Petroleum exploration and production can introduce potentially toxic metals into the soils and water bodies of host communities, with consequences for both ecosystem integrity and human exposure. This study assessed the concentrations and distribution of ten heavy metals: Ni, Cr, Cu, Co, Pb, Cd, Fe, Mn, As and Zn in soil and water from two oil-field communities, Apkai (Ndokwa East Local Government Area) and Umusedege (Ndokwa West Local Government Area), Delta State, Nigeria. A total of 63 soil samples and 11 water samples were collected across the two communities and a nearby control site (Obetim). Soil metals were determined by atomic absorption spectrophotometry (AAS) and, for Zn, Fe and Cu, cross-checked by X-ray fluorescence (XRF); water metals were determined by AAS alone. Overall mean soil concentrations were 148.58, 254.41, 53.15, 0.16, 229.98, 21.85, 2905.61, 1228.55, 0.58 and 175.87 mg kg⁻¹ for Ni, Cr, Cu, Co, Pb, Cd, Fe, Mn, As and Zn, respectively, with Fe as the dominant element throughout. Relative to the control, Cr, Cu, Co, Pb, Cd, Fe, Mn, As and Zn were all elevated in soil, while Ni was slightly lower; the largest soil enrichment ratios were recorded for Mn (2.10×), As (1.81×) and Cr (1.76×). In water, mean concentrations were 0.14, 0.04, 0.13, 0.35, 0.03, 6.91, 1.25 and 0.30 mg L⁻¹ for Ni, Cr, Cu, Pb, Cd, Fe, Mn and Zn, respectively (Co and As were not detected), with Pb (10.77×) and Zn (10.17×) showing by far the largest enrichment relative to the control. The AAS–XRF comparison showed statistically significant differences for Zn, Fe and Cu (p < 0.05 in all cases); XRF consistently returned higher values than AAS. Measured against the soil guideline values reproduced in the underlying study, Ni, Cr, Cu, Pb, Cd, Fe and Mn all exceeded their respective thresholds, most markedly Mn, Fe, Cd, Cr and Pb; in water, Fe, Pb, Cd, Ni and Mn were flagged as being of particular concern against U.S. EPA, WHO and SON reference values. Taken together, the results indicate substantial, spatially uneven alteration of soil and water metal concentrations in this oil-field environment relative to the surrounding background, consistent with a combination of lithogenic and anthropogenic contributions, and establish a concentration baseline for the pollution-index, fractionation and health-risk assessments that build on this dataset.
Sanda Yusuf Sadau, Ishaya Iliyasu, M. Alpha et al.· Physical Science Internation...· 0 citations
Oil and gas exploration can both introduce and redistribute potentially toxic metals and naturally occurring radioactive material across the soils and water bodies of surrounding communities, opening exposure pathways that reach well beyond the immediate production site. This study evaluated the human-health risk from heavy metals and the radiological risk from naturally occurring radionuclides in soil and water sampled from the Apkai and Umusedege oil-field communities in Ndokwa East and Ndokwa West Local Government Areas of Delta State, Nigeria. Sixty-three soil samples and eleven water samples were analysed using atomic absorption spectrophotometry, X-ray fluorescence spectroscopy, gross alpha/beta counting and gamma-ray spectrometry, covering Ni, Cr, Cu, Co, Pb, Cd, Fe, Mn, As and Zn. Human-health risk was modelled for children and adults using USEPA exposure equations across ingestion, inhalation and dermal-contact pathways; the pathway-level components were audited directly against their own reported totals by direct summation of their reported pathway contributions. Once audited, the combined soil-and-water hazard index came to 2.53 for children and 13.60 for adults, with ingestion the dominant soil pathway for both groups and an unusually large adult water-dermal contribution driving the adult total; both hazard indices exceed the HI = 1 screening threshold. Total excess lifetime cancer risk from heavy-metal exposure was 7.18×10⁻⁶ for children and 2.40×10⁻⁶ for adults, both remaining within the USEPA-adopted acceptable range. In water, gross alpha and beta activities averaged 1184 and 2164 mBq L⁻¹ respectively, peaking at 3160 and 6145 mBq L⁻¹, with corresponding mean annual effective doses of 2.154, 1.133 and 0.566 mSv y⁻¹ (alpha) and 4.087, 2.106 and 1.053 mSv y⁻¹ (beta) for adults, children and infants respectively. Gamma spectrometry of soil gave mean activity concentrations of 36.102 Bq kg⁻¹ for ²²⁶Ra, 50.237 Bq kg⁻¹ for ²³²Th and 251.903 Bq kg⁻¹ for ⁴⁰K, with a mean absorbed dose rate of 42.22 nGy h⁻¹, annual effective dose of 0.076 mSv y⁻¹ and radium equivalent activity of 91.627 Bq kg⁻¹. Mean external hazard, internal hazard, gamma representative-level and alpha indices were 0.247, 0.335, 0.376 and 0.162 respectively, and the calculated radiological cancer risks were 3.18×10⁻⁶ for adults and 4.32×10⁻⁶ for the whole population. Taken together, the audited results point to heavy-metal exposure with elevated hazard indices for both children and adults as the primary human-health concern, while soil NORM levels imply comparatively low external radiological hazard. Water, in contrast, showed elevated gross alpha/beta activity and associated doses alongside the dominant adult dermal hazard quotient, and therefore warrants continued radiological and chemical monitoring, more targeted radionuclide-specific follow-up, and independent verification of the adult water-dermal exposure calculation.
Sanda Yusuf Sadau, Ishaya Iliyasu, Atipo Kolawole M et al.· Asian Journal of Research an...· 0 citations
Heavy-metal contamination in oil-producing environments may create human-health concerns through ingestion, inhalation and dermal exposure. This study reassessed non-carcinogenic and carcinogenic risks associated with Ni, Cr, Cu, Co, Pb, Cd, Fe, Mn, As and Zn in soil and water from the Apkai and Umusedege communities, Delta State, Nigeria, while auditing inconsistencies between thesis narrative summaries and numerical appendices. Concentrations were determined using atomic absorption spectrometry, with X-ray fluorescence used to validate soil results. Risk was evaluated using average daily intake, hazard quotient, hazard index and excess lifetime cancer risk for children and adults. The audit confirmed soil hazard indices of 2.51 for children and 1.29 for adults. Recalculation of water components yielded hazard indices of 0.02 for children and 12.31 for adults, producing corrected overall values of 2.53 and 13.60, respectively. For carcinogenic risk, an exponent error in the adult soil total was corrected to 1.85×10⁻⁶. Corrected total excess lifetime cancer risks were 7.18×10⁻⁶ for children and 2.40×10⁻⁶ for adults, both below the adopted 1×10⁻⁴ upper screening level. Soil ingestion dominated non-carcinogenic soil risk, whereas ingestion was the principal carcinogenic pathway. The unusually large adult water dermal hazard quotient of 12.04 requires independent verification. Overall, the audited results identify non-carcinogenic risk as the main modelled health concern.
Sanda Yusuf Sadau, N. Rabi'u, N. Garba et al.· Asian Journal of Physical an...· 0 citations
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