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A screen house study was conducted to evaluate the effect of gemstone mining on the growth behaviour of maize Zea mays L. A completely randomized design involving two samples of soil (FUTA (control) and Ijero (mined soil)), two varieties of the maize (TMZ234 and Sammarz 39) was used. The seeds were sown into experimental pots containing the soils and the whole set up was left for eight weeks. Growth parameters (plant height, leaf area and stem girth were taken at a weekly basis up till the eight week. Eight heavy metal (Cd, Cu, Cr, Fe, Ar, Zn, Pb and Ni) concentration in the soils, roots and shoots of the plants was determined at the end of the experiment using atomic absorption spectrophotometer. Baseline data indicates that the mined soil is acidic (pH 4.12), with low organic carbon (0.92), low organic matter (1.59) and low total nitrogen (0.76). Results obtained from this study show that all growth parameters were negatively affected by the mined soil. Plant height was significantly higher in the control varieties (82.28 and 40.46, respectively) when compared with the mined soil varieties (30.5 and 29, respectively) at 8 weeks after planting (WAP). Leaf area also followed the same pattern with varieties grown on control soil having significantly higher leaf area (48.22 and 25.22, respectively) than varieties grown on mined soil (19.08 and 19, respectively). Stem girth of variety TMZ234 in control soil was also significantly higher than the rest (2.24 as against 1.68, 1.5 and 1.74). Heavy metals concentration in the soil, shoot and root of the plants grown in mined soils were all higher than in those grown on control soils. In the soil, Cr, Ni and Pb were 0.24, 0.15, 0.10 and 0.20, 0.13, 0.10, respectively, in both varieties grown on mined soils as against 0.03, 0.01, 0.00 and 0.03, 0.08, 0.00 for Cr, Ni and Pb, respectively, for both varieties grown on control soils. Bioaccumulation and translocation factors for the metals were less than 1 in all the soils except for Ni which had BCF of 2.80 and 6.90 for both varieties grown in the control soils. The results from this study has shown the negative effect of gemstone mining activities on the growth of two varieties of Zea mays.

Rapid urbanization and industrialization in communities of Nigeria contribute significantly to environmental pollution. Amongst the diversity of these environmental contaminants are heavy metals, a rarely biodegradable and toxic class of metals. Heavy metals are known to be harmful to plants, aquatic species, and subsequently endanger human health through bioaccumulation or biomagnification. Even at low concentrations, heavy metals may affect key soil microbial processes; inhibit plant metabolism and growth. Toxic metals in groundwater affect water quality and potability, and their presence in aquatic systems also facilitate the production of reactive oxygen species that can damage physiological processes in fishes and other aquatic organisms. This chapter highlights the occurrence and impact of heavy metals in different environmental matrices and organisms sampled across some Southwestern states in Nigeria. Various studies including those of the authors found varying levels of heavy metals, especially in concentrations that can imperil ecosystem functions. While results of studies included in this chapter may suggest heavy metal introduction through anthropogenic-urbanization means, the lack of proper implementation of environmental monitoring laws in Nigeria also clearly exist. As such, the mitigation of heavy metals amongst other pollutants demands better home-grown decentralized technologies.