Water pollution in relation to mineral exploration: a case study from Alayi-Ovim area of Southeastern Nigeria

Water samples from rivers, streams, springs, and shallow wells in Alayi-Ovim area of southeast Nigeria have been analyzed for Pb, Ca, Mg, Fe, Mg, PO₄, NO₃, CO₃, SO₄, Cl, and pH. The analyses were carried out using atomic absorption spectrometer and Hach Direct Reading Equipment. Results of the analyses from the area conform to the WHO (1995) standards for drinking water. However, the results show relative enrichment of Ca, pH, Mg, CO₃, and Cl. Low values were obtained for Fe, SO₄, and NO₃. While the Cl and Pb enrichment in the area north of Alayi-Ovim axis is attributed to proximity to the lead–zinc and chloride-rich formations of the Turonian Eze-Aku and the Albian Asu River; the Ca, Mg, SO₄, and CO₃ enrichment in Southern part of Alayi-Ovim is due to the limestone-bearing Late Maastrichtian Nsukka Formation. Furthermore, the very low values of less than 5 ppm for these characters in water in the central region correlate well with the relatively clean Maastrichtian quartz arenite Ajali Sandstone Formation. The Pb–Zn and Cl incursions into the water system from the Older Albian Asu River/Turonian Eze-Aku Formations in the northern part of Alayi-Ovim area and the leaching of Mg, and Ca into the water system in the Maastrichtian limestone area in the south thus constitute geochemical indices for chemical pollution and mineral exploration for brine and dolomitic limestone in the area.