伶仃洋河口泥沙絮凝特征及影响因素研究

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。     

Internal recycling of particle reactive organic chemicals in the Chesapeake Bay water column

Hydrophobic organic contaminants (HOCs) may be used as tracers of particle dynamics in aquatic systems. Internal cycling of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were studied in the mesohaline Chesapeake Bay to assess the role of resuspension in maintaining particle and contaminant inventories in the water column, and to compare settling and suspended particle characteristics. Direct measurements of sediment resuspension and settling conducted in conjunction with one of the sediment trap deployments indicate reasonable agreement between measurements of particle flux using the two different methods. Organic carbon and PCB concentrations in settling solids collected in near-surface sediment traps were remarkably lower than concentrations in suspended particles collected by filtration during the trap deployments, but higher PAH concentrations were found in the settling particles. The different behaviors of PAHs and PCBs in the settling particles are due to their different source types and association to different types of particles. Sediment trap collections in near bottom waters were dominated by resuspension. Resuspension fluxes of HOCs measured 2 m above the bay bottom were as high as 2.5 μg/m² day for total PCBs and 15 μg/m² day for fluoranthene, and were 25 and 10 times higher than their settling fluxes from surface waters, respectively. HOC concentrations in the near bottom traps varied much less between trap deployments than HOC concentrations in the surface traps, indicating that the chemical composition of the resuspended particles collected in the near bottom traps was more time-averaged by repeated resuspension than the surface particles.     

Suspended particles near the bottom in Osaka Bay

The vertical distributions of suspended particles in Osaka Bay were measured by using anin situ beam attenuation meter. The concentration of suspended particles near the bottom increases rapidly toward the bottom where size of sediment is in a range of silt. The settling velocity of suspended particles near the bottom was measured with the use of a settling tower in the laboratory. The settling velocity of the suspended particles with diameter from 10 to 100m is 2×10^–3cm s^–1 to 5×10^–2cm s^–1. The density of the particles ranges from 2.0 to 1.1 and decreases with increasing particle diameter.     

Recycling of manganese in the coastal sea,Funka Bay,Japan

The downward flux of Mn through the water column was directly measured using sediment traps. The Mn flux from the bottom sediment to the water column, and the removal rate of Mn in the bottom water were estimated from Mn gradients in the bottom water. The sediment traps were deployed more than ten times at the same station in Funka Bay, Japan. The trapped settling matter and filtered suspended matter samples were analyzed for Mn, Fe, Al and ignition loss. The observed downward flux of Mn through the water column in winter (1.3–2.8 μg/cm² /day) was generally an order of magnitude larger than that in summer (0.13–0.45 μg/cm² /day), and the Mn fluxes for both seasons were also greater than the accumulation rate of Mn in the bottom sediments (0.10 μg/cm ²/day). More Al was contained in the trapped settling matter than in the suspended matter, while Mn showed the opposite behavior. The Fe/Mn ratio of the residual fraction (obtained by subtracting the sediment component of the settling matter) was rather well correlated with the corresponding ratio in suspended matter. Settling particles are expected to scavenge suspended matter during their passage through the water column. The flux of Mn across the sediment—water interface was estimated from its vertical profiles in the water column to be 0.1–0.3 μg/cm² day. The residence time of Mn in bottom water was about one to several months. These results suggest that Mn is actively recycled between the water column and the sediments of the coastal sea.     

Examples of spatial and temporal variations of some fine-grained suspended particle characteristics in two Danish coastal water bodies

