Abstract
The shallow and deep aquifer horizons of the crystalline basement of Oban massif of (SE Nigeria) were studied during the dry and wet seasons. The criteria were ascertaining hydrogeochemistry relative to seasonal and spatial variations across the study region. The results obtained show that major elements such as Ca, Mg, Na and K were higher in the shallow aquifers than in the deep aquifers, during the study period. The major anions Cl, SO4, HCO3 and NO3 were higher in the deep aquifers compared to the shallow ones. Two water types were identified for both (shallow and deep) aquifers: Ca/Mg-HCO3 and Ca/Na-Cl/SO4. Most of the water parameters considered was within the international limits for drinking and domestic purposes. Assessment by use of Sodium Absorption Ratio (SAR), percent Sodium (% Na) and the Wilcox diagram reveal that the waters are suitable for irrigation purposes.
Highlights
Hydrogeochemical studies have over the years played an essential role in interpreting mineralogical composition of the sub-surface and inherent conditions in most geological settings
The waters from the shallow and deep aquifers are slightly acidic in the dry season and evolve to a slightly alkaline nature in the wet season
Calcium and magnesium are the dominant cations which are generally higher in the shallow aquifers
Summary
Hydrogeochemical studies have over the years played an essential role in interpreting mineralogical composition of the sub-surface and inherent conditions in most geological settings. Recent and on going investigations within the study area notably Edet (1993), Edet et al, (1994), Edet et al, (1998), Okereke et al, (1998), Edet and Okereke (2005) Okereke et al (1998), have led to the delineation of groundwater productive zones, quantitative and qualitative estimation of aquifer parameters within the massif These have been expressed by interrelations between lineaments frequency and density of regolith development. These assessments have all been achieved based on remotely sensed data, aerial photos, deep geophysics, and geologic logs from exploration boreholes within the ISSN 1916-9779 E-ISSN 1916-9787 www.ccsenet.org/jgg study area. This current research attempts to assess the hydrogeochemistry of the groundwaters relative to aquifer levels within the massif
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