The Geological Survey of Northern Ireland (GSNI) and the British Geological Survey (BGS) completed a regional geochemical survey of Northern Ireland's soils between 2004 and 2006. Sampling and quality control were undertaken according to the G-BASE protocol of BGS. 6,862 sites were sampled (at depths of 20 cms and 50 cms) an average of one site per 2 km2.
See https://www.opendatani.gov.uk/dataset/rural-soil-survey/resource/330e2a8f-db4e-42ec-9a66-145a5eb07c93 for methodology and detection limits.
