Changes in heavy metal elements in the sediments from Changjiang Estuary and their environmental responses in recent 1500 years

The sediment samples of the core ZK6 taken from the coastal muddy deposits of the Yangtze Estuary are analyzed for grain-size, isotopic activities and contents of eight heavy metal elements of As, Cd, Cr, Cu, Hg, Ni, Pb, Zn by the authors. Comprehensive evaluation of the vertical variation in grain size and the heavy metal elements are carried out for the past 1500 years. Human activities and their influence on the element distribution patterns are revealed based on environment changes. The sedimentation rate of ZK6 core is 1.85cm/a on average. Both As and Cd show an increasing trend from bottom to top, while Cr a trend of gradual decrease. The contents of Cu, Hg, Pb, Ni and Zn elements show a decrease trend in the beginning and turn to increase later on. In addition to Cr, several other elements significantly increase from 2m upwards. The response sensitivity of 8 heavy metal elements to environmental changes in the basin range in a descending order of Cd>As>Hg>Cu> Pb>Zn>Ni>Cr. Cd, As and Hg are the alarm of the urgent need in environmental risk monitoring. In such a circumstance, special attention is required.