GEOCHEMICAL STUDY OF RIVER WATERS AND SPRINGS IN ZAMBIA: PROVIDING INTERNATIONAL RESEARCH EXPERIENCE FOR STUDENTS

We conducted a geochemical survey of river water and hot springs in Zambia in order to determine the source of the spring water and the dissolved constituents. This study is one of a multifaceted study aimed at increasing our understanding of how continental rifting and accompanying magmatic activities affects near surface and surface water chemistry. The survey was conducted along a south to north transect across the country where nine hot springs and ten different rivers were investigated. Temperature, dissolved oxygen, pH, oxidation-reduction potential, specific conductance, total dissolved solids, and alkalinity were measured in situ. Samples were collected and used to measure major cations and anions, silica, trace metals, dissolved inorganic carbon and stable isotopes of carbon and stable isotopes of oxygen. Temperatures for the springs ranged from 35°C to 70°C, and generally decrease from the south to the north. The mean pH (7.2) for spring samples was higher than that of river water (6.2) and the mean dissolved oxygen concentrations for the springs samples (0.8 mg/l) was much lower compared to river samples (4.6 mg/l). The springs are Na-SO₄–HCO₃ or Na-SO₄–Cl type, while river water is Ca/Mg-HCO₃ type. The solute concentrations of the spring samples increase from south to north along the transect while river water samples show no spatial variations. On the average, the solute concentrations of the spring samples are 50 times higher than the solute concentrations of river water. The dissolved inorganic carbon concentrations of the spring samples are more than two times higher than river samples. The high solute concentrations of spring samples suggest extensive rock-water interaction. The results of this study suggest that the water from the hot springs likely have a meteoric origin, modified through addition of mass from magmatic processes and enhanced rock-water interaction. The results of the stable carbon isotopes will further constrain magmatic effects on mass transfer in spring samples and the stable oxygen isotopes will help verify the meteoric origin of the spring samples.