Ivan Kempson - In vivo - in vitro and XANES spectroscopy assessments of lead bioavailability in contaminated peri-urban soils

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      Publication Details (including relevant citation   information):

      E Smith, IM Kempson,   A Juhasz, J Weber, A Rofe, D Gancarz, R Naidu, R McLaren, M   Gräfe, In vivo - in vitro and XANES spectroscopy assessments of   lead bioavailability in contaminated peri-urban soils,   Environmental Science and Technology,  45,6145-6152, 2011.

      Abstract:

      Lead (Pb) bioaccessibility was assessed using 2 in vitro methods   in 12 Pb-contaminated soils and compared to relative Pb   bioavailability using an in vivo mouse model. In vitro Pb   bioaccessibility, determined using the intestinal phase of the   Solubility Bioaccessibility Research Consortium (SBRC) assay,

      strongly correlated with in vivo relative Pb bioavailability (R2   = 0.88) following adjustment of Pb dissolution in the intestinal   phase with the solubility of Pb acetate at pH 6.5 (i.e., relative   Pb bioaccessibility). A strong correlation (R2 = 0.78) was also   observed for the relative bioaccessibility leaching procedure

      (RBALP), although the method overpredicted in vivo relative Pb   bioavailability for soils where values were <40%. Statistical   analysis of fit results from X-ray absorption near-edge structure   (XANES) data for selected soils (n = 3) showed that Pb was   strongly associated with Fe oxyhydroxide minerals or the soil   organic fraction prior to in vitro analysis. XANES analysis of Pb   speciation during the in vitro procedure demonstrated that Pb   associated with Fe minerals and the organic fraction was   predominantly solubilized in the gastric phase. However, during   the intestinal phase of the in vitro procedure, Pb was strongly   associated with formation of ferrihydrite which precipitated due   to the pH (6.5) of the SBRC intestinal phase. Soils where Fe   dissolution was limited had markedly higher concentrations of Pb   in solution and hence exhibited greater relative bioavailability   in the mouse model. This data suggests that coexistence of Fe in   the intestinal phase plays an important role in reducing Pb   bioaccessibility and relative bioavailability.

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