Research Article

Risk evaluation and modeling of soils contaminated with Polycyclic Aromatic Hydrocarbons (PAHs) in parts of Bonny Island, Niger Delta, Nigeria

Nwankwoala HO*, Amadi AN, Omofuophu E and Ibrahim HA

Published: 05/27/2020 | Volume 4 - Issue 1 | Pages: 015-026

Abstract

Environmental impact of a recent oil spill incident in Bonny terminal using soil media was studied using a risk-based modeling approach. The establishment of the presence of contaminants of concern (CoC), evaluation/assessment, modeling spilled volume and ascertaining potential health risk associated with the spill incident was carried out. The Contaminant of Concern (CoC) included Total Petroleum Hydrocarbons (TPH) and Polycyclic Aromatic Hydrocarbons (PAHs). Soils and groundwater were sampled in the vicinity of the spill incident and further away into the surrounding communities. Soils were sampled into the depths (0.1 m, 0.5 m,1.0 m, 1.5 m), and the results of sieve analysis revealed that the area is predominantly silty sand in composition. This study also revealed that TPH concentration at all locations and depths exceeded DPR target value of 50 mg/kg. The TPH model revealed that a total volume of 222,500m3 of the spill area exceeded DPR intervention value of 5000 mg/kg. The results of PAH showed that only BS-1, BS-6, BS-8, BS-9 and BS-10 exceeded DPR target value of 1.0 mg/kg at some depths. All other sample depths and locations were within the target limit. The 3-D grid generated for PAH showed that 563,000m3 of the study area exceeded the DPR target value. The 3-D block models generated for TPH and PAH, along with the cross-sections and extracted time slices all showed that the concentration of the Contaminant of Concern (CoC) generally decreased with depth, and the centre of the spill located at the south-eastern part of the survey area. Based on these models, three spill zones were identified; Zone 1-highly contaminated areas (BS-8, BS-9, BS-10); Zone 2 - moderately contaminated areas (BS-1, BS-2, BS-6, BS-7); and low contaminated areas (BS-3, BS-4, BS-5). The entire soil in the area were contaminated with TPH and 47% of the area contaminated with PAH. This study has shown the effectiveness of the use of a model-based approach in quantifying hydrocarbon contamination volumes in the area. There is therefore the need for continuous monitoring of hydrocarbon spills in the area.

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References

  1. Aiyesanmi AF. Assessment of heavy metal contamination of Robertkiri oil field’s soil. Nigerian J Soil Sci. 2005; 15: 42-46.
  2. Olujimi JAB, Emmanuel AA, Sogbon O. Environmental implications of oil exploration and exploitation in the coastal region of Ondo State, Nigeria: A regional planning appraisal. J Geo Reg Plann. 2011; 4: 110-121.
  3. Roane TM, Kellogg ST. Characterization of bacterial communities in heavy metal contaminated soil. Canadian Microbiol. 1996; 42: 593-603.
  4. Ikelegbe A. The Economic of Conflict in the Oil Rich Niger Delta Region of Nigeria. J Third World Studies. 2005; 43: 24-50.
  5. Amadi AN, Nwankwoala HO, Olasehinde PI, Okoye NO, Okunlola IA, et al. Investigation of Aquifer Quality in Bonny Island, Eastern Niger Delta, Nigeria using Geophysical and Geochemical Techniques. J Emerg Tren Engineering Appli Scie. 2012; 3: 180-184.
  6. Ferguson C, Kasamas H. Risk assessment for contaminated sites in Europe. Policy Framework. LQM Press, Nottingham. 1999; 2: 1-6.
  7. USEPA. United States Environmental Protection Agency. Risk assessment guidance for superfund. Human health evaluation manual. 1989; 540: 1-89.
  8. ATSDR. Toxicological profile for polycyclic aromatic hydrocarbons (PAH). Atlanta, GA, U.S Department of Health and Human Services, Public health service, agency for toxic substances and disease registry, United States of America. 1995.
  9. Rizzardini CB, Goi D. Sustainability of domestic sewage sludge disposal. Sustainability. 2014; 6: 2424–2434.
  10. Anyanwu JO. Maritime Tanker Accident on Coastal Areas in Nigeria. Global J Res Engineering. 2014; 14: 7-11.
  11. Nwankwoala HO, Mzaga TM. Sub-Soil Properties of Hydrocarbon Contaminated Sites in Parts of The Eastern Niger Delta, Nigeria. Open Access J Environment Soil Sci. 2019; 2.
  12. Nwankwoala HO, Omofuophu E. Investigation of Hydrocarbon Contaminant Levels and Groundwater Quality Assessment in Parts of Bonny Island, Rivers State, Nigeria. Central Asian J Environ Sci Technol Innov. 2020; 1: 61 – 70.
  13. Stuart PC, Richard SJ. Gas chromatography. Analytical Chemistry. 1972; 44: 213-241.
  14. Pinedo J, Ibáñez R, Lijzen JPA, Irabien T. Assessment of soil pollution based on total petroleum hydrocarbons and individual oil substances. Journal of Environ. Manag. 2013; 130: 72–79. PubMed: https://www.ncbi.nlm.nih.gov/pubmed/24064142
  15. Kanaki M, Nikolaou A, Makri CA, Lekkas DF. The occurrence of priority PAHs, nonylphenol and octylphenol in inland and coastal waters of central Greece and the island of Lesvos. Desalination. 2007; 210: 16-23.
  16. Wan Y, Xiaohui J, Jianying H, Fen J. Trophic Dilution of Polycyclic Aromatic Hydrocarbons (PAHs) in a Marine Food Web from Bohai Bay, North China. Environ Sci Technol. 2007; 41: 3109-3114. PubMed: https://www.ncbi.nlm.nih.gov/pubmed/17539512
  17. IDPH (Illinois Department of Public Health). (2005). Environmental health fact sheet: polycyclic aromatic hydrocarbons.
  18. Nwankwoala HO, Mzaga TM. Geo-Environmental Assessment of Hydrocarbon Contaminated Sites in Parts of Central Swamp Depobelt, Eastern Niger Delta. MOJ Eco Environ Sci. 2017; 2: 00023.
  19. UNEP. Environmental Assessment of Ogoni Land (Executive Summary). Publication. 2010.
  20. United Nations Environment Programme. UNEP. Environmental Assessment of Ogoniland. 2011; 1–198. http://www.unep.org.
  21. USEPA (United States Environmental Protection Agency). Risk Assessment Guidance for Superfund, Volume I Human Health Evaluation Manual, Part B (Development of Risk-based Preliminary Remediation Goals); EPA/540/R-92/003; Office of Emergency and Remedial Response: Washington, DC, USA, 1991.
  22. USEPA (United States Environmental Protection Agency). CASRN—71-43-2 Integrated Risk Information System (IRIS); Chemical Assessment Summary; National Center for Environmental Assessment: Washington, DC, USA, 2000.
  23. USEPA (United States Environmental Protection Agency). The Air Toxics Hot Spots Program Guidance Manual for Preparation of Health Risk Assessments; Office of Environmental Health Hazard Assessment California Environmental Protection Agency: Sacramento, CA, USA, 2003.
  24. USEPA (United States Environmental Protection Agency). RAIS the Risk Assessment Information System, Glossary of Environmental Restoration Terms; United States Environmental Protection Agency: Washington, DC, USA, 2016.
  25. USEPA. United States Environmental Protection Agency. Technical factsheet on: polycyclic aromatic hydrocarbons (PAHs). Washington, DC: http://www​.epa.gov/OGWDW​/pdfs/factsheets/soc/tech/pahs.pdf