In June and September of 1999, a LISST-100 in situ laser diffraction particle sizer was used to analyse the temporal and spatial variation of the beam attenuation coefficient, the in situ median particle (aggregate) diameter and the median volume concentration of suspended matter in two Danish coastal water bodies. One of the study sites was generally exposed to wind, while the other was quite sheltered. Measurements of the mass concentration of total suspended matter and chl a were made simultaneously. The in situ median effective density, settling velocity and vertical flux of the suspended matter are computed. Results demonstrate that in September, the in situ median aggregate diameter, settling velocity and vertical flux was smaller (by a factor of up to 16) and the concentration higher (by a factor of up to almost two) than in June. This is attributed to varying degrees of turbulence in the water in the weeks preceding the field work, causing aggregates to break up (lowering in situ aggregate diameter and settling velocity) and sediment to be resuspended (increasing concentration) in September. The fractal dimension of the suspended aggregates is estimated. The fractal dimension is found to increase from June to September at both study sites, supporting the notion of aggregate break-up in September due to turbulence in the upper part of the water column. An algae bloom occurred at the sheltered study site in September. In situ particle size spectra from this site demonstrated increasing aggregate sizes towards the bottom. It is suggested, that the increase in size is due to biologically induced aggregation, causing large aggregates to settle out of the upper part of the water column, leaving finer particles and aggregates behind.     

Response of excised gill tissue from the New Zealand scallop Pecten novaezelandiae to suspended silt

The role of turbidity in scallop mortality was investigated for two size classes of Pecten novaezelandiae (70 ± 2 mm and 20 ± 1 mm shell height), by using the “crawl” velocity of excised pieces of gill tissue as an indicator of the response to suspended silt. The crawl velocity of 3 × 5 mm pieces of gill tissue was measured in six different silt concentrations (0.025, 0.05, 0.1, 0.2, 0.3. 0.5% silt, by dry weight) and two size classes (< 10 μm and 10–30 um) of silt. Results of the study indicate that juvenile (20 mm shell height) scallops may be less tolerant of suspended silt than larger (70 mm shell height) scallops and that both size classes may be less tolerant of fine (< 10 μm) silt/clay sized particles than coarse (10–30 μm) particles. These conclusions are supported in part by data from the mortality of whole 20 mm scallops exposed to two size classes (< 10 μm and 10–30 μm) and three concentrations (0.05, 0.3, 0.6%, by dry weight) of silt. Increasing concentrations and decreasing particle size of the suspended silt resulted in reduced gill piece crawl velocity and an increase in the mortality rate of the whole scallops. These results suggest controls on human‐induced disturbance of bottom sediments, such as bottom trawling and dredging, may benefit any further scallop bed enhancement programmes by the avoidance of deterioration in water quality and mechanical damage to scallop spat.     

Manganese recycling in coastal waters

Both water and suspended particulate matter in the deep water of the Gulf of St. Lawrence are greatly enriched in manganese. Maximum dissolved manganese concentrations are encountered close to the sediment-water interface whereas the particulate matter with highest manganese content occurs 30–100 m above the bottom. The elevated concentrations are attributed to the diagenetic release of dissolved manganese from the underlying fine-grained sediments and its subsequent precipitation in the water column. The rate of manganese precipitation is rapid compared to the rates of diffusion and mixing in the bottom water. Part of the manganese-enriched particulate matter becomes mixed throughout the water column by advection and diffusion. Thus, particles enriched in manganese can ultimately be carried into the open ocean by prevailing currents. This process, which appears to be widespread in eastern Canadian coastal waters, enables manganese originally associated with rapidly settling terrigenous particles to be transferred to slowly settling fine-grained suspended particles entering the ocean from coastal environments. In this way, riverborne manganese of terrigenous origin may well account for a major proportion of the excess manganese in pelagic sediments.     

In situ particle size spectra and density of particle aggregates in a dredging plume

An in situ laser particle sizer, the LISST-100, was used to describe the spatial variation of beam attenuation coefficient, in situ particle size spectra and aggregate densities in a dredging plume in the sound Øresund between Denmark and Sweden. The results proved that the above mentioned parameters varied significantly within the investigated length of the plume (approximately 2 km). It is shown how the small single primary particles aggregate and change the in situ particle size spectra into a slightly better sorted and coarser size distribution, and at the same time how the mean density of particles/aggregates decreases significantly. This shift in the state in which the particles exist in the water effectively changes the optical response of the mass of particles suspended in the water. It is shown that adequate correlations between mass concentrations and beam attenuation coefficients can only be obtained if parameters describing the in situ quality and state of the mass of particles, e.g. standard deviation of the size spectra and volume concentration, is included in the regression. From the spatial variation in mean density and in situ particle size, it was possible to calculate the spatial difference in settling velocity. It was found that the difference in settling velocity was only about a factor of 1.7, because increasing in situ particle size was counter-balanced by decreasing mean density. Furthermore, the time-scale of flocculation within the plume was found to be in the order of 50 min.     

