长江口滨岸潮滩重金属源汇通量估算

根据2002～2003年长江口滨岸潮滩16个站位1年的沉积物重金属含量、粒度和密度等季节性测试数据,结合其他文献的沉积物累积速率资料,初步估算了长江口滨岸潮滩重金属的源汇通量。结果表明,2002年徐六泾以下的河口地区,沉积物中Cu、Pb、Fe、Mn、Zn、Cr的年滞留量分别为3425t/a、2751t/a、3451599t/a、69505t/a、14045t/a和3176t/a,石洞口排污口和黄浦江仍然是这几种重金属的主要污染输入来源之一。潮滩能有效滞留河口水体中的重金属,在长江口0m线以上的潮滩沉积物中,Cu、Pb、Fe、Mn、Zn、Cr的年沉降量分别占到整个河口区重金属沉降量的24.3%、27.6%、32.3%、32.4%、20.5%和23.2%。从潮滩重金属的沉降通量来看,南汇边滩的沉降通量最大,长江口南岸潮滩明显高于长江口北支潮滩,说明位于排污口下游的滩地能有效削减入海重金属污染负荷。

Estimation of source and sink fluxes of heavy metals in tidal flat of the Yangtze Estuary

Source and sink fluxes of heavy metals in intertidal flat of the Yangtze Estuary were estimated based on the seasonal data of heavy metal concentration,particle size and density of sediments over a year period from 2002 to 2003,combined with the deposition flux of sediments from other documents.The results show that the annual deposition quantities of Cu,Pb,Fe,Mn,Zn and Cr were 3 425 t/a,2 751 t/a,3 451 599 t/a,69 505 t/a,14 045 t/a and 3 176 t/a in lower estuary from Xuliujing in 2002.Shidongkou sewage outlet and the Huangpu River were the major pollution sources of these six elements.Tidal flat can effectively reduce heavy metals in estuary water.Retention of Cu,Pb,Fe,Mn,Zn and Cr in intertidal flat above 0-meter isobath of the Yangtze Estuary was separately 24.3%,27.6%,32.3%,32.4%,20.5% and 23.2% of their total deposition quantity in lower estuary from Xuliujing.Spatially,the maximum deposition fluxes of heavy metals appeared at section Nanhui and the fluxes in southern coast were higher than those in the north branch of the Yangtze Estuary,suggesting that the intertidal flat located in the lower reaches of sewage outlet played an important role in reducing heavy metal pollutants entering the estuary water.