This study was aimed at examining the influence of pH on heavy metals availability in polluted and non-polluted soils. The findings showed that metal availability depends on soil solution which is pH dependent. The values of pH in Nkeleoken remediated soil (RSENa, RSENb, RSENc) in dry season were 6.01, 5.87, 5.78 and 6.64, 5.77, 5.68 in wet season with mean values of 5.89±0.05 and 6.03±0.53 while the pH of the contaminated soil ranged between 4.31 – 4.41. The mean values of heavy metals in Nkeleoken remediated soil are; Se (318±9.88; 326±11.6 mg/kg), Cd (3.65; 3.82±1.09 mg/kg), V (1095±71.05; 1189±149 mg/kg), Ba (8.98±1.53; 9.40±1.89 mg/kg), Cu (8.19±0.08; 8.84±0.14 mg/kg), Ni (0.02±0.01 mg/kg), As (5.52±2.35; 10.3±2.38mg/kg), Pb (1.73±0.32; 2.70±1.38 mg/kg) and Cr (23.1±4.05; 23.1±4.05 mg/kg). The results revealed that V and Se had the highest concentration level followed by As while the least concentrations were observed in Cd, Ba, Pb and Cr in both dry and wet season. The concentrations of heavy metals in the non-remediated soil ranged from 866 – 868 mg/kg, 1356 – 6332 mg/kg, 211 – 218 mg/kg, 73.6 – 79.0, and 866 – 868 mg/kg for Se, V, Ba Pb and as in dry and wet seasons. However, Cr concentrations ranged from 6.03 – 7.02 mg/kg. The concentrations of V and Se in the non-remediated soils (NRSENx - NRSENz) during dry and wet seasons were higher than their corresponding in the remediated soils likewise the recommended values set by DPR (2012).

The discharge of crude oil products to the environment (soil, water and air) has great negative impacts on the organisms living therein. Most of these effects are from heavy metals, total petroleum hydrocarbons (TPH), polyaromatic hydrocarbons (PAH) among others. This research adopts an extensive review of literatures such as conference papers, journal articles, internet sources, books to find out the amount of total metal concentrations and the total petroleum hydrocarbons (TPH) that are likely to be found on crude oil contaminated soil even after remediation or cleanup activities have been carried out. The driving force behind this research is the fact that the people living in most petroleum-contaminated areas such as the Niger Delta Region of Nigeria still experience some negative effects (such as health and agricultural effects) associated with the crude oil pollutants even after remediation. The study concludes that even though heavy metals were still present in the remediated soil, they are not bioavailable for plants uptake; hence their presence is negligible harmless. On the other hand, the total petroleum hydrocarbons (TPH) that remains after cleanup is still well above the background level. As such, it would impose negative impacts on the inhabitants of such areas. The study further recommends that more effective methods of remediation should be carried out, or a combination of more than one method should be adopted in other to obtain absolute cleanup of the polluted area..