珠江口磨刀门泥沙絮凝特征

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。     

三沙湾夏季底边界层动力过程及悬沙输运特征

基于2018年8月福建三沙湾湾内外共两个定点站位的船基和座底三脚架观测数据,研究了三沙湾底边界动力过程及悬沙输运特征。结果表明,三沙湾湾内湾外两个站位均表现出涨落潮历时相近但涨落潮流速明显不对称的现象,即湾内涨潮流速大于落潮流速,湾外则相反。湾内水体受淡水输入影响较大,表现出落潮期间显著的温盐层化,而涨潮期间水体混合良好;湾外水体受淡水影响不明显,表现为水体温度主导的层化。通过对底边界层动力过程的分析表明,湾内（距底0.75 m）、湾外（距底0.50 m）站位底边界层的平均摩阻流速分别是0.016 m/s、0.013 m/s,且两个站位拖曳系数基本相等（2.03×10-3）,表明在相同流速下湾内站位的底部切应力更大,近底沉积物再悬浮和搬运相对湾外站位更为显著。因此观测期间悬沙浓度最大值出现在湾内站位,为109 mg/L,且悬沙在垂向上的分布可达上层水体;湾外站位悬沙浓度更低,并且底部悬浮泥沙仅能影响至距底5 m的水体。悬沙通量机制分解结果表明,三沙湾夏季的潮周期单宽悬沙从湾外向湾内方向净输运,湾内站位向湾内方向净输运74.88 g/(m·s),平流输沙占主导作用,贡献率41.7%;湾外站位向湾内方向净输运10.57 g/(m·s),主要受平流输沙和垂向净环流的控制,贡献率94.9%     

Vertical diffusion in coastal areas—I

The suspended matter in seawater near the bottom is distributed by the effects of sinking and diffusion. The author developed a method of estimation of the vertical eddy diffusivity near the sea bottom and the particle size distribution of bottom sediment, in the case of equilibrium state. This estimation was made by the comparison of measured and computed vertical distribution of beam attenuation. The parameters which were used for the computation were (1) median of the particle size distribution of bottom sediment, assuming that the particle size was a log-normal distribution, and (2) the proportional constant of vertical eddy diffusivity which was proportional to the height from the bottom.As the suspended matter in seawater contains particles of different sizes, the computation of the diffusion and beam attenuation was made for each particle size, and summarizing the results, the vertical distribution of beam attenuation coefficient was computed.In order to estimate the beam attenuation in high particle concentration, an equation by which the effect of overlapping of particle shadow in the light beam was eliminated, was used.     

黄河口潮滩泥沙絮凝研究

本文基于现场观测的絮团粒径、悬沙浓度及水动力数据,研究了黄河口南部潮滩泥沙絮凝特征。研究发现,黄河口潮滩絮团粒径在25.42～264.44 μm之间,平均为95.20 μm。水体紊动对黄河口潮滩絮凝的影响存在差异,紊动对絮凝促进作用的上限约为G_l=3.76 s?1。紊动强度低于G_l时,紊动促进泥沙絮凝,絮团粒径随紊动加强而增大;反之水体紊动对絮凝主要起抑制作用,絮团粒径随紊动强度增大而减小。悬沙浓度对黄河口潮滩泥沙絮凝起抑制作用,同等紊动条件下高悬沙浓度对应的絮团粒径更小。黄河口潮滩絮团有效密度与粒径呈现负相关关系,沉速主要受粒径影响。本研究补充了对弱潮河口潮滩泥沙絮凝特性的认识。     

