Microbial Dissolution of Silver Jarosite: Examining Its Trace Metal Behaviour in Reduced Environments
Bibliographic record
Abstract
Iron sulfate minerals such as jarosite-group compounds (e.g., M Fe3(SO 4 ) 2 (OH) 6 ) can be of considerable environmental importance because of their ability to scavenge trace elements and thus contribute to some degree of metal cycling. Jarosite forms in low temperature hydrothermal, acidic, sulfate-rich environments often yielding a range of elemental substituted forms: plumbojarosite (M = Pb), argentojarosite (M = Ag), jarosite (M = K), natrojarosite (M = Na), hydroniumjarosite (M = H3O), and ammoniojarosite (M = NH4). Anthropogenic sources of jarosite are common in mine waste environments, most often associated with the waste products resulting from base metal recovery. Few studies have investigated the effect that dissimilatory metal reducing bacteria may have in the presence of these compounds following the onset of reducing conditions. Jarosite reactivity may differ systematically as a function of its chemical properties. For example, the incorporation of Ag in the mineral lattice may have inhibitory affects on the growth of microbial strains. In this study the reductive dissolution of argentojarosite (M = Ag) in the presence of Shewanella putrefaciens CN32 (10 9 cells ml 1 , pH 7.1) was examined. Using the silver (argento)jarosite, Ag Fe 3 (SO 4 ) 2 (OH) 6 , as a sole terminal electron acceptor we observed the reduction of structural Fe(III) and Ag(I) by CN32 through the release of Fe(II) ions to solution. Aqueous silver concentrations were below instrumental detection. Environmental SEM (ESEM) and TEM micrographs of the microbial clusters revealed the progressive heterogeneous nucleation of Ag(0) nanoparticles within cellular structures and also on adjacent mineral grains. The results of this study are the first presented for the anaerobic dissolution of silver jarosite. This has implications for understanding the processes leading to the mobility or retention of silver in mine waste and industrial landfill environments. It also provides insight into the microbial mechanisms of silver resistance and nanoparticle formation with potential applications for bioleaching and/or biotechnology.
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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 | 0.001 | 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 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".