Oil spills in the Niger Delta region of Nigeria has occurred frequently since oil extraction started in the 1950's. The oil spills originates from facilities and pipelines, leaks from ageing and abandoned infrastructure and from spills during transport and artisanal refining of stolen oil under primitive conditions. It is estimated that spills in Nigeria amount to 100 000 to 200 000 tons per year and have been doing so for almost 60 years. While a number of reports have been written about the Niger Delta and the civil unrest in this area during the last decades, very few scientific reports with actual data regarding the extent of the contamination has been published. This paper describes the contamination of sediments and water in a part of the Niger Delta, which has been particularly hard to assess for decades: Ogoniland. It does not discuss the origin of the oil spills.
During 2010, the United Nations Environment Programme (UNEP) conducted an extensive environmental assessment of Ogoniland. The assessment was conducted at the request of the Nigerian government. During the assessment, drinking water samples were taken in wells and sediment and surface water samples were collected from streams, ponds and wetlands in and around Ogoniland from April to November. The levels found in the more contaminated sites are high enough to cause severe impacts on the ecosystem and human health. Extractable Petroleum Hydrocarbons (EPHs) reached levels of up to 7420 μg/l in surface water and drinking water wells show up to 42 200 μg/l. Benzene levels were measured up to 9000 μg/l, which is more than 900 times the WHO guidelines. EPH concentrations in sediments were up to 17 900 mg/kg. Polycyclic Aromatic Hydrocarbon (PAH) concentrations in sediments reached 8.0 mg/kg in the most contaminated sites. The impacts of this pollution were obvious to be seen, with large slicks of crude oil visible in the water and large areas of mangroves suffocated by oil. However, most sites did not show extremely high levels of EPH and PAH concentrations.
Although the natural conditions for degradation of petroleum hydrocarbons are favorable with high temperatures and relatively high rainfall, the recovery of contaminated areas is prevented due to the chronic character of the contamination.
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