Isotopic and geochemical evolution of ground and surface waters in a karst dominated geological setting: a case study from Belize,Central America |
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| Institution: | 1. Instituto de Geología, Universidad Nacional Autónoma de México, D.F., Mexico;2. Facultad de Ciencias, Universidad Nacional Autónoma de México, D.F., Mexico;1. Departamento de Geología, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Carr. Ensenada-Tijuana 3918, 22860 Ensenada, B.C., Mexico;2. Instituto de Geología, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, 04510 Coyoacán, DF, Mexico;3. Institut für Geowissenschaften, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 236, 69120 Heidelberg, Germany;4. Centro de Geociencias, Campus UNAM 3001, 76230 Juriquilla, Querétaro, Mexico;5. Museum für Naturkunde, Leibniz Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, 10115 Berlin, Germany;6. Department of the Environment, Washington State University, Pullman, WA 99164, USA |
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| Abstract: | Analysis of stable isotopes and major ions in groundwater and surface waters in Belize, Central America was carried out to identify processes that may affect drinking water quality. Belize has a subtropical rainforest/savannah climate with a varied landscape composed predominantly of carbonate rocks and clastic sediments. Stable oxygen (δ18O) and hydrogen (δD) isotope ratios for surface and groundwater have a similar range and show high d-excess (10–40.8‰). The high d-excess in water samples suggest secondary continental vapor flux mixing with incoming vapor from the Caribbean Sea. Model calculations indicate that moisture derived from continental evaporation contributes 13% to overhead vapor load. In surface and groundwater, concentrations of dissolved inorganic carbon (DIC) ranged from 5.4 to 112.9 mg C/l and δ13CDIC ranged from ?7.4 to ?17.4‰. SO42, Ca2+ and Mg2+ in the water samples ranged from 2–163, 2–6593 and 2–90 mg/l, respectively. The DIC and δ13CDIC indicate both open and closed system carbonate evolution. Combined δ13CDIC and Ca2+, Mg2+, and SO42? suggest additional groundwater evolution by gypsum dissolution and calcite precipitation. The high SO42?content of some water samples indicates regional geologic control on water quality. Similarity in the range of δ18O, δD and δ13CDIC for surface waters and groundwater used for drinking water supply is probably due to high hydraulic conductivities of the karstic aquifers. The results of this study indicate rapid recharge of groundwater aquifers, groundwater influence on surface water chemistry and the potential of surface water to impact groundwater quality and vise versa. |
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