Environmental impact assessment of artisanal mining in parts of Isin LGA, southwestern Nigeria
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Date
2022
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Publisher
Water Utility Journal, E.W. Publications
Abstract
Impact of artisanal mining in parts of Isin LGA, southwestern Nigeria was carried out to ascertain the level of
degradation to the immediate environment. Samples from rocks, mines tailings, mine ponds water and rivers and
groundwater from immediate community were analysed to assess concentration of elements in the media. Rocks of
the study area consist mostly of schist, amphibolite, quartzites and pegmatites. Field relationship revealed that schist
and amphibolite were intruded by pegmatites and quartzites thus forming foliations whose major trends are NNESSW and eastward dip direction. Petrographic studies show that the dominant minerals are quartz, biotite, plagioclase,
microcline, hornblende, orthoclase and opaque minerals. Geochemistry of the solid media revealed average
abundance in order of Fe>Mg>K>Ca>Na>Mn>Cu>Zn>Ni, whereas pollution assessment indices using enrichment
ratio revealed that the area is unpolluted. Hydrochemical facies of the water using Piper’s diagram show that majority
of the samples belong to Ca2+-Mg2+-HCO3-
+CO32- with dominance of Ca2++Mg2+ over Na+
+K+ as well as HCO3-
+CO32- over SO42-
+Cl- while Gibbs diagram indicated an interplay of rock-precipitation dominance. Assessment for
irrigation purposes using sodium and magnesium hazards, Sodium Adsorption Ratio, Kelley’s ratio and Wilcox Plot
revealed the suitability. Though concentrations of evaluated parameters indicated low level degree of pollution,
continuous opening of mining sites for exploitation and consequence reactions with water bodies may spike up the
level of concentration of base metals in the surface and groundwater with resultant great threat to health of plants,
animals and humans.
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Keywords
Odu-Eku; artisanal mining; enrichment; water chemistry; facies; piper