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Heavy Metal Accumulation in the Fruits of Tomato and Okra Irrigated with Industrial Waste Effluents

Abstract

Effects of industrial waste effluents on the fruits of Tomato (Lycoperscon esculentum and Okra (Abelmoschus esculentus) irrigated with wastes from Global Soaps and Detergents Factory (GSD), Ilorin and Dangote Cement Factory (DCF), Ilorin were investigated so as to assess the safety of their consumption. The used wastes were collected before their discharge into the water bodies. Top soils were collected from unpolluted environment homogenously mixed together and stocked into plastic pots perforated at their bases. The collected wastes and soils were subjected to heavy metal: Pb; Zn; Cu; Cd; Fe and Hg determination with the aid of Atomic Absorption Spectrophotometer. The pH of the wastes and soil were determined electrometrically. The wastes were serially diluted with borehole water to give 100%, 75%, 50%, 25%, 20% ,10% ,5% and 1% concentrations with borehole water used for the control. Seeds of tomato and okra were sown differently into these pots and the prepared waste water was used to irrigate these plants twice a week and the stands per pot were reduced to 2. The fruits produced by these plants were appropriately digested and subjected to Pb, Zn, Fe, Cd, Cu and Hg determination with the aid of Atomic Absorption Spectrophotometer. The experiment was replicated twice. It was found that only the okra and tomato plants irrigated with only borehole water(Control), 1% and 5% GSD and 1% DCF wastewater fruited. The pH of the soil before irrigation was acidic (pH= 4.09), GSD waste, alkaline ( pH= 10.65) and DCF waste, highly alkaline (pH=13.65). The soil had 0.06 mg/g Pb, 0.21mg/g Zn, 4.94mg/g Fe, 0.00mg/g, Cd and Hg and 0.17mg/g Cu. The GSD waste contains 0.58mg/g Pb, 0.82mg/L Zn, 6.65mg/L Fe, 1.42mg/L Cd, 152mg/L Cu and 0.03mg/L Hg. The DCF waste has 0.37mg/L, 0.57mg/L, 5.24mg/L, 0.19mg/L, 1.04mg/L and 0.00mg/L Pb, Zn Fe, Cd, Cu and Hg respectively. Results of the analyses of the okra fruits gave a range of 0.15 – 0.35mg/L Zn, 0.44 – 0.92mg/L Fe, 0.00 – 0.03mg/L Pb, 0.02 -0.04mg/L Cd, 0.11-0.34mg/L Cu and 0.01-0.02mg/L Hg for both crops irrigated with GSD wastes .For crops irrigated with DCF waste water, 0.01 – 0.31mg/L Zn, 0.03 – 0.66mg/L Fe, 0.00 - 0.05mg/L Pb, 0.00 - 0.01 mg/L Cd, 0.02 - 0.52mg/L Cu and no Hg. However, the presence and accumulation of Pb, Hg and Cd in the fruits raised with GSD waste water pose a serious threat to life. It is therefore possible to recommend these wastes for the raising of okra and tomato at very low concentration less than 1% for GSD and less 10% for DCF to avoid accumulation of Pb, Cd and Hg.

P.O. Fatoba , A.O. Adepoju and Grace A.Okewole

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