Distribution, transport, and sources of metals in marine sediments near a coastal lead smelter in northern New Brunswick
Bibliographic record
Abstract
Significant variations in metal concentrations occur in marine sediments collected from Chaleur Bay, an estuary located between northern New Brunswick and Quebec's Gaspésie. The bay receives metals from many sources including a lead smelter, a mercury-cell chlor-alkali plant, and numerous mined and unmined base-metal deposits. This study examines the dispersal patterns of metals released to the bay from natural and anthropogenic sources, and the processes that collect and redistribute these elements in the marine environment. Bottom sediments were collected from 124 sites in the bay, at distances up to 100 km away from the smelter. The ranges in metal and metalloid concentrations of 918 sediment subsamples are as follows, in mg/kg: As, 2.8 to 74; Cd, 0.02 to 69; Cu, 3.4 to 200; Hg, <0.01 to 2.4; Pb, 0.3 to 2000; and Zn, 22 to 3200. Dispersion of smelter effluents and atmospheric emissions by wind and/or nearshore currents has resulted in an area of elevated As, Cd, Cu, Hg, Pb, and Zn concentrations in surficial sediments within approximately 10 to 20 km of the smelter. The concentrations of most metals decrease sharply with increasing distance from the smelter; however, Pb concentrations exceed background levels in surface sediments throughout the bay. In sediments adjacent to the smelter, metal levels are highest at approximately 5 to 10 cmdepth and decrease toward the sediment surface, which may reflect the significant reduction in smelter emissions since the mid-1970s. Lead isotope ratios suggest that the surface enrichment of Pb throughout the bay is mainly derived from smelter emissions and historical leaded gasoline combustion.
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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 | 0.002 |
| Science and technology studies | 0.001 | 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".