A Hydrochemical Study Of The Brine Fields Of Awe, Keana And Giza Areas, Middle Benue Trough, Nigeria

ABSTRACT

This research work presents findings of the extent and distributions of saline zone and the

hydrochemical characteristics of the groundwater of Awe, Keana and Giza areas in the

Middle Benue Trough of Nigeria.Staticwater levels(swl) of hand dug wells were measured

andthe results used to generate hydraulic head data and hydraulichead map. The static water

levels range from 1.0m to 13.5m at Awe, 1.0m to 4.5m at Keana and 2.2m to 9.2m at Giza.

The hydraulic head maps for the three areas show different patterns/directions of groundwater

flow for each area. Geophysical investigations, mainly vertical electrical sounding (VES)

using Schlumberger electrode configuration array were performed at 47 locations spread

across the entire study areas. Results of the VES revealed that the studyareas are

characterized by3, 4 and 5geo-electrical layers with 9 different curve type signatures. Also,

results of the VES show that Awe area has the highest occurrence of saline zone, followed by

Keana and Giza respectively. Multi-layer saline zones were observed only at Awe. Thirty

(30) groundwater samples (10 each from the 3 areas) were analyzed for physiochemical

parameters (rare earth elements, heavy metals, major cations and major anions).Results of

hydrochemical analysis revealed five (5) hydrochemical facies namely,Ca-HCO3, NaCl,

NaHCO3, Ca-Na-HCO3 and Ca-Mg-Cl facies. Principal component analysis of the

hydrochemical data revealed that the groundwater chemistry of the areas is controlled by the

mineralization of the host rocks, weathering of galena, uranite, felsdspathic minerals and

dissolution of limestone and dolomite. The spatial distribution pattern of the rare earth

elements of groundwater of the study areas showed a strong positive correlation exists

between brine and the elements. Uranium, however, showed a district distribution pattern

which may indicate a distinct source from the other elements. Of the three areas studied,

Keana has the most potable water supply. Awe and Giza groundwater have chloride (Cl),

nitrate (NO3) and lead (Pb) contaminations.It was observed that the groundwater quality of

the study areas is not only salinity dependent, but also influenced by anthropogenic activities

such agricultural wastes and domestic waste released into the environment.Based on the

irrigation water quality indexes employed, groundwater of the areasrange from unsuitable to

suitable for irrigation purposes.