Technical Guidance Sheet (TGS) on normal levels of contaminants in English soils : supplementary information : mercury (Hg) : technical guidance sheet supplementary information THS07s, July 2012

Relative to other inorganic contaminants, there is a paucity of data for Hg in the topsoils of England. This is because the analytical method used to determine total inorganic element concentration for systematic soil surveys (X-ray fluorescence spectrometry, XRFS) is not suitable to determine the low levels of Hg found in most soils. Sample preparation also requires precautions that prevent volatile Hg being lost at high temperatures. The results used for Hg domain attribution are discussed by Ander et al. (2012) and summarised in Table 1. There is an inherent problem in that, other than the Soil Herbage Survey rural data, surveys have targeted specific geographical areas and/or land uses. It is therefore very difficult to establish the extent to which systematic bias arising from sample collection, preparation, digestion and analytical methods contribute to the apparent difference between these data sources. Although Hg was determined on both phases of NSI original samples, the method had a relatively high detection limit (0.1 mg/kg), with over 50% of the data falling below that detection limit, and the remainder of the data being reported to only one significant figure; these data were thus not used.