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长江口表层沉积物生源要素时空分布特征及其影响因素研究
张珊珊
学位类型硕士
导师线薇微
2017-05-19
学位授予单位中国科学院大学
学位授予地点北京
学位专业环境工程
关键词长江口 表层沉积物 生源要素 分布特征 影响因素
其他摘要    碳、氮、磷、硅等生源要素是海洋生物生长所必需的重要营养元素,是海洋生态系统物质循环的基础。长江口作为世界第三大河的入海口,河口环境复杂,河口沉积物成为生源要素的“源”与“汇”,时刻进行着物质间的循环。本研究基于2014年4个季节航次(2月、5月、8月和11月)综合调查数据,对长江口表层沉积样品中总有机碳(TOC)、总氮(TN)、总磷(TP)和生源硅(BSi)四种生源要素含量进行测定,分析了生源要素的时空分布变化规律及其与环境参数的耦合关系,并探讨了沉积物生源要素在河口物质循环中的主要来源。主要研究结果如下:
    (1) 2014年长江口表层沉积物中TOC、TN、TP和BSi的含量分别是0.073~0.811%、0.005~0.214%、0.053~0.090%和0.045~0.650%,均值分别是0.366%、0.055%、0.066%和0.327%。表层沉积物TOC季节变化差异不显著,TN不同季节含量的变化有显著差异,TOC秋季最高冬季次之,TN冬季最高秋季次之,春、夏季含量均较低。TP含量季节波动不明显,总体含量春季略高,夏季较低。表层沉积物BSi含量存在显著季节波动,秋季最高,其次是夏季和冬季,春季含量最低,其中以东南外海区含量季节变化最为显著。
    (2) 2014年长江口表层沉积物中TOC、TN、TP和BSi的空间分布特征分别为:TOC和TN总体呈现河口附近高、外海低,南部高、北部低的平面分布特征;TP呈现出由口门向外海随离岸距离的增加而减少的平面分布趋势,北部存在随季节变化移动的高值区;BSi除春季北部海域为高分布区以外整体呈现南部高、北部低的空间分布特征。
    (3) 2014年长江口表层沉积物中值粒径在1.80~7.12φ之间,类型以砂和粉砂为主,黏土所占比例较小。不同季节各组分含量不同,春季主要以粉砂为主;夏季粉砂含量降低,砂质含量提高;秋季粉砂平均含量达到年度最高,黏土含量也有增加;冬季各组分含量与春季相似。该海域沉积类型主要表现为由河口向外海随离岸距离的增加呈黏土质粉砂-粉砂-砂质类型过渡,黏土质粉砂主要集中在河口最大浑浊区范围内,粉砂在最大浑浊区及东南外海均有分布,砂质组分则主要集中于北部海域。
    (4) 影响该海域表层沉积物中TOC和TN含量及分布的主要因素包括沉积物粒度,上覆水体表层盐度,上层水环境营养物质含量及其它部分水环境因子。细颗粒物质对TOC、TN有较强的富集能力,粒度对TP含量及分布的影响不大,BSi在秋、冬季节受沉积粒径影响较大。夏、秋季节表层水体盐度控制的长江冲淡水对表层沉积物中TOC和TN的分布有较大影响。上层水环境中的硅酸盐含量对表层沉积物中TOC和TN影响较大。不同季节其它水环境因子对表层沉积物中各生源要素影响程度不同。
    (5) 与2007年相比,2014年表层沉积物中TOC、TN含量均有降低,TOC含量在最大浑浊区降幅明显,TN含量在东南外海区降幅超过最大浑浊区,主要与近年来长江口最大浑浊区表层沉积物粒径变粗,长江径流量及输沙量减少有关。2014年长江口海域表层沉积物中TOC/TN比值范围是2.47~19.83,均值是8.22,表明TOC的来源受陆源输入和海洋自生共同影响,海洋自生总体优势较大。根据C/N比定量估算得到2014年TOC陆源输入的贡献较2007年下降幅度高达20%,与生物生产相比已不占优势,长江口表层沉积物中陆源输入的TN贡献同样存在明显的下降趋势。
; Biogenic elements which included carbon, nitrogen, phosphorus and silicon, are essential nutritive elements for the growth of marine life. It is the basis of marine primary production process and food chain. As the world’s third largest river estuary, the Yangtze River Estuary environment is particularly complex. The bottom of the sediment is the important sources and sinks of biogenic elements, which is playing an important role in the material cycle, energy flow and nutrient remineralization of marine ecosystems all the time. Based on the ecological environment investigation data from the fourth cruises carried out in February, May, August and November in 2014, the spatial-temporal distributions of biogenic elements (including Total Organic Carbon, Total Nitrogen, Total Phosphorus and Biogenic Sillicon) in the surface sediment were analyzed as well as their correlations with the environmental factors. At the same time, the main sources and influencing factors of sediment biogenic elements in estuarine material circulation were discussed. The main results are as follows:
    The concentrations of Total Organic Carbon (TOC), Total Nitrogen (TN), Total Phosphorus (TP) and Biogenic Sillicon (BSi) in the surface sediment of the Yangtze River estuary and its adjacent area were 0.073~0.811%, 0.005~0.214%, 0.05~0.090% and 0.045~0.650%, respectively. And the average contents of TOC、TN、TP and BSi were 0.366%, 0.055 %, 0.066% and 0.327% respectively. The seasonal variation of TOC in the surface sediments was not significant, and the variation of TN in different seasons was significantly different. TOC is the highest in autumn and second highest in winter. TN is the highest in winter and followed by autumn. spring and summer at the Spring and summer are at a low level. The seasonal fluctuation of TP contents is not obvious, which is slightly higher in spring and lower in summer. The order of BSi contents from high to low was autumn, summer, winter and spring. The change of BSi contents in the southeastern area was the most significant.
