Impacts Of Heavy Metals In Dumpsites On Soil And Vegetation In Selected Locations In Kwara State

Indiscriminate dumping of refuse is one of the major sources of pollution to the environment. Clean up of these wastes has led to appearance of dumpsites which has become preferable farmlands. This study was carried out to investigate the impacts of heavy metals (HMs) in dumpsites on soil and vegetation of selected locations and the possibility of reducing the availability of heavy metals (HMs) to the plants. The objectives of the study were to: (i) assess the heavy metal concentrations in the soil and plants from the dumpsites; (ii) develop methods rnfor production of biochar from the waste; (iii) assess the effects of biochar on the yields of Solanum lycopersicon, Amaranthus esculentus, Corchorus olitorious,Abelmoschus esculentum and Tithonia diversifolia; and (iv) assess the mobility potential of the biochar on the HMs in selected plants. rnrnPlants and soil samples were collected at 10 km intervals in Oko-Olowo, Offa, Omu-Aran (Urban), and Odo-Ore, Ipee and Aran-Orin (rural). The samples were digested using Aqua regia rnmethod after which Cd, Pb, Cr, Zn, Fe and Cu concentrations were determined with Atomic Absorption Spectrophotometer (AAS). Composite dumpsite soil was used to raise the plants and its HMscontent determined by AAS. Biochar was prepared by slow pyrolysis of maize cobs (MB). Scanning Electron Microscopy, Energy Dispersive X-ray and Fourier Transform Infraredwere used to identify the properties of the MB.Data were analysed with Analysis of Variance and Duncan Multiple Range Test at p <05.rnrnThe findings of the study were that:rni. Pb(0.00 – 75.00), Cd(0.00 – 4.00), Zn(4.50 – 1290), Ni(0.00 – 19.5), Cu (2.5 – 225) and Fe (1,390 – 20,850) mg/kg were present in the soils; rnii. Pb (0.00 – 7.00), Cd(0.00 – 0.50), Zn( 16.00 – 310.00), Ni(0.00 – 5.50), Cu(1.00 –9.50) and Fe(195.00 – 4,950.00) mg/kg were found in the plants;rniii.MB had well-defined pore structure and contained C, O, Si, K and Mg; rnv. MB increased the yieldsof S. lycopersicon(50%), C. olitorious (6.3%),rnAbelmoschus esculentum (40.1%) and T. diversifolia (7.5%) but reduced the yield of Amaranthus esculentus (50%);rnvi. there was significant reduction (p≤0.05) in the HMs content of the selected plants withMB. Abelmoschus esculentum, C. olitorious, Amaranthus esculentus, T. diversifolia and S. lycoperscon on dumpsite soil contained 2.78. 2.23, 2.29, 5.20, 3.50 mg/kg of Pb while those with biochar had 2.36, 0.90, 2.35, 3.67, 2.40 and 2.30 mg/kg, respectively; andrnvii.Abelmoschus esculentum accumulated Ni, Cu and Zn but excluded Cd, Pb and Fe, Amaranthus esculentus accumulated Cd and Zn but excluded Pb, Ni, Cu and Fe,T.diversifolia,accumulated Cd, Ni and Zn, C. olitorious accumulated Cd and Pb whileS. lycopersiconexcluded all the investigated HMs. rnrnThe study concluded that indiscriminate dumping of waste contributed to the HMs load of dumpsite soil and vegetation.It is recommended that remediation process be put in place to reduce the HMs load in order to avert the health hazards that may result in humans that consume the vegetables.

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