Assessment of Heavy Metals on Selected Crops on Polluted Soil Amended with Organic and Inorganic Materials and Associated Health Risk

An experiment was conducted in Rivers State University Research farm, Port Harcourt, to investigate the potentials of Leaf-litter and Hydrogen peroxide as bioremediators for Crude oil polluted soils. The experiment was arranged in a Block Design with various levels of pollution. The experiment had 14 treatments and 5 replicates: T1: 100ml C/O + 100ml H2O2, T2: 100ml C/O + 100g l/l, T3: 200ml C/O + 200ml H2O2, T4: 200ml C/O + 200g l/l, T5: 300ml C/O + 300ml H2O2, T6: 300ml C/O + 300g l/l, T7: 400ml C/O +400ml H2O2, T8: 400ml C/O + 400g l/l, T9: 500ml C/O + 500ml H2O2, T10: 500ml C/O + 500g l/l, T11: no pollution + 500ml H2O2, T12: no pollution + 500g l/l, T13: 500ml C/O + no amendment and T14: control. Garden-egg, Beans and cucumber seeds were used as test crops. Viability test was carried out.420 experimental bags of 10kg capacity were filled with 10kg soil and polluted with C/O at different levels, 140 bags for each plant. Organic and Inorganic manure were applied at 1 month interval after pollution for 4 months, and planting was done afterwards. Soil samples were analyzed for heavy metals. Result of soil analysis showed high levels of heavy metals which includes copper, lead and zinc after pollution and was deficient of essential macronutrients like phosphorus, potassium, nitrate etc (Lead: T1-T10 and T13=70-97, and T11, T12 and T14=22.0-28.0; Copper: T1-T10 and T13=17.0-22.0, and T11, T12 and T14=11.0-12.0; Zinc: T1-T10 and T13=28.1-31.0, and T11, T12 and T14=3.4-9.0; In the polluted soil which reduced to acceptable limits on the soils with the three crops after harvest (Lead: Org: T2-T10=0.11-0.19, Lead Inorg: T1-T9=0.16-0.32, T13=0.12-0.53, T11, T12 and T14=0.02-0.2 Copper: Org T2-T10=7.4-11.6 and Inorg: T1-T9=8.7-11.4, T13=10.7-11.5, T11, T12 and T14=2.1-9.5: Zinc: Org T2-T10=1.8-2.2 and Inorg: T1-T9=1.9-2.2, T13=1.6-2.3, T11, T12 and T14=0.4-1.4. Application of Leaf Litter Manure and H2O2 greatly degraded the PAHs in the soil thereby causing a reduction in soil heavy metals. Beans performed better in Leaf Litter amended soils than H2O2 amended soils, while cucumber and garden egg had poor yield in both leaf litter and hydrogen peroxide amended soils. Therefore, the use of leaf litter manure for the remediation of petroleum contaminated soil should be encouraged as this proved to amend the soils.