The present study clearly showed that the sediment in Nansha mangrove was severely contaminated with heavy metals. More importantly,the ecological risk of heavy metals was very high, largely due to Cd contamination. Such a high contamination can be related to high silt and clay contents of sediment (ca.45%intotal), which have a higher affinity to bind to heavy metals However,it is more likely that anthropogenic in puts,such as discharge of industrial and domestic sewage, combined with the effect of river flow,were