10 research outputs found
The importance of solid-phase distribution on the oral bioaccessibility of Ni and Cr in soils overlying Palaeogene basalt lavas, Northern Ireland
Potentially toxic elements (PTEs) including
nickel and chromium are often present in soils
overlying basalt at concentrations above regulatory
guidance values due to the presence of these elements
in underlying geology. Oral bioaccessibility testing
allows the risk posed by PTEs to human health to be
assessed; however, bioaccessibility is controlled by
factors including mineralogy, particle size, solidphase
speciation and encapsulation. X-ray diffraction
was used to characterise the mineralogy of 12 soil
samples overlying Palaeogene basalt lavas in Northern
Ireland, and non-specific sequential extraction coupled
with chemometric analysis was used to determine
the distribution of elements amongst soil components
in 3 of these samples. The data obtained were related
to total concentration and oral bioaccessible concentration
to determine whether a relationship exists
between the overall concentrations of PTEs, their
bioaccessibility and the soils mineralogy and geochemistry.
Gastric phase bioaccessible fraction
(BAF %) ranged from 0.4 to 5.4 % for chromium in
soils overlying basalt and bioaccessible and total
chromium concentrations are positively correlated. In
contrast, the range of gastric phase BAF for nickel was
greater (1.4â43.8 %), while no significant correlation
was observed between bioaccessible and total nickel
concentrations. However, nickel BAF was inversely
correlated with total concentration. Solid-phase fractionation
information showed that bioaccessible
nickel was associated with calcium carbonate, aluminium
oxide, iron oxide and clay-related components,
while bioaccessible chromium was associated
with clay-related components. This suggests that
weathering significantly affects nickel bioaccessibility,
but does not have the same effect on the
bioaccessibility of chromium