Personal photograph uploaded by Emlyn Davies

Mr Emlyn Davies

School of Marine Science and Engineering (Faculty of Science and Technology)
Address: B528, Portland Square, Drake Circus,
Plymouth, Devon, PL4 8AA
Email: emlyn.davies@plymouth.ac.uk

Role

PhD Researcher: "Scattering Signatures of Suspended Sediments"

NERC Studentship in collaboration with The National Oceanography Centre and Sequoia Scientific Inc.

Supervisors:

Aim:

To investigate the optical scattering characteristics of marine particles, with a view to improving the determination of their size.

Importance:

Improving the determination of marine particle characteristics is important because suspended particles:

Affect light penetration through the water,
Play an important role in the carbon cycle,
Influence sound propagation,
Affect the distribution of pollutants,
Affect sediment transport.

It is therefore crucial to have an accurate measurement of suspended particle characteristics so that we can effectively monitor the marine environment.

Many instruments for measuring particles rely on optical and acoustic scattering from the particles, and use Mie Theory or an alternate algorithm, to infer a particle size and concentration. However, these predictions have a number of significant restrictions. For example, Mie Theory assumes that the particles are spherical and of a known composition, and tested alternate algorithms do not cover the full range of particle sizes or types found within the marine environment. Various imaging techniques have proved that particles vary greatly in their shape and composition (Figure 1). As a result, there is significant uncertainty in the response of light scattering instruments to this diverse range of particles.

Figure 1: Examples of flocs recorded using digital holography in the Tamar Estuary.
(Grid spacing = 0.5 mm.)

Method:

A holographic camera will be modified to simultaneously record in-focus images of marine particles with their scattering characteristics by combining both Laser scattering and transmissometry with digital holography.
These results will be compared with theoretical models of particle structure and scattering.
The laboratory set-up may then be housed to allow in situ measurements of natural marine particles in estuarineand coastal waters.
Relationships between particle scattering, organicinorganic content, size and shape will be investigated, aswell as links with influential marine factors (e.g. water column turbulence) will be investigated.

Member of the Marine Physics Research Group

Qualifications & background
2006-2009: BSc (Hons) Ocean Science, School of Earth, Ocean and Environmental Science, University of Plymouth. Dissertation title: "Dynamics of Suspended Particulate Matter in the Lower Tamar Estuary".

Professional membership
Member of the American Geophysical Union
Member of the Challenger Society for Marine Science

Research interests

• Optical scattering and absorption by particulates

• Characterisation of particulates

• Impacts of scattering by complex particles on remote sensing of plankton

• Measurement technology

• Science communication and outreach

Other research

Contributions to NERC project: “Measurement of the abundance and optical significance of sub-micron sized particles in the ocean”, in collaboration with Plymouth, Bangor and Strathclyde Universities.

Grants & contracts

• February 2012: Ocean Sciences Meeting (Salt Lake City) student travel award. $500.

• January 2012: Plymouth Marine Science Education Fund travel grant for the Ocean Optics Meeting 2012. £250.

• April-June 2011: Higher Education Innovation Fund (HEIF) project for development of holographic reconstruction software and development of a fluorescence imaging system (in conjunction with Sequoia Scientific Inc.). ~£10,000 to Alex Nimmo Smith.

Publications
Peer Reviewed:

George W. Graham, Emlyn J. Davies, W. Alex M. Nimmo-Smith, David G. Bowers, and Katherine M. Braithwaite, (in-press), "Interpreting LISST-100X measurements of particles with complex shape using Digital In-line Holography", Journal of Geophysical Research - Oceans.

Emlyn J. Davies, W. Alex M. Nimmo-Smith, Yogesh C. Agrawal, and Alejandro J. Souza, (in-press), “LISST-100 response to

large particles”, Marine Geology, Available online 3 April 2012, ISSN 0025-3227, 10.1016/j.margeo.2012.03.006.

Emlyn J. Davies, W. Alex M. Nimmo-Smith, Yogesh C. Agrawal, and Alejandro J. Souza, (2011), "Scattering signatures of suspended particles: an integrated system for combining digital holography and laser diffraction," Opt. Express 19, 25488-25499.
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-25-25488

Forthcoming:

Emlyn J. Davies, George W. Graham, W. Alex M. Nimmo-Smith, Daniel Buscombe, (in-prep), “An evaluation of the performance of autonomous digital holographic image processing for characterising suspended particles”, Measurement Science & Technology.

Conference Abstracts:

Emlyn J. Davies, W. Alex M. Nimmo-Smith, George W. Graham, (2012), "Sequoia's LISST-HOLO: Results from a bedframe deployment in the Menai Strait, Wales", Oceanology International, London, UK. (Demonstration & Poster)

Emlyn J. Davies, George W. Graham, W. Alex M. Nimmo-Smith, (2012), "Towards understanding particle size distributions derived from laser diffraction", AGU/ASLO/TOS Ocean Sciences Meeting, Salt Lake City, Utah, USA. (Oral Presentation)

Emlyn J. Davies, W. Alex M. Nimmo-Smith, Yogesh C. Agrawal, and Alejandro J. Souza, (2010), "An integrated System for testing laser diffraction", Particles in Europe (PiE), Villefranche-sur-Mer, France. (Oral Presentation)

Emlyn J. Davies, W. Alex M. Nimmo-Smith, Yogesh C. Agrawal, and Alejandro J. Souza, (2010), "Scattering signatures of suspended sediments", Challenger Conference for Marine Sciences, Southampton, UK. (Oral Presentation)