【作者】 许淑梅；

【导师】 翟世奎；

【作者基本信息】 中国海洋大学 ， 海洋地质， 2005， 博士

【摘要】 长江口外存在缺氧区,缺氧区对环境的影响日益引起科学家们的重视,2003年6月份973项目海洋调查也发现了这一事实。长江口外底层水溶解氧亏损中心位于东海陆架泥质区东经122°45′和123°00′之间的北纬30°50′附近。低氧区(海水溶解氧浓度小于2mg/L)的面积约13 700 km~2。长江口外缺氧区所在的泥质区是未次冰消期高海面以来的沉积中心和“物质汇”,也是人类活动排放入海污染物的主要载体,对东海物质通量和陆海相互作用的研究至关重要。 本文以表层沉积物和沉积物岩心中的氧化还原敏感性微量元素Cu、Pb、Ni、U、Mo、Cd和V等为主要研究对象,结合研究区实测海水溶解氧数据和悬浮体中氧化还原敏感性元素丰度,比较详细地讨论了研究区底层海水溶解氧亏损对沉积物中氧化还原敏感性微量元素分布和富集的影响,探讨了长江口外缺氧区沉积物中氧化还原敏感性微量元素的环境指示意义。 本论文首次讨论了长江口外缺氧区的缺氧环境对沉积物中氧化还原敏感性元素分布规律的影响,并对长江口外缺氧区的还原程度、分布规律、还原环境变化趋势和底层水开始出现溶解氧亏损的时间等一系列问题进行了探讨。因此,论文在研究内容,研究思路和结论等方面都具有一定的创新性。 论文分析了长江口外泥质区沉积物组成的稳定性,认为长江口外缺氧区表层沉积物和沉积物岩心中的物质组成相对均一、稳定,长江口外泥质区的缺氧区和非缺氧区沉积物粒度和粘土矿物组成没有显著不同。“粒度控制效应”和粘土矿物的吸附作用对自生氧化还原敏感性元素组分分布的影响不大。可以排除多物源因素或沉积格局突变对沉积物中氧化还原敏感性元素富集特征的影响。 长江口外缺氧区的存在对沉积物中氧化还原敏感性微量元素V、Cd、Mo等的分布规律和富集特征有明显的制约。V、Cd、Mo等元素在研究区分布不均匀,在长江口外缺氧区表层沉积物和沉积物岩心中,V、Cd、Mo等元素具有明显的富集,在近岸带溶解氧正常海区沉积物中,亏损特征明显,表明长江口外底层水缺氧在沉积物中有明显的记录。研究区沉积物中氧化还原敏感性元素V、Cd、Mo等的分布规律和富集特征可以反映底层海水缺氧的现状、变化趋势及底质的更多还原

【Abstract】 The hypoxia zone near the Changjiang Estuary have been found, its influence on environment attract the attention of scientists. Bottom water dissolved oxygen depletion zone locate around 122° 45’ -123° 00’ E and 30° 50’ N. The area of hypoxia zone where dissolved oxygen ≤ 2mg/l is about 13 700 km2. The mud off Changjiang Estuary area are the modern accumulative centers on the East China Sea shelf since Holocene epoch, their formative process and storage of pollutant materials are essential for understanding of martial flux,it is a important question of Land-Ocean Interactions in the Coastal Zone(LOICZ) in the East China Sea.Based on the concentrations and enrichment characteristic of redox sensitive elements, such as Cu, Pb, Ni, U, Mo, V and Cd of the surface sediments and sediments cores, combined with field survey data of water dissolved oxygen in June 2003 and the measured concentrations of redox sensitive elements of the suspension, the paper discusses the bottom water hypoxia’s influence on the distribution and enrichment of the redox sensitive elements in sediments. This paper has studied the distribution, environment significance of redox sensitive elements and environmental changing trend of the Changjiang Estuary oxygen depletion zone.This is a first time researches on the relation of hypoxia zone and the distribution of redox sensitive elements in sediments and discusses the questions as follows: the reductive extent of the hypoxia zone, the changing trend of the hypoxia zone.The paper has analyzed the stability and uniformity of sediments, and believes that the components of the sediments are uniform and stable. So we can get rid of the influence of provenience and sediments pattern. There are no significant differences in grain size and clay minerals concentrations between the hypoxia zone and non-hypoxia zone off the Changjiang Estuary mud area. "Grain size effects" andadsorption by clay minerals have no effects on the distribution and enrichment of ihu redox sensitive elements in sediments.The paper believes that hypoxia zone off the Changjiang Estuary has important influence on the distribution of V, Cd, Mo in sediments. The distribution of redox sensitive element of V, Cd, Mo is not uniformity in the research area. They are significantly enriched in sediments of the hypoxia zone, and depleted in water dissolved oxygen normal zone off the Changjiang Estuary mud area. The results indicate that the distribution pattern and enrichment characteristic of V, Cd and Mo can be used as redox environment indicators of the bottom water hypoxia status, and can be used to study the redox status and changing trend of the environment.Redox sensitive elements, such as Pb, Cu, Ni, and U are also sensitive to redox conditions of bottom sediments theoretically. Many factors, such as the influence of adsorption by organic carbon^ scavenging by suspension and terrigenous component, can affect the distribution and enrichment of these redox sensitive elements, in that having no enrichment in hypoxia zone off the Changjiang Estuary, So the redox sensitive elements Pb, Cu, Ni, and U have no environment significance in the hypoxia zone of the research area.Based on the rules of the distribution and enrichment characteristic of redox sensitive elements of the surface and core sediments, compared with concentrations of V, Mo and Cd in the sediments from the different sea area in the world, the paper believes that Cd with low potential energy is enriched in hypoxia, V and Mo with high potential energy are also enriched in hypoxia zone. So the reductive extent of the Changjiang Estuary hypoxia zone is in moderate. It is weaker than that of Arabia Sea, but stronger than that of the Africa continental margin, the Northwest of American continental margin and the deposit environment of the shale.Environment of oxygen normal zone of the Changjiang Estuary approach to that of the Africa continental margin, and its reductive extent is weaker than that of Northwest of American continental margin. Compared with the deposit environment of shale, the environment of oxygen normal zone off the Changjiang Estuary is in oxidation state.The paper found the redox sensitive elements V\ Cd> Mo in core 17 begin to enrich at the depth of 28cm, and it is slightly enhanced in shallower depth. The paper concludes that the oxygen depletion zone off the Changjiang Estuary came into being since 1964, and its extent is enhanced these years.更多还原