Chemical characteristics of ground water from parts of the Basement Complex of Oban massif & Obudu plateau, SE Nigeria.

Abstract

Groundwater samples from 29 boreholes in the Basement areas of Obudu and Oban in Cross Rivers State have been analyzed for their major, minor and trace element constituents and some
physical characteristics. The results are evaluated with a view to determining its quality and potability. The Ca2+, Mg2+, −
3 NO , 2− 4 SO and Cl– concentration levels of 0.8 – 69.2mg/l, 0.8 – 22mg/l, 0.02 – 1.7mg/l, 0.3 – 22mg/l and 0.3 – 22mg/l respectively, for the water samples are lower than the WHO recommended highest desirable levels of 75, 50 and 200mg/l respectively. Total Iron and Mn2+ concentration are 0.02 – 1.6 and 0 – 0.66mg/l respectively. All the water samples, with the exception of some from Okodi and Sankwala for total Iron and Anineje for Mn2+ have their concentration levels below the WHO maximum permissible levels of 1.0mg/l and 0.5mg/l. The total hardness (as CaCO3) concentration levels of 10 – 220mg/l are in most cases higher than the WHO maximum permissible levels (of 500mg/l). The pH (5. 0 – 7.5) with the exception of those obtained from Sankwala, fall within the maximum permissible levels of 6.5 – 9.2 units. Generally, these chemical characteristics compare well with those of the groundwater
from other basement areas but differ in many respects from those from sedimentary terrains. The water is of good quality and therefore potable.
Keywords: Basement area, concentration level, permissible levels, potable.