Effect of Composting Mangrove Forest Litters on Remediation of crude-oil contaminated soil and Epigeal Emergence of Threatened Forest Tree Species

Abstract

The study evaluated the potency of three mangrove forest litter recombinant treatments and composting ages on the degradation of petroleum hydrocarbon. Contaminated soil samples from Shell Petroleum Development Company/Chevron Nigeria Limited Uto-Orogun right of way were infused with formulated composting mangrove forest litters balls at 5, 10 and 15-N (number) balls respectively in 10 replicates per treatments in a-4×3×10 completely randomized experimental design. These were allowed to degrade the crude oil molecules for a total period of 8 months and soil samples were analyzed for TPH, pH, and bulk density. Data were then subjected to analysis of variance (ANOVA) and significant means separated by the Duncan Multiple range test at 5%. The most decontaminated soil treatment was then used in the emergence trials of 400 seeds of IUCN-threatened Dacryodes edulis, Irvingia gabonensis, Garcinia kola and Gambeya albidum forest tree species at 100 seeds and 5 replicates per tree species under screen house conditions for 30days. Results showed TPH reduction that corresponded with increase in composting ages and number of decontamination balls with highest TPH reduction of 33% (1.33±0.15g/dmᶾ) recorded at 6 months by the 15-N decontamination balls with significant increases in pH (7.4) and decline in soil bulk density (1.50g/cmᶾ). Percentage epigeal emergence was Dacryodes edulis (43%) > Garcinia kola > Gambeya albidum > Irvingia gabonenisis (17%) at 4 weeks after planting. The study revealed composting mangrove forest litters as potential products for the remediation of crude oil-contaminated soil under sustained composting spectrum and in regeneration of the IUCN-threatened forest tree species in Delta State of Nigeria.