Phytoremediation Potential of Native Tree Species for Heavy Metal Contaminated Soils in Oil-Producing Communities of Imo State

Soil contamination by heavy metals including lead, cadmium, nickel, and chromium in oil-producing areas of Imo State represents a serious environmental and public health problem for which low-cost, ecologically compatible remediation approaches are urgently needed. Phytoremediation using native tree species offers a potentially sustainable, socially acceptable alternative to costly engineered remediation techniques. This study evaluates the phytoremediation potential of six native tree species (Daniellia oliveri, Alchornea cordifolia, Vitex doniana, Ficus exasperata, Terminalia catappa, and Treculia africana) for soils contaminated with a defined heavy metal mixture representative of oil spill affected soils. A greenhouse pot experiment with standardised contaminated soil treatments was used to assess metal uptake, translocation factors, and bioconcentration factors under controlled conditions. Above-ground and below-ground tissue samples were analysed by atomic absorption spectrophotometry after twelve weeks of growth. Plant growth parameters including height, biomass, and chlorophyll content were recorded as indicators of phytotoxicity. Alchornea cordifolia and Ficus exasperata demonstrated the highest bioconcentration factors for lead and nickel respectively, both exceeding the threshold criterion of 1.0 for phytoextraction classification. Translocation factors confirmed effective shoot accumulation in both species. Daniellia oliveri showed exceptional tolerance with minimal growth suppression even at elevated contamination levels, indicating phytostabilisation potential. The study recommends field-scale trials of Alchornea cordifolia and Ficus exasperata at priority spill sites in Imo State. Keywords: phytoremediation, heavy metals, oil contamination, native trees, Imo State