Halogenated flame retardants in the sediments of the lower Great Lakes and region-wide discoveries
Bibliographic record
Abstract
This work aims to provide updated information and insights on the contamination by halogenated flame retardants (HFRs) of the Great Lakes sediments. Thirty HFRs, including polybrominated diphenyl ethers (PBDEs), dechlorane plus (DPs), and other chlorinated (CFRs) or brominated (BFRs) chemicals, were measured in 400 sediment surface grab and core segment samples from Lakes Erie and Ontario. The data were combined with those from Lakes Superior, Michigan, and Huron to provide a comprehensive region-wide analysis. Together, the target HFRs in the Great Lakes sediment amount to approximately 420 tonnes. Among the five lakes, Lake Ontario had the highest concentrations of CFRs, while Lake Erie had the largest mass accumulation of BFRs. Regression analyses identified latitude and longitude of the sites, and sediment organic content, as the most descriptive of the observed spatial distribution patterns. The data from cores indicate that the net flux has been decreasing in recent decades for most HFRs, including PBDE replacements 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) and 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (EHTBB), with average halving time of 20–65 years. However, at most locations, inputs of decabromodiphenyl ethane (DBDPE) exhibited no clear declining trend. Concentration ratios of less halogenated compounds to their respective “parents” increase with increasing sediment depth, suggesting that dehalogenation has occurred over past decades. Principal component, correlation, and hierarchical clustering analyses of the data suggest similarities and differences among HFRs in their sources and environmental behavior. These findings contribute to the scientific knowledge basis for planning future surveillance, research, and management activities in the region and beyond. • Sediment in Lakes Erie and Ontario are heavily polluted by flame retardants. • The contamination tends to decrease northwards and westwards in the region. • Inputs to sediment are decreasing for PBDEs and some their replacement chemicals. • Dehalogenation has occurred within the sediment over past decades. • Correlations among analytes suggest commonality in their environmental behavior.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 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".