Regional Geochemistry

Sampling pair on the move

The Geochemical Baseline Survey of the Environment (G-BASE) project sets out to map and establish the natural geochemical baseline of the British Isles by collecting stream sediment, water, soil and more recently vegetation samples (at drainage sites) throughout the UK.

The regional geochemical baseline data is important in order to understand our environment and to measure changes, whether they be natural or man-made. This baseline data of the surface environment also allows us to model the migration of elements and provides a reference point against which we can monitor change.

For further reading and more detailed information download our G-BASE booklet or field procedures manual or publication by Johnson et al. (2005)

Stream sediment geochemistry

Sieving of stream sediment

Stream sediments are our primary sample media and have been collected strategically since the beginning of the project in 1968. The project has covered the UK landmass as far as the River Thames at an average drainage density of 1 site per 1.5 to 2 km sq. The sediment is collected from the centre of the stream and is sieved through two sieves to a grain size less than 150 µm. Excess material from the < 2mm fraction is panned to collect a heavy mineral concentrate.

Details on the sampling procedures are described in a field procedures manual – to find a copy, please go to downloads.

A selection of regional geochemical maps of elements Ba, Cu, Fe, K, Mg, Mn, Ni, Pb, U, V and Zn in stream sediments are listed below.

Download the Distribution of G-BASE stream sediments UK map




Water geochemistry

Water sample measurements at field base

The project also collects water samples at each drainage site. These are collected before the stream bed has been disturbed. Four different water samples are routinely collected - two filtered waters (for major and trace elements) and two unfiltered waters (for pH, conductivity and alkalinity). Determinations on unfiltered samples are made at the field base shortly after collection. Find more details in our field manual or view and download geochemical maps of ph and conductivity in stream waters across Great Britain.

Soil geochemistry

Soil sampling

The routine collection of soil samples was introduced in 1986 and now forms part of the national capability to establish the regional geochemical baseline of the UK. Soils were introduced to the geochemical mapping programme in areas for poor drainage density and was coincident with the project working in the agriculturally important lowland areas of England. A knowledge of the natural regional soil geochemical baseline enables us to estimate the anthropogenic burden on soils in urban areas.

Soils are very important sample media and have great relevance to recent environmental and soil protection policies. The adjacent map shows the current extent of G-BASE soil sample sites in the UK, including the distribution of urban soil sample sites.

Regional geochemical data

BGS Onshore GeoIndex

Visit BGS Onshore Geoindex to search for individual soil sample location of the urban areas sampled so far. Make sure the map theme is set to Geochemistry (top right hand corner) and one or all of the sample media are selected in the left hand panel.

Alternatively go to G-BASE enquiries for data sales and products.

Picture gallery of recent regional sampling campaign