Phytoremediation Plants in Oil Contaminated Soil: A Review of The Niger Delta Region

Petroleum hydrocarbon pollution caused by crude oil exploration,
transportation, and spill incidents remains a serious environmental
problem, especially in the Niger Delta region of Nigeria. This study
evaluated the effectiveness of phytoremediation and integrated
biological remediation strategies for restoring soils contaminated with 2
20% petroleum hydrocarbons. Both natural phytoremediation using
naturally occurring vegetation and technical phytoremediation involving
selected oil-tolerant and hyperaccumulator plants were examined under
greenhouse and field conditions. Alfalfa (Medicago sativa) and ryegrass
(Lolium perenne) were cultivated in contaminated soils for 60–120 days,
while untreated contaminated soils served as controls. Plant performance was assessed through
germination rate, shoot and root growth, biomass production, chlorophyll content, and root-to-shoot
ratio. Microbial activity in the rhizosphere was analyzed using microbial isolation, colony counts, and
PCR-based identification techniques. Total petroleum hydrocarbons (TPH) were quantified using GC
MS analysis, while soil enzyme activities were evaluated spectrophotometrically. Results showed that
vegetated soils consistently recorded lower residual TPH concentrations than unplanted soils,
confirming enhanced rhizosphere-mediated biodegradation. Combined plant–bacteria–fungi
treatments achieved greater hydrocarbon reduction than single remediation methods, demonstrating
strong synergistic interactions between plants and hydrocarbon-degrading microorganisms. Dominant
bacterial genera included Pseudomonas, Bacillus, Acinetobacter, and Rhodococcus, while fungal
genera included Aspergillus, Penicillium, Trichoderma, and Fusarium. Multi-Process
Phytoremediation Systems (MPPS), integrating landfarming, microbial inoculation, phytoremediation,
and plant growth-promoting rhizobacteria (PGPR), showed the highest remediation efficiency.
Indigenous tropical grasses and wetland plants also demonstrated strong adaptability and sustainable
remediation potential, supporting their use as low-cost, environmentally friendly solutions for oil
polluted soils in tropical ecosystems.