Changes in the Intrinsic Qualities of a Naturally Attenuated Waste Engine Oil Polluted Soil after Exposure to Different Periods of Heat Shock

This study was conducted to investigate the effect of heat shock in the remediation of poly aromatic hydrocarbons (PAHs) and heavy metals of a waste engine oil-polluted soil. This was also subjected to phytoassessment using Vigna unguiculata cv Kano white. Top soil (10kg) was collected and thoroughly mixed with waste engine oil (WEO) on weight basis, to obtain 5% w/w oil-in-soil. The buckets were divided into six sets, each receiving heat treatment at different times; twice per week (2PW), once a week (1PW), once in a fortnight (1PF) and once in a month (1PM). There were 2 controls which did not receive any heat treatment; the unpolluted soil (CTRL) and the polluted soil (NON). Heat was applied by carefully burying a stainless steel container, which received boiling water (100℃) at the designated intervals. The set up was allowed to remain in a well ventilated screen house with inherent room temperature for 3 months. Results showed significant reductions in heavy metal contents after the heat treatment. Heavy metal remediations were better in 1PM and 1PF. Total PAH was the lowest in 1PM (154.51mg/kg), compared to 504.48mg/kg in NON. Comparatively, the most frequent the heat shock received by soil, the lower the rate of remediation. Results of phytoassessment using cowpea also showed improved growth and yield parameters in the less frequently heated oil-polluted buckets, compared to the unheated ones (NON).