Heavy Metals’ Process In Water And Pollution Risk Assessment In Surface Sediments Of The Yellow River Estuary、Yangtze Estuary And Pearl River Estuary

Based on the data from the908survey, which include information in seawaterand sediments of the Yellow River, Yangtze and Pearl River estuaries in fourconsecutive seasons, the concentration distribution characteristics of heavy metals inseawater and sediments were analyzed. By mathematic statistic methods, we revealedthe correlation between heavy metals and other environmental factors. The mainpotential ecological risks in the surface sediments were evaluated with Hakansonpotential ecological risk index.The main results were as following:(1) The average contents of Cu, Zn, Cd, Cr and As were complied with theNational Seawater Quality Standard of China (NSQSC) Ⅰ in Yellow River estuaryand surrounding areas, except for the average contents of Pb in all four seasons andthe average contents of Hg in summer; both metals were the main seawater pollutionin Yellow River estuary. The average contents of Cu, Pb, Zn, Cd, Cr and As in all fourseasons were complied with the NSQSC Ⅰ in Yangtze estuary and surrounding areas,while the average contents of Hg belonged to the NSQSC Ⅱ. Therefore, the seawaterin the Yangtze estuary was mainly polluted by Hg. The average contents of sevenheavy metals (Cu, Pb, Zn, Cd, Cr, Hg and As) in Pearl River estuary and surroundingareas were all belonged to the NSQSCⅠ. The pollution of heavy metals in seawaterof Pearl River estuary was not obvious.(2) In the Yellow River estuary, the heavy metals’ main process was diluting andmixing, and affected by the effect of oxidation-reduction at the same time; the pHvariation and the SPM adsorption and desorption had little influence. The behaviourof heavy metals in Yangtze estuary was consistent with Pearl River estuary, whichmainly included diluting and mixing; heavy metals in SPM mainly desorbed underacidification effect, and oxidation-reduction had little influence.(3) There was a statistically significant correlation between the element Cu-Cd,Pb-Cr and Cr-As in sediments of the Yellow River estuary;16set of elements Cu-Pb; Cu-Zn; Pb-Zn; Cu-Cd, Zn-Cd, Cu-Cr, Pb-Cr, Zn-Cr, Cu-Hg, Zn-Hg, Cd-Hg, Cr-Hg,Cu-As, Zn-As, Cr-As and Hg-As in sediments of the Yangtze estuary; Cu-Zn, Pb-Zn,Cu-Cd, Pb-Cd, Zn-Cd, Pb-Cr, Zn-Cr and Cd-Cr in sediments of the Pearl Riverestuary; which indicated that they had similar geochemical properties and sources.(4) The main sources of the potential ecological risks of the sediments in YellowRiver estuary, Yangtze estuary and Pearl River estuary were Cd and Hg; it should benoted that the pollution levels and the potential ecological risks of Cd in sediments inPearl River estuary surged locally, which deserve special attention. The heavy metalsin sediments of Yellow River estuary were most environmentally hazardous, followedby Pearl River estuary, and the pollution level of Yangtze estuary was the lowest.(5) As in sediments of Yellow River estuary and Pearl River estuary had adverseeffects occasionally; other heavy metals in three estuaries did not.(6) The sources of heavy metals in sediments of three estuaries were influencedby natural and human activities.