin County, Alabama , 2008 .

[6]  Van Genuchten,et al.  A closed-form equation for predicting the hydraulic conductivity of unsaturated soils , 1980 .

[7]  C. Simmons,et al.  Effects of tidal fluctuations and spatial heterogeneity on mixing and spreading in spatially heterogeneous coastal aquifers , 2015 .

[8]  S. Huant,et al.  Interaction between shallow and deep impurity states in InSb , 1985 .

[9]  G. Davis,et al.  Hypoaigic influences on groundwater flux to a seasonally saline river , 2007 .

[10]  M. Suidan,et al.  Biodegradation of subsurface oil in a tidally influenced sand beach: Impact of hydraulics and interaction with pore water chemistry , 2015 .

[11]  D. A. Barry,et al.  Transport of variable-density solute plumes in beach aquifers in response to oceanic forcing , 2013 .

[12]  Badin Gibbes,et al.  Driving mechanisms for groundwater flow and salt transport in a subterranean estuary , 2006 .

[13]  Henning Prommer,et al.  Modelling the fate of oxidisable organic contaminants in groundwater. In C. T. Miller, M. B. Parlange, and S. M. Hassanizadeh (editors), , 2002 .

[14]  P. Domenico,et al.  Physical and chemical hydrogeology , 1990 .

[15]  B. Eyre,et al.  The driving forces of porewater and groundwater flow in permeable coastal sediments: a review , 2012 .

[16]  D. A. Barry,et al.  Seawater intrusion processes, investigation and management: Recent advances and future challenges , 2013 .

[17]  Hailong Li,et al.  Modeling solute transport and transient seepage in a laboratory beach under tidal influence , 2011, Environ. Model. Softw..

[18]  B. Ataie-Ashtiania,et al.  Tidal effects on sea water intrusion in unconfined aquifers , 1999 .

[19]  D. A. Barry,et al.  Groundwater flow and salt transport in a subterranean estuary driven by intensified wave conditions , 2014 .

[20]  Gour-Tsyh Yeh,et al.  Computational Subsurface Hydrology: Reactions, Transport, and Fate , 2000 .

[21]  W. Burnett,et al.  Investigation of submarine groundwater discharge , 2002 .

[22]  D. A. Barry,et al.  Effects of wave forcing on a subterranean estuary , 2010 .

[23]  M. Boufadel,et al.  Nutrient and oxygen concentrations within the sediments of an Alaskan beach polluted with the Exxon Valdez oil spill. , 2010, Environmental science & technology.

[24]  A. Werner,et al.  Tidal impacts on riparian salinities near estuaries , 2006 .

[25]  H. Prommer,et al.  Tide‐induced recirculation across the aquifer‐ocean interface , 2007 .

[26]  D. A. Barry,et al.  Numerical modeling of tidal influence on density‐dependent contaminant transport , 2007 .

[27]  Behzad Ataie-Ashtiani,et al.  Tidal effects on groundwater dynamics in unconfined aquifers , 2001 .

[28]  Thomas Graf,et al.  Modelling the effects of tides and storm surges on coastal aquifers using a coupled surface-subsurface approach. , 2013, Journal of contaminant hydrology.

[29]  Paul A Hsieh,et al.  Application of MODFLOW for Oil Reservoir Simulation During the Deepwater Horizon Crisis , 2011, Ground water.

[30]  Ling Li,et al.  Salt-freshwater dynamics in a subterranean estuary over a spring-neap tidal cycle , 2007 .

[31]  J. Jiao,et al.  Quantifying tidal contribution to submarine groundwater discharges: A review , 2013 .

[32]  Ling Li,et al.  Tidal influence on seawater intrusion in unconfined coastal aquifers , 2012 .

[33]  J. L. Robinson,et al.  Ground-water resources data for Baldwin County, Alabama , 1996 .

[34]  W. Moore The subterranean estuary: a reaction zone of ground water and sea water , 1999 .

[35]  L. Lebbe,et al.  Occurrence of salt water above fresh water in dynamic equilibrium in a coastal groundwater flow system near De Panne, Belgium , 2006 .

[36]  Jianfeng Wu,et al.  A modeling study of seawater intrusion in Alabama Gulf Coast, USA , 2009 .

[37]  D. A. Barry,et al.  Effect of tidal forcing on a subterranean estuary , 2007 .

[38]  J. Bear Conceptual and Mathematical Modeling , 1999 .

[39]  A. Cheng,et al.  Seawater intrusion in coastal aquifers : concepts, methods, and practices , 1999 .

[40]  Hailong Li,et al.  Tide-induced seawater–groundwater circulation in shallow beach aquifers , 2008 .

[41]  P. Burgherr In-depth analysis of accidental oil spills from tankers in the context of global spill trends from all sources. , 2007, Journal of hazardous materials.

[42]  R. Cowan,et al.  Effect of temperature and dissolved oxygen on the growth kinetics of Pseudomonas putida F1 growing on benzene and toluene. , 2004, Chemosphere.

[43]  H. Michael,et al.  Saltwater‐freshwater mixing dynamics in a sandy beach aquifer over tidal, spring‐neap, and seasonal cycles , 2014 .

[44]  T. Clement,et al.  Interaction between shallow groundwater, saline surface water and contaminant discharge at a seasonally and tidally forced estuarine boundary , 2005 .

[45]  D. A. Barry,et al.  Tidal influence on BTEX biodegradation in sandy coastal aquifers , 2009 .

[46]  J. Greskowiak Tide‐induced salt‐fingering flow during submarine groundwater discharge , 2014 .

[47]  Bruce B. Benson,et al.  The concentration and isotopic fractionation of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere1 , 1984 .