长江口沉积物化学相态分析及主泓变迁的指示  

Chemical Phases of Sediments in the Changjiang Estuary and the Indication for the Geomorphological Evolution of Changjiang Estuary

作　　者：倪和平 毕磊 郭玉龙[1] 何中发[3] 杨守业[1] NI HePing;BI Lei;GUO YuLong;HE ZhongFa;YANG ShouYe(State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China;Polar Research Institute of China,Shanghai 200136,China;Shanghai Institute of Geological Survey,Shanghai 200072,China)

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092 [2]中国极地研究中心,上海200136 [3]上海市地质调查研究院,上海200072

出　　处：《沉积学报》2023年第1期243-255,共13页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41730531,41991324);上海市“巽他陆架大洋钻探一带一路国际联合实验室”项目(18230750600)。

摘　　要：元素地球化学是沉积物源判别和环境研究的重要手段,但河口海岸地区沉积动力环境复杂多变,人类活动影响强烈,全岩沉积地球化学的示踪研究存在局限性和多解性。选择长江下游干流悬浮物、东海陆架表层沉积物以及长江口具有一百多年沉积记录的ZK6孔,通过化学相态分析(1 N HCl处理),探究酸溶态微量元素组成特征及其对河口环境变迁的指示。相较于钻孔全岩样品,酸溶态Sr/Ba比能更可靠地反映河口古盐度和海陆相沉积环境的变化。ZK6孔沉积物酸溶态稀土元素(REE)主要赋存于Mn氧化物中,Mn、ΣREE含量、Ce/Ce*以及Sr/Ba比在1899—2007年间呈三段式变化,主要反映长江河口流路分汊和主泓位置改变引起的河口沉积环境变化,进而影响河口环境中活跃元素和次生组分在沉积地层中的保存记录。该研究对今后深化认识复杂河口环境下微量元素地球化学行为以及微量元素示踪海洋环境变化具有借鉴意义。Elemental geochemistry is an important means for provenance discrimination and palaeoenvironmental reconstructing in marine and continental environments.However,a study based on the bulk sedimentary geochemistry is significantly influenced by the complex sedimentary dynamics in estuarine and coastal areas,as well as the influence of human activities.The Changjiang(Yangtze River)Estuary,as an important depocenter for the riverine sediments,is featured by the active hydrodynamic and depositional processes.Due to the combined effects of runoff and tidal currents,erosion and siltation processes interact,which causes the main stream channel to swing frequently,and the sedimentary environment of the estuary is constantly changing.Therefore,it is an ideal place to investigate the geochemical behavior of elements in a complex estuary environment.However,the evolution of geomorphology and sedimentary environment of the Changjiang Estuary in the historical period is mainly based on the studies of estuarine geomorphology and sedimentary dynamics,while few studies focus on the application of sedimentary geochemistry for tracing channel evolution and sedimentary environment.This study collected the suspended sediment samples in the main Changjiang stream,the seafloor sediments on the East China Sea(ECS)shelf,and the sediment samples of core ZK6 drilled from the Changjiang Estuary.In the lab,all of these samples were treated with 1 N HCl,and then the compositions of major and trace elements in the leachates and residues,as well as in the bulk samples,were measured.We then discuss their implications for the evolution of estuarine environment over the last hundred years.The Sr/Ba ratios in the leachates of the sediments in core ZK6 varied from 1.2 to 1.9,which is significantly higher than the average of the suspended samples in the main Changjiang stream(Sr/Ba=0.25)and significantly lower than the average of the seafloor sediments on the ECS shelf(Sr/Ba=8.0).The average Sr/Ba ratios in the residues of the above three fractions a

关 键 词：沉积物 相态分析 微量元素 长江 河口环境 

分 类 号：P736.4[天文地球—海洋地质]