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Heavy Metal Sources and Associated Risk in Response to Rapid Urbanization in Surface Sediments of Shantou Bay, South China

Shantou Bay in China is a good example of a site where human pressures and ecological values collide with each other. Twenty eight sediment samples collected from the bay were analyzed for grain size and geochemistry to reveal geochemical sources of selected metals and geochemical processes influencing their distribution, and to assess their enrichment and pollution in the sediments. Results showed that heavy metal concentrations in surface sediments varied from 0.7 mg/kg for Cd to 604.3 mg/kg for Mn. Four geochemical sources were identified as river input, runoff from city, sewage discharge and port pollution by the correlation analysis and principal component analysis. Hydrodynamic condition and input sources are major factors controlling the regional distribution of metals, reflected by a seaward decreasing pattern with some hotspots at the vicinity of river mouths and sewage outlets. Enrichment Factors reveal the anthropogenic sources for Cd, Cu, Zn and Pb. It is supported by the Geo-accumulation Index. The majority of the sediment samples can be occasionally and frequently associated to toxic biological effects, according to the effect-range classification for Cd, Cu, Pb and Zn.