Baseline concentration and sources of trace elements in groundwater of Cross River State, Nigeria

Groundwater samples were collected from wells in Cross River State (Nigeria) and analysed for trace elements including Ba, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Rb, Sr and Zn. The primary aim of the study was to determine the baseline concentrations of these metals, while the secondary aim was to assess the present level of pollution, as a basis for future impact of human and industrial activities on the groundwater quality. Multivariate statistical methods were applied to determine the relationships between the different trace elements and also infer their different sources. The results showed that the contents of Ba, Fe, and Pb in groundwater from some locations were higher than the World Health Organisation, WHO maximum admissible concentration (MAC) of 700μg/l, 300μg/l and 100μg/l respectively. The contents of Cd, Co, Cu, Fe, Mn, Ni, Pb, Rb and Zn were lower than the concentrations in freshwater, while the contents of Ba, Cr, Li, Mo and Sr in some of the locations exceeded the values in typical freshwater. Correlation and cluster analyses indicated common sources for some elements, while factor analysis suggested dissolution of brine, dissolution of barite mineral, weathering of the bedrock and prevailing oxidation-reduction potential of the environment as the main factors responsible for the occurrence of these trace elements in groundwater. The present data therefore is expected to serve as a good guide for future groundwater management of the area.