Transport, deposition and aggregation of metal oxide nanoparticles in saturated granular porous media: role of water chemistry, collector surface and particle coating
Notice bibliographique
Résumé
As a multitude of engineered nanomaterials (ENMs) are being incorporated into a growing number of consumer products, the potential release of these reactive and potentially toxic constituents into natural aquatic environments and soils is inevitable. Nanosized metal oxides such as cerium dioxide (nCeO2), titanium dioxide (nTiO2) and zinc oxide (nZnO) are examples of ENMs currently appearing in consumer products. Upon the release of such ENMs into natural and engineered aquatic environments, particle aggregation and deposition behavior will determine the particle transport potential and thus the environmental fate and potential ecotoxicological impacts of the released materials. The objective of this research was to examine the transport behavior of select nanosized metal oxides (namely, nCeO2, nTiO2 and nZnO) in saturated granular porous media using laboratory-scale column experiments. The influence of water chemistry (pH, ionic strength (IS) and cation type (Na+, Ca2+, or Mg2+)) and particle coating (uncoated (bare) and poly(acrylic acid) (PAA)-coated ENMs) on particle deposition was examined in quartz sand or loamy sand-packed columns. Select particle transport studies in natural groundwater were also conducted, and PAA-coated metal oxide transport was compared to that of an analogous nanosized PAA polymeric capsule (nCAP). All ENM suspensions were characterized over a range of environmentally relevant water chemistries using dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) to establish aggregate size and laser Doppler velocimetry to determine particle surface potential. To investigate aggregate morphology, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images were obtained under select conditions. Overall, bare ENMs exhibited high retention within water-saturated quartz sand-packed columns at NaNO3 solution IS as low as 0.1 mM for nTiO2 and 0.01 mM for nZnO. Furthermore, bare nTiO2 was found to exhibit extensive aggregation, regardless of pH and IS. At lower salt concentrations, the particle attachment efficiency (α) for the nTiO2 aggregates onto quartz sand increased with increasing IS. At higher IS, α (pH 7) > α (pH 3) > α (pH 9), likely due to enhanced particle aggregation at pH 7 and subsequent physical straining within the granular matrix. Bare nTiO2 and nZnO displayed dynamic (time-dependent) deposition behaviors under selected conditions. In contrast, PAA-coated nTiO2 and nZnO were less prone to aggregation and exhibited significant transport potential at IS as high as 100 mM NaNO3 or 3 mM CaCl2. Likewise, PAA-coated nCeO2 particles suspended in NaNO3 were highly mobile in quartz sand-packed columns. Nonetheless, heightened nCeO2 and nCAP particle retention and dynamic transport behavior was observed with increasing divalent salt concentrations and in natural groundwater. Moreover, enhanced particle retention was encountered in loamy sand in comparison to quartz sand. Finally, the nCAPs proved to be a good surrogate particle for the PAA-coated nCeO2. These findings illustrate the importance of considering the extent and type of particle surface modification when investigating metal oxide contamination potential in granular aquatic environments. Furthermore, the results obtained emphasize the need to consider the nature of the granular medium, along with the water chemistry, when evaluating ENM contamination risks.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».