DISTRIBUTION OF HEAVY METALS IN SURFACE SEDIMENTS OFF YANGTZE RIVER ESTUARY AND ENVIRONMENTAL QUALITY ASSESSMENT

Heavy metals (Zn、Cr、Pb、Cu、As、Cd and Hg) of 187 surficial sediments from the outer part of the Yangtze River estuary were tested for study of their spatial distribution pattern and contamination level in this paper. Our results indicate that the contaminations of heavy metals transported by the Yangtze River are mainly deposited along the Yangtze River estuary-ZheJiang shoreline. The content of heavy metals decreases with the increase in distance from the shore. The contours are almost paralleled with the waterfront. The extent of heavy metal contamination is evaluated by Sediment Enrichment Factor (SEF) method and Total Potential Ecological Hazard method. The enrichment factor is larger than 2 in the west of 122.5°E off the Yangtze River estuary and the Zhejiang nearshore as a medium-hazardous polluted environment. The other part of the open sea remains unpolluted or in a-low polluted level with low ecological risk. The spatial distribution pattern of heavy metal contamination level is controlled by the materials from the Yangtze River and the Min-Zhe Coastal Current.