Distribution and risk analysis of heavy metals in sediments from the Yangtze River Estuary, China

Sediments core within the Yangtze River Estuary was collected for metal and grain size analysis. The vertical distribution characteristics of eight metals along the core were investigated based on ¹³⁷Cs and ²¹⁰Pb radionuclide dating. The sediment was mainly composed of sand and silt. The metals concentrations were Al, 4.67-6.83; Fe, 2.3-3.94; Mn, 0.046-0.07; Cr, 69.5-103; Cu, 14.3-32.1; Zn, 47.3-96.7; Cd, 0.037-0.212; Pb, 13.7-23; Ni, 18.8-38.9 (mg·kg^-1, except Al, Fe, and Mn as %), respectively. Geoaccumulation indexes (I_geo) indicated that Cu, Zn, and Pb were of pollution-free level; Cd, Cr, and Ni were in a slight polluted level. Based on potential ecological risk factors (EI), Cd posed a moderate risk to the local environment. Correlation analysis showed that Fe, Al, and Mn had a close association with Cu, Zn, Pb, and Ni at p < 0.01. Clay was significantly correlated with other metals except Cr and Cd.