长江口潮滩沉积物中活性重金属的空间分异及控制机制

SPATIAL VARIATION OF ACTIVE HEAVY METALS IN INTERTIDAL SEDIMENTS OF THE YANGTZE ESTUARY

利用盐酸羟氨-25%醋酸溶液,提取了长江口潮滩沉积物中活性重金属含量。研究发现,长江口潮滩沉积物中活性重金属占总量的百分含量依次为Cu 26%,Pb 36%,Fe 7%,Mn 49%,Zn 32%,Cr 14%和Al 1.6%,沉积物基本未受到Cr污染,其余重金属污染程度处于中等偏下水平。除Zn、Cr外,其余活性重金属在夏季沉积物中的含量明显低于春季,其主要原因是夏季风暴潮将大量细颗粒泥沙及其富集的重金属带离潮滩进入了河口水体中。受点源污染排放及沉积物粒度影响,活性重金属在长江口南岸的浒浦、顾路和浦东机场出现峰值含量,且高潮滩含量明显高于中、低潮滩。在垂向上,重金属一般在沉积物表层或亚表层形成富集。在口门附近的滨岸潮滩沉积物中,Cu、Pb的空间分异主要受早期成岩作用的控制,在污染较为严重、水动力作用相对较弱的潮滩沉积物中,Cu、Pb的空间分异主要受沉积物中有机质含量变化的控制。

Concentrations of active heavy metals （available to hydroxylamine hydrochloride -25% acetic acid） were determined in surface sediments and sediments between 0 -20 cm depths from the intertidal zone of the Yangtze Estuary, China. It was found that the percentage of active heavy metal concentrations in the total was Cu 26%,Pb 36%,Fe 7% Mn 49%,Zn 32%,Cr 14% and Al 1.6% respectively in the intertidal sediments. No pollution of Cr was found in the sediments and the pollution level of other metals lied between the mid to lower ranges. Except for Zn and Cr,the concentrations of other active heavy metals in sediments in the summer were significantly lower than the spring, mainly because of the summer storm resulting in large number of fine sediment and its associated heavy metals away from the tidal flats into the estuary water. Influenced by the sewage discharge from point sources and particle size of sediments, active heavy metals appeared to be enriched in sediments of Xupu, Gulu and Pudongjichang distributed in south bank of the Yangtze Estuary and the high tidal flat along a same transect. In core sediments, active heavy metals showed surface or sub surface enrichment. The geochemical actions of Cu and Pb in coastal intertidal sediments were mainly controlled by the redox conditions near the river mouth. While in sediments with weak hydrodynamic conditions and being polluted by heavy metals, vertical distributions of Cu, Pb were mainly controlled by the variation of organic matter contents.