What drives bioaccessibility? An investigation of the solid phase speciation of Pb-bearing particulates in topsoils and metaliferrous wastes

Jane Entwistle, Andrew Hunt

Research output: Contribution to conferencePosterpeer-review

Abstract

Lead contamination of soil continues to pose an insidious public health issue. Evidence for the impact of even low-level environmental Pb exposure on human health, behaviour and cognition is well documented. Highly contaminated soils pose a particular risk, however not all forms of ingested Pb are solubilised in the gastrointestinal (GI) tract with clear implications for human health risk assessments. Oral bioaccessibility protocols seek to model extraction during the passage through the human GI system and the mineralogical form/solid phase partitioning of the contaminant has a large influence on its bioaccessibility. Here we report on samples from Mitrovica, northern Kosovo, with Pb levels ranging from 54 – 47,260 mg/kg, and in vitro oral Pb bioaccessibilities of between 1.2 and 92%. The aim of this study was to evaluate which Pb phases controlled the overall Pb solubility in these soils. The Pb mineral phases were determined by X-ray diffraction, and an approach based on Computer Controlled Scanning Electron Microscopy (CCSEM), coupled with energy dispersive X-ray spectroscopy (EDS) was utilized to identify specific Pb-particle associations (phases) in the samples (with approximately 4,000 particles analyzed per sample). Lead solubility was investigated at the bulk sample level by the Unified BARGE method (UBM), and by chemometric analysis of sequential extraction data, and at the individual particle level by Differential Individual Particle Analysis (DIPA). DIPA involves the collection of particle-by-particle information (elemental and morphological) on the particles in their original form, followed by removal from the SEM for chemical treatment of the sample in situ, followed by particle relocation and subsequent analysis of differential changes. Initial results suggest that across the suite of samples Pb-particles with Fe associations were less soluble than Pb-particles with Ca associations. Other Pb-particle associations that are sample specific were also found to be important in controlling Pb solubility.
Original languageEnglish
Publication statusPublished - Sep 2015
EventSociety Annual Meeting 2014: Delving into the dark - emerging techniques, approaches and tools for soils research - Manchester
Duration: 1 Sep 2015 → …
http://soils.org.uk/

Conference

ConferenceSociety Annual Meeting 2014: Delving into the dark - emerging techniques, approaches and tools for soils research
Period1/09/15 → …
Internet address

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