ASSESSMENT OF SELECTED MAJOR AND TRACE CONSTITUENTS IN THE GROUND WATER OF SOME PARTS OF SOUTHWESTERN NIGERIA

One hundred and twenty samples from groundwater made up of hand dug wells and boreholes were collected at Ago Iwoye, Oru and Ijebu Igbo within the Basement Complex in some part of Southwestern Nigeria. The purpose was to establish preliminary baselines for these constituents in the ground water of the study area and also to determine the quality.

The analysis of trace elements and cations in water were carried out using inductively coupled plasma optical emission spectrometry (ICP-OES at Actlabs, Ontario Canada.;

Concentrations of 34 elements which include trace and major elements such as Al, As, B, Ba, Be, Ca, Cd, Ce, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Sb, Se, Si, Te, Ti, Tl, U, V, W and Zn were determined.

The pH ranges from 4.00 to 7.90 and can be classified between acidic to slightly alkaline. Total Dissolved Solids (TDS) and Total hardness of the samples range from 92 - 793mg/l and 20 -221mg/lCaCO₃ respectively. 80% the water samples can be classified as fresh water and are within the recommended standards of 500mg/l for TDS (EPA 2012). Total Hardness (TH) indicates that the water samples in the study area are between soft to slightly hard.

Trace elements like Si, Bi and Ti were below detection level; of 0.05ppb, 0.05ppb and 10ppb respectively for all the samples. As, Be, Cd, Cr, Cu, Mn, Se and Zn were below Maximum Contamination Level (MCL) of; EPA 2012 for all the samples. Al, Br, Fe, Mn, Ni, Pb, Sb were above the EPA standard and generally pose health or environmental hazard for most of the samples with the following ranges <1-2686ppb, 5.48-2199.35ppb, <10-22450ppb, <0.05-52.8ppb and 0.09-11.64ppb respectively. The pollution index among all sites varied from 0.075 to 6.26 and exceeded the acute and chronic effect levels proposed by the United States Environmental Protection Agency in 2007.