Geochemical evaluation of groundwater quality in Abakaliki area, Southeast Nigeria

The study area comprises Abakaliki town and the mineralized villages in the south, 14km away from the town. It lies between latitudes 6008’N and 6024’N, and longitudes 8000’E and 8016’E, and is underlain by the Abakaliki Shale which belongs to the Asu River group of Albian age. The study aimed at determining the groundwater quality of the area as evaluated from both physical and chemical conditions. Eighteen (18) parameters, (11 chemical and 07 physical) were analyzed for each of twenty (20) samples collected from three different sources; sixteen (16) from boreholes, three (03) from hand-dug wells and one (01) from pipe borne town water supply. Spectrophotometer of HACH DR/ 2010 series was used to analyze the ions. The laboratory results were compared with water quality criteria according to the World Health Organisation (WHO, 2004), European Union (EU, 1998) and United States Environmental Protection Agency (USEPA, 2004) for drinking water. Results showed that about 50% of the samples are polluted with nitrate (N03) with values above the maximum permissible limit of 50mg/l in many places. Concentrations of Fe are also above the permissible limits of 0.30mg/l, in some places, especially in the southern part of the study area. The sources of nitrates are suspected to be from agricultural fertilizers as well as sewage effluents. The iron is suspected to be from dissolution of iron-rich ore minerals (siderites and pyrites) which occur in the southern part of the area. The groundwater of the area is moderately hard (due to bicarbonate (HCO3)) and fresh (due to TDS 1000 mg/l at temperature range of 270C to 310C), and is dominantly alkaline.