Measurement uncertainty arising from sampling of environmental samples.

In 2017, a new revision of the ISO/IEC 17025 standard was issued. One of the important changes is that the uncertainty arising from sampling has to be evaluated. Based on this new requirement, we evaluated the contribution of the sampling procedure to the total uncertainty budget of the high-resolution gamma-ray spectrometry of environmental soil, tap water and aerosol filter samples. We performed statistical analyses of measurements of sets of samples taken from the same target in the same general time period. The determination of sampling uncertainty was based on the evaluation of the standard deviation of the set of measurement results and the combined uncertainty budget of sample preparation and analysis. When the spatial and temporal heterogeneities are low, the sampling uncertainty is estimated to be around 5% (k = 1) for soil samples and 30-40% (k = 1) for air samples. For single tap water samples collected consecutively, sampling uncertainty does not have a significant contribution to the complete uncertainty budget.