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Geochemical and quality assessment of groundwater in some Nigerian basement complex
Odukoya, A. M.
Abstract
Fifty samples from hand dug wells and boreholes
were collected at Ijebu Igbo and its environs within
the basement complex of some part of southwestern
Nigeria. The purpose was to establish preliminary baselines
for constituents in the groundwater and also to determine
the quality for both drinking and irrigation purposes.
Physical parameters were determined in situ using the appropriate
digital meters, while the analysis of trace elements
and cations in water was carried out using
inductively coupled plasma optical emission spectrometry
at Actlabs, Ontario, Canada. The order of relative abundance
for major elements is Na>Ca>K>-
Si>Mg>P>Fe>Al>S. Al, Fe, Na, K and P were
above the EPA 2012 recommended standard for drinking
water in 79, 23, 3, 37 and 6 % of the water samples, respectively,
and geochemical process is being influenced by
both man activities and weathering of silicate minerals.
Sodium absorption ratio ranges between 0.12 and 10.43
and falls within excellent and good for irrigation purpose.
Only 78 and 22 % of water samples were suitable for irrigation
based on the soluble sodium percentage and
magnesium adsorption ratio, respectively, while all the
water samples were good for irrigation purpose based on
Kellys ratio. Concentration of Te and Ti was below the
detection limit for all the samples. As, B, Cd, Cr, Cu, Mo,
Ni, U and Zn though present in water were below recommended
standards for all the samples. Ni and Sb exceeded
recommended standard only in sample W24, and Ba exceeded
recommended standard in W20 with value as high
as 909.76 ppb. Mn and Pb were higher than recommended
standard in 12 % of the samples, respectively. The pollution
index varied from 0.09 to 1.66 with 8 % of the water
samples showing pollution index above 1. Generally,
groundwater in the study area is suitable for both domestic
and irrigation uses except samples W4, W20, W24, W47
and W49. However, since heavy metals are not
biodegradable, they tend to bioaccumulate and biomagnify
in the body and eventually become harmful to human
health.
Keywords
Irrigation; Major elements; Nigeria; Trace element
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