Regional Hydrogeochemistry of a Modern Coastal Mixing Zone

Wicks, Carol M.; Herman, Janet S.

doi:10.1029/95wr03244

Cited by 44 publications

(19 citation statements)

References 19 publications

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“…Carrizo Sand groundwaters are Ca-Na-HCO 3 -Cl type waters near the recharge area (well depths less than 150 m), become Ca-HCO 3 and Ca-Na-HCO 3 waters along the mid-reaches of the studied flow path (well depths between 150 and 760 m) and are Na-HCO 3 waters further down gradient (well depths [ 760 m; Tang and Johannesson 2005;Basu et al 2007). Within the recharge area, Upper Floridan groundwaters are Ca(Mg)-HCO 3 type waters, change to Ca-Mg-SO 4 -HCO 3 type waters with flow beyond *46 km, and become Ca-Mg-SO 4 type waters near the end of the studied flow path (Sacks et al 1995;Wicks and Herman 1996;Tang and Johannesson 2005;Basu et al 2007). Near the recharge zone, Aquia aquifer groundwaters are characterized as Ca-Mg-HCO 3 type waters (Chapelle 1983).…”

Section: General Geochemistrymentioning

confidence: 99%

Arsenic and Antimony in Groundwater Flow Systems: A Comparative Study

2011

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Arsenic (As) and antimony (Sb) concentrations and speciation were determined along flow paths in three groundwater flow systems, the Carrizo Sand aquifer in southeastern Texas, the Upper Floridan aquifer in south-central Florida, and the Aquia aquifer of coastal Maryland, and subsequently compared and contrasted. Previously reported hydrogeochemical parameters for all three aquifer were used to demonstrate how changes in oxidation-reduction conditions and solution chemistry along the flow paths in each of the aquifers affected the concentrations of As and Sb. Total Sb concentrations (Sb T ) of groundwaters from the Carrizo Sand aquifer range from 16 to 198 pmol kg -1 ; in the Upper Floridan aquifer, Sb T concentrations range from 8.1 to 1,462 pmol kg -1 ; and for the Aquia aquifer, Sb T concentrations range between 23 and 512 pmol kg -1 . In each aquifer, As and Sb (except for the Carrizo Sand aquifer) concentrations are highest in the regions where Fe(III) reduction predominates and lower where SO 4 reduction buffers redox conditions. Groundwater data and sequential analysis of the aquifer sediments indicate that reductive dissolution of Fe(III) oxides/oxyhydroxides and subsequent release of sorbed As and Sb are the principal mechanism by which these metalloids are mobilized. Increases in pH along the flow path in the Carrizo Sand and Aquia aquifer also likely promote desorption of As and Sb from mineral surfaces, whereas pyrite oxidation mobilizes As and Sb within oxic groundwaters from the recharge zone of the Upper Floridan aquifer. Both metalloids are subsequently removed from solution by readsorption and/or coprecipitation onto Fe(III) Electronic supplementary material The online version of this article (oxides/oxyhydroxides and mixed Fe(II)/Fe(III) oxides, clay minerals, and pyrite. Speciation modeling using measured and computed Eh values predicts that Sb(III) predominate in Carrizo Sand and Upper Floridan aquifer groundwaters, occurring as the Sb(OH) 3 0 species in solution. In oxic groundwaters from the recharge zones of these aquifers, the speciation model suggests that Sb(V) occurs as the negatively charged Sb(OH) 6 -species, whereas in sufidic groundwaters from both aquifers, the thioantimonite species, HSb 2 S 4 -and Sb 2 S 4 2-, are predicted to be important dissolved forms of Sb. The measured As and Sb speciation in the Aquia aquifer indicates that As(III) and Sb(III) predominate. Comparison of the speciation model results based on measured Eh values, and those computed with the Fe(II)/Fe(III), S(-II)/SO 4 , As(III)/As(V), and Sb(III)/Sb(V) couples, to the analytically determined As and Sb speciation suggests that the Fe(II)/Fe(III), S(-II)/SO 4 couples exert more control on the in situ redox condition of these groundwaters than either metalloid redox couple.

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Section: General Geochemistrymentioning

confidence: 99%

Arsenic and Antimony in Groundwater Flow Systems: A Comparative Study

2011

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“…Most of the information on intruding seawater/rock interaction processes comes from studies analyzing the deviation of the chemical and isotopic composition of the groundwater at the FSI from a simple mixing line (e.g., Magaritz and Luzier, 1985;Price and Herman, 1991;Wicks et al, 1995;Appelo and Postma, 1996;Wicks and Herman, 1996;Barker et al, 1998;Panteleit et al, 2002). These studies suggest processes such as cation exchange, oxidation of organic matter in aerobic or anaerobic conditions, and CaCO 3 dissolution or precipitation.…”

Section: Introductionmentioning

confidence: 99%

Geochemical evolution and timescale of seawater intrusion into the coastal aquifer of Israel

Sivan

Yechieli

Herut

et al. 2005

Geochimica et Cosmochimica Acta

133

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“…Seawater intrusion phenomena have been reported with different degree, in almost all coastal aquifers around the globe. In the United Sates, saltwater intrusion into coastal aquifers has been identified in the eastern Atlantic [8][9][10][11][12][13][14], and the southern [15] and western Pacific [16][17][18][19] coasts.…”

Section: Overview Saltwater Intrusion Into Coastal Aquifersmentioning

confidence: 99%

Groundwater Overexploitation and Seawater Intrusion in Coastal Areas of Arid and Semi-Arid Regions

Alfarrah

Walraevens

2018

Water

247

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Abstract:The exploitation of groundwater resources is of high importance and has become very crucial in the last decades, especially in coastal areas of arid and semi-arid regions. The coastal aquifers in these regions are particularly at risk due to intrusion of salty marine water. One example is the case of Tripoli city at the Mediterranean coast of Jifarah Plain, North West Libya. Libya has experienced progressive seawater intrusion in the coastal aquifers since the 1930s because of its ever increasing water demand from underground water resources. Tripoli city is a typical area where the contamination of the aquifer in the form of saltwater intrusion is very developed. Sixty-four groundwater samples were collected from the study area and analyzed for certain parameters that indicate salinization and pollution of the aquifer. The results demonstrate high values of the parameters Electrical Conductivity, Na + , K + , Mg 2+ , Cl − and SO 4 2− , which can be attributed to seawater intrusion, where Cl − is the major pollutant of the aquifer. The water types according to the Stuyfzand groundwater classification are mostly CaCl, NaCl and Ca/MgMix. These water types indicate that groundwater chemistry is changed by cation exchange reactions during the mixing process between freshwater and seawater. The intensive extraction of groundwater from the aquifer reduces freshwater outflow to the sea, creates drawdown cones and lowering of the water table to as much as 25 m below mean sea level. Irrigation with nitrogen fertilizers and domestic sewage and movement of contaminants in areas of high hydraulic gradients within the drawdown cones probably are responsible for the high NO 3 − concentration in the region.

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Regional Hydrogeochemistry of a Modern Coastal Mixing Zone

Cited by 44 publications

References 19 publications

Arsenic and Antimony in Groundwater Flow Systems: A Comparative Study

Arsenic and Antimony in Groundwater Flow Systems: A Comparative Study

Geochemical evolution and timescale of seawater intrusion into the coastal aquifer of Israel

Groundwater Overexploitation and Seawater Intrusion in Coastal Areas of Arid and Semi-Arid Regions

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