Analysis of Metal Contaminants and Mercury Speciation in Fishes from the Slave and Athabasca Rivers
Bibliographic record
Abstract
The Slave and Athabasca are two connected rivers impacted by a variety of anthropogenic activities such as oil sands extraction, metal mining, pulp mills and agriculture. Concerns have been raised regarding the health of these two rivers especially the Athabasca River which runs through areas of oil sands development. The health of fish in these rivers is one of the primary concerns due to the cultural and economic importance of the fish to local community members. Metal contaminants in fish can have an impact on fish health and can pose a risk to the health of consumers of fish, including humans. This thesis investigates metals in five fish species (burbot, goldeye, northern pike, walleye, and whitefish) from sites along the Slave and Athabasca Rivers during four seasons (summer, fall, winter, and spring). A suite of 25 metals were analyzed by ICP-MS and the majority of the metal concentrations showed little location associated variability nor were they detected at concentrations of concern. One metal, Hg, was detected at concentrations of concern and four metals (As, Se, Tl, and V) demonstrated statistically significant variations in concentrations between sampling sites with greater concentrations in the sites on the lower Slave River compared to the upper Slave River, Athabasca River, and Peace River sites. The concentrations of these metals were not of sufficient magnitude to be of concern to fish or human health, but the trend is of interest due to concerns regarding industrial activities on the Athabasca River. Mean Hg concentrations in fish muscle exceed Health Canada consumption guidelines in 2.6% of fish groups separated by species, location, and season. These concentrations exceeded subsistence advisory Hg guideline concentrations in 47.4% of fish groups. The magnitude of Hg concentrations was not new information as other researchers have found similar concentrations in fish in the region and fish consumption advisories are already in place for the Athabasca River due to Hg concerns. The two species of Hg found in fish are Hg(II) and methylmercury. Methylmercury is the predominant form of Hg in fish and has the potential to biomagnify, increasing concern for fish and human health. A method to analyze for the two Hg species was developed utilizing sodium tetraethylborate derivatization with headspace solid-phased microextraction (SPME) followed by gas chromatography and orbitrap mass spectrometry (GC-Orbitrap MS) analysis. The use of GC-Orbitrap MS allows for the scanning of a wide range of mass/charge (m/z) at high resolution (>200,000). This resolution and scan range were utilized to quantify each Hg species and Hg isotopes. The percent of total Hg represented by methylmercury in a subsample of the fish collected from the Slave and Athabasca Rivers were found to be 82.4% for goldeye, 90.2% in northern pike, 87.2% in walleye, 92.3% in whitefish, and 87.5% in burbot. Isotope patterns of Hg were also determined for these samples though the method was not sensitive enough to detect subtle differences in stable isotope patterns. Mercury concentrations are nearing, and in certain circumstances exceeding, Canadian guidelines. Overall, metal concentrations, with the exception of Hg, in the Slave and Athabasca Rivers do not appear to be at levels of concern for fish or human health at this time. The trend of four metals being greater in the lower Slave River provides an interesting opportunity for further research into metal chemodynamics.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".