中国东部近海现代沉积环境

Modern sedimentation environments in the coastal zone of East China

  • 摘要: 东海近岸海域岛屿、入海河流众多,大量陆源物质随沿岸流自长江口向东迁移,是海陆相互作用最为强烈的区域之一。对2016和2017年夏季采集的570个东海近岸表层沉积物样品进行了沉积物物理化学性质、粒度特征、有机质含量等测试分析。结果表明,这些特征参数明显受区域沉积环境的控制。杭州湾区域沉积物偏弱碱性, 氧化还原电位(Eh)<0, 有机质含量北部偏高, 沉积物组成以黏土质粉砂为主,抗剪强度较低(普遍<0.5kpa),各指标无明显分布规律,相关性较强。浙江东部沿海区域沉积物近中性至弱酸性,Eh较高(>0),Eh与pH自陆向海降低,象山港、乐清湾海域有机质含量较高; 舟山至台州海域以粉砂为主,台州以南分布斑块状泥质区,抗剪强度比杭州湾区域偏高,各指标无明显相关性。整体来看,杭州湾与浙江东部沿海属于两个完全不同的沉积环境体系,主要是因杭州湾物质来源较为稳定,区域水动力较强,导致沉积物分布相对均一; 而浙江东部海域河流、岛屿较多,各个区域物质来源和水动力环境都存在较大差异。

     

    Abstract: Abundant islands and rivers occur in the waters off Zhejiang coast of East China. Huge amount of terrestrial materials carried by the Yangtze River moves to the east by coastal current. It is an area with the most intense land-sea interaction. In the summers of 2016 and 2017, 570 surface sediment samples were collected from the East China Sea, and physical and chemical properties, grain size distributions and organic matter contents of sediments were tested. Results show that sediments in Hangzhou Bay are dominated by clayey silt with high pH (> 7), low Eh (< 0) and low shear strength (< 0.5kPa). The content of organic matters is higher in the north rather than in other regions. Generally, no obvious distribution pattern is observed for those parameters, but they are significant correlated. In the east coast of Zhejiang, for example, the sediments are dominated by silt in the north (Zhoushan-Taizhou), but by mud in the south (Taizhou- Wenzhou). Both pH and Eh are decreasing seaward. Higher content of organic matters have been found in the Xiang-shan Port and Yue-qing Bay. However, there is no significant correlation between different parameters. Therefore, the sedimentary environment of Hangzhou Bay and the eastern Zhejiang coastal area is obviously different. In Hangzhou Bay, the sediment distribution is more regular due to the rather stable sources and strong hydrodynamic environment. However, the sediment sources and hydrodynamic environment vary significantly due to widely distributed islands and rivers to the east coast of Zhejiang.

     

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