Abstract
This study was based on a geochemical soil survey of Stoke-on-Trent in the UK of 747 surface soil samples analysed for 53 elements. A subset of 50 of these soil samples were analysed for their bioaccessible As and Pb content using the Unified Barge Method. Random Forest modelling, using the total element data as predictor variables, was used to predict bioaccessible As and Pb for all 747 samples. Random Forest modelling, using inverse distance weighed predictors and bedrock and superficial geology, was also used to map both total and bioaccessible As and Pb on a 400 × 400 spatial prediction grid with a 50 m resolution. The predicted bioaccessible As ranged from ca. 1 to 8 mg/kg and the total As ca. 8 to 45 mg/kg. The bioaccessible Pb and the total Pb both covered the range ca. 16–1200 mg/kg, with the highest values for both forms of Pb showing similar spatial distributions. Predictor variable importance and information on past industry suggest that the source of both of these elements is driven by anthropogenic causes.
Highlights
Soils act as sinks and sources of potentially harmful elements (PHE), which can be associated with the underlying geology and deposition of contaminants from previous land use
When the bioaccessibility of the
The bioaccessibility maps represent an important resource for contaminated land risk assessments and land use planning and could be applied as a standard approach for urban centres
Summary
Soils act as sinks and sources of potentially harmful elements (PHE), which can be associated with the underlying geology and deposition of contaminants from previous land use. The range and distribution of past and present industrial activity provides a challenge for understanding the complex mixtures of contaminants in soils. The potential hazard to human health from reuse of this land (e.g., housing and greenspace) can be assessed by the identification and quantification of the total soil PHE content, but this can overestimate the potential hazard to human health, as it assumes that the total content will be available for uptake in the human body after accidental exposure [1,2]. To reflect solubility of soil PHE after accidental exposure, bioaccessible studies provide a physicochemical estimation of the amount of contaminant available for uptake in the body. Stoke-on-Trent is a post-industrial city in North Staffordshire, UK. The city, an amalgam of six towns (Burslem, Longton, Stoke, Tunstall, Fenton and Hanley), covers an area of 36 square miles (93 km2 ) and has a combined population of ca. 250,000 (Figure 1) [3]
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