2013 年夏秋季黄、渤海悬浮颗粒物粒径分布特征

悬浮颗粒物及粒径是水质重要参数,研究其分布特征有助于加深对海洋生态环境的了解。利用2013年6月和2013年11月LISST-100观测数据,研究了黄、渤海区域悬浮物粒径和浓度的分布情况,浓度分布整体上近岸高远岸低,粒径分布呈现近岸细远岸粗的特征,季节分布特征明显。通过典型断面分析发现,悬浮物粒径和浓度随着水深变化明显,连续站数据分析结果表明,大风对底层颗粒物的再悬浮作用显著,潮流对悬浮物的时空分布有着重要影响;水体衰减系数随着体积浓度变化明显。此外,还研究了悬浮颗粒物粒径Junge分布在黄、渤海区域的适用性。     

胶州湾水域重金属铬的分布及迁移

根据1979年的胶州湾水域调查资料，分析了重金属铬在胶州湾水域的分布、迁移和季节变化。研究结果表明；春季，胶州湾水城铬污染较轻，大部分海域水质状况较好，而到夏季没有受到污染。在时空分布上，春季，铬污染形成了明显的梯度，由东北向西南方向递减，从112．3μg／L降低到0．2μg／L。夏季，铬的水平分布比较均匀，表层水体铬的含量较低，范围在0．10～1．40μg／L之间波动。因此认为，1979年整个胶州湾水域的重金属铬属于面污染源。而且，当铬进入胶州湾海域后，很快吸附在水体中的悬浮颗粒上，并被水流较快地带离胶州湾水城，几乎没有在胶州湾水域表、底层留下污染痕迹。     

Over time and space changing characteristics of estuarine suspended particles in the German Weser and Elbe estuaries

Fine cohesive, suspended sediments appear in all estuarine environments in a predominately flocculated state. The transport and deposition of these flocs is influenced by their in-situ and primary particle size distribution. Especially the size of the inorganic particles influences the density and hence the settling velocity of the flocculated material. To describe both the changes in primary particle size of suspended particulate matter as well as the variability of floc sizes over time and space, the data of In-Situ Particle-Size Distributions (ISPSDs), Primary Particle Size Distributions (PPSDs) and Suspended Sediment Concentrations (SSCs) were collected. For this, Laser In-Situ Scattering and Transmissiometry (LISST) measurements as well as the water samples were collected in the German Elbe and Weser estuaries, covering seasonal variability of the SSC.The data of the ISPSDs show that the inorganic and organic Suspended Particulate Matter (SPM), as found in the Elbe and Weser estuaries, mostly appears in a flocculated state. The substrate for organic matter is mainly imported from the seaside and transported into the estuaries as indicated by an upstream decrease of the amount of fine particles. In winter, when the freshwater discharge is high, different PPSDs are found in the case of the Elbe estuary in the Turbidity Maximum Zone (TMZ) as well as in the landward and in the seaward sections close to the TMZ. In summer, the distance between the seaward and the landward section is too low to obtain an individual PPSD within the Elbe TMZ.A missing correlation between the PPSD and ISPSD shows that the inorganic constituents do not have an influence on the in-situ floc size. Although flocs aggregate and disaggregate over a tidal cycle and with changing SSC, they do not change their PPSD. The microflocs are therefore strong enough to withstand further breakage into their inorganic constituents.     

Grain-size distribution patterns of suspended sediment in response to hydrodynamics on the Dafeng intertidal flat, Jiangsu, China

1Introduction The sediment dynamics of intertidal flats in-volves erosion, transport, and settling processes. A-mong these, the mechanisms of sediment transportare a key question. Progress has been made in awide range of associated areas, including sedime…     

