SEASONAL VARIATIONS IN THE PHYSICO-CHEMICAL AND MICROBIAL CHARACTERIZATION OF GROUNDWATER IN LOKOJA NORTH CENTRAL NIGERIA

Abstract

Physico-chemical and bacteriological characteristics of groundwater in relation to seasonal changes, was carried
out around Lokoja Metropolis with a view of determining its potability. Sixty (60) groundwater samples were
collected from both boreholes and hand dug wells. Thirty (30) samples were collected during the rainy season
while the remaining thirty (30) samples were collected during the dry season. The pH, Total Dissolved Solid
(TDS), Electrical Conductivity (EC) and Dissolved Oxygen (DO) were determined using Hanna HI9813
GROCHEK model. The turbidity of the water samples were investigated with Hach Dr/2000 spectrophotometer.
Atomic absorption Spectrophotometer, model 210 VGP was used in analysis of the cation. Results of the
geochemical analysis obtained during the wet and dry seasons for physical, chemical and biological analyses
reveals that groundwater of the study area is soft to very hard during the wet season and soft during the dry
season. On the basis of TDS, groundwater in the area is moderately fresh. The mean concentrations of ions
Cu2+, Zn2+, Mn2+, Fe2+, Pb2+, Cd2+,Cr4+, Mg2+, Ca2+, Na+, Cl-, SO4
2-, NO3
-, HCO3
- are within the World health
Organization (WHO) and the Standards Organization of Nigeria (SON) maximum permissible levels for human
consumption in both seasons. The biological analysis showed a rise in the number of coliform counts during the
rainy season compared with the dry season. Coliform counts in the study area are more in the hand-dug wells
than in boreholes. The Piper Trilinear Diagrams constructed indicated Calcium–Magnesium–Bicarbonate,
Sodium-Sulphate-Chloride and Calcium-Magnesium-Sulphate-Chloride water types during the wet season and
Calcium-Magnesium-Bicarbonate water type during the dry season. The mean concentrations of major cations
are of the order Ca2+>K+>Na+ >Mg2+ while the anions are of the order HCO3
- > Cl-> SO4
2-> NO3
- during the
rainy season. During the dry season cation concentrations are of the order Ca2+> K+>Na+>Mg2+ and the
anions are of the order HCO3
->SO4
2->Cl- >NO3. The physico-chemical, bacterial and water types are
susceptible to seasonal variation. A pre-use treatment for the water is recommended before human consumption.