Spatial distributions and sources of heavy metals in sediment from public park in Shanghai, the Yangtze River Delta

• We examined the spatial distribution of heavy metals in sediment from public parks in Shanghai.
• Significantly higher Cd, Cu, Pb, and Zn were found in the sediment from the central urban core area.
• The levels of Cd, Cu, Pb, and Zn showed strong associations with density of road network in Shanghai.

As one of the largest and most modern cities in China, Shanghai has experienced rapid urban expansion over the last three decades, which may cause environmental pollution. This study collected the surface sediments from 35 lakes in public parks in different areas of Shanghai and explored the relationship between heavy metals (HM; Co, Cr, Ni, Cd, Cu, Pb, and Zn) distribution and city urbanization factors. The concentrations of Co, Cr, and Ni in sediment were similar to those in background soil of shanghai, whereas the levels of Cd, Cu, Pb, and Zn were elevated. Overall, sediments from the central urban core area (CUC; inside the inner-ring highway) contained significantly higher levels of Cd, Cu, Pb, and Zn than those from the developed urban area (DDU; between the inner- and middle-ring highway), the developing urban area (DIU; between the middle- and outer-ring highway), and the suburban area (SU; outside the outer-ring highway), suggesting potentially large contributions from point sources related to human activities in the highly urbanized regions. For Co, Cr, and Ni, no significant differences of concentration and enrichment were found among different areas. The levels of Cd, Cu, Pb, and Zn showed strong associations with density of road network (R2 > 0.84) in six urban administration districts of Shanghai, quantitatively confirming that these four metals mainly originated from traffic emission. However, the percent of residential and industrial lands had no correlation with HM (Cd, Cu, Pb, and Zn) concentrations in sediment from Shanghai.

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