Spatial distribution of trace metals in urban soils and road dusts : an example from Manchester, UK

Urban soil quality is of concern under current UK contaminated land legislation in terms of potential impacts on human health, due to the legacy of industrial, mining and waste disposal activities and the fact that soils can act as a sink for potentially harmful substances (PHS) in the urban environment. As part of the the Geochemical Baseline Survey of the Environment (G-BASE) project of the British Geological Survey (BGS), 27 UK cities have been surveyed to establish baselines and assess the quality of urban soils. The G-BASE soil geochemical dataset for Manchester forms the basis of this project. Another medium that is a likely sink for PHS in urban environments is road dust sediment (RDS). RDS forms as an accumulation of particles on pavements and road surfaces, and has been shown to be both spatially and temporally highly variable in composition, as it is more susceptible to remobilisation and transport. RDS has been documented as carrying a high loading of contaminant species, including significant amounts of trace metals. Geochemical data from both soils and RDS, despite having different properties, are essential for environmental assessment in urban areas. Although studies of PHS in RDS and soils have been published, little is known about the spatial, geochemical and mineralogical linkages between these two media. The aim of this research is to define and establish these linkages, and produce novel mineralogical data on the PHS–particulate relationships within soils and RDS.