Soil samples collected in urban areas throughout the UK are analysed for their major and trace element geochemistry, their pH and organic matter content. Samples are collected at two depths; 0-15cm and 35-45cm at sites selected using a stratified, random design. The data can be used to identify and prioritize contaminated sites. In 1993, the Geochemical Baseline Survey Of The Environm (G-BASE) rural geochemical mapping programme was extended to include sampling in urban areas and to date around 22 urban centres have been sampled. Data is available on key inorganic contaminants including Cr, Cu, Cd, Ni, As, Pb, Zn, Sn and Sb. Results have been standardised to ensure seamless joins between geochemical sampling campaigns. Urban centres are selected in areas where rural sampling is undertaken or where the BGS urban programme is active. Urban centres will continue to be sampled until completion of the rural programme, scheduled for 2015.

[This metadata record has been superseded, see http://data.bgs.ac.uk/id/dataHolding/13480412].The G-BASE programme involves systematic sampling and the determination of chemical elements in samples of stream sediment, stream water and soil, to build up a picture of the surface chemistry of the UK. G-BASE for SW England is the most recent area of the UK sampled by this on-going project The average sample density for stream sediments is approximately one site per 2km square. Density for soils in SW England is variable across the area, ranging from 1 per 2km square to one per 5km square, depending on underlying parent material. Analytical precision is high with strict quality control to ensure countrywide consistency. Results have been standardised to ensure continuity with existing G-BASE geochemical data. The data provide baseline information on the natural abundances of elements, against which anomalous values due to such factors as mineralisation and industrial contamination may be compared. Analytical data for the sub150 microns fraction of stream sediment and the sub 2mm fraction of soil samples are available for some or all of: Ag, Al, As, Ba, Bi, Br, Ca, Cd, Ce, Cl, Co, Cr, Cs, Cu, Fe, Ga, Ge, Hf, I, In, K, La, Mg, Mn, Mo, Na, Nb, Nd, Ni, P, Pb, Rb, S, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Te, Th, Ti, Tl, U, V, W, Y, Yb, Zn, and Zr.

The Estimated Urban Soil Chemistry data are derived by spatial interpolation of the Measured Urban Soil Chemistry data. A unique feature of this dataset is the inclusion for the first time of estimated bioaccessible arsenic and lead data. The Estimated Urban Soil Chemistry data indicates the estimated geometric mean concentrations (mg kg-1) of Arsenic, Cadmium, Chromium, Nickel and Lead in topsoil derived by spatial interpolation of the Measured Urban Soil Chemistry data. Estimated bioaccessible As and Pb concentrations are derived using linear regression models of the relationship between total and bioaccessible concentrations. The Estimated Urban Soil Chemistry data can be used to assist Local Planning Authorities to identify those areas where a risk assessment may need to be carried out by developers. Comparison of this spatially referenced geochemical data with information on current or historic land use and geological information might help environmental professionals decide whether high potentially harmful element (PHE) concentrations in topsoils can be attributed to geogenic or anthropogenic sources. The dataset is based on, and limited to, an interpretation of the records in the possession of the BGS at the time the dataset was created. This dataset consists of two shape files Estimated Urban Soil Chemistry (As, Cr, Ni) and Estimated Urban Soil Chemistry (Cd, Pb).

The BGS digital estimated urban soil chemistry data (GB_EstimatedUrbanSoilChemistry_v3) indicates the estimated geometric mean concentrations (mg kg-1) of Arsenic (As), Cadmium (Cd), Chromium (Cr), Nickel (Ni) and Lead (Pb) in topsoil derived by spatial interpolation of the point source urban soil chemistry data. The information is relevant for the first stage of any assessment of risks to human health required by regulatory authorities in relation to land use and also assessing ecological risks. Estimated topsoil PHE (Potentially Harmful Element) concentrations above respective SGVs (Soil Guideline Value) do not necessarily imply a significant health risk but they do highlight the need to consider whether or not there may be a risk. Comparison of this spatially referenced geochemical data set with information on current or historic land use and geological information might help environmental professionals decide whether high PHE concentrations in topsoils can be attributed to geogenic or anthropogenic sources. The dataset is based on, and limited to, an interpretation of the records in the possession of the BGS at the time the dataset was created. An indication of high estimated PHE concentrations in soil does not necessarily mean that an individual site will have a high PHE concentration. Topsoil concentrations in urban areas are frequently characterised by strong spatial variation over short distances so this data should be interpreted and used with caution. The original urban topsoil samples were collected and analysed as part of the BGS Geochemical Baseline Survey of the Environment (G-BASE) project.

The BGS digital Measured Urban Soil Chemistry data comprises the locations and concentrations (mg kg-1) of Arsenic (As), Cadmium (Cd), Chromium (Cr), Nickel (Ni) and Lead (Pb) in urban topsoil samples. The data is derived from the national, high resolution urban soil geochemical data from the BGS Geochemical Baseline Survey of the Environment (G-BASE) project. The information is relevant for the first stage of any assessment of risks to human health required by regulatory authorities in relation to land use and also for assessing ecological risk. Although point source PHE (Potentially Harmful Element) concentrations above respective SGVs (Soil Guideline Value) do not necessarily imply a significant health risk, they do highlight the need to consider whether or not there may be a risk. The urban soil chemistry data can be used to assist Local Planning Authorities to identify those areas where a risk assessment may need to be carried out by developers. Comparison of this spatially referenced geochemical data with information on current or historic land use and geological information might help environmental professionals decide whether high PHE concentrations in topsoils can be attributed to geogenic or anthropogenic sources. The point source data is based on an interpretation of the records in the possession of the BGS at the time the dataset was created.

