Changes in Heavy Metal Contents of a Waste Engine Oil Polluted Soil Exposed to Soil pH Adjustments

The present study investigated the role of soil pH adjustments in heavy metals concentrations in waste engine oil (WEO) - polluted soils. Sun-dried top soil (0-10cm) was measured into buckets. WEO was added to soil and mixed thoroughly to obtain similar concentrations of 2.5% w/w oil in soil. The polluted soil was thereafter amended with NPK (15:15:15) fertilizer to enhance microbial activity. The buckets were transferred into a well ventilated screen house with inherent constant room temperature (27ºC). The entire setup was divided into 5 sets. Each set was wetted daily with 200ml of different pH solutions (pH 3, 5, 7, 9, and 11) for a period of 3 months. There were significant reductions in heavy metal concentrations particularly at pH of 5. There were significant reductions in total hydrocarbons contents (THC) of polluted soils at 2 months after pollution from 1882.32 mg/kg at pH 3 to 325 mg/kg at pH 5, compared to THC of soil at 1 week after pollution at pH 7 (3425.63mg/kg).