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Sustainable management of groundwater resources in geological transition zones (GTZ) is essential due to their complex geology, increasing population, industrialization, and climate change. Groundwater quality monitoring and assessment represent a viable panacea to this problem. Therefore, there is a great need to investigate groundwater resources in terms of their chemistry and pollution to ascertain their quality and implement robust pollution abatement strategies. This study focused on the characterization of groundwater in a typical geological transition zone in northeastern Nigeria. Eighty-seven (87) groundwater samples were collected from dug wells and boreholes during the 2017 dry season. pH, conductivity, and total dissolved solids (TDS) were measured in situ using a multiparameter probe, while major cations and anions were measured using atomic absorption spectrometry and ion chromatography, respectively. Data were analyzed using descriptive statistics, principal component analysis (PCA), water quality index, and standard hydrochemical plots. TDS ranged between 95 and 1154 mg L−1 in basement terrains and between 49 and 1105 in sedimentary areas. pH ranged between 6.8 and 7.7 mg L−1 in basement terrains and between 5.0 and 6.5 in sedimentary areas, suggesting a moderately acidic to alkaline low mineralized groundwater. Calcium (2.6–128.0 mg L−1) was the dominant cation in the basement areas, suggesting silicate weathering/dissolution, while sodium (1.9–106.0 mg L−1) dominated the sedimentary zones due to base exchange reactions. The PCA analysis suggests that mineral dissolution (mostly silicate weathering) controls the hydrochemistry of the basement aquifers, while ion exchange and albite weathering, with some influence of anthropogenic factor, control the sedimentary aquifers. The water quality index revealed that the basement setting was predominated by poor to unsuitable groundwater, while the sedimentary terrain was characterized by potable groundwater. The dominant hydrochemical facie in the basement areas was Ca2+–(Mg2+)–HCO3− characteristic of recharge meteoric water. The Na+– (K+)–HCO3− facie characterized the sedimentary zones, indicative of cation exchange reactions, while the mixed water facie typifies the geological contact zones. The shallow nature of the basement groundwaters makes them more susceptible to geogenic and anthropogenic pollution compared to the sandstone aquifers. However, the basement aquifers have better irrigation indices (Kelly ratio and soluble sodium percent) as compared to the sandstone aquifers, which exhibit poor Kelly ratios (< 1) and soluble sodium percent (> 50) ratings. Results from the study clearly highlight the poor-unsuitable groundwater quality in parts of the studied GTZ and can be very instrumental to the policymakers in implementing sustainable water treatment strategies and cleaner production technologies in GTZ to forestall the incidence of water-related diseases. [ABSTRACT FROM AUTHOR]

Groundwater quality assessment is essential for groundwater resource management, especially as it concerns the health of those that consume it. Consequently, we assembled resistivity and hydrogeochemical data to assess the adverse effect of anthropogenic sources on groundwater quality in Ogbe-Ijoh, a coastal area of the western Niger Delta. Geoelectrical data showed no evidence of quality degradation as reflected by high resistivity values that ranged from 29.3 to 349.9 Ωm. Aquiclude of adequate thickness capping aquifers was uncovered in most areas assessed, with the exception of areas near the bank of the river. The delineated clay sedimentary horizon probably enhanced groundwater quality sustainability by acting as a barrier to migrating contaminants, especially from leachate and septic tanks. The physical properties of groundwater sampled indicated moderate pH, TDS and EC magnitudes, with a majority having magnitudes lesser than the requisite standards. The geochemistry of groundwater revealed cations and anions with magnitudes that are distinctively lesser than the desired ranges. Piper plot revealed two different water types: NaCl− and Ca2+ + Mg2+ + Cl− + SO4, which implied that cation exchange has a weighty effect on quality of groundwater. Overall, the hydrogeochemical results are consistent with resistivity data and revealed the efficacy of the pairs in groundwater quality assessment in the absence of lithologic information. The groundwater condition is relatively safe for consumption; nevertheless, due to health implications we recommend that pH should be increased to the required standard before drinking. [ABSTRACT FROM AUTHOR]

Abstract: Cation exchange reactions affect ionic composition of soil solution from which plants draw their nutrients. With routine potassium (K+) fertilization of savanna soils, there is little or no information on K exchange equilibria of the soils. We studied Ca–K and Mg–K exchange reactions of a surface (0–15 cm) and sub-surface layer (15–30 cm) of an acid savanna soil with a view to providing baseline data for the efficient management of Ca2+ and Mg2+ fertility without inducing their deficiencies through unfavourable cationic ratios. Calculated selectivity coefficients consisting of the Vanselow (K V), Gapon (K G) and Gaines and Thomas (K GT) selectivity coefficients were greater than one across a wide range of exchanger phase composition, indicating a preference for K+ to Ca2+ and Mg2+. The plots of the charge fraction of adsorbed K+ (E K(exch)) versus the charge fraction of K+ in aqueous solution (E K(aq)) showed that the experimental points were above the non-preference isotherm line, indicating a marked selectivity of K+ over Ca2+ or Mg2+. The thermodynamic exchange constant (K ex) for the 0–15 cm layer was 4.62 for Mg–K, and 4.31 for Ca–K, while in the 15–30 cm layer K ex was =2.75 for Mg–K and 2.67 for Ca–K exchange. The free energy of exchange (ΔG ex ), for Mg–K system was between −3.79 and −2.51 kJ mol−1, while in the Ca–K system, it varied from −3.62 kJ mol−1 in the 0–15 cm to −2.43 kJ mol−1 for the 15–30 cm layer. The negative ΔG ex values were consistent with preferential K+ retention and affinity by this savanna soil. [Copyright &y& Elsevier]