OPTICAL AND ACOUSTIC DETERMINATION OF THE PROPERTIES AND FLUX OF ESTUARINE SUSPENDED PARTICULATE MATTER UNDER WAVES AND TIDAL CURRENTS.

波浪和潮汐流下河口悬浮颗粒物的性质和通量的光学和声学测定。

• 批准号: NE/F01225X/1
• 金额: $ 8.6万
• 依托单位: Bangor University
• 依托单位国家: 英国
• 项目类别: Training Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF01225X%2F1
• 关键词: OPTICAL; ACOUSTIC; DETERMINATION; PROPERTIES; FLUX

It is anticipated that climate change will impact water quality, biogeochemical cycling and flux, and ecosystem functioning and sustainability, in estuaries. All of these are significantly mediated by suspended particulate matter (SPM) since SPM determines turbidity (which constrains primary production), generates benthic fluff on the seabed (which modifies biogeochemical exchanges and benthic productivity), and carries important biogeochemical components (e.g. carbon, nitrogen, contaminants and pollutants). Quantification of the role of SPM is difficult because we have poor knowledge of the properties of SPM (i.e. particle size, density, settling velocity) and, in particular, the key processes of fine particle entrainment (i.e. pick-up from the bed) and sedimentation (i.e. settling to the bed) that depend on SPM properties. This is because most SPM in estuaries is in the form of flocs (i.e. aggregates of dead and living organic matter, cohesive inorganic matter, and water) that undergo aggregation and disaggregation, as well as settling and resuspension, on short time scales, particularly in response to the turbulence field. Flocs are not easily measured since they are dramatically modified by conventional sampling methods (they are easily ruptured and/or they may aggregate during sampling). We lack reliable and comprehensive information on key parameters such as pick-up functions and settling velocities of flocs, especially since floc properties change on a range of time scales: tidal (due to turbulence), lunar (the spring-neap cycle), and seasonal (due to storm resuspension and biological production of particulate matter). It is proposed to carry out an intensive field measurement campaign in the Dee estuary, in concert with an ongoing NERC-funded research programme (FORMOST), to win a unique dataset of SPM properties using a variety of optical and acoustic techniques. FORMOST is using state-of-the-art acoustic and optical technologies to characterise bed geometry, boundary layer dynamics, and suspended sediment characteristics in the near-bed (1 m above bed) region of the outer Dee estuary. FORMOST will provide new information on pick-up and transport rates of coarse and fine particles in relation to bed composition (a mixture of sand and mud) and geometry (rippled) in response to waves and currents. The research studentship will extend the study of SPM through the entire water column using cutting-edge technologies to determine floc sizes and concentrations (Laser In-Situ Scattering and Transmissometry (LISST), optical backscatter sensors (OBS), and transmissometers), and floc settling velocities (LISST-ST and settling velocity tubes, SVTs); the influence of phytoplankton on floc composition will be assessed using a Fast Repetition Rate Fluorometer (FRRF). Turbulence energy production through the water column will be determined using a seabed Acoustic Doppler Current Profiler (ADCP) using the proven variance method. The instrumentation, used in profiling and mooring deployments, will provide information on the interrelationships of floc size, density and settling velocity, and how these vary in response to changing SPM provenance and history. Measurements will be made over tidal and lunar cycles during 4 Prince Madog cruises in February and May (3 cruises are funded and Bangor University will provide 1 additional free cruise). The observations will be used to develop further an existing 1-D model, incorporating resuspension and aggregation, to investigate vertical flux of SPM in response to changing floc properties. The 1-D formulations will then be utilised in the POLCOMS area model for the Dee estuary to investigate how fine sediment fluxes in the estuary vary with changing SPM properties.

预计气候变化将影响河口的水质、生物地球化学循环和通量以及生态系统功能和可持续性。所有这些都在很大程度上受到悬浮颗粒物（SPM）的介导，因为悬浮颗粒物决定浑浊度（限制初级生产力），在海底产生底栖绒毛（改变生物地球化学交换和底栖生产力），并携带重要的生物地球化学成分（例如）碳、氮、污染物和污染物）。SPM的作用的量化是困难的，因为我们有SPM的属性（即颗粒大小，密度，沉降速度），特别是，细颗粒夹带（即从床上拿起）和沉降（即沉降到床上），取决于SPM的属性的关键过程知识贫乏。这是因为大多数悬浮颗粒物在河口是在絮凝体的形式（即聚集的死和活的有机物，粘性无机物和水），经历聚集和解聚，以及沉降和再悬浮，在短时间尺度上，特别是在响应湍流场。絮凝物不容易测量，因为它们被常规取样方法显著改变（它们容易破裂和/或它们可能在取样期间聚集）。我们缺乏可靠和全面的信息，如拾取功能和絮凝物的沉降速度等关键参数，特别是因为絮凝物的性质在一系列时间尺度上发生变化：潮汐（由于湍流），月球（春季小潮周期）和季节（由于风暴再悬浮和颗粒物的生物生产）。建议在迪河口进行密集的实地测量活动，与正在进行的NERC资助的研究计划（FORMOST），赢得一个独特的数据集SPM属性使用各种光学和声学技术。FORMOST正在使用最先进的声学和光学技术，以监测底床几何形状、边界层动力学和外迪河口近床（床以上1米）区域的悬浮沉积物特性。FORMOST将提供关于粗颗粒和细颗粒随波浪和水流的沉积物组成（沙和泥的混合物）和几何形状（波纹状）的拾取和迁移率的新信息。该研究奖学金将使用尖端技术将SPM的研究扩展到整个水柱，以确定絮凝物的大小和浓度（激光原位散射和透射仪（LISST）、光学反向散射传感器（OBS）和透射仪）和絮凝物沉降速度（LISST-ST和沉降速度管，SVT）;浮游植物对絮凝物组成的影响将使用快速重复率荧光计（FRRF）进行评估。通过水柱产生的湍流能量将使用海底声学多普勒海流剖面仪（ADCP），采用经验证的方差法来确定。在剖面分析和系泊部署中使用的仪器将提供有关絮凝物大小、密度和沉降速度之间相互关系的信息，以及这些信息如何随着SPM来源和历史的变化而变化。将在2月和5月的4次马多格王子巡游期间对潮汐和月球周期进行测量（3次巡游得到资助，班戈尔大学将提供1次额外的免费巡游）。观测结果将被用来进一步发展现有的1-D模型，将再悬浮和聚集，调查响应于不断变化的絮体特性的SPM的垂直通量。1-D配方，然后将利用在POLCOMS区域模型的迪河口，调查如何在河口细泥沙通量变化与SPM属性。