    The spatial distribution of TOC in the surface sediments demonstrated that the higher values appeared in the near-shore zones and in the southern area, the lower TOC was in the off-shore areas and in the northern area, which had subtle difference between different seasons. The highest contents of TN occurred in southern coastal zone, while lower contents distributed in northwest offshore area. The distribution of TN had varied factors during different seasons. The distribution of TP decreased gradually from the inner mouth zones to the near-shore and off-shore areas with the increasing in distance. And also there was not obvious seasonal variations. Spatial distribution showed that BSi concentration decreased seaward and the highest value occurred in the coastal zones, with the higher content appearing in the south area while the lower in northern zones.
    The median size of the surface sediments in the Yangtze River estuary and its adjacent area was between 1.80 and 7.12φ. The surface sediments was mainly comprise of sand and silt, the proportion of clay is less. There were some differences of the surface sediments in different seasons. The surface sediments was mainly comprised of sand in the spring. In summer, the content of silt was decreased and sand conponent was increased. The content of silt reached maximum value in autumn, and the content of clay was also increased. In winter, the components of the surface sediments was similar to spring. The types of the sediments in the Yangtze River estuary were mainly characterized by the transition from the clay silt to silt and sandy from the estuarine to the offshore sea with the increase of the offshore distance. The types of clay silt was mainly concentrated in the Turbidity Maximum Zone, while the silt was distributed in the Turbidity Maximum Zone and the southeastern sea, and the sand was mainly concentrated in the northern areas.
    It had been recognized that The main factors influencing the content and distribution of TOC and TN in surface sediments included sediment grain size, hydrodynamic factors and some water environmental factors. The concentrations of TOC and TN had a strong enrichment capacity that existed in fine particles, the finer the particle size, the TOC and TN content is higher. Factors affecting the content and distribution of TP and BSi in surface sediments were different in different seasons. The distribution of the dilution water in the Yangtze River, which is controlled by hydrodynamic factors, with the warm current in Taiwan as well as the coastal flow in Zhejiang affect the distribution of biogenic elements. The influence of the water environmental factors to each biogenic elements from surface sediments in different seasons is different.
    Compared with 2007, the contents of TOC and TN in the surface sediments from the Yangtze River Estuary decreased in 2014. The concentrations of TOC decreased significantly in the Turbidity Maximum Zone, and the conent of TN in the southeast of the sea decreased more than the Turbidity Maximum Zone. Which was related to the grain size increased in the turbidity maximum zone in the Yangtze River estuary and the decrease of the runoff as well as the sediment delivery of the Yangtze River. The TOC/TN ratios ranged from 2.47 to 19.83 with an average 8.22 in the surface sediments in the Yangtze River estuary and its adjacent area. It had been indicated that TOC and TN were significantly influenced by terrestrial inputs and the marine autogenic materials. According to the C/N ratio estimation, the contribution of terrestrial inputs TOC was reduce 20% in 2014 than that in 2007, which was not dominant compared with the marine autogenic materials. TN mainly comes from the marine autogenic materials input. The main reason was that the Yangtze River land input reduced in recent years.
学科领域河口、海岸学
语种中文
文献类型学位论文
条目标识符http://ir.qdio.ac.cn/handle/337002/136584
专题海洋生态与环境科学重点实验室
作者单位中国科学院海洋研究所
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张珊珊. 长江口表层沉积物生源要素时空分布特征及其影响因素研究[D]. 北京. 中国科学院大学,2017.
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