Spatial and temporal distribution of polycyclic aromatic hydrocarbons in sediments from the Canadian Arctic Archipelago
Bibliographic record
Abstract
In Arctic, because of the ongoing diminution of the sea ice coverage, it is speculated that anthropogenic activities such as cargo transportation and oil explorations/exploitations could increase in the Canadian Arctic Archipelago (CAA). However, the vast majority of the channels within the CAA, as well as the adjoining continental shelf and slopes, are characterized by a substantial knowledge gap regarding the regional-scale sediment composition and associated contaminants. Overall, knowing that sediments are a sink for pollutants, a wider spatial coverage of sedimentary records across the marine CAA is essential to provide fundamental baseline information on the physical and geochemical sediment properties in this Arctic region. In this context, a total of 118 surface sediment samples were collected over a large area covering the Canadian Beaufort Sea to the Baffin Bay in order to characterize the modern spatial distribution patterns and the temporal trends of polycyclic aromatic hydrocarbons (PAHs) within the CAA. Sampling was performed in 2016, 2017, 2018 and 2019 aboard the CCGS Amundsen as part of the ArticNet program. Extractions were performed using one-step accelerated solvent extraction and clean-up, followed by gas chromatography coupled to a mass spectrometer analysis. To characterize the temporal concentrations of PAHs, the top 10 cm of 8 push-cores distributed across the archipelago were sub-sampled and analyzed just as the surface samples. Sedimentation rates for each core were obtained by 210Pb dating and allow to reconstruct the PAHs inputs from the last century. Results of the surface sediment samples indicate that the sum concentrations of 23 PAHs ranged from 6 ng/g (dry weight basis) in the North Baffin Bay to 437 ng/g in the Canadian Beaufort Shelf, with a mean value of 67 ng/g. PAHs source characterization was investigated through diagnostic ratio: fluoranthene over the sum of fluoranthene and pyrene. This ratio tends to point a profile with mainly petrogenic sources (i.e., igneous rock-derived, petroleum or crude oil spill) for the majority of the CAA. Some samples in the Beaufort Sea have a mixed profile with petrogenic sources and pyrogenic sources from incomplete combustion of fossil fuel that could indicate an anthropogenic input. Along Ellesmere Island, ratios are mainly pyrogenic from biomass combustion. Results of the push-cores suggest that the inputs of PAHs to the sediment in CAA were relatively stable during the last years. Taken as a whole, our study will provide a baseline of PAHs levels in surface sediment within the CAA before an increase in maritime transport in this area and a comparison of the modern concentrations versus the last century tendencies.
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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 | 0.004 | 0.005 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".