This dataset has now been superseded, please see the Estimated Ambient Background Soil Chemistry Scotland dataset. The BGS digital soil chemistry data indicates the estimated geometric mean concentrations (mg kg-1) of Arsenic (As), Cadmium (Cd), Chromium (Cr), Nickel (Ni) and Lead (Pb) in surface soil. The soil chemistry data is based on GBASE (Geochemical Baseline Survey of the Environment) soil geochemical data where these are available. Elsewhere the stream sediment data are converted to surface soil equivalent potentially harmful element(PHE) concentrations. This dataset covers Scotland but data is available for the whole of Great Britain, with the exception of the London area where an inadequate number of geochemical samples are available at the moment.

This dataset has now been superseded, please see the Estimated Ambient Background Soil Chemistry England and Wales dataset. This dataset indicates the estimated topsoil Arsenic(As), Cadmium (Cd), Cr (Chromium), Nickel (Ni) and Lead (Pb) concentrations (mg kg-1) derived by spatial interpolation of the point source urban soil PHE (potentially harmful elements) data. Urban soil geochemical data generally have large positive skewness coefficients so were transformed by taking natural logarithms. To overcome the bias associated with traditional measures of location (mean) and scale (standard deviation) for log-normal data, the inverse distance weighted (IDW) mean and standard deviation of log transformed element concentrations were used for mapping the spatial variation in As, Cd, Cr, Ni and Pb concentrations. The soil chemistry data is based on GBASE (Geochemical Baseline Survey of the Environment) soil geochemical data where these are available. Elsewhere the stream sediment data are converted to surface soil equivalent potentially harmful element(PHE) concentrations. This dataset covers England and Wales but data is available for the whole of Great Britain, with the exception of the London area where an inadequate number of geochemical samples are available at the moment.

This dataset has now been superseded, please see the Measured Urban Soil Chemistry dataset. The BGS digital point source urban soil chemistry data (GB_PointSourceUrbanSoilPHE_v1) comprises the locations and concentrations (mg kg-1) of Arsenic (As), Cadmium (Cd), Chromium (Cr), Nickel (Ni) and Lead (Pb) in urban topsoil samples. The data is derived from the national, high resolution urban soil geochemical data from the BGS Geochemical Baseline Survey of the Environment (G-BASE) project. The information is relevant for the first stage of any assessment of risks to human health required by regulatory authorities in relation to land use and also for assessing ecological risk. Although point source PHE (Potentially Harmful Element) concentrations above respective SGVs (Soil Guideline Value) do not necessarily imply a significant health risk, they do highlight the need to consider whether or not there may be a risk. The urban soil chemistry data can be used to assist Local Planning Authorities to identify those areas where a risk assessment may need to be carried out by developers. Comparison of this spatially referenced geochemical data with information on current or historic land use and geological information might help environmental professionals decide whether high PHE concentrations in topsoils can be attributed to geogenic or anthropogenic sources. The point source data is based on an interpretation of the records in the possession of the BGS at the time the dataset was created.

This dataset has now been superseded, please see the Estimated Urban Soil Chemistry dataset. There are two themes to BGS urban soil chemistry, the point source dataset and the estimated dataset. The point source urban soil chemistry data comprises the locations and concentrations (mg kg-1) of Arsenic (As). Cadmium (Cd), Chromium (Cr), Nickel (Ni) and Lead (Pb) in urban topsoil samples. The Estimated Urban Soil Chemistry data indicates the estimated geometric mean concentrations (mg kg-1) of As, Cd, Cr, Ni and Pb in topsoil derived by spatial interpolation of the Point Source Urban Soil Chemistry data. Both urban soil chemistry datasets are derived from high resolution urban soil geochemical data from the BGS Geochemical Baseline Survey of the Environment (G-BASE) project. The Urban Soil Chemistry data can be used to assist Local Planning Authorities to identify those areas where a risk assessment may need to be carried out by developers. Comparison of this spatially referenced geochemical data with information on current or historic land use and geological information might help environmental professionals decide whether high PHE concentrations in topsoils can be attributed to geogenic or anthropogenic sources. The dataset is based on, and limited to, an interpretation of the records in the possession of the BGS at the time the dataset was created.

The BGS Geochemical Baseline Survey of the Environment (G-BASE) was the national strategic geochemical mapping programme in Great Britain. The project set out to establish 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. The routine collection of regional soil samples was introduced in 1986 in areas of poor drainage density, with an average sample density of one site per 2 square kilometres. Urban soil sampling commenced in 1991, with an average density of four samples per square kilometres, for the urban areas of Belfast, Cardiff, Corby, Coventry, Derby, Doncaster, Glasgow, Hull, Ipswich, Leicester, Lincoln, Manchester, Mansfield, Northampton, Nottingham, Peterborough, Scunthorpe, Sheffield, Swansea, Stoke, Telford, Wolverhampton and York. Topsoil samples were collected between depths of 5 cm and 20 cm, and were sieved through a 2 mm mesh and milled to less than 150 microns. The data include XRF and direct-reading optical emission spectrometry (DR-OES) analyses for some or all of the following elements: Ag, As, Ba, Bi, Br, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, Hf, I, K, La, Mg, Mn, Mo, Nb, Ni, P, Pb, Rb, Sb, Sc, Se, Se, Sn, Sr, Ta, Te, Th, Ti, Tl, U, V, W, Y, Zn and Zr. Loss on Ignition (LOI) and pH (in a slurry of 0.01 M CaCl2) were also routinely determined on 50% of regional and all urban samples. For more information about accessing these samples and their analytical results, contact BGS Enquiries (enquries@bgs.ac.uk).