Heavy metal contamination in green space soils of Beijing, China

Abstract

ABSTRACTUrban green space soil heavy metal pollution seriously affected the lives of residents, and soil environmental quality data is important for urban planning and functional construction. In this study, the concentrations of arsenic (As), cadmium (Cd), chromium (Cr),copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), and zinc (Zn) in 148 soil samples collected from green spaces in Beijing City, China were measured. The mean concentrations were 7.60, 0.29, 50.32, 31.61, 1.53, 23.89, 29.68, and 76.53 mg/kg, respectively. With the exception of Ni, the concentrations of the seven other heavy metals were greater than their background values. Additionally, the concentration of Hg was 3.06 times greater than the Grade 2 value (0.5 mg/kg) of Environmental quality standard for soils in China (GB 15618-1995), also exceeded the limit value (1–1.5 mg/kg) for Hg in soil of European Union (86/278/EEC). Soil pollution assessment was carried out using the geoaccumulation index (Igeo), the value of Cd and Hg were 0.70 and 4.11, respectively. It suggested that, the green space soil of Beijing was slightly polluted by Cd and seriously polluted by Hg, which posed great harm to public health. A positive correlation exists between Cu and Hg, Pb, and Zn, as well as between Hg and Pb, suggesting the metals in the green space soils originated from similar sources. Multivariate statistical analysis, such as principal component analysis (PCA) and cluster analysis (CA), were adopted to identify heavy metal sources. The results suggest that the sources of heavy metals in Beijing green space soils differ. Cd, Cu, Hg, and Zn derived from vehicular transport; Cd and Cr originated from industrial activities and phosphate fertilisers; As and Ni mainly contributed by parent materials. The spatial distribution characteristics of the eight heavy metals varied greatly, and the presence of these metals was strongly associated with anthropogenic activities.