Pipeline-Related Residential Benzene Exposure and Groundwater Natural Attenuation Capacity in the Eastern Niger Delta, Nigeria

Abstract

This study was conducted to investigate the presence of benzene in the ground and drinking water in the eastern Niger Delta, where multiple oil and gas production facilities are present. Samples from drinking water wells were collected for measurements of benzene, toluene, ethylbenzene, and xylenes (BTEX). Additionally, the dissolved organic carbon (DOC) concentration was determined for the first time to establish the groundwater’s total hydrocarbon and non-hydrocarbon load. The groundwater BTEX and benzene levels were up to 3904 µg/L and 3500 µg/L, respectively. DOC concentrations were up to 49 mg/L. The highest benzene concentrations were detected in wells near an underground petroleum pipeline. However, the concentrations decreased with distance from the pipeline to levels less than 0.1 µg/L. Despite benzene contamination, the aquifer has shown promising aerobic attenuation potential, having up to a 7.5 (95%) mg/L DO level and 2.11 mg/L BTEX biodegradation capacity for DO. However, the high groundwater temperature of up to 32.5 °C may weaken attenuation. The benzene and BTEX point attenuation rates ranged from 0.128 to 0.693 day−1 and 0.086 to 0.556 day−1, respectively. Hence, by natural attenuation alone, up to 66.5 and 85 years would be required to reach Nigeria’s groundwater benzene and BTEX remediation goals, respectively.