Groundwater Contamination and Environmental Risk Assessment of a Hydrocarbon Contaminated Site in Eastern Niger Delta, Nigeria.

Abstract

This work evaluated existing and potential adverse impacts in a remediated hydrocarbon spill site impacted by an unquantified volume of petroleum hydrocarbon where  depth to groundwater level may be less than one metre during  peak rainy season.  Pre-remediation concentration of  Total Petroleum Hydrocarbon in soils was 30,000mg/kg to 160,000mg/kg while post remediation  values were below the intervention values of 5,000mg/kg, but still higher than the target values of 50mg/kg specified for the Petroleum Industry in Nigeria. Similarly, BTEX levels reduced from 5mg/kg to less than 1mg/kg in soil and from 400µg/l to ˂3µg/l in groundwater. Post-remediation Primary Aromatic Hydrocarbon concentrations  reduced from 700mg/kg to 5mg/kg in soil and from 10µg/l to ˂3µg/l in groundwater. Seasonal fluctuations of the groundwater level imprinted a hydrocarbon smear of about 3-6m within the silty and sandy  soil profile. The presence of the post-remediation  residual contaminants at these concentrations constitutes substantial risk to the environment.

Keywords: Contaminants, Bioscreen, BTEX, Hydrocarbon, Remediation, TPH, Niger Delta