Contamination assessment and distribution characteristics of heavy metals in sediment core in costal zone of QiAo Island in Pearl River Estuary

Due to understand the heavy metals contamination in the Pearl River Estuary in last three decades,a 108 cm long sediment core(ZH1) was taken from the coastal zone along the Qiao Island in the Lingding Bay in the Pearl River Estuary.The subsamples sliced from the core were analyzed for concentrations of twelve trace metals and grain size.Four vertical distribution patterns of the heavy metals were identified respectively.The results showed that the grain size is not a main controlling factor for the vertical distributions of the heavy metals except some elements.TOC might be a main controlling factor.The contamination assessment on the heavy metals in the sediment core adopting Index of Geo-accumulation(Igeo) showed that Cr,V,Be,Se,Sn and Tl were unpolluted,while Cu,Ni,Pb,Zn,Cd and Co were polluted in different degrees throughout the core.It is presumed that the contaminations or enrichments of these metals might be related to gradually intensive anthropogenic activities(industrial,agricultural and domestic) in the estuary since early 1980s.In addition,hydrodynamic condition might be another important influencing factor.