Leaf Litters and Hydrogen Peroxide on Some Physicochemical Properties of Crude Oil Polluted Soil

Abstract

A study was carried out in Rivers State University Research Farm, Port Harcourt, to investigate the potentials of leaf litters and hydrogen peroxide as bio remediating agents on crude oil-polluted soils. The experiment was arranged in a randomized complete block design with various levels of pollution. The experiment had 14 treatments and 5 replicates: T1:100ml Crude Oil (CO) + 100ml Hydrogen peroxide (H₂O₂), T2:100ml CO + 100g Leaf litters (LL), T3:200ml CO + 200ml H₂O₂, T4:200ml CO + 200g, T5:300ml CO + 300ml H₂O₂, T6:300ml CO + 300g LL, T7:400ml CO +400ml H₂O₂, T8:400ml CO + 400g LL, T9:500ml CO + 500ml H₂O₂, T10:500ml CO + 500g LL, T11:no pollution + 500ml H₂O₂, T12:no pollution + 500g LL, T13:500ml CO + no remediation and T14: (no pollution + no remediation) control. A total of 420 experimental bags filled with 10kg soil each and polluted with crude oil at different levels, H₂O₂ and leaf litters were applied at a 1-month interval after pollution for 4 months. Soil samples were analyzed for the physicochemical properties. The pH of the soils varied in all the treatments in all the months. The average pH before pollution was 6.3 but after pollution T7 had a pH of 7.6; pH of T9 was 7.3; pH of T10 was 7.5 and pH of T13 was 7.1 all having slightly alkaline pH which later reduced upon leaf litters and hydrogen peroxide application to acidic and finally to a neutral pH 4 months after remediation in the treatments. The results obtained from this study indicated that the introduction of leaf litters greatly increased the soil electrical conductivity in treatments it was applied especially in T12 (no pollution + 500g LL) in all the months. T12 was 520.68-533.42 µS/cm followed by T11 (500.4-501.8 µS/cm). The nitrate content of the soil greatly increased upon the introduction of both leaf litters and hydrogen peroxide in soils without pollution (T11: 0.606-0.633 mg /kg and T12: 0.555-0.588 mg /kg). T11 (0.606-0.633 mg /kg) had the highest nitrate content upon the application of amendments followed by T12 (0.555, 0.565-0.588 mg /kg). T9 (0.512-0.602 mg /kg) and T10 (0.51-0.62 mg /kg). Conclusively, crude oil pollution alters the soil pH, conductivity, and nitrate levels. The addition of leaf litters and H₂O₂ to crude oil polluted soil neutralizes the pH and increases the conductivity and nitrate levels in the soil.