Phytoremediation of Crude Oil Polluted Agricultural Soil Using Schwenkia americana L. and Spermacoce ocymoides Burm. f.

Aims: To remove hydrocarbons from crude oil polluted agricultural soil using two selected plant species.

Study Design: Mature seeds of Schwenkia americana L. and Spermacoce ocymoides Burm. f. were propagated onto a sterile unpolluted agricultural soil. Seedlings were transplanted into an 8 kg potted homogenised polluted soil for remediation.

Place and Duration of Study: Polluted agricultural soil collected from Ogoniland, Rivers State, Nigeria, Ecological Centre of the University of Port Harcourt Nigeria, between May 2017 and February 2018.

Methodology: Standard methods were employed for laboratory analyses. Reagents used were of analytical grades with high purity.

Results: Twelves weeks after planting (WAP), total petroleum hydrocarbons (TPH) decreased from 17962.11±1000.00 mg/kg to 117.64±30.27 and 117.45±14.76 mg/kg in S. americana and for S. ocymoides remediated groups respectively, while polycyclic aromatic hydrocarbons (PAH) decreased from 440.97±1.00 mg/kg to 120.99±50.05, and 181.97±158.69 mg/kg for S. americana and for S. ocymoides remediated groups respectively. While oil content decreased to 1.02±0.09 and 1.15±0.21 ppm for S. americana and S. ocymoides remediated groups respectively from an initial 3.19±0.10 ppm recorded at the onset of remediation, organic carbon decreased from 2.78±0.01% to 2.16±0.06 and 2.07±0.18% for S. americana and S. ocymoides remediated groups respectively. With regards to TPH, the percentage recovery moved towards normal values (510.27 and 509.02%), however, with regards PAH, the values nosedived indicating a failure in restoration. By 4, 8 and 12 WAP, the treatment restored the values towards normal values (1.08, 7.30, 10.58, 10.81 and 14.05%), however, the treatment using S. ocymoides, by 12 WAP, plunged, indicating failure to restore the polluted soil, especially with regards to the oil content, while by 8 and 12 WAP, the treatments restored the polluted soil towards normal values (3.33, 11.11 and 13.33), with regards to the organic carbon.

Conclusion: The quality of the crude oil polluted agricultural soil was enhanced through phytoremediation with these plant species. This contention is supported by the diminution of hydrocarbons, organic carbon and the oil content of the remediated groups after the 12 weeks remediation.