Application of (234)U/(238)U activity ratios to investigations of subterranean groundwater discharge in the Cádiz coastal area (SW Spain).
The activity ratios of (234)U/(238)U were used to investigate processes of subterranean groundwater discharge into coastal marine waters in a study location at Bay of Cádiz (southwest Spain). Marine waters in the bay and surrounding open ocean exhibited U concentrations of 3.4 ± 0.1 μg/L and activity ratios of 1.15 ± 0.01, in agreement with the expected composition of seawater ((234)U/(238)U activity ratio = 1.148 ± 0.002). Three water samples obtained from the discharge zone of the Guadalete River exhibited activity ratios of 1.17-1.22 along with slightly lower U concentrations compared to seawater, which is likely due to mixing between seawater and a groundwater end-member. One possible source of groundwater was characterized by sampling and analyzing a well water sample collected in the neighboring village of El Puerto de Santa María; this water sample exhibited an activity ratio of 1.34 ± 0.03 and a U concentration of 1.22 μg/L. Water from the Guadelete River estuarine zone can be explained to result from a two-component mixture of seawater and groundwater from the El Puerto de Santa María well; however, if there are several groundwater reservoirs with different U activity ratios that discharge to the coastal water, then, it may be difficult and more studies are being conducted to address this issue.
Departamento de Física Aplicada, Universidad de Cádiz, Av. República Saharaui s/n, 11510 Puerto Real, Cádiz, Spain.
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Rodrigo
Departamento de Física Aplicada, Universidad de Cádiz, Av. República Saharaui s/n, 11510 Puerto Real, Cádiz, Spain. Electronic address: melquiades.casas@uca.es.
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Casas-Ruiz
Departamento de Construcciones Navales, Universidad de Cádiz, Av. República Saharaui s/n, 11510 Puerto Real, Cádiz, Spain.
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Vidal
Departamento de Ciencias de la Tierra, Universidad de Cádiz, Av. República Saharaui s/n, 11510 Puerto Real, Cádiz, Spain.
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Barbero
Department of Geology, Wayne State University, Detroit, MI 48202, USA.
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Baskaran
Department of Chemistry and Biochemistry, Northern Arizona University, Flagstaff, AZ 86011-5698, USA.
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Ketterer
D060587:Groundwater / Q000032:analysis*; D013058:Mass Spectrometry; D011834:Radiation Monitoring; D045483:Rivers / Q000737:chemistry; D012623:Seawater / Q000032:analysis; D013030:Spain; D014501:Uranium / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
D014875:Water Pollutants, Radioactive; D014501:Uranium
(234)U/(238)U activity ratios; Coastal aquifers; ICP-MS; Submarine groundwater discharge (SGD)