Synthetic reference sampling target for the estimation of measurement uncertainty

The concept of constructing a synthetic reference sampling target (RST), for the purpose of estimating bias and uncertainty caused by the process of sampling, has been shown to be feasible. An example of an RST has been prepared for measuring the concentration of contaminants, and delineating their spatial extent in 'hot spots', in contaminated land investigations. A circular hot spot was prepared by spiking a defined volume of top soil with barium sulfate in a previously 'clean' site in Ascot, UK. The assigned values for the concentration and spatial distribution of the contamination were based largely on the mass and position of the spike added to the site. These values were corroborated and refined by thorough sampling of the whole RST and of the hot spot in detail. The temporal stability and heterogeneity of the RST were tested and found to be acceptable for the intended use of the RST. The use of the site for inter-organisational sampling trials to estimate measurement uncertainty will be reported in subsequent papers.