Bioaccessibility, environmental and human health risk of potentially toxic elements (PTE) in crude oil contaminated soils

The contamination of soil with crude oil is a major problem worldwide, especially in Nigeria. During transportation and distribution, crude oil spills into the soil and aquatic environment via pipeline rupture, resulting from corrosion, illegal bunkering and pipeline vandalism.1 Crude oil contains several potentially toxic elements (PTE). Due to their non-biodegradable nature, PTE may persist in soil for a long time, bioaccumulate, and sometimes leach into underground water, posing risk to the environment, plants, animals and human health.2 Their accumulation in the soil threatens human health through various exposure routes including direct ingestion, dermal contact and inhalation. However, not all the PTE species found in soil are labile and can equally pose a threat to human health. This means that measuring the pseudototal concentration of PTE in soil may not give an accurate indication of risk.
This study therefore aims to assess the bioaccessibility of PTE (As, Cd, Cr, Pb and V) in crude oil contaminated soil via the dermal, ingestion and inhalation pathways. Soil samples were collected from five communities, K-dere, B-dere, Bodo, Bomu and Lewe, all in Gokana Local Government Area of Rivers State, Nigeria. At each community, two points of worst contamination were selected. Ten grab samples were collected from each point and composited to get a representative sample for that point. The samples were air dried at room temperature, crushed, sieved (<250 μm) and transported to the UK. Physicochemical parameters such as pH, electrical conductivity, cation exchange capacity, organic matter content and particle size distribution will be analysed using standard methods. The pseudo total concentration of PTE will be determined by digesting 1 g of each sample with 20 mL aqua regia using microwave-assisted digestion. Fractionation of the PTE will be carried out using the modified Community Bureau of Reference sequential extraction procedure. Bioaccessibility of PTE through inhalation, ingestion and dermal contacts will be tested on the samples, using simulated body fluids. All the extracts will be analysed using ICP-MS. The results obtained will the used to calculate the environmental and human health risks of PTE in the sample.
Acknowledgement: Petroleum Technology Development Fund (PTDF) Nigeria for providing a PhD scholarship to RNV.


1. Aigberua A.O., Ekubo A.T., Inengite A.K., Izah S.C., Assessment of Some selected heavy metals and their pollution indices in an oil spill contaminated soil in the Niger Delta: Acase of Rumuolukwu community. Biotechnological Research 2017, 3 (1), 11-19.
2. Wuana R. A.; Okieimen F. E., Heavy Metals in Contaminated Soils: A Review of Sources, Chemistry, Risks and Best Available Strategies for Remediation. ISRN Ecology 2011, 2011, 1-20