Rate of Cd2+ Release from Dissolved Fulvic Acid and Natural Dissolved Organic Carbon as a Function of UVB Dose
Bibliographic record
Abstract
Environmental Context. Atmospheric ozone depletion results in an increase of UVB radiation impinging on the surface waters of aquatic ecosystems. Radiative absorption by dissolved humic substances results in bleaching and photochemical decomposition to smaller molecular weight dissolved components. With respect to the lake biota, this can reduce the effectiveness of a natural absorptive protective UV screen, as well as enrich the surface waters with microbial substrates and previously bound biologically unavailable trace metals. In controlled experiments using low-level Cd-contaminated dissolved fulvic acids and natural lakewater dissolved organic carbon, we examine the relationship between increasing UV dose and cadmium free-ion (Cd2+) concentrations. Abstract. Using controlled UVB exposures in a laboratory incubator, the photolytic release of bound cadmium from cadmium-contaminated dissolved fulvic acid and cadmium-amended natural lakewater dissolved organic carbon was examined using an ion-exchange technique, developed to measure the cadmium free-ion concentration (Cd2+). In the fulvic acid experiments, with increasing UVB dose, the increasing cadmium free-ion concentration followed an exponential saturation function, whereas the decrease in dissolved organic carbon was linear. Experiments using natural lakewaters did not reveal any increase in Cd2+, even at high UVB exposures. Given the much greater dissolved iron concentration in humic natural lakewaters, relative to the fulvic acid medium, iron photoreduction and reoxidation produces fresh amorphous iron oxide surfaces. We hypothesize that these bind the cadmium free-ion, thus reducing its aqueous concentration. Depending on Cd2+ affinity to biological surfaces, this mechanism might thus competitively further protect the biota from trace metal toxicity.
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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 | 0.000 | 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) | 0.002 | 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".