Trace the sample's path
Compare the sample identifier in the sampling record, on the packaging and in the laboratory test report. It must be clear who collected the material, where and when, how it was stored and how it was transferred. A mismatch between identifiers does not always make the examination useless, but requires an explanation before the result is interpreted.
Consider the area and the timing
Assessing a proposed source requires consideration of the location of the suspected impact, background areas and changes in conditions. A sample from one location does not automatically describe the entire area. Data obtained after soil removal or precipitation may relate to conditions that have already changed.
Separate the parameter from the proposed cause
The expert compares test results with the characteristics of possible sources, documents and the spatial distribution of the observed features. A match in a single component does not in itself explain how it arrived. It is also necessary to determine which question the methods used answer and what they cannot establish.
What to prepare
- Test reports with all appendices.
- Sampling records and a plan showing the sampling locations.
- Sample identifiers and documents recording transfer to the laboratory.
- A description of the condition of the area and known changes.
- Information on suspected sources and the period of the impact.
What to bear in mind
The result from a single sample must not be extended to unexamined areas or used as standalone proof of a particular source. The plan for further examinations depends on the task and site conditions.
Outcome of preliminary preparation
Checking the initial set of materials helps determine which conclusions the data already supports and where additional information, repeat sampling or a specialist laboratory is needed.
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