| Abstract: | A trace elements study of various samples from the Keana brines field, middle Benue Trough was carried-out to determine the
extent to which Pb–Zn–S and BaSO4 mineralisations have affected the quality of the brines and the waters in the area. Different sample media such as well-water,
pond water, brine spring pool water, stream water, stream sediments etc. were analysed. Geochemical results show that Cu,
Zn, Pb, As and S are concentrated in the waters (0.3, 0.36, 0.05, 0.07 and 1 1.5 ppm respectively). These elements are more
concentrated in both the spring and pond waters, suggesting that the spring water could have acted as the transport medium
for these elements released from deep-seated sources. Transitions elements (Ti, V, Cr, Fe, Co, Ni and Sr) are concentrated
in the waters. Compared to the World Health Organization (WHO) admissible limits, the well waters present very high concentrations
in Cd (0.56 ppm) and Sb (0.40 ppm) (200× and 70× WHO admissible values respectively). There is a preferential concentration
of transition elements (Ti, V, Fe, Co and Ni) in the sediments (41.38, 362, 52.21, 269 and 54 ppm respectively) than in the
waters (0.70, 0.05, 5.6, 0.04 and 0.02 ppm respectively). Similarly, Cu, Zn, Pb and As are concentrated in the sediments (44,
72, 41 and 14 ppm respectively). The concentrations of transition elements (Ti, V, Cr, Fe, Co and Ni) in the refined salt
were highly elevated (784, 363, 283, 105, 59.2 and 42.6 ppm respectively) (7000–10,000× well water). Similarly, the concentrations
of As, Pb, Br and Sr in the refined salt were also alarming (11.6, 16.4, 16.4 and 122 ppm respectively), (1000, 700, 3000
and 20,000× well water values respectively). S on the other hand is absent. One of the striking features is the absence of
I, Cd, Sb and Se in the refined salt crystals which were detected in the waters and the brines. Compared to WHO admissible
values, the refined salt crystal concentrations for Ni (426 ppm) and Cr (283 ppm) were also very high (2000× WHO values respectively)
and to a lesser extent Cu (26.9 ppm) and Zn (21.7 ppm) (12 and 7× WHO values respectively). |
