EVALUATION OF HEAVY METALS PROFILE FROM SOILS IN MECHANIC WORKSHOPS WITHIN OKITIPUPA, ONDO STATE, NIGERIA

Abstract

Auto mechanic workshops in Okitipupa Ondo State, Nigeria generate waste containing hazardous contaminants such as heavy metals which are disposed of indiscriminately. Soils Samples were collected from ten selected automobile workshops in the study area at the depths of 0-15cm, 30-45cm, 45-60cm, 60-75cm and 75-100cm. A total of sixty (60) soil samples were collected in ten different locations the in ancient town of Okitipupa. Six control samples were also collected in a farm land about 3km away from auto mechanic activities. The soils were analysed for their heavy metals levels and physicochemical characteristics. Ten heavy metals (Cd, Zn, Cu, Cr, Pb, Fe, Mn, Co, Ni and Mg) were analysed using AAS techniques. The heavy metal concentration for the ten metals determined in soil was in the order; Fe >Mg > Zn >Mn> Cu >Pb> Ni > Cr > Cd > Co. Heavy metal concentrations (mg/Kg) ranged from Co (0.03±0.00) to Fe (88.64±0.00). The auto work shop site C which is about ten years older than others and the workshops with highest traffic volume at sites G and J recorded the highest concentrations of heavy metals in all the sites. The physicochemical parameters such as soil composition based on particle size in percentage, ranged 7.65-10.71 for clay, 1.93-6.99 for silt to 85.36-89.98 for sand. pH values ranged from 4.57-5.93 and electrical conductivity (EC) (ʯscm˗1) ranged 31.67- 143.67. The percentage soil composition was in this order; Sand > Clay >Silt. Assessment of pH showed acidity increased down the depth of the profile and EC followed the same trend. Comparing the results of the study area with the control shows that the study area is moderately contaminated since the values obtained were below the department of petroleum resources (DPR) permissible limit for soil. It is therefore recommended that a need for consistence monitoring of the auto mechanic workshop environments and its ground water is imperative as it is done in some cosmopolitan area in this country.