An Appraisal of the Chemical Composition of the Groundwater in Minna Metrolpolis, central Nigeria

Abstract

Groundwater in recent years has become the main source of water supply for domestic use in Minna metropolis following rapid expansion of the town and fledging services provided by the state’s public water service. Minna is the capital of Niger state and lies between latitudes 9032’ and 9041’ N and longitudes 6028’ and 6037’ E covering an approximate surface area of 105km2. The geology of Minna comprises mainly of rocks belonging to the Precambrian Basement Complex System of Nigeria. The main rock types include granite, gneisses, migmatites and schists. Mapping of the area was conducted using a hand-held GPS (Garmin Etrex Legend). The geology of the area was studied using the traverse method on a topographic map (Minna Sheet 164) on a scale of 1:50,000. Water samples were obtained from various locations on a grid basis in glass and plastic bottles. Physical properties of the water were measured at the time of sampling. Water analysis was conducted in the laboratory to determine the chemical composition, instrumentation was by Atomic Absorption Spectrometry, Colourimetry and Titmetri. Major, minor and trace element composition of the water were determined. The cations with the greatest concentration are Mg, Ca, and Na while the dominant anions are HCo3, CO3 and NO3. Trace elements with higher concentration are Mn, Cu, As, and Pb. The groundwater regime can generally be classified into two: a calcium carbonate water and the other in which no cation or anion predominates. The results generally indicate that the groundwater is of good quality, however the water shows signs of gradual enrichment in Mn, As and Pb.