Investigation of how oral bioaccessibility of potentially toxic elements in urban soils is affected by contaminant source and sampling techniques

  • Tatiana Cocerva

Student thesis: Doctoral ThesisDoctor of Philosophy


Potentially Toxic Elements (PTEs) in urban soils often originate from both geogenic and anthropogenic sources. Understanding their mobility, distribution, and geochemical interactions provides the necessary evidence to effectively assess the risks posed to people from exposure to soil contaminants.

The human health risk assessment often relies on total PTEs concentrations and assumes that contaminants are 100% bioavailable to humans. This assumption sometimes may overestimate the risks and result in unnecessary remediations. Therefore, in vitro bioaccessibility tests are applied to estimate the bioavailable contaminant fraction providing more precise information.

However, the controlling factors over PTEs bioaccessibility in urban soils are not adequately understood. This research aims to address this gap by investigating the influence of contaminant source, solid-phase distribution of contaminants and soil sampling techniques, to enhance understanding of the controlling factors over PTEs bioaccessibility.

Belfast metropolitan area was selected as the study area because of the existence of Tellus geochemical dataset, various potential contaminant sources and a variety of bedrock geology. Oral bioaccessibility of seven PTEs, including As, Cr, Cu, Ni, Pb, V, and Zn has been measured in 103 Tellus soil samples using a low-cost modified Unified BARGE Bioaccessibility Method.

The results showed that historical development zone was related to higher PTE bioaccessibility while factors linked to geogenic sources were associated with a reduction in oral bioaccessibility fractions.

Bioaccessibility results were combined with CISED data to understand the solid phase distribution of PTEs among soil components and ”locate” the bioaccessible fraction in the soil matrix.

This research was completed by investigating the uncertainties associated with soil sampling technique used in bioaccessibility testing.

Overall, the outcome of this research work provides an initial screening of the PTEs oral bioaccessibility and its controlling factors across the urban area of Belfast and the influence of the sampling technique over bioaccessibility results.
Date of AwardDec 2021
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsEC-Horizon 2020
SupervisorSiobhan Cox (Supervisor), Rory Doherty (Supervisor) & Ulrich Ofterdinger (Supervisor)


  • Oral bioaccessibility
  • potentially toxic elements
  • urban soils
  • contaminant source
  • human health risk assessment
  • soil sampling

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