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Assessment of arsenic speciation and bioaccessibility in mine-impacted materials
Citation:
Ollson, C., E. Smith, K. Scheckel, A. Betts, AND A. Juhasz. Assessment of arsenic speciation and bioaccessibility in mine-impacted materials. Diana Aga, Wonyong Choi, Andrew Daugulis, Gianluca Li Puma, Gerasimos Lyberatos, and Joo Hwa Tay (ed.), JOURNAL OF HAZARDOUS MATERIALS. Elsevier Science Ltd, New York, NY, 313:130-137, (2016).
Impact/Purpose:
As a consequence of physical and thermal processes for the extraction of Au, As mineralogy, concentration and other physicochemical properties of the contaminated matrix may vary which may impact on human health exposure assessment. Previous research has evaluated As bioaccessibility from these three mine-impacted materials; however, despite their different properties, it is often reported under a generic descriptor, i.e. mine waste. The purpose of this research was to (1) evaluate the bioaccessibility of As from multiple mine waste sources (tailing, calcinated and slime materials) using the Solubility/Bioaccessibility Research Consortium (SBRC) assay, (2) use X-ray Absorption Near Edge Structure (XANES) analysis to evaluate if mineralogy is responsible for differences in As bioaccessibility, (3) evaluate the differences in As bioaccessibility between the three materials by assessing the relationship between As bioaccessibility and both total and reactive iron (citrate dithionite extractable Fe), (4) determine if particle size can account for differences in As bioaccessibility, (5) assess the appropriateness of default values for As RBA by evaluating exposure for all mine-impacted materials.
Description:
Mine-impacted materials were collected from Victoria, Australia and categorized into three source materials; tailings (n = 35), calcinated (n = 10) and grey slimes (n = 5). Arsenic (As) concentrations in these materials varied over several orders of magnitude (30-47,000 mg kg-1), with median concentrations of 500, 10,800 and 1500 mg kg-1, respectively. When As bioaccessibility was assessed using the Solubility Bioaccessibility Research Consortium (SBRC) assay, As bioaccessibility ranged between 4 and 90%, with mean gastric phase values of 30%, 49% and 82% for tailings, calcinated and grey slimes, respectively. An analysis of variance (ANOVA) determined that As bioaccessibility was significantly different (P < 0.05) between source materials. This was due to differences in As mineralogy, soil particle size as well as the concentration and nature of Fe present. X-ray Absorption Near Edge Structure (XANES) analysis identified arseniosiderite, yukonite, realgar, loellingite and mineral sorbed arsenate species in mine-impacted materials. Despite differences in physicochemical properties, ‘mine wastes’ are often reported under a generic descriptor. Outcomes from this research highlight that variability in As bioaccessibility can be prescribed to As mineralogy and matrix physicochemical properties, while categorizing samples into sub-groups can provide some notional indication of potential exposure.
