Chemical partitioning of heavy metal contaminants in sediments of the Pearl River Estuary

Sequential extraction was used to study the operationally determined chemic al forms of four heavy metals (Zn, Cu, Ni and Co) and their spatial distrib ution in the sediments of the Pearl River Estuary. It was found that the re sidual fraction was the most important phase for the four metals in these s ediments. Among non-residual fractions, Zn, Ni and Co were mainly associate d with the Fe-Mn oxide fraction while Cu was associated with the organic fr action. The Zn bound to the Fe-Mn oxide fraction had significant relationsh ips with reducible Mn and reducible Fe concentrations (Fe-Mn oxides), sugge sting that Fe-Mn oxides may be the main carriers of Zn from the fluvial env ironment to the marine body. There was a significant relationship between C u bound to the organic fraction and sediment organic contents. The Zn bound to the Fe-Mn oxide fraction and Cu bound to the organic fraction showed ge neral distinctive decrease from the west side to the east side of the estua ry, and from upstream in the north to the sea in the south. This was in the same trend with the total Zn and Cu concentrations in these sediments. The results may reflect the anthropogenic inputs of heavy metals to the top se diments from recent rapid industrial development and urbanisation in the su rrounding area.