Geology and Water Quality Assessment of Okpoma Salt Lake Areas in Yala Local Government Area of Cross-River State, Nigeria

ABSTRACT

Geology and Water Quality Assessment of the Salt Lake areas of Okpoma and its environs in Yala Local Government Area of Cross River State has been carried out. The study area lies between longitude 08o 361 E to 08o 411 E of the equator and latitude 06o 321 N to 06o 371 N of the meridian respectively. They belong to the Eze-Aku Group of the Late Cenomanian- Turonian age Southeastern Nigeria. Lithologically the area is underlain by shales and intercalation of sandstone. Igneous intrusions were also observed in the area. pH, electrical conductivity, turbidity, TDS, major anions (Cl-, SO42-, NO3-, CO32-), major cation (Ca2+, Mg2+, Fe2+, Na+,  K+) and trace element (Co, Se, Mo, Pb, Ni, Zn, Cu, Ag, Hg, Cd) were measured as physicochemical parameters of groundwater and surface water in the area. Results of hydrochemical analysis revealed that the pH value of the five water samples (6.44, 9.19, 7.16, 4.74 and 6.16) in the area is slightly acidic to basic in most area and this might cause the water to be corrosive. The turbidity (193, 40, 26, 38 and 37mg/l) are far above the World Health Organisation WHO (2011) recommended standard for drinking water. Highest concentrations of chloride (Cl-) (930mg/l and 372mg/l) were noticed within the salt lake area with its value exceeding the WHO (2011) recommendation. Concentration of Trace element such as lead (Pb), silver (Ag), selenium (Se), cadmium (Cd), and mercury (Hg) ranges from 0.184mg/l-0.265mg/l for lead, 0.054mg/l-0.397mg/l for silver, 0.086mg/l-0.895mg/l for selenium, 0.046mg/l-1.046mg/l for cadmium, and 0.049-0.151mg/l for mercury. These values were above the WHO (2011) recommendation. Thus, the contaminated groundwater must be treated and disinfected before usage for drinking or human consumptions.