An investigation of the distribution, fractionation and bioaccessibility of potentially toxic elements in urban soils of Lagos, Nigeria

  • Abimbola Oladimeji Famuyiwa

Student thesis: Doctoral Thesis

Abstract

Lagos is one of the fastest-developing metropolises in the world, with a population of 21 million, increasing by 2.8 % annually. The impact of this rapid development and industrialisation on levels of potentially toxic elements (PTE) in the city’s soils is of concern, and requires investigation, because of possible effects on human health.Soil samples were collected from different land-use types and socioeconomic areas in Lagos state in February and August of 2014 and returned to Scotland, UK. The microwave-assisted aqua regia digestion, the revised BCR sequential extraction, and the simplified bioaccessibility extraction test (SBET) were applied to the soils. The analytes Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined in soil extracts and digests by ICP-MS.Mean pseudototal PTE concentrations at locations remote from point sources of pollution were generally low, but soils taken from locations close to industrial activities such as foundries, dumpsites, and e-waste recycling sites were often highly contaminated. Principal component and cluster analysis identified Cr-Fe-Mn-Ni and Cu-Pb-Zn groupings. Correlation coefficient analysis further confirmed these relationships; grouping the lithogenic PTE (former) separately from ‘‘urban metals’’ (latter). Sequential extraction result indicated that Cr, Fe and Ni were mainly of geogenic origin, whilst the ‘urban metals’ Cu, Pb and Zn were in more labile forms of greater environmental concern. The SBET indicated that PTE uptake by a hypothetical 10 kg child with pica tendencies (consuming 10 g of soil per day) would greatly exceed tolerable daily intake (TDI) values for Cu, Pb and Zn at many locations. Finally, the last stage of the work revealed that, the exposure of PTE in PM10 fractions of Lagos urban soils to the general public may not likely pose any serious health effects considering inhalation pathway as the only route by which PTE enters into human body.
Date of Award1 Feb 2016
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorChristine Davidson (Supervisor) & Lorraine Gibson (Supervisor)

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