东太湖围网拆除前后水生植被群落遥感监测及变化     

杨井志成  罗菊花  陆莉蓉  孙喆  曹志刚  曾庆飞  毛志刚 《湖泊科学》2021,33(2):507-517

为削减东太湖养殖污染,改善湖泊水质,苏州市于2018年底基本完成东太湖养殖围网拆除工作.围网拆除后,湖泊生态环境对此如何响应,已成为学者及相关管理部门关注的重点.水生植被在维持湖泊生态系统平衡、物质循环和净化水质方面发挥着重要的作用,是诊断湖泊生态系统健康状态的关键指标.本研究基于Sentinel-2卫星数据,利用分类决策树模型和基于生活史的沉水植被优势种群提取方法,监测了东太湖2017年(围网拆除前)和2019年(围网拆除后)的水生植被类群和沉水植被优势种群的空间分布.经验证,水生植被类群监测精度为82.66%,Kappa系数为0.77;沉水植被优势种群的监测精度为62.08%,Kappa系数为0.56.结果表明:围网拆除后,东太湖水生植被优势类群由围网拆除前的沉水植被转变为浮叶植被;沉水植被分布面积减少,且种群由优势度相差不大的七大优势种群逐步向菹草和伊乐藻占据绝对优势发展,逐渐趋于单一化.  相似文献   

Study on Coastal Protection Engineering in the Area of Abandoned Yellow River Mouth     

ZHANG Yifan  YU Guohua  SHENG Zhaoci  XU Ming Senior Engineer  River  Harbour Department  Nanjing Hydraulic Research Institute 《中国海洋工程》1998,(2)

This paper reviews the history of coast evolution and coastal protection in the area of theabandoned Yellow River mouth in Jiangsu Province,analyzes the erosion characteristics and dynamic en-vironment,evaluates the efficiency of coastal protection engineering works and designs the dimensions ofthe main seadike and offshore submerged dam.A gerneral scheme of shore protection for this area is pro-posed.  相似文献   

回声测深仪在水下地形测量中的应用   总被引：1，自引：0，他引：1  

张正惕  胡辉 《海洋技术学报》1998,17(4):39-43

本文在介绍回声测深仪基本工作原理的同时,介绍了回声测深仪在杭州湾口外一拟建大型码头下地形测量的一个应用实例。  相似文献   

不同浸没长度下串列双立管涡激振动数值模拟     

武磊  赵伟文  万德成 《海洋工程》2020,38(3):52-61

深海柔性立管涡激振动问题广受关注,其中多立管涡激振动较传统单立管涡激振动更为复杂。使用基于Open FOAM自主开发的深海柔性立管流固耦合求解器viv-FOAM-SJTU,对阶梯流中串列双立管涡激振动展开研究。首先针对阶梯流中串列双立管模型试验工况开展验证计算,下游立管的位移响应以及频率响应与试验结果基本吻合;而后改变立管浸没长度,分别选取浸没长度为0.4L(工况1)、0.55L(工况2)以及0.7L(工况3)的三种工况进行数值计算,其中L为立管长度。数值结果表明:3种浸没长度下,上下游立管的横流向振动均为一阶模态,且工况2和工况3中上下游立管的横流向位移均方根均大于工况1;上下游立管的顺流向主振模态在工况2和工况3中均为二阶,而在工况1中为一阶,且下游立管在工况2和工况3中的顺流向振动均表现出明显的多模态振动特性。  相似文献   

Effect of offshore waves and vegetation on the sediment budget in the Virginia Coast Reserve (VA)     

William Nardin  Sara Lera  Jaap Nienhuis 《地球表面变化过程与地形》2020,45(12):3055-3068

The potential for rapid coastline modification in the face of sea-level rise or other stressors is alarming, since coasts are often densely populated and support valuable infrastructure. In addition to coastal submergence, nutrient-related water pollution is a growing concern for coastal wetlands. Previous studies found that the Suspended Sediment Concentration (SSC) of coastal wetlands acts as a first-order control of their sustainability, but SSC dynamics are poorly understood. Our study focuses on the Virginia Coast Reserve (VCR) Long Term Ecological Research (LTER) site, a shallow multiple tidal inlet system in the USA. We apply numerical modelling (Delft3D-SWAN) and subsequent analyses to determine SSC dynamics within the VCR. In particular, we consider two important controls on SSC in the system: vegetation (seagrass and salt marsh) and offshore waves. Our results show that vegetation colonies and increased wave energy lengthen water residence time. The reduction in the tidal prism decreases SSC export from the bay via tidal inlets, leading to increased sediment retention in the bay. We found that alongshore currents can enhance lagoon SSC by importing fine sediments from an adjacent inlet along the coastline. Our numerical experiments on vegetation seasonality can improve the understanding of wave climate impact on coastal bay sediment budget. Offshore waves increase sediment export from coastal bays, particularly during winter seasons with low vegetation density. Therefore, our study can help managers and stakeholders to understand how to implement restoration strategies for the VCR. © 2020 John Wiley & Sons, Ltd.  相似文献   

