Contamination of water sources by potentially toxic elements around agricultural and quarry land uses of Oban Massif and environs southeastern Nigeria

Water quality was assessed by analyzing potentially toxic elements in water sources around agricultural and quarry land uses in Oban Massif and environs, southeastern Nigeria. Mean levels of most elements agreed with the World Health Organization standard for potable water. However, acidity (pH) and barium (Ba) mean concentrations exceeded their limits of 6.5-8.5 and 2ppm, respectively recommmended for potable water by WHO. Analysis of variance revealed that stream, pond, and groundwater sources tested significant (p <0.05), but spring source tested insignificant. Multivariate analyses of geochemical data showed that rock-water interaction, cation exchange, weathering of silicate minerals, and salinity through mineralized waters influence the water quality. Classification of water samples based on metal load shows a dominance of near neutral-low metal load. Borehole water sources recorded near neutral/high metal classification compared to shallow water sources. Speciation modeling shows that metals exist more as free ions and water samples are oversaturation with respect to gibbsite, brocantile, alunite, diaspore, and boehmite. Contamination index (Cd) values show about 70% low, 10% medium, and 20% high degree of contamination in the sample locations The mean value of contamination index falls under low contamination (Cd <1). Potentially toxic element evaluation and pollution indices attained values below 100, which is the critical value for water pollution. The water quality status in the study area is unpolluted with potentially toxic elements due to quarrying and agricultural activities. Spring water sources are mostly unaffected by elemental contamination. The water sources are recommended for drinking and other domestic uses after minor treatment for acidity. © 2021, Saudi Society for Geosciences.