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1.
Coastal salt marshes represent an important coastal wetland system.In order to understand the differences between boundary layer parameters of vegetated and unvegetated areas,as well as the mechanisms of sediment transport,several electromagnetic current meters (AEM HR,products of Alec Electronics Co.Ltd.) were deployed in coastal wetlands in Quanzhou Bay,China,to measure current velocity.During the low tide phase,the surficial sediment was collected at 10 m intervals.In situ measurements show that the current velocities on the bare flat were much higher than those in the Spartina alterniflora marsh.Current velocity also varied with distance from marsh edge and plant canopy height and diameter.Around 63% of the velocity profiles in the tidal creek can be described by a logarithmic equation.Over the bare flat and Spartina alterniflora marsh,a logarithmic profile almost occurs during the flood tide phase.Sediment analysis shows that mean grain size was 6.7 Φ along the marsh edge,and surface sediments were transported from bare flat to marsh;the tidal creeks may change this sediment transport pattern.The hydrodynamics at early flood tide and late ebb tide phases determined the net transport direction within the study area. 相似文献
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伶仃洋河口泥沙絮凝特征及影响因素研究 总被引：1，自引：1，他引：0
泥沙絮凝对河口细颗粒泥沙运动过程起着极其重要的作用。本文通过LISST-100激光粒度仪等仪器实测伶仃洋河口2013年洪季悬浮泥沙絮凝体现场粒径及水动力、泥沙条件,结合实验室悬沙粒径分析,研究大小潮期间伶仃洋河口泥沙絮凝特征,探讨紊动剪切强度、含沙量、盐度分层及波浪等因素对伶仃洋河口泥沙絮凝的影响。结果表明:伶仃洋河口水体中现场粒径平均值为148.53 μm,大于实验室悬沙分散粒径36.74 μm,河口絮凝现象明显;沉速与有效密度、粒径呈正相关,絮团平均有效密度为153.49 kg/m3,平均沉速达1.13 mm/s;小潮时絮团平均粒径大于大潮,垂向上表底层絮团粒径小、中层大,中底层絮团沉速大于表层。伶仃洋河口水动力、泥沙条件是影响其泥沙絮凝的重要因素,低剪切强度（小于5 s-1）、低含沙量（小于50 mg/L）及高体积浓度有利于细颗粒泥沙之间的相互碰撞,促进絮凝作用;当剪切强度与颗粒间碰撞强度高于絮团所能承受的强度时,絮团易破碎分解成小絮团或更细的泥沙颗粒;伶仃洋河口盐度层化引起的泥沙捕获现象增大中层泥沙体积浓度,有利于中层絮凝体的发育;观测期相对较大的波浪增强水体紊动,增大了水体细颗粒泥沙的碰撞几率,表层絮团粒径随波高峰值的出现而增大。 相似文献
3.
互花米草对泉州湾盐沼表层沉积物输运的影响 总被引：1，自引：0，他引：1
海岸盐沼是海岸湿地系统的重要组成部分，具有很强的环境调节功能．互花米草（Spartina alterniflora）的引种对海岸盐沼的沉积动力产生很大影响．粒度分析结果表明，互花米草盐沼边缘与沉积物平均粒径为6．7φ的等值线分布一致．现场观测表明，互花米草对流速具有明显的阻滞作用，使得光滩流速明显大于互花米草内的流速；在互花米草滩内，随着离盐沼边缘距离、植被高度、植株直径的不同，涨落潮流速也表现出不同的变化趋势．粒径趋势分析结果显示，互花米草盐沼边缘的表层沉积物由光滩向盐沼内输运，潮水沟的存在对沉积物的输运格局具有显著影响．对比分析表明落潮后期的水动力条件控制着研究区内表层沉积物的净输运方向． 相似文献
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互花米草对福建泉州湾海岸湿地沉积环境影响 总被引：3，自引：0，他引：3
泉州湾淤泥质海岸湿地分布广泛,互花米草分布面积较大.利用小型电磁式流速仪进行流速观测,结果显示,水流由光滩湿地进入互花米草湿地后速度迅速减小,但随着互花米草带宽度地增加,减小程度逐渐变小且不显著.利用PVC管采集短柱状样并现场以一定间隔分样,进行粒度分析、TOC和TN分析及重金属分析结果显示,光滩湿地沉积物颗粒较粗,互花米草湿地边缘沉积物颗粒粗细均有且分选较差,密集互花米草湿地内沉积物粒径较细且分选较好,红树林湿地内沉积物颗粒最细且分选最好;稀疏互花米草湿地作为盐沼发育演化的青年阶段,对C、N具有很强的富集能力,红树林则对C、N的富集能力最弱,人类的排污活动增加了海岸湿地沉积物中的TOC含量;互花米草的存在拦截和吸附了陆源污染物,并使重金属富集在互花米草湿地沉积物中. 相似文献
5.
