Browsing by Author "Hodgson, I.O."
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Item Hydrochemical appraisal of groundwater evolution within the Lower Pra Basin, Ghana: a hierarchical cluster analysis (HCA) approach(Environmental Earth Sciences, 2014-08) Tay, C.K.; Hayford, E.; Hodgson, I.O.; Kortatsi, B.K.The most relevant controls on groundwater quality within the Lower Pra Basin in Ghana were assessed using Q-mode hierarchical cluster analysis (HCA). The objective was to determine the chemical characteristics of the various water groups and subgroups responsible for the groundwater evolution and identify the groundwater recharge and discharge zones within the basin. The Q-mode HCA have characterized hydrochemical data from a total of sixty-eight (68) boreholes and two (2) streams within the basin into four (4) water groups and five (5) subgroups. Results showed that, Group 1 waters had the lowest mean pH (5.6 pH units) with EC and TDS in the range 64.9–295 µS/cm and 32.5–162.0 mg/L respectively, while, Group 4 waters had intermediary mean pH (6.3 pH units) with highest EC and TDS in the range 1,221.2–1,601.0 µS/cm and 661–691 mg/L respectively. Two main water types—the Na–HCO3 and Ca–Mg–HCO3 with Na–Cl and Ca–Mg–Cl as minor water types have also been delineated. Results also showed that, Groups 1 and 2 waters both represents transition zones between Ca–Mg–HCO3/Na–HCO3 and Na–Cl/Ca–Mg–Cl type waters and therefore, can be regarded as transition zones between naturally circulating groundwaters which have not undergone pronounced water–rock interaction/aggressive recharging alkali carbonate waters and limited recharging local rain/permanent hard water. Thus, groundwater within the basin perhaps evolves from fresh- Ca–Mg–HCO3/Na–HCO3 type waters to permanent hard- Ca–Mg–Cl type waters and limited recharging local rain- Na–Cl type waters along its flow paths principally due to ion-exchange reactions. However, Zion Camp areas may be serving as discharge areas to groundwater within the basin. © 2014, Springer-Verlag Berlin Heidelberg.Item Origin of major dissolved ions in groundwater within the Lower Pra Basin using groundwater geochemistry, source-rock deduction and stable isotopes of 2H and 18O(Environmental Earth Sciences, 2013-11) Tay, C.K.; Kortatsi, B.K.; Hayford, E.; Hodgson, I.O.Hydrochemical and stable isotopes (18O and 2H) analyses of groundwater samples were employed to establish the origin of major dissolved ions in groundwater within the Lower Pra Basin. Results showed that, the major processes responsible for chemical evolution of groundwater include: silicate (SiO4)4- dissolutions, ion exchange reactions, sea aerosol spray and pyrite (FeS2) and arsenopyrite (FeAsS) oxidations. The groundwater is strongly acidic to neutral, with pH generally range from 3.5 to 7.0 pH units and mean 5.9 (±0.5). Approximately 89 % of boreholes had pH values outside the World Heath Organization (WHO, Guidelines for drinking water quality, 2004) guideline value for drinking water due principally to natural biogeochemical processes and therefore, not suitable for potable purposes. Electrical conductivity (EC) range from 57.6 to 1,201 μS/cm with mean 279.3 (±198.8) μS/cm. Total dissolved solids (TDS) range from 32 to 661 mg/L with mean 151.7 (±106.8) mg/L, with 98.6 % of groundwater as fresh (TDS < 500 mg/L). The chemical constituents generally have low concentrations and are within the WHO (Guidelines for drinking water quality, 2004) guideline value for drinking water. The relative abundance of cations and anions is in the order: Na+ > Ca2+> Mg2+ > K+ and HCO3 - > Cl- > SO4 2-, respectively. A plot of ∂18O ‰ against 2H ‰ showed that, ground and surface waters clustered on or closely along the Global Meteoric Water Line, suggesting that, the waters emanated principally from meteoric source with evaporation playing an insignificant role on the infiltrating water. © 2013 Springer-Verlag Berlin Heidelberg.