Spatial and temporal distributions of nitrogen, phosphorus and heavy metals in the intertidal sediment of the Chang jiang River Estuary in China

Spatial and temporal distributions of nutrients （N and P） and heavy metals （Cu, Zn, Pb and Cd） in the intertidal sediments at Dongtan wetland of the Changjiang River （Yangtze River） Estuary were examined by laying one transect running seaward to landward during January, April, June, August and October of 2005. Total nitrogen （TN） and heavy metal concentrations in the intertidal sediment showed an increasing trend from open bare flat to the high marsh, with the maximum concentrations in the high marsh and the minimum values in open bare flat. In contrast, sediment total phosphorus （TP） concentrations changed little among sampling sites. One-way ANOVA found that there were significantly temporal variations of nutrients and heavy metals concentrations in the intertidal sediment （P 〈0.05）. The concentrations of heavy metals generally showed an increasing trend from January to October. As compared with other large estuaries, heavy metal contamination in the intertidal sediment of the Changjiang River Estuary was relatively low.