Heavy Metal Status of Major Vegetable Farmsoils in Ilorin Metropolis, Kwara State, Nigeria

Soils in developing areas have been confirmed by researchers to be contaminated with heavy metals which are a major category of pollutants.  Previous projects had been carried out to ascertain different levels of heavy metals in soils but this paper targets heavy metals and degree of pollution of major vegetable farm soils in Ilorin metropolis, Kwara State, Northern Nigeria. Therefore, this work aimed at determining the;  concentrations of total heavy metals (HMs) and the pollution index of the major vegetable farm soils. Total cadmium (Cd), copper (Cu) and lead (Pb) in soils were determined by acid digestion and Atomic Absorption Spectrophotometry method. Data generated were subjected to Analysis of Variance (ANOVA) and mean separated using Duncan Multiple Range Test (DMRT) at 5% significance. HMs in soils were: Cd (0.00-4.67), Cu  (1.71-30.08) and Pb (1.29-82.00) mg/kg with pH range of 6.62-9.33 and pollution index range of Cd (0.00-2.90), Cu (0.86- 11.72) and Pb (0.70-14.30). Some soils showed elevated concentration of Cd and Pb higher than the recommended permissible – limit (Cd=1.00 mg/kg, Pb=70.00mg/kg) with pollution index of HMs ranged from low pollution to very strong pollution (0.00±0.00- 14.30±1.77). The study therefore, suggested that there could be a risk of Cd and Pb associated diseases on the consumption of vegetables planted on some of these soils. Keywords: Heavy metal content,  pollution index, vegetable farmsoils, Ilorin metropolis

Heavy Metal Uptake Responses in Plants Grown on Crude Oil-Polluted Soils as Prospects for Phytoremediation

The demand and utilization of petroleum products have re-energized its exploration and exploitation globally and this upsurge in world production, refining and distribution of petroleum products have brought with it various problems of environmental pollution, which have effects on the ecosystems. Twenty (24) polyethylene pots each containing 7 kg of sandy loam soil mixed with 50 ml of crude oil, were arranged in the Botanical garden of the University of Ilorin, Nigeria, to assess their ability to phytoextract heavy metals in Crude oil-polluted soil. Seeds of Amaranthus hybridus L., Tithonia diversifolia, Abelmoschus esculentus L. and Zea mays were sown in polyethylene containers containing 7 kg of contaminated or Control soil. The containers were arranged in a complete randomized design. Plants were left to grow for two months with regular watering. Plants were harvested, separated into roots and shoots and oven-dried to constant weight. The experimental plants have been able to reduce the concentration of Cu in both soils by about 45% to 85%, Cr in the soil by 92.08% to 96.72%, as the residual concentration varied between 66.00 mg/kg and 99.00 mg/kg, Cd in the soil was reduced to 4.00 mg/kg and 17 mg/kg which represented 96.8% and 86.4% reduction. Tithonia had the highest Pb reduction in crude oilpolluted soil. Ni concentration was reduced by 85.84% by Tithonia planted in crude oil-polluted soil, 94.59% by Amaranthus hybridus planted in Control soil. These show that all the test plants were good phytoextractors of the metals. Keywords: Heavy metals, phytoremediation, Amaranthus hybridus L., Tithonia diversifolia, Abelmoschus esculentus L, Zea may