The Chan Hol cave near Tulum (Quintana Roo,Mexico): evidence for long‐lasting human presence during the early to middle Holocene          下载免费PDF全文

Fabio Hering  Wolfgang Stinnesbeck  Jens Folmeister  Eberhard Frey  Sarah Stinnesbeck  Jerónimo Avilés  Eugenio Aceves Núñez  Arturo González  Alejandro Terrazas Mata  Martha Elena Benavente  Carmen Rojas  Adriana Velázquez Morlet  Norbert Frank  Patrick Zell  Julia Becker 《第四纪科学杂志》2018,33(4):444-454

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国产深海准实时传输潜标系统设计   总被引：2，自引：2，他引：0  

于非  陈永华  周春  张孝薇  邓锴  韩云峰  刘岩松  刘庆奎  王蓓  胡贺岗  姜静波  倪佐涛  姜斌  李晓龙 《海洋科学》2020,44(7):194-200

基于海洋环境安全保障、海洋环境预报和海洋科学研究的需要，开展国产深海准实时传输潜标系统的设计，重点进行锚泊系统水动力分析、观测设备工作同步性、准实时通讯系统安全可靠和系统低功耗等整体技术设计；开展轻型感应耦合传输缆制作、大深度感应耦合传输和智能收放通讯等数据实时通讯技术的研究；进行适用于准实时传输潜标系统的多种类国产设备的稳定性和可靠性优化、规模化集成和系统化的应用示范，形成半潜升降式准实时通讯潜标与浮子式准实时通讯潜标各1套。所设计的准实时传输潜标系统集成了1台抗污染CTD、19台感应耦合CTD、8台感应耦合T、4台感应耦合传输的ADCP、2台单点海流计和6台感应耦合数据传输仪，并配有2套声学释放器；潜标系统本体设计含有3个水下流线型浮体、1套通讯浮子、1套准实时卫星通讯装置（半潜式水下绞车或海面浮子）和1套锚泊缆系，可实现深达2 000 mm的剖面温盐深和海流等海洋要素的高频率、多要素、多层次的长期连续观测和数据准实时传输，以便对科学问题解决和海洋环境安全保障等提供及时的数据支撑。  相似文献   

岛礁附近浮式平台运动响应特性数值分析     

夏可  万德成 《海洋工程》2018,36(3):10-17

利用基于开源平台Open FOAM自主开发的船舶与海洋工程水动力性能求解器naoe-FOAM-SJTU,数值模拟了近岛礁环境下规则波的演化特性以及带有系泊系统的浮式平台在相应波浪作用下的水动力性能。对于平台的水动力性能的研究发现,仿真结果与试验结果在平台自由衰减运动固有周期及RAO(response amplitude operator)方面吻合良好。对于波浪在近岛礁地形下的演化现象的研究,分析了波浪演化不对称性特性的成因,并分别给出了不同参数下波浪在地形上爬升时演化的具体特性,对于波高变化及波浪演化的频率成分进行量化的探究。研究发现,波浪周期越大,波高变化越明显,演化的非线性现象越明显,且波浪随着传播距离的增大演化出的阶数也在增大。  相似文献   

Macrophyte‐driven transient storage and phosphorus uptake in a western Wisconsin stream          下载免费PDF全文

Katherine J. Bohrman  Eric A. Strauss 《水文研究》2018,32(2):253-263

Investigations of phosphorus cycling and transport in streams lend insight into potential mechanisms of nutrient sequestration and can help mitigate human impacts. In this study, we examined the relationship between transient storage and phosphorus uptake in a cold‐water stream in western Wisconsin. Hydrological characteristics, nutrient spiralling metrics, macrophyte biomass, and geomorphological properties were quantified in 7 reaches of Spring Coulee Creek using injections of a conservative tracer alone or with added PO₄^3?. Fraction of median travel time due to transient storage (F_med²⁰⁰) was correlated with macrophyte biomass (r = .794, p = .033), and PO₄^3? uptake velocity was correlated with F_med²⁰⁰ (r = .756, p = .049). Stepwise linear regression was used to build models for transient storage and uptake velocity. Macrophyte biomass, stream bed slope, and riffle to pool ratio accounted for 99.6% of the variation in transient storage (p < .001). Transient storage, canopy cover, and slope accounted for 98.0% of the variation in uptake velocity (p = .002). This study shows that transient storage, primarily resulting from macrophyte beds, can be a significant factor regulating phosphorus uptake in stream ecosystems.  相似文献   

Plant Growth Promoting Rhizobacteria Impact on Typha latifolia and Phragmites australis Growth and Dissolved Oxygen          下载免费PDF全文

Faiza Rehman  Arshid Pervez  Bahadar Nawab Khattak  Rafiq Ahmad 《洁净——土壤、空气、水》2018,46(8)

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