Corrosion Scale Characteristics and Lead Oxide Dissolution in Chloraminated Water
Bibliographic record
Abstract
The presence of lead in drinking water is a common issue for utilities where lead pipes are used as service lines in drinking water distribution systems. Dissolved lead concentrations have been linked to the destabilization of stratified lead corrosion scales formed at the inner walls of lead pipe used as drinking water service lines. To develop a framework for lead dissolution control, it is necessary to fully describe the characteristics of the surface layer of the lead corrosion scale in direct contact with drinking water. In the first part of this thesis, a thorough lead corrosion scale characterization is carried using lead pipes collected from four Canadian drinking water systems. The results obtained are contextualized in terms of the preferential presence of lead oxides and aluminosilicates at the surface layer of the corrosion scales. The different phases identified are linked to the corresponding water quality, particularly pH values and dissolved silicate concentrations. In the second part of this work, PbO2 dissolution processes in the presence of monochloramine were studied. A detailed chemical synthesis protocol, characterization for the PbO2 solid, analysis of monochloramine decomposition and corresponding lead dissolution profiles have enabled us to identify a surface reaction between PbO2 and NH2Cl. Two different reaction regimes for this interaction were revealed. At high PbO2/NH2Cl molar ratios, where NH2Cl is the limiting reagent and the presence of PbO2 accelerated the decomposition of NH2Cl. PbO2 was reduced only by water, resulting in the release of limited amounts of dissolved lead (<10 >μg/L). In contrast, at low PbO2 solid to NH2Cl molar ratios, monochloramine decomposition rates were similar to those observed for its auto-decomposition. The monochloramine decomposition process triggered the formation of defects in PbO2, resulting in elevated levels of dissolved lead released to the aqueous phase. The activity of PbO2 for monochloramine decomposition is determined by its crystal structure, crystallite size, and surface properties in the form of defects. Based on these observations, a proton-containing species in PbO2 is proposed as the active species for monochloramine decomposition.
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 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 | 0.000 | 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) | 0.001 | 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".