Spatial Distribution of Heavy Metals and Associated Risks in Sediment of the Urban River Flowing into the Pearl River Estuary, China

Twenty-eight transects in six urban rivers located in the Qianhai area of Baoan District, Shenzhen, China, were selected to study the contamination of heavy metals in its sediment, reveal the spatial distribution of heavy metals in these rivers, and assess the ecological risk of heavy metals in the urban river sediment. The result showed that the concentration of heavy metals displayed considerable variation in the study area. The results showed that southern airport drainage river had exposure to high concentrations of Cu, Nanchang Chung exposure to high concentrations of Zn, Cr, and Pb, Gongle Chung exposure to high concentrations of Ni, and Xixiang River exposure to high concentrations of Hg. The results of correlation analysis and cluster analysis indicated that Cu had significant correlations with Zn and Cr respectively (P < 0.05). There was significant correlation, and the same cluster existed among Zn, Cr, and Pb (P < 0.01), whereas Hg was not significantly correlated with other metals. The potential risk of the six rivers could be sorted as Gushu Chung < Gongle Chung < Tiegang reservoir flood discharge river < Xixiang River (a), Nanchang Chung < and Southern Airport drainage river.