The fate of fine particulate material in aquatic environments is closely linked to aggregation and disaggregation processes. Understanding the mechanisms controlling these processes is fundamental to the development of predictive models of fate and effects for particulate discharges in the coastal zone from such sources as offshore hydrocarbon exploration and development. One of the variables required for the development of these models is maximal floc size. Using a non-invasive imaging technique, the significance of turbulence, composition, and concentration on maximal floc size in an inverting column flocculator was determined for materials commonly discharged during offshore hydrocarbon development. The settling velocity of the suspension was determined from volume concentrations of samples obtained by pipette during still water settling in a manner similar to that of Owen tubes. After 20 h, both maximal floc size and settling velocity showed a highly significant dependence on turbulence and type of material in suspension, but showed no effect from concentration. 相似文献
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珠江口磨刀门泥沙絮凝特征 总被引：3，自引：3，他引：0
本文利用激光粒度仪实测得到珠江口磨刀门河口2013年夏季悬浮泥沙现场絮凝及絮凝体特征,同时对比悬沙分散粒径和含沙量,研究表明:悬沙分散粒径平均值为27.9μm,现场实测絮团粒径平均值为91.6μm,表明磨刀门口外的悬浮泥沙絮凝现象显著;实测絮团平均粒径变化范围为13.0~273.8μm,小潮期间絮团粒径平均值为131.5μm,大于大潮平均值76.9μm;絮凝体粒径在垂向上的变化表现为由表及底先变大再变小。絮团体积浓度、沉速与粒径的关系在不同情况下有差异,体积浓度和絮团粒径在表层和中层有明显正相关关系,絮团沉速在大潮时刻随着粒径的增大而增大。综合分析影响絮凝的因素,得知在珠江口盐度对于絮团大小影响不明显;而流速大小的差异是影响大小潮之间絮团大小不同的主要因素。研究结果有助于了解珠江口细颗粒泥沙输移特性和相关生物化学过程。 相似文献
7.
Yang Yang Ya Ping Wang Chunyan Li Shu Gao Benwei Shi Liang Zhou Dandan Wang Gaocong Li Chen Dai 《Geo-Marine Letters》2016,36(2):135-149
Interactions between turbulence, suspended sediment concentration (SSC), settling velocity, effective density, fractal dimension, and floc size were studied on the tide-dominated, muddy coastal shelf of the southwestern Yellow Sea, China. The measurements were carried out in July 2013 at two sites located in water depths of 21.2 and 22.1 m. Negative correlations were observed between shear rate, SSC, effective density, and mean floc size, which supports the results of previous numerical, experimental, and field studies. A significant positive correlation was observed between near-bed SSC and shear rate, an indication that SSC variations are controlled by turbulence and re-suspension. In addition, significant linear relationships were found between settling velocity and other parameters (floc size, turbulence, SSC, effective density, and fractal dimension) at the two sites, indicating that the controlling factors on settling velocity are spatially variable. Principal component analysis was applied to determine the relative importance of turbulence, flocculation ability, and SSC as controls on