DISTRIBUTION OF HEAVY METALS IN SURFACE SEDIMENTS OF NORTHWESTERN SOUTH CHINA SEA AND POLLUTION ASSESSMENT

A total of 385 surface sediment samples were collected during the period of 2006-2011 from the northwestern SCS for investigation of heavy metal distribution pattern and assessment of pollution status. Heavy metals, such as Cu, Pb, Zn and Cr were selected as major indicators. The total and average concentrations (in mg·kg^-1 for dry weight)of the elements change in ranges as follows:Zn:16 to 281(average 83.2); Cr:14.9 to 175(average 64.68); Cu:2.25 to 77.6 (average 20.10) and Pb:2.96 to 218(average 19.60). Positive correlations obviously occur between Cu-Zn, Cu-Sc, and Zn-Sc,as well as between Cu、Zn、Sc and OrgC,Al₂O₃, and mean grain size, while negative correlation between Cr-OrgC and between Cr-mean grain size. Enrichment factors (EF) and geoaccumulation indexes (Igeo) suggest that Pb, Cr contamination exist only in few restricted areas, such as the area near the coast and parts of shelf area. No Cu and Zn contamination has been discovered in the study area.