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 (delta(18)O) and hydrogen (deltaD) isotope ratios for surface and groundwater have a similar range and show high d-excess (10-40.8parts per thousand). 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 delta(13)C(DIC) ranged from -7.4 to -17.4parts per thousand. SO42, Ca2 and Mg2 in the water samples ranged from 2-163, 2-6593 and 2-90 mg/l, respectively. The DIC and delta(13)C(DIC) indicate both open and closed system carbonate evolution. Combined delta(13)C(DIC) and Ca2, Mg2 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 delta(18)O, deltaD and delta(13)C(DIC) 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. (C) 2003 Elsevier Ltd. All rights reserved