The Effect of Spent Engine Oil Discharge on Soil Properties in an Automobile Mechanic Village in Nekede, Imo State, Nigeria

Abstract

The study investigated the concentration of heavy metal in soil around Nekede automobile mechanic village in Southeastern Nigeria. Sample plots were established in a randomized method along a transect at 100m interval for five (5) different locations within the study area, these sample point were constantly receiving spent engine oil (SEO) and were labeled treatment SA, SB, SC, SD, SE. A composite soil sample was drawn from depths of 0-15cm and 15-30cm for each of the five treatments. These were air dried, passed through a 2mm sieve and properly labeled for laboratory analysis. Soil samples were then analysed for heavy metal (Pb) using Atomic Absorption Spectrophotometer (AAS). Two (2) soil samples were collected at each sample point and two (2) soil samples CF and CG were also collected 2 km away from the study area in an undisturbed forest as control. Soil pH, cation exchange capacity (CEC) and particle size distribution were also determined. Results showed that the concentrations of Pb from soil samples were random across sample point. The concentration of Pb in the contaminated soil at a depth of 0-15cm (topsoil) varies, the highest value was observed at SD (482.2mg/kg) and the lowest value at SE (146.8mg/kg). At the depth of 15-30cm (subsoil) concentration of Pb is highest at SB (397.6mg/kg) and lowest at SC (140.1mg/kg). The mean concentration of Pb in the contaminated soil sample has its highest concentration at SB (382.9mg/kg) and lowest at SC (157.8mg/kg). The level of Pb in the control site was lower (CF, 46.5mg/kg and CG, 11.8mg/kg) when compared to the various concentrations of the contaminated soil. pH range was between 5.43 and 6.79. CEC varied across the sample area and showed no variation within the control site. The highest value was observed at CF and CG (3.65cmol/kg) respectively while the lowest value was observed at SA (2.15cmol/kg). The % sand distribution varied across the sample point and showed a higher distribution in the study area than % clay and % silt, the soil texture (sandy loam) was not significantly affected by the SEO. The study concluded that improper disposal of SEO in the study area elevated the soil Pb content thereby causing Lead pollution.