Soil Geochemical Baselines in UK Urban Centres: The G‐BASE Project

Abstract

in the United Kingdom. G-BASE is a long-established systematic geochemical mapping project that is indirectly funded by the British Government through the UK Natural Environment Research Council (NERC). When sampling commenced in the late 1960s, the work was stimulated by mineral exploration and the need to assist geological mapping. The current high-resolution survey is very relevant to contemporary environmental science, and much of the current demand for baseline geochemical information relating to the surface environment is legislatively driven (Johnson et al., 2005). The early years of the G-BASE project were based entirely on rural drainage sampling, utilizing methodologies described in the regional geochemical atlas publications (e.g. BGS, 1993). Results were presented in map form in a series of hard-copy regional geochemical atlases, and little consideration was given to the urban environment. G-BASE methodologies have evolved considerably, since the mid 1970s, to meet the need for improved environmental information. The key aspects of progression include: use of a wider range of sample media, especially soils and stream waters; inclusion of, and focus on, baseline geochemistry in urban areas; continuous improvement in the range and quality of analytes reported; utilization of digital data processing and mapping methodologies and adoption of diverse publication media. Currently, approximately 88% of the British land area has been sampled by G-BASE. Sampling is carried out in the summermonths (June-September) by Earth and Environmental Sciences students during their vacation. Continuous progress has been made, sampling between 2000 and 5000 sites each summer, but resources for the project have varied according to the BGS's commitments to other projects. To date, over 105 000 stream sediments, 50 000 soils and 90 000 stream waters have been collected. A programme of baseline geochemistry in urban centres was adopted by G-BASE in 1992, when Wolverhampton became the first UK urban centre to be sampled (Bridge et al., 1997). At this time, it was acknowledged that, as the regional geochemical sampling campaign passed through * the country, urban centres should be routinely included. By 2010, a baseline geochemical survey had been completed in 26 urban centres (Figure 13.1), including Belfast and Londonderry in Northern Ireland (Nice, 2008), using standardized GBASE methodologies. The largest urban geochemical mapping exercise to be undertaken so far has been that in Greater London, known as the 'London Earth' project, where sampling was completed in 2010 (Knights and Scheib, 2010) and geochemical maps due for publication in 2011.

Modelling lead bioaccessibility in urban topsoils based on data from Glasgow, London, Northampton and Swansea, UK

“…Data for regression modelling in the Glasgow area is for the G-BASE samples reported in Broadway et al (2010) and page 7 of 35 Farmer et al, (2011) which were originally selected to provide a range of total Cr, Pb or As concentrations. Summary statistics for all the samples from the four urban areas are reported in Flight and Scheib (2011).…”

“…A significant proportion of the urban landscape in Great Britain has elevated topsoil concentrations of lead (Pb; Rawlins et al, 2005;Thums et al, 2008;Broadway et al, 2010;Farmer et al, 2011;Flight and Scheib, 2011). In a study of the background concentrations of potentially harmful elements (PHEs) in soils in England, Cave et al (2012) and Ander et al (2012) used a classification based on the ratio of built to open space to show that 4% of the land area could be classified as Urban and that systematically surveyed soil samples in this category (n=7529) had median and 95 th percentile lead concentrations of 170 mg kg -1 and 790 mg kg -1 respectively.…”

Variation in soil chemistry related to different classes and eras of urbanisation in the London area

“…Soil data for areas classified as built-up using LCM2007 land cover data in 20 other urban centres in England and Wales (Scheib and Nice, 2007;Fordyce et al, 2005;Flight and Scheib, 2011) exhibit similar or stronger enrichment in As, Cd, Cu, Pb, Sn and Zn in pre-1940 urbanised areas (OLD) compared with post-1940 urbanisation (NEW) ( Table 5). There is some variation in the OLD/NEW ratios between the urban areas but the ratios are broadly similar for most areas.…”

“…Soil samples were collected from open ground on a 500 m grid with a sample being taken as close as possible to the centre of each 500 m grid square giving a density of approximately 4 samples per km 2 (BGS, 2011;Flight and Scheib, 2011). However, the actual distribution of sample sites did not follow the systematic rule exactly in that the soil samples are, for various reasons, located relatively randomly within the 500 grid squares (Supplementary material,.…”

Geogenic signatures detectable in topsoils of urban and rural domains in the London region, UK, using parent material classified data

“…In the London urban area, soil samples were collected from open ground on a 500 m grid at a density of approximately 4 samples per km 2 (BGS, 2011;Flight and Scheib, 2011). At each site, composite samples, based on 5 sub-samples taken at the centre and four corners of a 20 m square were collected from the topsoil (5-20 cm depth).…”