Effectiveness of Vetiver (Vetiveria Zizanioides) in Heavy Metal and Total Hydrocarbon Content Removal from Spent Oil Contaminated Soil in Portharcourt and Obio/Akpor Nigeria

A pot experiment was conducted at University of Port Harcourt Teaching and Research farm to examine the effectiveness of vetiver grass to remove heavy metals: (Zn), Nickel (Ni) and Lead (Pb) and Total Hydrocarbon Content (THC) from spent oil contaminated soil. Composite soil samples were collected randomly at a depth of 0-15, 15-30 and 30-45 cm from around Elikohia and Choba automobile workshop respectively in Rivers State, Nigeria. A control soil samples at same depths were taken at 100 meters awa y from uncontaminated areas. Ten (10) kg each of harmonized soil samples of contaminated without vetiver (cont no vetiver), contaminated remediated with vetiver (cont+vet) were placed in a 10 litre perforated plastic buckets. Two slips (seedlings) of vetiver grass were transplanted per bucket. Twelve weeks later, soil, roots and shoots of vetiver plants were analysed for THC, Zn, Ni and Pb. Results of the study on THC, Zn, Ni and Pb showed significant (P<0.05) increased between the contaminated soil over control. Remediation of the soil with vetiver grass significantly (P<0.05) reduced the contamination of the soil from 452.07 and 562.73mg/kg in contaminated without vetiver (cont no vet) to 235.83 and 241.80mg/kg for THC in cont + vet; 1885.47 and 2033.03 to 929.13 and 1013.70mg/kg for Zn in cont no vet and cont + vet; 1023.53 and 1355.90 mg/kg to 631.70 and 642.63mg/kg for Ni and 1761.9 and 1854.47 to 935.60 and 968.13 mg/kg for Pb in cont no vet and cont + vet respectively for Choba and Elikohia respectively. The THC and heavy metals in the soil decreases with increase in depth of soil profile in the two sites studied. The uptake of THC, Zn, Ni and Pb were observed to be significantly (P<0.05) higher in the roots than the shoots portions of the plant in all the depths in the two sites. The order of uptake for heavy metals was Zn>Pb>Ni in both roots and shoots in both Choba and Elikohia. The results therefore showed that vetiver grass was effective in removing significant quantity of THC, Zn, Pb and Ni contents from spent automobile contaminated soils.