A comprehensive assessment of anthropogenic impacts, contamination, and ecological risks of toxic elements in sediments of urban rivers: A case study in Qingdao, East China

Urban river sediments usually serve as a sink for potentially toxic elements (PTEs) during the process of urbanization. A systematic evaluation of human influence, contamination, and risk assessment of PTEs in urban river sediments is essential for sustaining river health. In this study, 24 sediment samples were collected from 5 rivers in Qingdao, a coastal urbanized city in East China. Zinc had the highest concentration (141 ± 134 mg/kg), followed by Cr, Cu, Pb, Ni, Co, As, and Cd. Generally, the PTE concentrations were higher in eastern rivers than those in western rivers affected by intensive industrialization and urbanization. The principal component analysis identified three principal components: natural origins (As, Co, Cr, and Ni), urban activities (Cd, Cu, Pb, and Zn), and atmospheric deposition (Pb), respectively. The excessive concentrations of Cd and Pb were frequently appeared in the sampling sites, with the anthropogenic contribution rates of 8.4%–77% and 6.6%–87%, respectively. Additionally, the river sediments experienced moderate contamination of As, Cd, Cu, Pb, and Zn. Among the PTEs, Cd had moderate ecological risk and others had low risk. The results of Monte Carlo simulation were generally in accordance with the detected contamination and risk levels, except for several elements (Cu and Zn) with huge spatial heterogeneity. According to the Monte Carlo simulation, the river sediments could undergo extremely high contamination and high ecological risk of the PTEs in the worst situation. Thus, it becomes essential that PTEs in the urban rivers should not be overlooked before their discharge into the sea.