Searching for the Origin of a Contaminant or Raw Material

The Quick Detection module, Origin Search tab, identifies the most probable geochemical source of a sample whose isotopic signature is known. It queries the IsoFind database while accounting for the transformations the material underwent between its source and the sampling point.

The Problem This Tab Solves

A contaminant is detected in a groundwater aquifer. Three industrial facilities are located upstream. The isotopic signature of the contaminant has been measured, but it does not match any known sources in the database, because the contaminant underwent partial adsorption onto soil iron oxides before reaching the aquifer, shifting its signature by approximately +0.3‰ relative to the initial emission.

Without correcting this shift, a direct database search returns no match. Using the AMD (acid mine drainage) workflow in the Quick Detection module, IsoFind reverses the adsorption process, recalculates the probable emission signature, and identifies the source compatible at 1-sigma.

This scenario (a signature transformed between the source and the measurement point) is the most common situation in environmental, industrial, and forensic studies. This is precisely what this tab is designed to handle.

Why Use Stable Isotopes to Trace an Origin

Every raw material, every deposit, every industrial process produces a characteristic isotopic signature. This signature is stable over time and resistant to moderate dilution. Two antimony deposits located 500 km apart systematically produce ores whose δ¹²³Sb/¹²¹Sb values differ by 0.1 to 0.4‰, a difference measurable with precision.

Unlike conventional chemical analyses (ICP-MS, XRF), isotopic ratios do not measure a concentration but a ratio that does not change upon dilution. A metal smelted and then diluted into an alloy retains the isotopic signature of the original ore. A pollutant diluted a thousandfold in a river retains its isotopic ratio intact. This is what makes isotopic tracing applicable to situations where elemental analyses are ineffective.

Accessing the Tab

The Quick Detection module is accessible from the IsoFind main menu.

The interface is divided into three panels. The left panel collects the signature of the sample to be analysed. The central panel allows selecting a geochemical transformation template. The right panel displays the matches found in the database, ranked by sigma distance.

Step-by-Step Workflow

1. Enter the Isotopic Signature of the Sample In the left panel, enter the tracer element (e.g. Sb), the measured ratio (e.g. 123Sb/121Sb), the δ value in ‰ and its analytical uncertainty at 2σ. For antimony, use the NIST SRM 3102a standard as the reference, which is used for all data in the IsoFind database. Multiple tracers can be entered simultaneously via the Add a Tracer button: each additional tracer strengthens discrimination between candidate sources.
2. Select the Signature from the Database (Optional) If the sample is already registered in the IsoFind database, switch to the From Database tab and search for its name. The signature is filled in automatically. When a sample has multiple isotopic measurements, a tracer selector allows choosing which ratio to use.
3. Choose a Transformation Template In the central panel, select the geochemical scenario best suited to the study context. The template represents the processes the material underwent between its source and the sampling point. IsoFind applies these fractionations in reverse to recover the probable emission signature.
   
   No known transformation? Select None for a direct search without correction.
   Custom scenario? Use Custom to enter your own steps, or My Workflows to load an existing Nexus workflow.
4. Adjust the Sigma Threshold The sigma threshold determines the stringency of the matching filter. At 2-sigma (95%), only sources compatible within 2 times the combined uncertainty are returned. At 3-sigma (99.7%), the filter is broader. For an exploratory study, start at 3-sigma.
5. Run the Search Click Run Search. IsoFind applies the inverse fractionation chain to the measured signature, then queries the database and returns sources ranked by increasing sigma distance.

Available Templates

Each template encodes a realistic geochemical scenario. The choice of template is the most important step: it determines which transformation is reversed to recover the source signature.

Reading the Results

The results panel displays the list of candidate sources ranked by sigma distance. Each result shows the sample name and type, the reference δ value, the sigma distance relative to the corrected signature, and the GPS location if available.

The geographic map at the bottom of the results panel positions candidate sources on a world map. This visualisation makes it easy to identify whether matches are concentrated in a particular region, or whether they are dispersed, which may indicate a representativeness issue in the database for the studied area.

Practical Case: Antimony Contamination, Oruro Basin (Bolivia)

A river water sample collected 8 km downstream from a mining area shows δ¹²³Sb/¹²¹Sb = +0.764‰ ± 0.028. The value is significantly higher than those of stibnite ores known in the database (+0.40 to +0.47‰). The hypothesis is that antimony underwent partial adsorption onto soil iron oxides between emission and the sampling point (ε_adsorption ≈ +0.34‰ for this type of system).

Configuration in the Quick Detection module:

• Element: Sb, ratio: 123Sb/121Sb, δ = +0.764‰, uncertainty = 0.028
• Template: Fluvial Tracing / Sediments
• Threshold: 3-sigma

Result: after reversing the adsorption process, the corrected signature is +0.424‰ ± 0.043. All three Bolivian ores in the database (Oruro, Potosí, Huanuni) appear within 1σ. The most probable source is identified as the Oruro district, consistent with the watershed geography.

Exporting and Citing Results

Once the search is complete, the Export Report button generates a self-contained HTML file with all results, parameters used, the corrected signature, and the list of matches. This file can be attached to an expert report or archived with project data.

The Export LIMS JSON button produces a structured file compatible with laboratory management systems, including complete analysis traceability (engine version, template parameters, timestamp).

Going Further

For a scenario with several mixed sources contributing to the measured signal, see the Multi-Source Unmixing. To verify whether a material genuinely has the geographic origin declared by its supplier, see the Counterfeit Detection. For full modelling with geochemical conditions, ML and mass balance, see the Workflow Nexus.