Geochemical baseline survey of the environment (G-BASE)

The BGS Geochemical Baseline Survey of the Environment (G-BASE) is a national geochemical mapping programme of Great Britain. The G-BASE project set out to survey the chemistry of the surface environment by the collection and analysis of stream sediment, stream water and soil samples.

Beginning in the late 1960s in northern Scotland, and moving southwards across the country, the primary focus was mineral exploration, however, the project quickly developed to address important environmental concerns. The final G-BASE samples were collected in southern England in 2014.

The outputs from the G-BASE project provide an invaluable systematic baseline of geochemical information for Great Britain, serving as a marker of the state of the environment, against which to measure future change.

Soil samples were collected by hand auger, from two depths - 5 to 20 cm (shallow soil) and 35 to 50 cm (deep soil) at an average density of 1 every 2 km² in regional environments. In urban areas, samples were collected at a higher density of 4 samples per 1 km².

Samples have been collected over large areas of England and Wales, the Clyde Basin in Scotland, and from 23 urban centres across Great Britain. From the resulting samples, geochemical data are available for over 50 inorganic analytes.

The largest urban centre sampled is London, with samples collected within the entire area of the Greater London Authority boundary. The 'London Earth' project stands as a sub-set of the overall G-BASE project.

Most recently, a series of maps presenting the shallow soil chemistry of South West England have been published.

G-BASE soil data are delivered under the terms of the Open Government Licence, subject to the following acknowledgement accompanying the reproduced BGS materials: "Contains British Geological Survey materials © [2021]".