| Titre | The relationship between mineralogy and bioaccessibility in complex arsenic-contaminated materials |
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| Auteur | Jamieson, H; Walker, S; Meunier, L; Parsons, M ; Koch, I; Reimer, K |
| Source | 5th SETAC (Society of Environmental Toxicology and Chemistry) World Congress, 2008 abstracts volume; 2008, 1p. |
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| Année | 2008 |
| Séries alt. | Secteur des sciences de la Terre, Contribution externe 20080196 |
| Éditeur | Society of Environmental Toxicology and Chemistry |
| Réunion | 5th SETAC (Society of Environmental Toxicology and Chemistry) World Congress; Sydney; AU; août 3-7, 2008 |
| Document | livre |
| Lang. | anglais |
| Media | CD-ROM |
| Sujets | arsenic; résidus; analyses des résidus; sols; études pédologiques; sulfures; arsénopyrite; pyrite; goethite; scorodite; hématite; maghémite; minéralogie; géologie de l'environnement; pédologie |
| Programme | Environnement et santé |
| Résumé | (disponible en anglais seulement)
A suite of 29 samples of arsenic (As)-bearing mine tailings and soils have undergone simultaneous mineralogical characterization and bioaccessibility testing.
Particular attention was paid to identification of multiple As-bearing minerals, particle size and textural relationships. We have developed a micro-analytical method to characterize complex samples at the micron scale combining petrography, electron
microprobe, and synchrotron-based grain-by-grain microXANES and microXRD. Each tailings sample typically contains four or more As-bearing minerals, including sulfides (arsenopyrite and pyrite), Fe arsenates (scorodite, kankite, amorphous forms),
Ca-Fe arsenates (yukonite, amorphous forms), As-bearing Fe oxyhydroxides (goethite, lepidocrocite, akaganeite, amorphous forms), tooeleite (ferric arsenite-sulfate) and roaster-generated As-bearing Fe oxides (hematite, maghemite).
The
bioaccessibility of As in the samples was measured using a physiologically-based extraction test (PBET) and ranges from 0.5 to 48.5% of total As. These values appear to be controlled by the relative proportions of the As-bearing phases, although
grain size and texture also play a role. The higher percent As bioaccessibility values are associated with the presence of Ca-Fe arsenates. These samples also contain carbonate minerals indicative of pH-neutral conditions, thus it is not surprising
that they leach As readily in an acid gastric extraction. The relatively low As bioaccessibility of samples rich in microcrystalline scorodite (FeAsO4•2H2O) is consistent with the known geochemical behaviour of this mineral, including stability at
low pH and transformation to amorphous Fe hydroxides at higher pH. In the PBET tests, scorodite exhibits very low bioaccessibility in the gastric leach. Sluggish kinetics with or without transformation to a more As-poor amorphous form may explain the
relatively small release of As in the pH-neutral intestinal leach. The low measured bioaccessibility of samples rich in arsenopyrite indicates very slow dissolution or barriers to oxidative attack. One arsenopyrite-rich sample containing minor
yukonite exhibited intermediate bioaccessibility, supporting the hypothesis of mineralogical control. |
| GEOSCAN ID | 225400 |
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