Spatial and statistical analysis approaches to investigate the oral bioaccessibility of potentially toxic elements in Northern Irish soils

  • Sherry Beth Palmer,

    Student thesis: Doctoral ThesisDoctor of Philosophy


    The basis for assessing human health risks from contaminated land often relies upon measuring total soil contaminant concentrations. However, human health risks are dependent on the bioavailable fraction of a soil contaminant. Measuring oral bioaccessibility in vitro can be an acceptable estimate of contaminant oral bioavailability, eliminating the need for in vivo toxicology studies to estimate health risks from oral soil contaminant exposure.

    Using soil samples from the Northern Ireland Tellus Survey soil archive, the oral bioaccessibility of cadmium, chromium, arsenic, nickel, lead and vanadium was measured in Northern Irish soils on a national scale. As identified by the Tellus geochemical survey, all of these elements are present at elevated concentrations in Northern Ireland soils, in some cases exceeding available human health soil screening criteria. Oral bioaccessibility testing results were combined with a pre-existing Northern Ireland oral bioaccessibility data set derivedfrom analysis ofdifferent soil samples. From thisjoined data set, interpolated maps were generated to illustrate geographical trends in trace element oral bioaccessibility across the study area. Oral bioaccessibility data and previously measured geochemical variables from the same soil sample locations were then subjected to statistical analyses to underpin factors that affected trace element bioaccessibility in study area soils. Correlation analysis, factor analysis and linear regression techniques identified clay, peat, anthropogenic, igneous and sedimentary geology components each exerting unique controls over trace element oral bioaccessibility.

    Clay and peat factors were related to higher trace element bioaccessibility while factors linked to igneous minerals generally were associated with a reduction in oral bioaccessible fractions. The oral bioaccessible fractions of nickel and vanadium in particular were often higher in soils overlying sedimentary geology, regardless of their high total concentrations in soils overlying igneous bedrock. Chromium bioaccessible concentrations and fractions were among the lowest of all the trace elements studied. Higher measured bioaccessible fractions of lead and cadmium were concluded to result from their higher solubilities and anthropogenic source appointment. Lastly, given the established links between oral exposure to lead and arsenic and the potentialfor serious toxic health effects, thefindings of this research suggestfurther site specific investigations may be justified in some areas iforal exposure to either ofthese contaminants is likely to occur in the study area.
    Date of AwardJul 2015
    Original languageEnglish
    Awarding Institution
    • Queen's University Belfast

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