Towards an exposure narrative for metals and arsenic in historically contaminated Ni refinery soils: Relationships between speciation, bioavailability, and bioaccessibility
Bibliographic record
Abstract
Archived soils contaminated with Ni, Cu, Co, and As from legacy operations of a nickel refinery at Port Colborne, Ontario, Canada were speciated using mineral liberation analysis. Four Ni minerals were identified as fingerprint compounds of the historical refinery emissions. Cu and Co were present in solid solution in these minerals due to their presence in the refinery's feed. The highest concentrations of Ni, Cu, Co, and As in these soils were 18,553, 1915, 196, and 79 mg/kg, respectively, these elevated contaminant concentrations attesting to the importance of incidental soil ingestion to the oral exposure pathway in Port Colborne. The in vitro gastric bioaccessibility (BAc) was determined for these contaminants, as was in vivo oral bioavailability (BAv), using a mass balance approach in male Sprague-Dawley rats. In spite of the elevated soil concentrations of Cu, the BAv of this physiologically important metal could not be distinguished from that in commercial rat chow, suggesting low potential for exposure. Co and As also had low apparent BAv (<2%). For Ni, baseline oral BAv of naturally sourced dietary Ni was found to be approximately 2%, as was the oral BAv of Ni from nickel sulfate hexahydrate. The mass balances of NiSO4·6H2O were fully accounted-for in urine and feces after a single gavage dose, indicating little to no organ incorporation from this highly soluble salt. Therefore, the urinary estimates of Ni BAv for these soils were assumed to represent true BAv despite variable fecal recoveries. The high Ni concentrations enabled BAc-BAv relationships to be developed for these contaminated soils. For absolute bioavailability (ABA) and relative bioavailability (RBA) the relationships were: ABA = 0.0116(BAc)-0.0479 and RBA = 0.5542(BAc)-2.2817. These findings will advance the development of robust exposure narratives for soil metal contamination in Port Colborne and elsewhere.
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How this classification was reachedexpand
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 | 0.005 | 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 | 0.003 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".