floc size in situ. The relative contributions of turbulence, flocculation ability, and SSC to floc size (at both sites) were ~33.0%, 30.3%, and 29.7%, respectively, this being a new field-based quantitative analysis of the controls on floc size. The findings demonstrate that, in nature, flocculation ability affects floc size to the same degree as turbulence and SSC. Therefore, predictions of floc size in coastal marine environments require constraints not only on turbulence and SSC, but also on flocculation ability. 相似文献
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互花米草盐沼土壤有机质分布特征 总被引：7，自引：1，他引：7
互花米草是我国从美国引进的外来物利，目前在我国沿海已形成大面积的互花米草盐沼，对潮滩土壤等环境产生重大影响。为了分析互花米草盐沼土壤有机质的分布特征，本文通过对江苏东台沿海不同地点(生长年数)的互花米草盐沼土壤样品的-仃机质含量分析，发现互花米草盐沼在由海堤向外的水平方向上变化的平均梯度为每100m土壤有机质含最减少0.87g/kg，垂直方向上的平均梯度为每向下1cm土壤有机质含量减少0.05g/kg。互花米草盐沼土壤订机质的含量与互花米草生长年数相关程度较高，而与植株的生长状况相关较低。 相似文献
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选取海州湾近岸潮流和含沙量实测资料，分析水体紊动强度与含沙量对近岸絮凝体沉降速度的影响，提出了新的沉降速度确定方法。研究表明：淤海州湾近岸泥沙沉降速率大部分在 0.05 ~ 2.50 mm/s 之间，潮周期内泥沙絮凝体的沉降速度
有明显变化。于含沙量较小时，泥沙絮凝体的沉降速度基本随含沙量的增加而增加；含沙量较大时，含沙量与沉降速度呈现出负相关，无论是大潮还是中潮，当含沙量达到 0.7 kg/m3左右时，絮团沉降速度最大，而随着含沙量的增大，絮团沉降速度开始减小。盂在涨落潮垂线平均流速最大时刻，紊动强度达到峰值，含沙量较低时，随着紊动强度增加，沉降速度也随之增加，大潮期间紊动强度对泥沙沉降速度的影响高于中潮。榆新的泥沙沉降速度计算公式不仅考虑了含沙量，还计入了紊动强度 G，大大提高了沉降速度计算值与实测值的相关性。 相似文献
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文章依据2021年9月黄河口盐沼湿地沉积物调查数据，分析了沉积物粒度、容重、有机碳分布特征，并对黄河口盐沼湿地沉积物碳密度及碳储量进行评估。结果显示，黄河口盐沼湿地沉积物类型以粉砂为主，部分层次为砂质粉砂和黏土质粉砂；4种植被类型中，不同深度的沉积物容重差异性不大，互花米草和盐地碱蓬分布区容重整体大于柽柳和芦苇分布区；互花米草、盐地碱蓬、芦苇和柽柳分布区沉积物中有机碳含量分别为0.199%、0.200%、0.184%和0.161%,互花米草和盐地碱蓬分布区底质中有机碳含量较芦苇和柽柳分布区偏高，这与互花米草和盐地碱蓬分布区含有更多的黏土组分有关；计算得出，黄河口盐沼湿地沉积物总碳储量为33.47万t,其中互花米草分布区为14.31万t,芦苇分布区为12.05万t,柽柳分布区为5.27万t,盐地碱蓬分布区为1.84万t。 相似文献
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互花米草对江苏潮滩沉积和地貌演化的影响 总被引：18，自引：1，他引：18
江苏潮滩面积大,岸滩冲淤动态变化复杂.人工引种互花米草对江苏海岸潮滩沉积地貌演化有较大影响,主要体现在影响潮滩沉积速率、物质分布及潮水沟地貌系统的发育等方面.根据定点站位不同年代的高程数据,分析Pethick-Allen模型在江苏潮滩盐沼的适用性;在现场采集柱状样并在室内进行137Cs分析,根据分析结果及前人研究结果,利用P-A模型分析计算江苏潮滩不同时期的沉积速率,结果表明互花米草的引种加快了潮滩沉积速率,它使潮滩沉积地貌演化脱离了原来的渐进函数关系.在选择的典型断面上采集表层底质样,在激光粒度仪上进行粒度分析,结果表明,互花米草易使细颗粒沉积物沉积,大米草滩和盐蒿滩表层沉积物主要来自潮水沟输送.根据野外调查并结合遥感分析,互花米草滩内潮水沟宽深比小,密度大,水道稳定,有别于光滩或大米草滩的潮水沟形态. 相似文献
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长江口细颗粒泥沙絮凝沉降影响因素分析 总被引：33，自引：4，他引：33
根据静水和动水条件下的细颗粒泥沙沉降试验结果,应用灰色模型分析中的关联度分析理论,分析了影响细颗粒泥沙絮凝沉降的主要因素.根据关联度的大小指出,影响细颗粒泥沙絮凝沉降的主要因素依次为水温、沉降历时、盐度、粒度、含沙量和流速,其中盐度和粒度是阈值型影响因素,沉降历时、含沙量和流速是连续型影响因素,水温是具有阈值型和连续型双重特性的影响因素.只要阈值型影响因素达到或超过了阈值,细颗粒泥沙就发生絮凝作用,因素值的变化对沉降强度影响不大.连续型影响因素对细颗粒泥沙絮凝沉降的影响是连续的,它们不仅影响絮凝作用发生,而且影响絮凝沉降强度. 相似文献
