The biogeochemical cycling and anthropogenic inputs of cadmium and silver in the Strait of Georgia, British Columbia
Bibliographic record
Abstract
We present the temporal and spatial variations of two toxic trace metals, cadmium (Cd) and silver (Ag) in the Salish Sea, with a focus on the southern Strait of Georgia (SoG). Our results from field measurements and a box model application show that conservative mixing between riverine discharge and oceanic input largely governs the distribution of dissolved Cd, and anthropogenic influence is negligible. Conservative mixing between low-Cd river water and high-Cd Pacific water largely governs the spatial distribution and temporal variability of dissolved Cd in the Salish Sea. Spatially, concentrations decrease as the Pacific source water flows from the deep basin of Juan de Fuca Strait (818 ± 6 pmol/kg) towards the SoG basin (maximum of 717 pmol/kg) due to riverine dilution. Time-series sampling in the southern SoG between 2017 and 2018 reveals a small but significant decrease of dissolved Cd concentrations (17 ± 7 pmol/kg) in deep waters during the winter. We attributed the decline to a downward flux of dissolved Cd across the sediment-water interface due to Cd sulfide precipitation in sediment porewaters. In addition, enrichment of particulate Cd at 50 m in the water column of the southern SoG may be reflective of sulfide formation within anaerobic microenvironments associated with sinking particles, potentially released from municipal effluent. There is a scarcity of data on dissolved Ag in the open ocean and coastal waters due to analytical challenges in the quantitative determination of its extremely low concentrations in pristine environments. This study provides the first water column measurements of dissolved Ag in the SoG, using a commercially available seawater preconcentration system (seaFAST, Elemental Scientific) combined with analysis on an inductively coupled plasma mass spectrometer (ICP-MS). Dissolved Ag concentrations are variable with depth and season, ranging from 3.4 pmol/kg to 12.8 pmol/kg in the southern SoG. Results suggest that incorporation of dissolved Ag into sinking particles and subsequent desorption in deep waters play an important role in its biogeochemical cycling. Anthropogenic Ag loadings from three major sewage outfalls located in the Metro Vancouver and Capital Regional District are low compared to riverine and oceanic inputs.
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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 | 0.000 |
| Scholarly communication | 0.001 | 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".