Transformation/dissolution characterization of tungsten and tungsten compounds for aquatic hazard classification
Bibliographic record
Abstract
Abstract The transformation/dissolution protocol (T/DP) for metals and sparingly soluble metal compounds was applied to determine the transformation/dissolution (T/D) characteristics of yellow tungsten trioxide, WO3; blue tungsten oxide, WOx, x taken as 2.9; tungsten disulphide, WS2; tungsten metal, W; 3 samples of tungsten carbide, WC; sodium tungstate, Na2WO4 · 2H2O; ammonium paratungstate (APT), (NH4)10(H2W12O42) · 4H2O; and ammonium metatungstate (AMT) (NH4)6(H2W12O40) · 3H2O. The T/D data were used to derive aquatic hazard classification outcomes under the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS) and European Union Classification, Labelling and Packaging of Substances and Mixtures (EU CLP) schemes by comparing the data with selected acute and chronic ecotoxicity reference values (ERVs) of 31 and 3.37 mg W/L, respectively. In addition to the concentration of total dissolved tungsten (W), the T/D solutions were analyzed for the concentration of the tungstate anion, because speciation can be an important factor in establishing the ecotoxicity of dissolved metals. Results show that the tungstate anion was the predominant W-bearing species in solution for all substances examined at pH 6 and 8.5. It was found that the 100 mg/L loadings of both the yellow WO3 and the blue WOx exceeded the 31 mg/L acute ERV, so they would classify as Acute 3-Chronic 3 under the UN GHS scheme but they would not classify under the EU CLP. An effect of pH on the reactivity of the W metal was observed with 3% and 16% W dissolution at pH 6 and 8.5, respectively. Tungsten metal would not classify under either the UN GHS or EU CLP schemes nor would the WS2. The WCs were the least reactive in terms of the 1% or less dissolution of the contained W at pH 6. A critical surface area for WC was calculated. The sodium tungstate, APT and the AMT all yielded, at pH 8.5, total dissolved W concentrations that would result in UN GHS Acute 3-Chronic 3 classifications. Integr Environ Assess Manag 2018;14:498–508. © 2018 Her Majesty the Queen in Right of Canada. Integrated Environmental Assessment and Management © 2018 SETAC Key Points Transformation/Dissolution characteristics of W metal and 7 W compounds were examined for aquatic hazard classification. An adaption of the existing high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) method is reported to provide quantitative determinations of the concentrations of total dissolved W and the tungstate anion in the same run. Results show that the tungstate anion was the predominant W-bearing species in solution for all substances examined, which is important for ecotoxicity. An effect of pH on the reactivity of the W metal and the W compounds was observed, with the substances being more reactive at pH 8.5 than at pH 6.
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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 | 0.000 |
| 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 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".