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Between April 2002 and April 2003, in situ measurements of water depth, current velocity and suspended sediment content were carried out in edge region of East Chongming salt marsh and neighboring bald flat in the Changjiang (Yangtze) Estuary under different weather conditions. Cross-shore suspended sediment flux was calculated and analyzed. The results show that under calm weather conditions, the current velocity process in bald field and salt marsh area varied differently during semidiurnal tidal cycles. Owing to current velocity asymmetry, mean SSC during flood tide phase was 1.8 times higher than that of ebb tide phase. As a result, net onshore sediment flux controlled cross-shore suspended sediment transport process and salt marsh pioneer zone was generally accreting. There was significant positive correlation between total sediment flux and quartic power of maximum water depth. It indicates that tidal ranges dominate suspended sediment transport and sedimentation process in the salt marsh pioneer zone under the calm weather condition. The sedimentation rate on the adjacent mudflat was higher than the salt marsh, which induced stable accreting of salt marsh towards the sea. The wind events enhanced SSC and current velocity during the semidiurnal tides. And the remarkable onshore net sediment flux could occur on the high marsh and mudflat close to the marsh fringe during the short period under the rough weather condition. 相似文献
15.
底边界层中沉积物的再悬浮和沉降是控制陆架海悬浮沉积物的输运的关键过程。沉积物输运过程的数值*模拟也依赖于沉积物侵蚀和沉降的关键参数的研究。本文根据济州岛西南泥质区的坐底观测估算了此处临界应力。通过底边界层声学仪器ADV和PC-ADP的流速和悬浮物浓度同步观测,基于湍生成与耗散平衡假设,使用惯性耗散法计算沉降速度。这种方法得到的沉降速度ws平均值为0.91 mm s-1,标准差为0.20 mm s-1,此结果远大于Soulbsy（1997）和LISST-ST现场观测粒径分析仪等经验方法的结果。这主要是由于两种方法的本质不同,惯性耗散法形象的刻画了底边界层的水动力,并且更加合理的现场估计沉降速度ws,然而Soulsby的方法通常适用于静水环境。我们提出了一种估计临界应力的新方法,根据悬浮颗粒物浓度时空变化的统计分析（深度平均的悬浮颗粒物浓度对时间求导数）和对应的底应力估算侵蚀临界应力τce和沉降临界应力τcd。侵蚀临界应力τce和沉降临界应力τce的变化范围为0.11-0.25 Pa,对应的中值分别为0.20 Pa和0.16 Pa,这也证实了侵蚀临界应力略大于沉降临界应力。除此之外,我们还使用了另一种方法估算临界应力,通过沉降速度间接估算的临界应力范围为0.06-0.17 Pa。 相似文献
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基于MODIS的沿海带状植被NDVI/EVI季节变化研究——以江苏沿海互花米草盐沼为例 总被引：3，自引：0，他引：3
植被指数的时空变化是目前全球变化研究的热点问题。该文以江苏沿海互花米草盐沼为例,运用MODIS数据探索沿海带状植被NDVI/EVI的季节变化规律。结果表明,互花米草的返青(出苗)、抽穗、种子成熟等主要物候期在VI曲线上均能得到很好体现。本研究可为监测互花米草盐沼扩展趋势、加强管理、趋利避害提供基础数据,同时也为沿海其它带状植被监测提供借鉴。 相似文献
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滨海盐沼作为重要的湿地生态系统，有极大的社会、经济和生态价值。文章采用多源国产高空间分辨率卫星数据，结合野外现场调查，对广东和广西滨海盐沼开展遥感调查与分析。2019年年底，广东和广西滨海盐沼分布面积分别为1 258.00 hm2和1 450.36 hm2。广东14个沿海市除茂名市外均有滨海盐沼分布，珠海市、江门市、湛江市的分布面积分别为438.89 hm2、331.83 hm2和162.36 hm2，占广东滨海盐沼总面积的34.89%、26.38%和12.91%。广西3个沿海市均有滨海盐沼分布，北海市、防城港市和钦州市的分布面积分别为1 354.87 hm2、49.73 hm2和45.76 hm2，占广西滨海盐沼总面积的93.41%、3.43%和3.16%。广东和广西互花米草分布面积分别为327.96 hm2和1 312.02 hm2。广东海岸带互花米草主要分布在江门市、阳江市、湛江市和潮州市，分布面积分别为179.07 hm2、73.64 hm2、69.72 hm2和5.52 hm2。广东近5年海岸带互花米草面积较为稳定，没有大范围暴发式扩散。广西海岸带互花米草主要分布在北海市和钦州市，分布面积分别为1 309.04 hm2和2.98 hm2。广西海岸带互花米草面积比最早引种时增加了1 311.08 hm2。互花米草在广西北海东海岸、铁山港、廉州湾和大风江口不断扩张，廉州湾的互花米草仍处于种群扩散的暴发期，需加强对互花米草的监测和防控工作。 相似文献
19.
