ARSENIC MINERALOGY OF NEAR-SURFACE TAILINGS AND SOILS: INFLUENCES ON ARSENIC MOBILITY AND BIOACCESSIBILITY IN THE NOVA SCOTIA GOLD MINING DISTRICTS
Why this work is in the frame
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Bibliographic record
Abstract
The mineral form, grain size and texture of As-bearing particles are important factors influencing the risk to human health associated with exposure to As-contaminated soils, sediments and mine wastes. Mining of arsenopyrite-bearing gold ores in Nova Scotia in the late 1800s and early 1900s has left a legacy of weathered, As-rich tailings deposits in more than 60 gold districts across the province. Fourteen samples of near-surface tailings and one of soil from several former gold mines frequented by the public were sieved to 20% As) mill concentrates exposed at the surface within the tailings deposits are dominated by a single As mineral, fine-grained scorodite (FeAsO4·2H2O) in one case, and massive unweathered arsenopyrite in the other. In the tailings (0.7 to 7% As), scorodite and amorphous hydrous ferric arsenate (HFA) are the most common As-bearing major components, occurring as discrete grains or grain coatings on gangue minerals. Other major As phases identified in the tailings include As-bearing amorphous hydrous ferric oxyhydroxides (HFO), kaňkite (FeAsO4·3.5H2O), pharmacosiderite [KFe4(AsO4)3(OH)4·6–7H2O], yukonite [Ca7Fe12(AsO4)10(OH)20·15H2O], amorphous Ca–Fe arsenates, and arsenopyrite. Minor or trace constituents include: As-bearing ferric oxyhydroxides with up to 10% As (HFO, goethite, lepidocrocite and akaganeite), As-bearing sulfates (jarosite [(K,Na,H3O)Fe3(SO4)2(OH)6], tooeleite [Fe6(AsO3)4(SO4)(OH)4·4H2O]) and realgar (As4S4). Arsenic-bearing HFO (2.5% As) and goethite (0.08% As) were identified in the single B-horizon soil sample. This study is part of a broader coordinated effort by a multi-department federal and provincial advisory committee formed to coordinate the study of ecosystem and human health risks associated with historical gold mine sites in Nova Scotia. Our study shows that (i) the mineralogy of As in weathered tailings is highly variable, with aggregates of more than one As-bearing phase common in a given sample, and (ii) major differences in As mineralogy in the tailings are mainly controlled by factors that influence the weathering history ( e.g. , presence or absence of mill concentrates, degree of water saturation, and abundance of relict carbonate minerals). The variable solubility of these primary and secondary As-bearing minerals influences both the environmental mobility and the bioaccessibility of As in near-surface tailings and soil samples.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it