KINETICS OF 2,4-DICHLOROPHENOXYACETIC ACID (2,4-D) ADSORPTION BY METAL OXIDES, METAL OXIDE–HUMIC COMPLEXES, AND HUMIC ACID
Why this work is in the frame
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Bibliographic record
Abstract
Metal oxides and humic substances have a large and physicochemically active surface area and thus provide a major sink for the retention of pesticides. Although organic and inorganic components are closely associated in soil, the kinetics of 2,4-D adsorption by metal oxide–humic complexes in comparison with metal oxides and humic acid (HA) remains obscure. In the present study, the kinetics of 14C-labeled 2,4-D adsorption by Al, Fe, and Mn oxides, the metal oxide–humic complexes that were formed in metal oxide–catechol systems, and the standard soil HA from the International Humic Substances Society were investigated. The results show that the amounts and rate of 2,4-D adsorption greatly varied with the type and the surface properties of the metal oxides. The 2,4-D adsorption by the metal oxides, metal oxide–humic complexes, and HA can be described by multiple 1st-order kinetic models (the fast and slow reactions) and the rate-limiting step of 2,4-D adsorption was a diffusion process as indicated by their activation energy values, which ranged from 16.6 to 25.9 kJ mol−1. The complexation of humic macromolecules with the metal oxides substantially reduced the amount and the rate of 2,4-D adsorption as the result of the resultant alteration of the surface properties. The specific surface of the Al oxide–, Fe oxide–, and Mn oxide–humic complexes, respectively, decreased by 49, 92, and 66%, compared with the metal oxides. The rate coefficients of the fast reaction of 2,4-D adsorption by metal oxides were 2.2 to 3.1 times higher than the respective metal oxide–humic complexes. Humic acid had a much lower reactivity than the metal oxides and a similar reactivity with the metal oxide-humic complexes to 2,4-D. The findings of this study are significant in understanding the ability of soil components to bind the pesticide such as 2,4-D, as influenced by catechol polymerization and the impact on the transformations and degradation of the pesticide in soil environments.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.004 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| 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 it