Chemical analysis in the field by x-ray fluorescence spectroscopy, an example from the Lac Dasserat study, Quebec
Bibliographic record
Abstract
Two types of X-ray fluorescence (XRF) spectrometers were deployed on site to analyse stream and lake surface waters as well as lake sediment chemistry. Water and sediment samples were collected downstream of the abandoned Aldermac VMS mine, 15 km west of Rouyn-Noranda, Quebec. The goals of the study are to identify the spatial and temporal extent of metal contamination as a result of decades of acid mine drainage from the Aldermac site and to evaluate and compare rapid data collection in the field by XRF with laboratory-based inductively coupled plasma mass spectrometry (ICP-MS) for Cu, Zn and Mn. Water chemistry was determined by a Bruker S2 PICOFOX total reflection X-ray fluorescence (TXRF) spectrometer from filtered and acidified samples spiked with Ga as an internal standard. The instrument demonstrated high accuracy for the certified reference material (CRM), TMDA-51.3. Data obtained for Cu, Zn and Mn concentrations were within acceptable limits of the certified values. Analytical results by ICP-MS of lake and stream samples showed excellent correlation (r2 > 0.99) with field analysis by TXRF for the three metals. Lake sediment geochemistry was determined by a handheld Olympus Innov-X Delta Premium DP-4000 X-ray fluorescence spectrometer. Sample preparation in the field included drying and reducing samples to a powder. High accuracy of analytical results was obtained using CRM LKSD-1 for Cu, Zn and Mn. Comparison of Cu, Zn and Mn concentrations determined by handheld XRF with ICP-MS analyses of aqua-regia and four-acid digestions of sediment samples also yielded excellent correlations (r2 > 0.98). Results suggest that TXRF analysis of surface waters and handheld XRF analysis of lake sediments provide practical and accurate diagnostic tools for rapid field analysis of Cu, Zn and Mn concentrations. Overnight results allowed quick testing of scientific hypotheses (e.g., contaminant flowpaths, locations of potential control sites) without waiting for laboratory results (e.g., by ICP). Rapid data acquisition also provided guidance for and optimization of daily sampling strategies during field work. Rapid field-based analytical results from XRF spectrometry have the potential to provide efficiencies for environmental risk assessments conducted by industrial project proponents and environmental consultants.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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".