Groundwater Contamination Assessment in a Petroleum Impacted Sites in Parts of the Niger Delta, Nigeria

Abstract

The assessment of the contaminant status of groundwater in an oil impacted site in Eneka community in Obio-Akpor local Government Area of Rivers State, located in the Niger Delta area has been carried out in this work through groundwater sampling from 20 water wells made by percussion drilling to depths of 15m and the chemical quantification of petroleum-related contaminant species (Mineral oil/EPH, PAH`s, VOC`s) by gas chromatography-mass spectrometry (GC-MS) testing. Free phase oil was found in the subsurface on top of the water table at depths range of 3.84 – 6.76m (av. = 5.59m) in sixteen wells. Four wells in the perimeter area of the site (BH- 8, - 13, - 16 and -18) were free of free phase oil. Groundwater level for the twenty (20) boreholes ranged from 4.56 – 8.81m (av. = 6.26m). Results of chemical quantitation of contaminants from four randomly selected boreholes, showed ranges of values of EPH (5710 – 325,000), total PAH (68.3 – 676), naphthalene (62.2 -58), fluoranthrene (0.0588 – 1.95), anthracene (<0.03 - <0.15), phenanthrene (0.918 – 41.1) and Benzo(a)anthracene (<0.034 – 0.922). For the VOC`s, ranges of 1180 – 141,000, 8.99 – 13,600, 80.6 – 1310, were recorded for benzene, toluene and ethylbenzene respectively, while a range of 378 – 7570 were recorded for the xylenes (p-xylene, m-xylene and o-xylene). Contaminant concentration compared against the EGASPIN intervention values revealed various exceedences. Four exceedences was recorded each for EPH, benzene and the xylenes, while three and two exceedences each was recorded for ethylbenzene and toluene. Total PAH recorded three exceedences. One exceedence each was recorded for naphthalene, fluoranthrene and benzo(a)anthracene, while phenanthrene had two exceedences.