基于声学仪器与粒径分析仪研究东海浮游动物昼夜垂直迁移过程

浮游动物的昼夜迁移活动与其种群变动和摄食节律紧密联系,浮游动物昼夜移动的研究已经成为种群动力学研究的一个重要组成部分。2013年夏季在浙江东部近海,结合声学多普勒流速剖面仪(ADCP)和激光粒径分析仪(LISST-100)等仪器进行了一次定点周日连续观测。通过声学反演方法,得到后向散射强度剖面的时间变化,结合LISST-100得到的水体悬浮物粒径谱,研究了浮游动物垂直迁移及其习性。分析发现了可能是精致真刺水蚤的一次昼夜垂直迁移过程,其在夜间进入跃层附近进食,白天蛰伏于底层低温高盐的台湾暖流水中,垂向迁移速度达到了0.05 m/s。LISST-100观测还发现在夜间跃层边界处大粒径颗粒聚集和100～150 μm大小的颗粒物的减少,水体中不同粒径的悬浮颗粒物有明显的昼夜变化节律,推测水体中不同层次生物群落结构存在昼夜差异。     

九龙江口海沧港区17～-18^#码头基槽浮泥成因分析

九龙江口海沧港区因建设17—18^#泊位而开挖的基槽处发育厚层浮泥．通过对该处浮泥及其周边的水体悬浮颗粒、海底表层和沉积物柱状样的激光粒度分析，发现浮泥的颗粒物主要由峰值粒径在7～10μm的粘土粉砂质细颗粒组分构成，但在浮泥层的下部还含有小部分峰值粒径为200—500μm的砂质粗颗粒组分．浮泥中细颗粒组分的粒度特征和水体中的悬浮颗粒、底质沉积物中的细颗粒组分一致，而浮泥中粗颗粒组分的粒度特征，和九龙江口洪水事件成因的中粗砂的粒度特征一致．结合现场调访和水文观测，得出17—18^#泊位基槽处浮泥的成因主要受海沧港区建设过程中产生的大量再悬浮泥沙以及受水下地形的影响，水动力条件适宜悬浮泥沙在17—18^#泊位基槽处聚淤．此外，台风引发的洪水也是增加悬浮泥沙含量的辅助因素．随着海沧港区的建成，水动力条件的改变，17～18^#泊位港池及调头区浮泥的厚度将小于基槽区浮泥厚度．     

Pathways of suspended particles transport in the bottom layer of the southern Baltic Sea depending on the wind forcing (Numerical Simulation)

A random-walk model for a nonuniform diffusivity media coupled with an ocean circulation model has been applied to describe the pathways of suspended particles transport in the bottom boundary layer (BBL) of the southern Baltic Sea. The circulation model is based on the Princeton Ocean Model, in which the vertical grid size is logarithmically refined towards the bottom in order to resolve the BBL. Fields of the flow velocity and eddy diffusivities simulated by the POM, along with the settling velocity of the suspended particles, are used as an input for the random-walk model. A number of numerical experiments were performed to study the pathways of suspended particles in the southern Baltic BBL depending on the wind conditions. In particular, the suspended particles introduced into the BBL in the center of the Bornholm Basin at westerly and southerly winds are found to be trapped in the basin provided that the particles’ settling velocity is equal or greater than 2 m/day. The trapping phenomenon is explained by the combined effect of the Ekman transport convergence in the BBL due to the cyclonic gyre and the gravitational settling of the particles.     

江苏大丰潮滩悬沙级配特征及其动力响应

根据2002和2003年夏季在江苏大丰潮滩的现场观测资料,详细分析了悬沙级配的时空分布特征、影响因素及其对再悬浮、沉降和流速的响应.研究结果表明,悬沙颗粒较细,以粉砂为主,悬沙级配在潮周期内的变化模式有两种类型:一是稳定型,悬沙级配的时空(垂向和平面)变化很小;二是双峰型,悬沙级配的时空变化显著,粗细峰高度不断变化.再悬浮、沉降、涨潮时输入潮滩的悬沙和底质级配是影响悬沙级配的重要因子.再悬浮使粗颗粒悬沙的含量增加,悬沙与底质级配不断接近,沉降对悬沙级配的影响与再悬浮相反.再悬浮发生时悬沙级配对流速有明显响应.在没有再悬浮和沉降影响的情况下,潮滩不同部位、不同时间的悬沙级配趋于稳定和相同,对这种状态下的悬沙级配可称为背景悬沙级配,大丰潮滩背景悬沙级配的平均粒径为7μm.