Check the path from sampling location to result
The location plan, record, container identifiers and laboratory test report must be linked unambiguously. If identifiers do not match, the reason for the discrepancy is clarified first, rather than selecting a result that suits the proposed explanation.
Do not confuse a measurement with a causal conclusion
Detection of a substance characterises the sample submitted. Conclusions on the spread of contamination and its source may require additional sampling locations, background data, the history of activities and spatial distribution. A single concentration does not automatically determine the entire volume of affected soil.
- Consider the depth, soil horizon and heterogeneity of the site.
- Keep information on filling, repairs and other changes to the area.
- Agree on parameters and sample requirements before collection.
- Reflect missing materials in the limits of the conclusion.
Results from different periods are assessed for comparability on the basis of sampling conditions and methods. Without this check, a change in a numerical value does not always prove improvement or deterioration across the entire area.
On this subject: Why one sample does not always describe the condition of an entire site.