Mercury and Heavy Metal Origin and Contamination of the Puyango-Tumbes River System, Ecuador
Bibliographic record
Abstract
Worldwide Artisanal Gold Miners (AGM) use significant amounts of mercury, accounting for more than 30% of all industrial uses. UNEP (2013) estimates that AGM is emitting and releasing 1400 tonnes/a of mercury. Processing centres were established in the 1990s in Portovelo, Ecuador to provide miners with gold extraction services. Miners amalgamate a portion of the gold, but centre owners retain the residual Hg-contaminated tailings using cyanidation to recover the remaining 60 - 80% of the gold. Based on surveys of 52 out of 87 centres, 1.1-1.85 tonnes of metallic mercury contained in over 880,000 tonnes of tailings are discharged into the Puyango-Tumbes River annually. This mercury represents a loss of approximately 14% of the total mercury used by AGM/a in the region. An additional 19% of the mercury is lost when amalgam is evaporated. An average of 5.7 tonnes of cyanide per month (a total of over 4,500 tonnes/a) is consumed by approximately 68 centres. In total, 39 river-bank sediments and 31 soils were sampled. Mercury contamination in sediment exceeded the CCME TEL - Canadian Council of Ministers of the Environment threshold effect level in 23 sites. The highest level detected was 30.79 mg/kg in sediment; all soil samples were below 2 mg/kg. An abandoned tailings pit recorded a mercury level of 744.2 mg/kg. Elevated mercury levels in sediment were detected 160 km distant from source, demonstrating that AGM-discharged mercury can flow long distances attached to particulate matter. Arsenic, Cadmium, Copper, Lead and Zinc levels in water, sediment and soil samples were also found to be above safe standards at many sites. In sediments, Arsenic levels were exceeded at 31 sites, the highest recorded was 12,580 mg/kg; Cadmium – 8 sites ( A total of 25 fish samples were taken from 3 sites in the river system 45 to 93 km from the source. Dorado fish recorded mercury levels ranging from 0.02 to 0.99 mg/kg; Aquila fish (a bottom feeder) had levels from 0.18 to 0.98 mg/kg. KEYWORDS: Ecuador, Puyango-Tumbes, mercury, ASGM, AGM, miners, mining, heavy metals, cyanide, water, sediments
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 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".