Trace metal geochemistry of metalliferous black shales in the Mamfe basin (South West Cameroon): Implication for heavy metal assessment
Bibliographic record
Abstract
This study is focused on assessing the contamination levels of heavy metal elements (Cu, Cd, Cr, Ni, and Zn) in black metalliferous shales of the Mamfe basin in South Western Cameroon and identifying the possible pollution sources. Forty (40) black shale samples collected from seven outcrops from different sites in the Mamfe basin were subjected to geochemical analysis by inductively coupled plasma-mass spectrometry (ICP-MS). The results obtained from these analyses were used to calculate the contamination factor (CF), geo-accumulation index (Igeo), and Pollution Load Index (PLI). Person's correlation coefficient was applied in this work to assess the metals origin. The values of heavy metals in the shales were compared with experimental values of TEL (Threshold Effects Level), PEL (Probable Effects Level), ERL (Effects Range Low), and ERM (Effects Range Medium) to assess the long-term adverse biota effect if the shales weathers and release the hosted heavy metals. The average heavy metal concentrations in the studied shales were 35 mg/kg, 89 mg/kg, 0.24 mg/kg, 82 mg/kg and 37.3 mg/kg for Cu, Zn, Cd, Cr and Ni respectively with some above the threshold values of United State Environment Protection Authority (USEPA), average shale (ASV), toxicity reference values (TRV) and Indian River system (IRS). The shales are poorly to moderately enriched in heavy metals which may cause a long-term effect on the surrounding soils and waters after degradation. The heavy metal values of the studied shales compared with the experimental results of TEL, PEL, ERL, and ERM indicate that a little adverse biota effect of Ni, Cu and Cr to the ecosystem after degradation of the studied shales. The geo-accumulation index ranged between 0 and 0.06 indicating that the black Mamfe shales are uncontaminated to moderately contaminated and may have adverse effects on the freshwater ecology and surrounding soils. The pollution load index (between 0.0 to 0.05) and contamination factor (0.18-1.84) indicate that the shales have a low level of contamination and their long-term degradation and weathering will have a limited effect on the soils and water ecosystems. The positive correlation between Cu, and Zn, suggest the same source of contamination input. The positive correlation between Zn, Cu, Cr, and Ni indicates a natural origin of these elements in the shales. A rapid weathering/degradation of large quantity of theses shales may increase the concentration of heavy metals in the surrounding rivers and soils in the near future.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| 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 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".