Acoustic and optical backscatter from flocculating sediments (FLOCSAM)

絮凝沉积物的声学和光学反向散射 (FLOCSAM)

• 批准号: NE/E00573X/1
• 负责人: Jan Alexander
• 金额: $ 27.09万
• 依托单位: University of East Anglia
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FE00573X%2F1
• 关键词: Acoustic; optical; backscatter; flocculating; sediments

Fine suspended particles exert a profound influence on water quality in estuaries and coastal seas through their propensity to adsorb contaminants such as metals and organic compounds and by acting as a barrier to the penetration of light affecting growth of benthic biota; they impact on sensitive marine ecosystems and influence nutrient cycling and have considerable socio-economic impacts related to dredging and dumping activities around ports and harbours as sediment flocculates due to enhanced settling. Marine scientists, engineers and managers therefore need to be able to measure fine sediment fluxes to assess their impact on the coastal environment. However, fine suspended particles rarely exist in their primary state but form flocs which are typically aggregated, heterogeneous assemblages of mineral grains, biogenic debris, bacteria and organic material. Acoustic and optical instruments are used to measure suspended sediment mass concentrations but we have very little understanding of how sound in particular interacts with complex flocs. Instruments such as Acoustic Doppler Current Profilers (ADCPs), which are frequently used to 'measure' fluxes of fine material through the water column, are usually 'calibrated' against water samples from which sediment mass concentration is measured. We intend to investigate this long-standing and scientifically-challenging problem of how sound responds to muddy sediments and develop, through a combination of theory and experiment, algorithms capable of quantitatively inverting acoustic backscatter signals from cohesive sediment to predict mass concentration, and to combining these with the best features of optical sensors. The theoretical component of this study will build on the existing experience with backscatter models from non-cohesive sediment (sand) and developments will be informed by the tank, flume and field results. Small-scale (Couette-type tank) and medium-scale (flume) laboratory experiments will be conducted, where a degree of control can be exerted on the flocculation processes using simple clay suspensions (without the complexity of mixtures of sediments or of biological components) and culminating in a full-scale field campaign at a muddy estuarine site. Both the laboratory and field trials will use a variety of acoustic (ABS, ADV and ADCP) and optical instruments (OBS, LISST-100 and imaging-technology) together with pumped-sampling, velocity and turbulence measurements. The imaging technology will build on the INSSEV programme and will be especially valuable, allowing digital images of individual flocs to be processed and their fall velocity measured.

细悬浮粒子具有吸附金属和有机化合物等污染物的倾向，并对影响底栖生物群生长的光线的穿透起到屏障作用，因此对河口和沿海海域的水质产生深远影响；它们对敏感的海洋生态系统产生影响，影响养分循环，并对港口周围的疏浚和倾倒活动产生相当大的社会经济影响，因为泥沙会因沉降加剧而絮凝。因此，海洋科学家、工程师和管理人员需要能够测量细微的沉积物通量，以评估它们对沿海环境的影响。然而，细小的悬浮颗粒很少以其原始状态存在，而是形成絮凝体，这些絮凝体通常是矿物颗粒，生物碎屑，细菌和有机物的聚集，非均质组合。声学和光学仪器用于测量悬浮沉积物质量浓度，但我们对声音特别是如何与复杂絮凝体相互作用知之甚少。诸如声学多普勒电流分析器（ADCPs）之类的仪器经常用于“测量”通过水柱的细物质的通量，通常是根据测量沉积物质量浓度的水样进行“校准”的。我们打算研究这个长期存在且具有科学挑战性的问题，即声音对泥泞沉积物的反应，并通过理论和实验的结合，开发能够定量反演粘性沉积物的声后向散射信号以预测质量浓度的算法，并将这些算法与光学传感器的最佳特性相结合。本研究的理论部分将建立在现有的非粘性沉积物（沙）后向散射模型的经验基础上，并将根据水槽、水槽和现场结果进行开发。将进行小规模（库埃式水槽）和中型（水槽）实验室实验，其中可以使用简单的粘土悬浮液（没有沉积物或生物成分混合物的复杂性）对絮凝过程施加一定程度的控制，并最终在泥泞的河口地点进行全面的实地运动。实验室和现场试验将使用各种声学（ABS， ADV和ADCP）和光学仪器（OBS， list -100和成像技术）以及泵送采样，速度和湍流测量。成像技术将以INSSEV方案为基础，将特别有价值，允许处理单个絮凝体的数字图像并测量其下落速度。

项目成果

Acoustic scattering from a suspension of flocculated sediments

• DOI: 10.1002/jgrc.20197
• 发表时间: 2013-05
• 期刊: Journal of Geophysical Research
• 作者: Iain T. MacDonald;Christopher E. Vincent;Peter D. Thorne;Benjamin D. Moate

A flocculi model for the acoustic scattering from flocs

• DOI: 10.1016/j.csr.2015.05.002
• 发表时间: 2015-08
• 期刊: Continental Shelf Research
• 影响因子: 2.3
• 作者: C. Vincent;Iain T. MacDonald

Modelling acoustic scattering by suspended flocculating sediments

通过悬浮絮凝沉积物模拟声散射

• DOI: 10.1016/j.csr.2014.07.003
• 发表时间: 2014
• 期刊: Continental Shelf Research
• 影响因子: 2.3
• 作者: Thorne P