R.J. Uncles A.J. BaleJ.A. Stephens P.E. FrickersC. Harris 《Estuarine, Coastal and Shelf Science》2010
Measurements are presented of median floc diameters and associated environmental data over spring-tide tidal cycles at two stations in the muddy Tamar Estuary, UK, for winter, spring and summer conditions. The particulate organic carbon and particulate total carbon contents of mudflats and SPM (suspended particulate matter) at the stations, together with other evidence, indicates that much of the SPM was derived from mud sources that were located between the two stations during winter and spring, and from very mobile sediment sources in the upper estuary during summer. Observed in-situ median floc sizes varied widely, from <50 to >500 μm and rapid settling of particles close to HW and LW (high and low water) left only the smaller flocs in suspension. Time-series of depth-averaged median floc sizes generally were most closely, positively, correlated with depth-averaged SPM concentrations. Floc diameters tended to reach maximum median sizes near the time when SPM concentrations were highest. These high concentrations were in turn largely generated by resuspension of sediment during the fastest current speeds. Although such correlations may have arisen because of SPM-driven floc growth - despite fast tidal currents - there is also the possibility that tough aggregates were eroded from the intertidal mudflats and mudbanks. Although a hypothesis, such large aggregates of fine sediment may have resulted from the binding together of very fine bed particles by sticky extracellular polymeric substances (EPS) coatings, produced by benthic diatoms and by other biologically-mediated activity. A rapid reduction of SPM occurred at the up-estuary station within 2.5 h of HW on the flood, when decelerating currents were still relatively fast. It appears that at least two processes were at work: localised settling of the largest flocs and up-estuary transport in which large flocs were transported further into the estuary before settling into the Tamar's ETM (estuarine turbidity maximum) over the HW-slack period. Up-estuary advection of large flocs and their eventual settling would place the down-estuary edge of the ETM above the upper-estuary station during summer, spring-tide conditions. This position of the ETM was observed close to HW during longitudinal surveys of the estuary. 相似文献
20.
浙江省三门湾地区潮滩互花米草扩散迅速,已成为潮滩主要植被类型,挤占滩涂生态空间,降低海湾纳潮量,引起滩涂淤长和水交换能力下降,互花米草入侵和扩散问题引起当地生态环境和海洋管理部门高度关注。本文利用Landsat和Sentinel-2系列卫星遥感数据,结合无人机摄影测量,对三门湾北部潮滩近20年来互花米草分布和变化进行分析,结果表明,近20年间三门湾北部潮滩互花米草快速扩张,面积由2000年的21.8 km2增加到2017年高峰值为38.6 km2,年扩展面积近1 km2,主要分布在宁海县的一市港、双盘涂、三山涂和象山县的蟹钳港等湾顶潮滩区。2017年后,部分互花米草生长的上部潮滩被改造为海水养殖池,总体上互花米草面积有所下降,到2020年4月份统计的互花米草面积为34.9 km2,但潮滩下部米草扩增趋势仍然持续。扩增主要为沿潮沟两侧及先斑块后连续的特征。高程、人类活动引起的水动力环境改变是互花米草面积变化的主要因素。 相似文献