Seasonal and spatio-temporal patterns, evolution and quality of groundwater in Cross River State, Nigeria: implications for groundwater management

摘要

A systematic study was carried out to understand the spatial, temporal and seasonal variability of the hydrochemical processes controlling the water chemistry in Cross River State (Nigeria). This is based on the fact that existing aquifers are prone to contamination and no comprehensive study exists in the literature to address this problem. Results of the study showed that the groundwater samples are moderately acidic (pH 4.01-7.57), fresh (TDS < 1000 ppm) and soft-hard (hardness 8.67-194.38 mg/1). The groundwater samples had concentrations within the WHO maximum admissible concentration (MAC) with respect to Na, Ca, Mg, HCO_3, CI and SO_4. The concentrations of As, Cd, Cr, Cu, Cu, Mn, Pb and Zn are also below the MAC. However, no limits are listed by WHO for Co and Mo. The abundance of major cations and anions were in the following order: Ca~(2+)> Na~+ > Mg~(2+)> K~+ and CP > HCO_3~- > SO_4~(2-) for all the different sampling scenarios. Interpretation of the analytical data showed predominance of water types such as Na~+-CP > Ca~(2+)-CP > Ca~(2+)-HCO_3~-. Chemical data indicate that irrespective of the scenario considered, the water chemistry is controlled by silicate and carbonate weathering, brine dissolution, ion exchange, biological and human activities. The results also suggest good quality water for drinking and agricultural applications based on national and international indices and standards. The findings of this study will act as a guide against future pollution of groundwater and sustainable development of groundwater resource in Cross River State.