Abstract

Phytoremediation is a non destructive and cost effective in situ technology that can be used for the cleanup of contaminated soils. The potential for this technology in the tropics is high due to the prevailing climatic conditions which favour plant growth and stimulates microbial activity. The present study investigated the use of use of 4 common weeds in Nigeria - (Phyllanthus amarus Schum and Thonn.,Hyptis spicigera Lam., Sida rhombifolia L. and Mariscus alternifolius Vahl.) for their reaction to spent lubricating oil contamination and subsequent reduction of the contaminant by the plants. Shoot length, leaf area and root length and chlorophyll contents were determined for these plants grown in spent lubricating oil contaminated soils. The residual hydrocarbons were extracted from soil and percentage degradation was gravimetrically determined for the total hydrocarbons and saturated hydrocarbons present in the spent lubricating oil. The contamination caused a reduction in the shoot length, leaf area, root length and total chlorophyll content of the test plants used. A statistically significant influence of spent lubricating oil on the test plants could not however be established. The degradation of total petroleum content was low as the highest degradation recorded was 35.30% for the plant P. amarus, however appreciable degradation of the saturated hydrocarbons as the plant S. rhombifolia and M. alternifolia removed over 60% of the saturated hydrocarbons present. H. spicigera recorded the least degradation for the saturated hydrocarbons (39.04%). The growth of the plants- S. rhombifoliaand M. alternifolius which caused a reduction of over 60% of the saturated hydrocarbons makes these 2 plants choice plants for the remediation of spent lubricating oil from contaminated soils. The 2 plants are unwanted plants indigenous to Nigeria and can be found growing abundantly in the wild.

Key words: Phytoremediation, phyto-assessment, contamination, spent lubricating oil.