Distribution, sources and ecological risk assessment of heavy metals in sediments of the Yangtze River estuary
长江口沉积物重金属的分布、来源及潜在生态风险评价

In order to understand the pollution characteristics of heavy metals in surface sediments of north and south branches of the Yangtze River estuary and Hangzhou bay, the concentrations of 10 heavy metals including Cu, Pb, Ni, Ag, As, Cd, Zn, Sn, Sb and Hg in 27 sediment samples were analyzed by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and the potential ecological risks of each heavy metals were evaluated. The total concentrations of 10 metals in the sediment samples ranged from 102.9 mg·kg-1 to 326.4 mg·kg-1, the mean concentrations of heavy metals in sediments of north branch, south branch and Hangzhou bay were 180.9, 244.7 and 155.6 mg·kg-1, respectively. The average concentration of north branch sediments was different significantly from those of south branch and Hangzhou bay (p < 0.01), indicating the pollution extent of south branch of the Yangtze River was aggravated by industrial wastewater and domestic sewage. The source of most heavy metals in sediments were similar, and came mainly from industrial and agricultural wastewater, shipping, and the use of pesticide and chemical fertilizer. The pollution extent of heavy metals in sediments by geo-accumulation index (Igeo) followed the order: Cd >Hg>Sb>Ag>As>Cu>Zn>Ni>Sn>Pb. The pollution extent of Cd and Hg were at class 3 (moderately to heavily polluted) and 4 (heavily polluted) at most sampling sites. The potential ecological risk of 7 heavy metals in sediments by the potential ecological risk factors followed the order: Cd>Hg>As> Cu>Ni>Pb>Zn. Cd and Hg contributed the most to the total potential ecological risk, accounting for 62.6% and 34.0%, respectively. The potential ecological risk indexes (RI) of 7 heavy metals at all sampling sites were in the range of 563.0 and 1431, and posed very high potential ecological risks for the Yangtze River estuary.