Details of Award
NERC Reference : NE/M009726/1
Three-dimensional floc architecture
Training Grant Award
- Lead Supervisor:
- Professor K Spencer, Queen Mary University of London, Geography
- Grant held at:
- Queen Mary University of London, Geography
- Science Area:
- Freshwater
- Marine
- Overall Classification:
- Marine
- ENRIs:
- Natural Resource Management
- Pollution and Waste
- Science Topics:
- Sediment/Sedimentary Processes
- Earth Surface Processes
- Technol. for Environ. Appl.
- Abstract:
- In lakes, rivers and estuaries mineral and organic particles can be transported long distances in suspension. This suspended material transports particle-associated nutrients and pollutants in the environment, can provide a source of food for filter feeding organisms and once settled is an important habitat. Conversely, accumulations of fine sediment can cause problems for navigation and infrastructure e.g. ports and harbours. Therefore understanding the composition, behaviour and transport characteristics of this suspended material is important for environmental managers. Rather than being transported in suspension as individual particles, this material forms "flocs"; loosely bound aggregates incorporating mineral grains, organic material, bacteria and water, ranging from 10s to 1000s microns in diameter. These flocs are very fragile, complex and irregularly shaped and their settling and transport characteristics are determined by their size, shape, density and porosity. Current techniques to measure and predict their transport and settling rates rely on assumptions that these flocs are spherical and are based on 2-dimensional (2D) observations of these complex 3D objects. In addition, current methods for observing small particles are effective at scales < 1 micron and > 20 micron meaning that there is a "scale of observation" gap. We have developed novel protocols to collect and analyse these flocs, adapting techniques previously used to observe biological materials (Bushby et al. 2011), using volume electron microscopy (FIB-SEM; focused ion beam scanning electron microscopy) we have visualized the fine structure of flocs, with a 3D resolution of 20nm over volumes of 1000s of cubic microns for the first time to bridge this knowledge gap. The aim of this PhD is to provide new knowledge of micro-scale floc architecture (size, shape, structure and composition). The objectives are to; 1) develop protocols to quantify 3D floc characteristics, 2) determine whether 2D measurements of gross floc characteristics translate to the 3D micro-scale and 3) understand how structure varies with changes in floc composition and the transporting medium (water chemistry and hydrodynamics). We will work with HR Wallingford Ltd, an independent research and technology organisation who work in all aquatic environments to provide specialist solutions for industry and to help develop policy. A particular focus of their current research is improved practical solutions for the measurement and modelling of fine sediment transport and improved theoretical understanding of floc dynamics. They will help direct the PhD, provide training in sediment transport modelling and ensure that our work meets the needs of end-users of this research. Flocs will be sampled, stained to identify organic material and then embedded in resin (Bushby et al. 2011). Using FIBSEM, floc constituents (pore space, mineral grains, microorganisms and organic material) will be identified by size, shape and electron density. These image datasets will be analysed to quantify the spatial arrangement and relative proportions of floc constituents. This will enable estimations of density and porosity. Working with HR Wallingford these data will be compared to those conventionally derived using settling velocity and size. Laboratory experiments will be run to understand how changes to water chemistry, turbulence and floc composition affects structure and behaviour. Using FIB-SEM we will be able to quantify these changes in 3D and at scales previously impossible to observe. The main outputs of this work will be new knowledge of 3D floc structural characteristics and composition. This has the potential to improve model predictions of fine sediment dynamics and to improve the understanding of how flocs interact with physical, chemical and ecological processes in aquatic sediments, for example improving our understanding of the mechanisms of pollutant transport in water bodies.
- NERC Reference:
- NE/M009726/1
- Grant Stage:
- Completed
- Scheme:
- DTG - directed
- Grant Status:
- Closed
- Programme:
- Industrial CASE
This training grant award has a total value of £93,122
FDAB - Financial Details (Award breakdown by headings)
| Total - Fees | Total - Student Stipend | Total - RTSG |
|---|---|---|
| £16,587 | £65,538 | £11,000 |
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