Contamination and ecological risk of heavy metals in sediments of urban rivers in a typical economic development zone, southern China

Abstract

Urban rivers are one of the main water sources for local residents. However, the rapid industrialization and urbanization caused serious heavy metals pollution in urban rivers, which posed harmful impact on human health and ecosystem. In this study, 134 sediment samples were collected from urban rivers in a typical Economic and Technological Development Zone (ETDZ) to evaluate the contamination status, ecological risk, biotoxicity, and potential source of 8 heavy metals including arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), plumbum (Pb), and zinc (Zn). Results showed that the average concentrations of all 8 metals exceeded their corresponding background values and followed the trend: Cr (248.67 mg/kg) > Pb (123.58 mg/kg) > Zn (67.06 mg/kg) > Ni (47.19 mg/kg) > Cu (27.40 mg/kg) > As (16.15 mg/kg) > Cd (0.62 mg/kg) > Hg (0.21 mg/kg). A high contamination and accumulation tendency of Cd and Cr were found in the sediments. Moreover, Cd and Hg were the main contributors of ecological risk, and posed moderate to high risk. In terms of biotoxicity, all the sediment samples were harmful to benthic organisms. Two possible pollution sources of heavy metals were identified: one is a combined source of industrial and traffic pollution dominated by Cr and Pd, the other is an industrial pollution source consisting of six heavy metals (Ni, Zn, Cd, Hg, As, and Cu). This study provides insights into heavy metals pollution management and risk control in the ETDZ and similar urban rivers worldwide due to intense industrialization.