| 摘要: |
| 台风作为事件性的强动力因素,其对河口海域沉积环境的影响目前研究较少,开展典型台风事件对长江口外海域悬浮体分布的影响研究对于深入理解长江径流挟带陆源物质向东海陆架扩散机制等具有重要意义。利用2015年09号台风"灿鸿"过境前后长江口外海域现场调查数据,分析台风前后长江口外水体结构和悬浮体粒度分布变化,结合同期环境观测数据与开源数据,阐明台风对河口外海域悬浮体分布的影响机制。结果表明:长江口外海域悬浮体中细颗粒组分(≤ 128μm)主要为无机矿物颗粒,而粗颗粒组分(>128μm)主要是生源有机颗粒。生源有机粗颗粒主要分布于中上层水体,而无机细颗粒主要分布于底层水体,使得长江口外海域悬浮体平均粒径分布呈双层结构。台风前后悬浮体粒度分布变化反映了台风对长江口外海域物理和生物过程的双重影响,其中物理过程主要影响无机细颗粒分布变化,生物过程主要影响有机粗颗粒。台风期间强烈的偏北风使得长江冲淡水在口门外海域由东北输运转为往东输运,与长江冲淡水输运方向一致的表层无机细颗粒在台风后输运方向同样往东。另外,台风作用在河口区产生的下降流将12250-4站位底部再悬浮的泥质沉积物向东搬运至12300-4站,导致12300-4站底层悬浮体浓度增加、粒度变细。台风过境还造成长江口外海域初级生产力提高,而浮游植物生长对悬浮体中有机粗颗粒的形成有促进作用,使得口门外海域上层水体中有机粗颗粒体积浓度升高。长江口外海域由于台风过境导致悬浮体中无机细颗粒和生源有机颗粒含量均增加,使得其平均粒径整体变化不大。 |
| 关键词: 台风 悬浮体 粒度 体积浓度 长江口外 |
| DOI：10.11693/hyhz20220300062 |
| 分类号: |
| 基金项目:中国科学院战略性先导科技专项,XDB42010203号,XDA9060401号;国家自然科学基金面上项目,42176090号。 |
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| THE IMPACT OF TYPHOON CHAN-HOM ON THE DISTRIBUTION OF SUSPENDED PARTICULATE MATTER OFF THE CHANGJIANG RIVER ESTUARY |
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LONG Xiao-Zhi1,2, WANG Zhen-Yan1,2,3,4
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1.Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2.University of Chinese Academy of Sciences Beijing 100049, China;3.Laboratory for Marine Mineral Resources, Pilot National Laboratory for Marine Science and Technology(Qingdao), Qingdao 266071, China;4.Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China
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| Abstract: |
| As a strong episodic dynamic factor, the impact of typhoons on the sedimentary environment of estuary is less studied. It is of great significance to study the impact of typical typhoon events on the distribution of suspended particulate matter off the Changjiang River (Yangtze) estuary for deeply understanding the mechanism of the dispersal of terrestrial materials transported by Changjiang River to the East China Sea shelf. Based on the field survey data, environmental observation data, and open-source data before and after the passage of Typhoon Chan-hom (typhoon #9 in 2015), we analyzed the variations of water column structure and particle size distribution of suspended particulate matter off the Changjiang River estuary before and after typhoon passage and clarified the influencing mechanism of typhoon on the distribution of suspended particulate matter. Results show that fine particles (≤ 128 μm) are composed mostly of inorganic particles, while coarse particles (>128 μm) are dominated by organic aggregates. The organic coarse particles are mainly distributed in the upper layer, while the inorganic fine particles are mainly distributed in the bottom layer, which resulted in a double-layer structure in the mean particle size distribution of suspended particulate matter off the Changjiang River estuary. The variation of particle size distribution of suspended particulate matter before and after typhoon passage reflects the impacts of typhoon on both physical and biological processes. Moreover, physical processes mainly affect the distribution of inorganic fine particles, while biological processes modified organic coarse particles. The Changjiang River diluted water off the estuary transported from northeast to east due to strong northerly wind during typhoon, and the surface inorganic fine particles also transported eastward after typhoon in the same direction to the Changjiang River diluted water flow. In addition, suspended muddy sediments transported from the bottom layer in Stations 12250-4 to 12300-4 because of the downwelling that generated during typhoon, and resulted in the fining of suspended particulate matter at the bottom layer of Station 12300-4. The primary productivity off estuary regions increased after typhoon, and phytoplankton growth promoted the formation of coarse organic particles, thus the volume concentration of coarse organic particles of upper layer off the estuary increased. The mean particle size of suspended particulate matter off the Changjiang River estuary had little change due to the increase of both inorganic and organic particles after typhoon passage. |
| Key words: typhoon suspended particulate matter grain size volume concentration off the Changjiang River estuary |
