Concentrations of Total Mercury and Methylmercury in Sediment Adjacent to Offshore Drilling Sites
Bibliographic record
Abstract
Abstract This paper presents results from a study of concentrations of total mercury (Hg) and methylmercury (MeHg) in seabed sediments near six offshore drilling sites in the Gulf of Mexico. Surface (0-2 cm) and subsurface (2-20 cm) sediment samples for this study were collected within three zones at each drilling site: <100 m (nearfield), 100-250 m (midfield) and >3 km (farfield). Total Hg levels in sediments from this study range from 11-92 ng/g (parts per billion, dry weight) for all farfield (background) samples and 25-558 ng/g for all nearfield samples. Concentrations of total Hg are significantly higher at nearfield stations than at farfield stations for five of the six drilling sites due to inputs from drilling discharges. Concentrations of MeHg range from 0.11-1.05 ng/g for all farfield sediments and <0.03-2.7 ng/g for all nearfield sediments. In contrast with results for total Hg, concentrations of MeHg in surficial (0-2 cm) sediments from all six drilling sites do not vary significantly between nearfield and farfield stations. Statistical comparisons of MeHg levels in nearfield versus farfield sediments at the six drilling sites, along with data from two of those sites that show lower levels of MeHg in some nearfield sediments than in farfield sediments, suggest that elevated levels of MeHg in sediments around drilling sites are not a widespread phenomenon in the Gulf of Mexico.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 teacher head, 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".