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

预计气候变化将影响河口水质、生物地球化学循环和通量、生态系统功能和可持续性。所有这些都主要由悬浮颗粒物（SPM）介导，因为悬浮颗粒物决定浊度（限制初级生产），在海底产生底栖生物蓬松物（改变生物地球化学交换和底栖生物生产力），并携带重要的生物地球化学成分（如碳、氮、污染物和污染物）。量化SPM的作用是困难的，因为我们对SPM的性质（即粒度、密度、沉降速度）知之甚少，特别是对细颗粒夹带（即从床上拾取）和沉降（即沉降到床上）的关键过程依赖于SPM的性质。这是因为河口的大多数SPM以絮凝体的形式（即死的和活的有机物、粘性无机物和水的聚集体），在短时间尺度上经历聚集和分解，以及沉降和再悬浮，特别是对湍流场的响应。絮凝体不容易测量，因为它们被传统的采样方法极大地改变了（它们很容易破裂和/或在采样过程中可能聚集）。我们缺乏关于絮凝体拾取功能和沉降速度等关键参数的可靠和全面的信息，特别是因为絮凝体的特性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）和季节性（由于风暴再悬浮和颗粒物质的生物生产）。建议在Dee河口开展密集的实地测量活动，与正在进行的nerc资助的研究计划（FORMOST）相配合，利用各种光学和声学技术获得独特的SPM属性数据集。FORMOST正在使用最先进的声学和光学技术来表征迪河口外近河床（离河床1米）区域的河床几何形状、边界层动力学和悬浮沉积物特征。FORMOST将提供有关粗颗粒和细颗粒的吸收和传输速率的新信息，这些速率与床的组成（砂和泥的混合物）和几何形状（波纹）对波浪和水流的响应有关。该研究项目将在整个水柱上扩展SPM的研究，使用尖端技术来确定絮团大小和浓度（激光原位散射和透射测量（LISST）、光学后向散射传感器（OBS）和透射计），以及絮团沉降速度（LISST- st和沉降速度管，SVTs）；将使用快速重复率荧光计（FRRF）评估浮游植物对浮体组成的影响。通过水柱产生的湍流能量将使用海底声学多普勒电流剖面仪（ADCP），使用已验证的方差方法来确定。该仪器用于剖面分析和系泊部署，将提供有关絮团大小、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。在2月和5月的4次王子马多格游轮期间，将对潮汐和月球周期进行测量（3次游轮由资助，班戈大学将提供1次额外的免费游轮）。这些观测结果将用于进一步发展现有的1-D模型，包括再悬浮和聚集，以研究SPM的垂直通量对絮体性质变化的响应。1-D公式随后将用于迪河口的POLCOMS区域模型，以研究河口的细泥沙通量如何随SPM性质的变化而变化。

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.