A preliminary study of heavy metal contamination in Yangtze River intertidal zone due to urbanization

Three short sediment cores (<20 cm) were collected in the high, middle and low tidal flats in the Yangtze River Estuary near the Southern (Nanqu) Sewage Outlet, one of the three largest sewage outlets in Shanghai, China. All samples were analyzed for Al, Cu, Pb, Zn, ²¹⁰Pb and ⁷Be. The ²¹⁰Pb _xs profile shows a non-steady-state sedimentation pattern in the study area and ⁷Be is only found in the upper 1 cm layer of sediment in high and middle tidal flats. In this study, we found that Cu, Pb and Zn contaminants are present in the upper 20 cm of the tidal flat sediment and, after normalizing with Al, the contamination is more striking in the upper ∼5 cm sediment. Relationships between the metal (Cu, Pb and Zn) enrichment factor and ²¹⁰Pb _xs activity suggest that contamination increases with time. Factor analyses shows that differences in sediment grain size have insignificant effects on Cu and Pb concentrations, but have some influence on Zn concentration in the study area. This preliminary study shows that urbanization and recent coastal wetland reclamation have had an environmental impact on this area.