Lubricant Automobile Oil: Effect on Chemical and Heavy Metal Status of Soil in Rivers State, South-South, Nigeria

Abstract

A study was conducted at the department of crop and soil science teaching farm, University of Port Harcourt to examine the effect of lubricant automobile oil on some soil chemical properties and heavy metals status of the soil. Composite soil samples were collected randomly at a depth of 0-20cm from the back of the department. The soil was placed in a 10kg bucket, spent lubricant oil collected from Ozuoba automobile mechanic workshop was used to contaminate the soils at 0 (control), 2, 4, and 6% w/v. Okra (Abelmoschus esculentus) a dominant vegetable crop in Nigeria was used as test crop. Three okra seeds were planted two weeks after contamination and later thinned to two. The experiment was replicated thrice and the design is completely randomized. Result of the study revealed that the soil pH, % total nitrogen, % total organic carbon and total hydrocarbon content of the spent lubricant contaminated soil significantly (P<0.05) increased over control samples. The contents of these parameters increased as the level of contamination increased. On the other hand, the concentrations of available phosphorus, soluble potassium and exchangeable cations (calcium and magnesium) were significantly (P<0.05) lower in contaminated soil than in control. Increase in percentage of spent oil lubricant decreases the concentrations of these elements. The concentration of the three heavy metals (Zn, Pb and) investigated were significantly higher in lubricant oil contaminated soil than control samples.  The higher the increase in % lubricant oil, the higher the concentration of the three heavy metals studied. Generally, the study showed that spent lubricant oil had negative (adverse) effects on some soil chemical properties which may indirectly affect the plant that uptake these nutrients from the soil.