苏北辐射沙洲岸滩沉积物元素地球化学记录的百年尺度环境变化

Centennial scale environmental changes in the elemental geochemistry of tidal flat sediments in the northern Jiangsu radial sand ridges

苏北辐射沙洲是分布于江苏岸外的典型沉积堆积体,受长江、黄河泥沙供给和近岸潮流动力的共同影响,发育了典型的粉砂淤泥质潮滩,沉积物元素可以记录潮滩环境变化的重要信息。在辐射沙洲岸滩采集了3个短柱沉积物岩芯,建立可靠的年代框架,采用高分辨率XRF元素扫描仪进行地球化学元素测试,选用XRF信号强度高的14种元素进行聚类和相关性方法提取环境信息,研究过去百年尺度人类活动和海岸环境变化下的苏北辐射沙洲岸滩沉积环境变化。结果表明,该区典型潮滩剖面岩芯沉积物中Si、Ca、As和Fe元素相对含量较高,且自北向南其含量不断增加,Mn、Ba、Cu和Zn元素含量较低,在所有剖面含量变化不大。在垂向上,Si、Ca和Fe元素变化趋势一致,而Ni、Zn和S元素在不同柱状岩芯中呈现与Si、Ca和Fe相反的变化趋势。相关关系和聚类分析显示,Si、Ca和Fe元素之间具有较高的相关性,即具有近似的地球化学行为和一致的物质来源;与元素Ni、Cu和Zn呈负相关,暗示了这几种元素与前者具有不同的地球化学行为。苏北辐射沙洲潮滩沉积物沉积环境发生了明显变化且在不同区域呈现不同的变化规律,物质来源、水动力环境、人类活动等因素是导致沉积环境变化的主要原因。

The radial sand ridges is a typical sedimentary accumulation body distributed off the coast of Jiangsu Province.Under the influence of the sediment supply of the Changjiang River and the Huanghe River as well as the coastal tidal current,the typical silty-muddy tidal flats are developed,and the sediment elements can record the important information of the environmental changes of the tidal flats.Three short core samples were collected in the tidal flat of radial sand ridges to establish a reliable chronological framework and geochemical element testing,and 14 elements with high X-ray fluorescence(XRF)core scanner analysis signal strength were selected for clustering and correlation method to extract environmental information.The sedimentary environment changes of the northern Jiangsu radial sand ridges under the influence of human activities and coastal environment changes in the past 100 years were studied.The results indicate that the contents of Si,Ca and Fe in the core sediments of typical tidal flat profile in this area are relatively high,and the contents of Si,Ca and Fe increasing from north to south,while the contents of Mn,Ba,Cu and Zn are low,and the little changes in contents at all profiles changes.In terms of vertical change,Si,Ca and Fe have the same vertical change trend,while Ni,Zn and S have the opposite change trend with Si,Ca and Fe in different sediment cores.Correlation and clustering analysis show that Si,Ca and Fe have high correlation,that is,they have similar geochemical behavior and consistent material source.In addition,it is negatively correlated with elements Ni,Cu and Zn,suggesting that these elements have different geochemical behaviors with the former.The sedimentary environment changes of the tidal flat are obvious and show different patterns in different regions in the northern Jiangsu radial sand ridges,and the material source,hydrodynamic environment and human activities are the main reasons leading to the change of the sedimentary environment.