Source identification and ecological risk assessment of heavy metals in topsoil using environmental geochemical mapping: Typical urban renewal area in Beijing, China

• High-density geochemical mapping of heavy metals in soils was performed.
• Potential ecological risk was quantitatively estimated and mapped.
• Multivariate geostatistical analysis was used to identify the sources.
• Chemical industry activities led to Cu, Pb, Cd, Zn and Hg contamination.

Environmental geochemical mapping with high-density soil sampling was conducted to determine the spatial distribution, possible sources and potential ecological risk of heavy metals at a former chemical industry area in Beijing. A total of 550 surface soil samples were collected and the concentrations of heavy metals, such as Ni, Cr, V, As, Cu, Pb, Cd, Zn and Hg, were analyzed. The spatial distribution characteristics of these metals were demonstrated by environmental geochemical mapping. Enrichment factors show that the soil concentrations of Cu, Pb, Cd, Zn and especially Hg were higher than the background values. Multivariate geostatistical analyses suggested that Cu, Pb, Cd, Zn and Hg in the topsoil were strongly influenced by anthropogenic or chemical industry activities while Ni, As, V and Cr mainly originated from the natural parent materials of the soils. The potential ecological risk was quantitatively estimated for each site and the risk map was plotted for assessment. Among the metals, Cd and Hg showed a higher potential ecological risk than the others.