Assessment on Heavy Metal Pollution and its Change in the Sediment of the Aquatic Culture Zone on Coastal Mudflat along the North Branch of Yangtze River Estuary

The pollution level of heavy metals in the sediment of the mudflat was investigated in aquatic culture zone along the north branch of Yangtze River estuary.The results showed that the heavy metal contents met the standardⅠof Ocean Sediment Quality Standard and the pollution belonged to the level in safe Class I,of which the potential ecological harm reached a level of light pollution.The ecological risk of heavy metals was ranked as Cd﹥Hg﹥Cu﹥Cr﹥Pb﹥As.During 2005~2011 the heavy metal pollution was under a safe level of Class I.